The hardness value of brass L63 after annealing. Heat treatment of non-ferrous metals
Parshev 01-09-2005 02:01
“The temperature can be determined quite accurately using a small (about the size of a match head) piece of copper foil, which is placed on the surface of the heated part. At a temperature of 400? C, a greenish flame appears above the foil.
Hardening of a preheated copper part occurs by slow cooling in air. For annealing, the heated part is quickly cooled in water. When annealing, copper is heated to red heat (600? C), when hardening - up to 400? C, determining the temperature also using a piece of copper foil.
In order for brass to become soft, bend easily, forge and stretch well, it is annealed by heating to 500°C and slowly cooling in air at room temperature.”
It is interesting that annealing of copper and brass occurs in the opposite way - there with rapid cooling, there with slow cooling.
When molding sleeves, it is recommended to anneal after 2 operations.
Remus 02-09-2005 01:49
After what 2 operations?
Parshev 02-09-2005 02:11
Case molding operations. For example, re-crimping to a different size is done by running it through the dies.
ABAZ 05-09-2005 08:12
sorry, translit zaklinilo.
Anyman 06-09-2005 08:27
capercaillie 11-09-2005 15:13
Take a gas-foam brick, drill holes in it for your caliber, one-third of the product deep, insert the workpiece into the holes bottom up, and use a gas burner or hairdryer to heat the product until it glows lightly and drop the product into water or cool to room temperature in a jig (brick).
TSV 11-09-2005 22:29
What if you just stuff the cartridges into the holder, place the holder in a bath of water, which should be poured below the slope, and heat the protruding barrels with a burner?
The cartridges are naturally without primers so that water can flow inside.
The dulce will be annealed, and the rest will remain untouched
And there is no need to drill bricks
Machete 12-09-2005 12:54
The couple will be like in a bathhouse.
capercaillie 12-09-2005 13:18
Try. Tell us.
TSV 12-09-2005 20:34
Nothing. No burner. Can't heat it up with a hairdryer.
I tried it on a regular gas burner. I wrapped it in a wet rag and into the fire. Seems to be OK. Only the fire is weak.
TSV 12-09-2005 23:34
The couple will be like in a bathhouse.
There shouldn't be a couple. Now, if I heated it up and lowered it, then yes, I would get a steam room.
But in this case, everything would heat up, and not just the barrel.
Machete 13-09-2005 12:23
When you say "should" - knock on wood ( folk saying Mayan tribe).
TSV 13-09-2005 12:29
quote: Originally posted by Machete:
When you say “should”, knock on wood (Mayan folk saying).
Then let's say this - it didn't happen when I kept it on the gas in a wet rag.
If you anneal it properly, then you need the sleeve to rotate around its axis. Otherwise, the side heats up, but the rest remains unheated. Visible by the trace of tarnish.
Machete 13-09-2005 02:02
I somehow like Gennady Mikhailych’s version better. Although our interest is purely gastronomic - for now.
TSV 13-09-2005 21:10
Do you like drilling holes in bricks?
I don’t know what that brick is, but the metal needs to be cooled, except at the heating point.
capercaillie 13-09-2005 21:56
Sergey, regarding the technology, write to the bullet manufacturer.
And the brick is cut with a knife.
Machete 13-09-2005 22:05
You can't cool the sleeve with water while simultaneously heating the barrel - it's brass, the thermal conductivity is bad.
TSV 13-09-2005 22:45
quote: Originally posted by Machete:
You can't cool the sleeve with water while simultaneously heating the barrel - it's brass, the thermal conductivity is bad.
I won’t be able to try it for a while (I’m running errands), then I’ll test the brass in water.
Although metal is thermally conductive, it cannot heat up below the water level. We are only interested in the annealed butt.
Machete 14-09-2005 01:13
quote: Originally posted by TSV:Although metal is thermally conductive, it cannot heat up below the water level.
Not completely screwed. What is meant?
TSV 14-09-2005 01:28
If the sleeve is stuffed into something porous, there will be poor heat dissipation. And heating the barrel will heat up the rest at the same time. The sleeve should definitely warm up until halfway and turn black, or even warm up more.
The water takes away heat, and the part further from the water will warm up more.
Last time I wrapped the cartridge case in a rag and wet it so that the water would drain. Then he put it in the fire. A wet rag prevented the body of the cartridge case from heating up. The muzzle and slope have warmed up.
Next time I'll try heating the cartridge case sticking out of the water. I'll write about the result. I don't have a gas burner at hand right now.
Machete 14-09-2005 01:39
So this running water is needed, like cooling a coil in moonshine still, otherwise there will be no movie.
TSV 15-09-2005 20:22
Actually, I checked the version.
Basically it works. But the power of a gas soldering iron is not enough to heat it up, since the water takes away the heat. But the sleeve does not anneal below water. There is no hissing or bubbling. Not the right temperature to instantly warm up all the water.
I tried it without water, empty. It warmed up quickly, but due to heat transfer, half of the sleeve had time to warm up.
If the view doesn’t bother you that it’s below the slope, then it will do without water. But you still need to turn it. Otherwise, on one side the stain burns out, and on the other the heating is weaker
Parshev 16-09-2005 17:05
2 ParshevWhere did the information come from? The writing style is not similar to technical literature, closer to housewifery
Do you want checkers or go?
Anyman 20-09-2005 08:27
quote: Originally posted by Parshev:Do you want checkers or go?
Technical literature describes how to do it in factory or laboratory conditions, do you have them?
Anyman 20-09-2005 08:54
quote: Originally posted by wood grouse:
Bullet manufacturers recommend:
Take a gas-foam brick, drill holes in it for your caliber, one-third of the product deep, insert the workpiece into the holes bottom up, and use a gas burner or hairdryer to heat the product until it glows lightly and drop the product into water or cool to room temperature in a jig (brick).
2 capercaillie
Do you mean regular building bricks or something special like fireclay?
capercaillie 20-09-2005 10:12
Yes, they sell it at every construction fair.
Gas-foam-brick bought a block and sawed myself any bricks I wanted.
I use a gas torch for annealing.
They also sell it, refilled from lighter cans.
RAY 27-09-2005 15:20
quote: Originally posted by Anyman:On the one hand, you are right. But remembering from the time of training that heat treatment is not the easiest thing, I would certainly consult with a thermist or look in the appropriate reference book. After all, if with copper everything can be more or less unambiguous, then brass can be very different in chemical composition and, accordingly, suitability for heat treatment.
For example, annealing temperature for brass:Brass L96: 540 - 600 degrees;
Brass L90 - L62: 600 - 700 degrees;Since people have gathered here to count every grain of powder, then everything must be accurate.
-----------
Yeah... they brought me so many shell casings for analysis - there were more and more L63...
L96 and L90 - even in color - COPPER... more and more L63 and L65 seemed to always be used for cartridges...
Anyman 27-09-2005 20:00
So, in L96 there is 95-97% copper, which is why the color is copper. In L63 62-65%
tov_Mauser 14-10-2005 11:04
ingredients: Naganov revolver cartridges
tools: pliers, rag, gas burner on the stove
We wet the rag and wring it out, wrap the handles of the pliers, take the sleeve by the pliers and heat it in the flame at an angle of 45 (preferably in the twilight - so that the glow of the metal can be seen), heat the neck until dull red, then put the sleeve aside to cool. When heated, massive pliers remove heat from the base of the sleeve - which is clearly visible by the way the metal warms up
The output is high-quality cartridges that do not crack during repeated reloading and rolling/flaring of the gun
Brass is double or multi-component alloy based copper, where the main alloying element is zinc, sometimes with the addition tin, nickel, lead, manganese, gland and other elements.
Brass- an alloy of copper and zinc (from 5 to 45%). Brass content from 5 to 20% zinc called red (tompak), with a content of 20–36% Zn - yellow. In practice, brasses with a zinc concentration exceeding 45% are rarely used.
Zinc is a cheaper material compared to copper, so its introduction into the alloy, while simultaneously increasing the mechanical, technological and anti-friction properties, leads to a reduction in cost - brass cheaper than copper. Electrical conductivity and thermal conductivity brass lower than copper.
Brass- double and multicomponent copper alloy, with the main alloying element - zinc. Compared to copper, they have higher strength and corrosion resistance. Plain brass is designated by the letter L and a number indicating the copper content as a percentage. In special brasses, after the letter L, write the capital letter of additional alloying elements and, through a dash after the copper content, indicate the content of alloying elements as a percentage. Brasses are divided into casting and wrought. Brass, with the exception of lead-containing brasses, can be easily processed by pressure in a cold or hot state. All brasses can be easily soldered with hard and soft solders.
The main alloying elements in multicomponent brasses are aluminum, iron, manganese, lead, silicon, nickel. They have different effects on the properties of brass.
Marking:
The following markings are accepted. The brass alloy is designated by the letter “L”, followed by the letters of the main elements that form the alloy. In grades of wrought brass, the first two digits after the letter “L” indicate the average copper content as a percentage. For example, L70 is brass containing 70% Cu. In the case of alloyed wrought brasses, letters and numbers are also indicated indicating the name and amount of the alloying element, LAZH60-1-1 means brass with 60% Cu, alloyed with aluminum (A) in the amount of 1% and iron in the amount of 1%. The Zn content is determined by the difference from 100%. In cast brasses, the average percentage of alloy components is placed immediately after the letter indicating its name. For example, brass LTs40Mts1.5 contains 40% zinc (Z) and 1.5% manganese (Mts).
Heat treatment of brass
Heat treatment of brass consists only of annealing. When pressuring or hammering out parts made of brass, it is desirable to increase its ductility. To do this, brass is heated to a temperature of slightly more than 500 ° C and allowed to cool in air. After annealing, brass becomes soft and easily bends and knocks out. With further processing by pressure, rolling and beating, the brass again hardens and becomes hard. In this case, repeated annealing is performed. When deep drawing, in order to avoid the formation of cracks, the brass has to be annealed several times.
69. Bronze, composition, marking:
Bronze - alloy copper, usually with tin as the main alloying component, but bronzes also include copper alloys with aluminum, silicon, beryllium, lead and other elements, with the exception of zinc(This brass) And nickel. As a rule, any bronze contains additives in small quantities: zinc, lead, phosphorus and etc.
Bronze marking is based on the same principle as brass marking. In front are the letters Br (bronze), followed by the letter designations of the elements that make up the alloy, and behind them are numbers indicating the average percentage of elements. The bronze marking consists of letters and numbers. The first letters Br indicate the name of the alloy - bronze, followed by the letter designations of the elements that make up the alloy, followed by numbers indicating the average percentage of these elements. For example, BrOF6 5 - 0 15 - tin phosphorus bronze, containing 6 5% tin, 0 15% phosphorus, the rest is copper.
The main properties of bronzes are high corrosion resistance, good casting and wear-resistant properties. Bronze is supplied in accordance with GOST 5017-74, GOST 613-79, GOST 1320-74.
According to their structure, tin bronzes are divided into single-phase (containing up to 10% Sn) and two-phase (containing 10-22% Sn), which are a mixture of crystals of a solid solution of tin in copper and crystals of a chemical compound of copper with tin (Cu 3 Sn).
To improve the quality of tin bronzes, lead is introduced into them (increases anti-friction properties and promotes better workability), zinc (improves casting properties), phosphorus (increases casting, mechanical and anti-friction properties).
BRASS
Brasses are the most common copper-based alloys. A summary list of standard brasses according to GOST 15527 and their foreign analogues is given in table. 1.
The state diagram of the copper-zinc alloy is shown in Fig. 1
And changes in the temperature of evaporation, melting and casting of copper-zinc alloys depending on the zinc content - in Fig. 2.
Change in the normal elastic modulus of copper-zinc alloys depending on the zinc content - Fig. 3.
Basic parameters of intermetallic phases of system alloys Cu-Zn are given in table. 2.
During the transition from a disordered β-phase to an ordered one β ’-phase in the specified temperature range there is a decrease in the coefficient of mutual diffusion and the growth rate of the phase. The activation energy of mutual diffusion in the β’-phase increases, and in the β-phase it decreases with increasing zinc concentration, while itapproximately 1.5 times greater in the β' phase than in the β phase. Partial atomic diffusion coefficients Zn 2 times more than Cu atoms in the disordered β-phase, and almost coincide with the ordered β’-phase.
Simple brass having a phase composition have practical applications α, α + β, β and β + γ .
The chemical composition of brass processed by pressure, according to domestic standards, is given in the appendix. 1.
SIMPLE BRASS
Simple brass, depending on the phase composition, is divided into two types: single-phase α (up to 33% Zn) and two-phase α + β (over 33% Zn).
In single-phase brasses, in which the zinc content is close to the saturation limit, small amounts of the β-phase are sometimes present as a result of slow diffusion processes. However, inclusions of the /3-phase, observed in very small quantities, do not have a noticeable effect on the properties α - brass. Thus, although these brasses have a two-phase structure, in terms of their physical, mechanical and technological properties it is advisable to classify them as single-phase brasses.
Pressure processing of plain brasses
Single-phase (A)brass during hot deformation is very sensitive to the content of impurities, especially fusible ones ( Bi, Pb ). Bismuth in the alloy can segregate along the boundaries, so even a monatomic layer of it can cause red brittleness in single-phase brasses with a high zinc content. Machinability α - When brass is hot, it deteriorates with increasing zinc content. When cold, single-phase brass can be processed well.
Two-phaseα + β - brasses are processed in a hot state better than single-phase ones due to the presence of highly plastic properties elevated temperatures β -phases and are less sensitive to impurities. However, they are sensitive to temperature and cooling speed conditions. For this reason, a non-uniform structure is often observed in hot-pressed semi-finished products. For example, the front end of a rod (strip or pipe) has a predominantly fine needle-like structure and high mechanical properties, at the rear end of the rod, as a result of cooling, the structure is granular and the mechanical properties are reduced.
In the cold state, two-phase brass is processed worse than single-phase brass. Their plasticity in a cold state depends on the structure. If α -phase is located on the main background of crystals β -phases in the form of thin needles, then the workability of two-phase brass in the cold state improves.
The effect of zinc content in brasses on the temperature range of hot pressure treatment is shown in Fig. 4.
In brasses, in the temperature range of 200-600°C, depending on the phase composition and zinc content, a zone of reduced ductility is observed.
When cold rolling, drawing and deep stamping of brasses, regardless of their phase composition, a structure with a grain size of no more than 0.05 mm is preferred.
The total degree of cold deformation of simple brasses is determined by a certain limit, above which the ductility drops sharply. This limit of permissible total cold deformation, which decreases with increasing zinc content, is set for each brand of brass.
If we assume the highest hot ductility in a homogeneous region β -phase, and at room temperature in the region α -phase for 100%, then the workability of brass by pressure can be assessed quantitatively ( table. 3).
Such assessments of the workability of metals and alloys by pressure and other technological characteristics are often used in foreign practice.
Heat treatment of plain brasses. Main view heat treatment For simple brasses, recrystallization annealing and stress relief annealing are used. The recrystallization process of brasses is determined by the zinc content and phase composition.
Recrystallization onset temperature α -brass decreases with increasing zinc content. Recrystallization α -phase in highly deformed two-phase brass begins at 300°C. Under these conditions, the β-phase remains unchanged and its recrystallization begins at a higher temperature. Therefore, when choosing the annealing temperature to obtain the optimal structure, it is necessary to take into account this feature of two-phase brasses.
The grain sizes of single-phase brasses are determined according to microstructure standards (GOST 5362).
When brass semi-finished products are annealed in an air or oxidizing atmosphere, spots form on their surface - oxidation products that are difficult to remove during etching. Reducing the oxygen partial pressure (vacuum annealing) prevents staining but poses the risk of dezincification. Therefore, it is recommended to carry out annealing at a minimum temperature and in a protective atmosphere. In production conditions, stains are most difficult to avoid in brasses containing 37-40% zinc.
Machinability of simple brass by cutting. The machinability of brass by cutting (turning, milling, planing, grinding) depends on the phase composition of the brass. When cutting single-phase brass, the chips are long. Two-phase ( A + β ) brasses are processed better than single-phase α - brass. As the /3-phase content increases, the chips become more brittle and shorter. A quantitative assessment of the machinability of simple brass by cutting is determined by comparison with brass LS63-3, the machinability of which is taken as 100%. Single-phase α -brasses are highly polished, two-phase ones are somewhat worse. The machinability of brass by cutting and polishability is given in table. 4.
Soldering and welding of simple l atuney. Plain brass is very easy to join with soft solders. Before soft soldering, the surface is cleaned either by grinding or acid etching. It is preferable to use alloys containing 60% tin as solder. The antimony content in solder due to its strong affinity for zinc should be no more than 0.25-0.5%. Soft soldering is preferably performed with chloride fluxes.
Single-phaseα -brasses can also be easily joined by soldering with hard solders, including silver, two-phase A + β - somewhat worse.
Copper-phosphorus solders are self-fluxing, so soldering of brass with these solders is carried out without fluxes. When soldering with other hard solders, appropriate fluxes must be used.
The lead content in hard solders is limited to 0.5%.
Quantitative assessment of the solderability of plain brasses,%: single phaseα - brass (soft solders) – 100%, single-phaseα - brass (hard solders) – 100%, two-phaseα+ β - brass (soft solders) – 100%, two-phaseα+ β - brass (hard solders) – 75%.
The weldability of simple brass is somewhat worse than the solderability. General quantitative assessment of the weldability of brass -75% compared to oxygen-free copper, taken as 100%. The following types of welding are used to join brass: arc with a carbon electrode, arc with a consumable electrode, arc with a tungsten (non-consumable) electrode in a protective (inert gas) environment, arc with a consumable electrode in an inert gas environment, oxygen-acetylene, electric contact (spot) , roller, butt).
Brass content 20% Zn does not lend itself well to electric contact welding, lighter - brass with 40% Zn . The high zinc content in two-phase brasses makes it difficult arc welding due to its evaporation. Therefore, filler materials used in arc welding must contain relatively small amounts of zinc. Brasses containing more than 0.5% Pb are usually difficult to weld. To improve the wettability of the metal during the welding process, preheating to a temperature of 260 ° C is necessary, especially for brass with a high copper content. Carbon electrode welding of brasses containing 15-30%, Zn , is best done using filler rods (wire) made of Cu alloy + 3% Si . For single-pass welds, copper rods (wire) alloyed with a small amount of tin can be used; for multi-pass welds it is better to use alloy rods Cu + 3% Si.
Brasses containing more than 30% Zn , can be welded with a carbon electrode with filler rods (wire) made of brass Cu + 40% Zn or Cu + 3% Si . To improve the quality of welding, it is necessary to preheat the metal to a temperature of 210°C. Wire or rods made of tin-phosphorus bronze or aluminum bronze are used as consumable electrodes.
Arc welding of brass with a tungsten electrode in an inert gas environment is complicated by the release of zinc oxide vapors, which suppress the action of the arc. Therefore, welding should be carried out at high speeds.
Oxy-acetylene welding gives good results. For welding brass with a content of 15-30% Zn it is necessary to use filler rods (wire) made of alloy Cu + 1.5% Si. Ifterms of Use finished products do not cause local corrosion (dezincification), you can use brass with 40% Zn (L60). For welding brasses containing more than 30% Zn an alloy is used as a filler material Cu + 3% Si.
The influence of impurities on the properties of simple brasses. Impurities do not have a significant effect on the mechanical, physical (with the exception of iron, which, with a content of > 3.0%, changes the magnetic properties of brasses) and Chemical properties simple brasses, but noticeably affect their technological characteristics. During hot pressure treatment, single-phase brasses are especially sensitive to low-melting impurities.
The quality of products obtained from brass by deep stamping depends on the purity of the alloy, therefore, in simple brasses intended for deep stamping, the impurity content should be minimal.
The influence of impurities on the quality of semi-finished brass products:
aluminum deteriorates the quality of casting, causing foaming in castings; bismuth causes hot brittleness of brasses, especially single-phase ones; iron complicates the recrystallization process;
siliconimproves soldering and welding processes, increases corrosion resistance; nickel increases the temperature at which recrystallization begins;
leadcauses hot brittleness of brass, especially single-phase brasses containing zinc in the range of 30-33%;
antimonynegatively affects the workability of brass by pressure. Antimony microadditives (<0,1 %) к двухфазным латуням частично локализуют коррозию, связанную с обесцинкованием;
arsenicimpairs the ductility of brasses as a result of the release of brittle phases at concentrations above its solubility limit: in brasses in the solid state (>0.1%). Arsenic additives in small quantities (< 0,04%) предохраняют латуни от коррозионного растрескивания и обесцинкования при контакте с морской водой;
phosphorus refines the structure in the cast state and prevents cracking when heated, accelerates grain growth during recrystallization; reduces corrosion associated with dezincification; not recommended as a deoxidizing agent for copper-zinc alloys;
tinreduces the ductility of brasses and may cause heat cracking if the iron content is > 0.05%.
Modification of brasses carried out by introducing into the melt:
additions of elements that form refractory compounds, which, if structurally consistent, will serve as crystallization centers;
surface active metals, which, concentrating on the faces of nascent crystals, slow down their growth.
Elements such as iron, nickel, manganese, tin, yttrium, calcium, boron, and misch metal are used as modifiers in brasses.
Corrosion properties of brasses. Brasses have satisfactory resistance to industrial, marine and rural atmospheres. They fade in air. Corrosive effect on brasses containing >15% zinc, are caused by carbon dioxide and halogens.
Brasses containing <15% Zn , in terms of their corrosion resistance are close to industrial purity copper.
Under the influence of oxidizing acids, brass corrodes intensively. The limiting concentration of nitric acid at which no noticeable corrosion is observed is 0.1% (by weight). Sulfuric acid acts less aggressively on brass, however, in the presence of oxidizing salts K 2 SG 2 ABOUT 7 And Fe 2 (S0 4) 3the corrosion rate increases 200-250 times. Of the non-oxidizing acids, hydrochloric acid has the most corrosive effect.
The corrosion resistance of brass to most acids that do not have oxidizing ability is satisfactory. Brass is also resistant to dilute hot and cold alkaline solutions (with the exception of ammonia solutions) and cold concentrated neutral salt solutions. Brass is inert towards river and salt water. When in contact with river water containing small amounts of sulfuric acid, or in sea water, plain brass noticeably corrodes. The rate of corrosion depends on temperature, concentration, degree of contamination and flow rate around the metal surface. Brasses have good corrosion resistance to soil and are neutral to food products. The corrosion rate of brass in soil ranges from 0.0005 mm/year (in loamy soil with pH 5.7) to 0.075 mm/year (in ash soil with pH 7,6).
Dry gases - fluorine, bromine, chlorine, hydrogen chloride, hydrogen fluoride, carbon dioxide, carbon and nitrogen oxides at temperatures of 20°C and below have practically no effect on brass, however, in the presence of moisture, the effect of halogens on brass increases sharply; sulfur dioxide causes corrosion of brass when its concentration in the air is 1% and air humidity > 70%; Hydrogen sulfide has a significant effect on brass under all conditions, but brasses containing Zn > 30% more resistant than brass with low zinc content.
Fluorinated organic compounds, such as freon, have virtually no effect on brass.
In humid saturated steam at high speeds (about 1000 m 3 / c ) pitting corrosion is observed, so brass is not used for superheated steam.
Corrosion resistance of brasses in different environments given in table. 5.
In mine waters, especially if there is Fe2(SO4 ) 3 brass is highly corroded. Fluoride salts present in water have a weak effect on brass, chloride salts have a stronger effect, and iodide salts have a very strong effect.
Brass, in addition to general corrosion, is also subject to special types corrosion: zinc plating and “seasonal” cracking.
Dezincification is a special form of corrosion in which a solid solution of zinc is dissolved in copper and copper is electrochemically deposited at the cathode sites. Zinc corrosion products can be removed or retained in the form oxide film. The solution in which brass is dezincified typically contains more zinc than copper.
As a result of dezincification, brass becomes porous, reddish spots appear on the surface, and mechanical properties deteriorate. Dezincification is observed when brass comes into contact with electrically conductive media (acidic and alkaline solutions) and manifests itself in two forms: continuous and local. The dezincification process intensifies with increasing zinc content, as well as with increasing temperature and aeration. Single-phase brass containing >15% Zn , are subjected to dezincification in acidic solutions (nitrates, sulfates, chlorides, ammonium salts and cyanides). In two-phase brasses, the dezincification process is noticeably enhanced and can occur even in aqueous media. The most vulnerable isβ phase.
Small additions of arsenic, phosphorus and antimony partially localize the corrosion associated with dezincification. Arsenic and antimony protect against dezincification mainlyα -phase.
"Seasonal" or intergranular cracking is observed in brasses as a result of exposure to corrosive agents in the presence of tensile stresses. Corrosive agents include: ammonia vapors or solutions, condensates with sulfur dioxide gases, wet sulfuric anhydride, solutions of mercury salts, various amines, components of etching solutions, wet carbon dioxide. If the atmosphere contains traces of ammonia, wet carbon dioxide, sulfur dioxide and other corrosive agents, then “seasonal” cracking occurs when temperature fluctuations result in condensation of corrosive agents on the surface of parts.
Brasses containing up to 7% zinc are little sensitive to “seasonal” cracking. In brasses containing from 10 to 20% zinc, intergranular cracking is not observed if internal tensile stresses do not exceed 60 MPa. Brasses containing 20-30% Zn , are subject to corrosion cracking only in the cold-deformed state in aqueous solution ammonia. Single-phase brasses with a zinc concentration close to the saturation limit and two-phase brasses are most prone to corrosion cracking. They are resistant to seasonal cracking only in the presence of tensile stresses< 10 МПа.
The tendency to corrosion cracking of copper-zinc alloys in ammonia vapor is shown in Fig. 5.
To prevent corrosion cracking of brasses, it is necessary to use low-temperature annealing and protect them from oxidation during storage. To relieve internal stresses, pre-recrystallization annealing is performed.
To protect brass from oxidation, it is recommended to passivate them in the following environments: a slightly acidic aqueous solution containing about 6% chromic anhydride and 0.2% sulfuric acid; aqueous solution containing 5 % chromium and 2% chrome alum.
Brass is also protected using corrosion inhibitors, for example, benzotriazole or toluenetriazole. Benzotriazole forms a film on the surface (< 5 нм), которая предохраняет латуни от коррозии в водных средах, различных атмосферах и других агентах. Коррозионные ингибиторы могут быть введены в состав лаков и защитной оберточной бумаги.
In the case of electrochemical corrosion, brass, when in contact with various metals and alloys, manifests itself in two ways: in some cases as an anode, in others as a cathode ( table 6 ).
When brass comes into contact with silver, nickel, cupronickel, copper, aluminum bronze, tin and lead, electrochemical corrosion does not occur.
When heated, brass oxidizes. The rate of oxidation of brass increases exponentially with increasing temperature, doubling approximately every 360K. At temperatures above 770K, zinc evaporation is most intense if its concentration in the alloys exceeds 20 %.
The change in some physical and mechanical properties of brasses depending on the zinc content is shown in Fig. 6-9.
Typical physical, mechanical and technological properties brasses are given in P ril. 2, 3, 4.
Special brasses, pressure treated
Special or multi-component brasses are copper-zinc alloys of complex compositions in which the main alloying elements are aluminum, iron, manganese, nickel, manganese, nickel, silicon, tin and lead. These elements are usually introduced into brass in such quantities that they are completely dissolved inα andβ phases. In addition to the indicated elements, small additions of arsenic, antimony and other elements are introduced into brass.
The influence of alloying elements is manifested in two ways: phase properties change (Aand/3) and their relative quantities, i.e. boundary of phase transformations.
To determine the boundaries of phase transformations in the system or the “apparent” (“fictitious”) copper content when adding an alloying element, use the empirical equation:
A ’ = A *100/(100+ X *(K e-1)),
Where A'- apparent (fictitious) copper content, % (by weight); A -actual copper content, % (by weight); X- content of the third component, % (by weight); Ke- Guinier coefficient, characterizing the influence of the alloying element on the phase composition (at K e> 1, the number increasesβ '-phase).
Meaning Kefor various elements: for Ni K uh from -1.2 to -1.4, for Co K e=-1, for Mn K e=0.5, for Fe K e=0.9, for Pb K e=1, for Sn K e=2, for Al K e=6, for Si K e from 10 to 12.
Lead brasses
Lead brasses are copper-zinc alloys alloyed with lead. System State Diagram Cu - Zn - Pb presented on rice. 10.
The solubility of lead in alloys in the solid state is negligible. In two-phase copper-zinc alloys (containing Zn 40%) lead solubility at 750°C inβ -phase a little more than 0.2%; At room temperature, lead is practically insoluble. In two-phase brasses (in equilibrium), lead is located insideα Andβ -phases and partially at the boundaries of these phases. Lead, when released along phase or grain boundaries, noticeably worsens the deformability of brass in a hot state.
Lead in alloys A + β performs a dual role: on the one hand, it is used as a phase that promotes chip grinding, on the other - as a lubricant that reduces the coefficient of friction during cutting. The effectiveness of lead additives is determined by its quantity and the structure of the alloy, the size and nature of the distribution of lead particles, and the grain size a -phase, quantity and distributionβ phases.
By improving machinability, lead significantly reduces the impact strength of brass, impairs workability by pressure, soldering and welding, polishability, and complicates galvanic surface treatment of products.
The strength characteristics of lead brasses decrease more rapidly with increasing temperature compared to simple brasses. The tensile strength of brasses containing about 2% lead at a temperature of 600°C is 10 MPa, at a temperature of 800°C - practically equal to zero.
Depending on the processing of finished deformed semi-finished products, lead brass is classified into three main types: for cold forming, for hot stamping, for processing on automatic lathes.
Structure lead thick brass. processed by cold pressure condition, consists ofα -phase and lead, the content of which must be within such limits as to ensure high machinability. Such alloys include brass grades LS74-3, LS64-2, JIC 63-3 and LS63-2.
Svintsovs e lat un and hot pressure treated condition and intended for hot forging and stamping - two-phase (α +β). The zinc content in brasses must be such that the transformation α + β into the clearβ -phase occurred completely and at a relatively low temperature.
Estimated content β -phase is about 20%. Lead content from 1 to 3%. Such brasses include lead brasses of the LS60-1, LS59-1 and LS59-3 brands. Svintsovs e latu ni. used for processing on automatic lathes and in microtechnology (i.e. for the manufacture of parts that are very small in size, about 1 mm) - two-phase, with a high lead content; LS63-3 (low content/3-phase) and LS58-3 (high content β -phases).
Brasses used in microtechnology are subject to special requirements for uniformity of chemical composition, tolerances on the main components and microstructure (size and distribution of lead particles, quantity and distribution β -phases, grain size α -phases). Uniformity of the chemical composition (homogeneity of the alloy) must be ensured in small areas.
The limits for optimizing the microstructure of lead brasses for “micro-parts” are determined by the content β -phase from 10 to 30%, grain size α -phase - from 10 to 50 microns with an average diameter of lead particles of 1-5 microns.
Processing of lead brasses. Oxides of various elements impair the machinability of lead brass by cutting, therefore, when melting and casting them, careful control over their content is necessary. Of the impurity elements, iron has the most negative effect on machinability, therefore special restrictions are set on its content. Casting is carried out in two ways: in molds and semi-continuous (continuous) method. To achieve stability of the chemical composition, it is preferable to cast lead brasses in a continuous (semi-continuous) manner.
Lead does not affect the temperature and crystallization process of copper-zinc alloys; it solidifies at 326°C and, in the case of precipitation along grain (phase) boundaries, impairs the hot deformability of two-phase alloys.
The composition ranges of standard hot and cold processed lead brasses are shown in Fig. eleven.
When hot stamping lead brasses containing 56-60% Cu (LS59-1), the tendency to crack formation is determined mainly by the deformation temperature. The optimal temperature range at which cracks do not form is quite narrow and is located in the temperature range that makes up the lines on the phase diagram Cu-Zn , delimiting the two-phase α + β Andsingle-phaseβ -regions
The content of lead, as well as low-melting impurities (bismuth, antimony and others) does not affect the tendency to crack formation during hot stamping of two-phase leaded brasses (α + β ).
The influence of the chemical composition on the cutting and pressure machinability of lead brasses is shown in Table. 7.
Leadα -brass is processed in a cold state, but under certain conditions hot pressing is also possible.
The main types of heat treatment for lead brasses are full recrystallization annealing and low-temperature annealing to relieve internal stresses.
Leaded brass is not as good as plain brass in joining with solders, welding and polishing. To join lead brass, it is not recommended to use oxygen-acetylene welding, gas-shielded arc welding, or arc welding with a consumable electrode.
Co. corrosion resistance of lead brasses . Lead brasses have: excellent resistance to the effects of pure bicarbonates, freon, fluorinated bicarbonate coolants and varnishes; good resistance to industrial, marine, rural atmospheres, alcohols, diesel fuel and dry carbon dioxide; moderate resistance to crude oil and hydrocarbon dioxide; poor resistance to ammonium hydroxide, hydrochloric and sulfuric acids.
Tin yannaya la t uni
Tin has little effect on changing the boundaries of phase transformations, but noticeably changes the nature β -phases. System State Diagram Cu - Zn - Sn shown on rice. 12.
Dual-phase tin brasses have high corrosion resistance in many environments. With an increased tin content in brasses, a new γ phase appears. The γ phase is a brittle component that significantly impairs the cold workability of brass. Appearance γ -phases in two-phase brass (a +/3) observed at tin contents above 0,5% (if the tin content exceeds this limit, then during the transformation β the δ-phase is released, enveloping α -phase. The appearance of brittle phases limits the alloying of brass with tin. Tin content more 2% in brasses, it impairs their hot workability. Standard tin brasses can be divided into two types: single phase (α - solid solution) and three-phase ( α + β + γ ).
Aluminum brass
Aluminum brasses are copper-zinc alloys in which the main alloying additive is aluminum.
Aluminum, due to its high Guinier coefficient (Ke = 6) and significant solubility in the solid state compared to other elements (except silicon), has even small quantities noticeable effect on the properties of brass. Aluminum additives increase the mechanical properties and corrosion resistance of brass, but somewhat impair their ductility. The amount of introduced aluminum is limited to the limits above which brittleness appears. γ -phase ( rice. 13).
With copper content,% (by weight): 70; >/ J 65; 60 limiting aluminum content, % (by weight): 6; 5 and 3 respectively. In pressure-processed brasses, the aluminum content does not exceed 4%, in cast high-strength brasses - 7%.
Alloying of brass is carried out with aluminum alone or in certain proportions with other elements (iron, nickel, manganese and etc.).
As a rule, single-phase brasses (LA85-0.5, LA77-2) are alloyed with aluminum alone. To localize dezincification and prevent corrosion cracking upon contact with sea water in single-phase aluminum brasses containing more than 15% Zn, introduce 0.02-0.04 As (LAMsh77-2-0.05).
Excess arsenic (> 0.062%) impairs the ductility of brasses. Aluminum together with iron (LAZH60-1-1) and nickel (LAN59-3-2) are introduced mainly into two-phase brasses.
Iron improves the ductility of brasses containing lead, when hot, it crushes the structure and increases their mechanical properties; Nickel increases corrosion resistance. Iron and nickel somewhat reduce the ductility of brass when cold.
Alloying brass with aluminum, nickel and small additions of manganese and silicon (LANKMts75-2-2.5-0.5-0.5) makes them dispersion-hardening and significantly improves mechanical properties, especially elastic characteristics.
Single-phase aluminum brasses are satisfactorily processed by pressure in a hot state and well in a cold state; two-phase - good when hot and satisfactory when cold. Cutting machinability ranges from 30 to 50% (compared to LS63-3 brass).
Aluminum brass, compared to lead, is less easily joined by solders, but is slightly better welded; in terms of polishability, they are close to two-phase simple brass ( tab l. 8).
Iron-containing brasses
Iron additives significantly refine the structure of brass, thereby improving mechanical properties and technological characteristics. However" alloys system Cu - Zn - Fe rarely used. Multi-component brasses have become widespread.
Manganese brass
Alloying brass with manganese significantly increases their corrosion resistance when in contact with sea water, chlorides and superheated steam.
Alloy System Diagram Cu - Zn - Mn shown in Fig. 14.
Manganese additions have a minor effect on the structure of brass. However, manganese reduces the stability of the ordered phase lattice β . When the Mn content is > 4.7% (at.), a partially disordered state is observed in the alloy at a quenching temperature of 520°C.
Manganese has the most favorable effect on the properties and technological characteristics of brass in combination with other alloying elements (aluminum, iron, tin, nickel).
Silicon brasses
Silicon in the solid state is soluble in brass in significant quantities, but its solubility decreases with increasing zinc content. Solid solution region Aunder the influence of silicon and zinc, it shifts sharply towards the copper angle (Fig. 15 ) .
With increasing silicon content in the alloy structure Cu - Zn - Si a new phase appears Tohexagonal syngyny, which is plastic at elevated temperatures and, unlike β -phase is polarized. As the temperature decreases (below 545°C), eutectoid decomposition of the k-phase occurs intoα + γ ".
Silicon brasses containing 20% Zn and 4% Si not suitable for pressure treatment due to low ductility. To obtain deformed semi-finished products, silicon brasses containing<4% Si.
Small additions of silicon improve the technological characteristics of brass during casting and hot forming, increase mechanical properties and anti-friction properties
Nickelbrass
Alloying brasses with nickel increases their mechanical properties and corrosion resistance. Nickel brasses are more resistant to dezincification and corrosion cracking than other brasses.
As can be seen from the phase diagram of the alloy system Cu - Zn - Ni (rice. 16), nickel has a noticeable effect on the structure of brasses, expanding the region of the solid solution α
When alloying with nickel, some two-phase brasses can be converted to single-phase.
Alloying L62 brass with nickel in an amount of 2-3% (by weight) makes it possible to obtain a single-phase alloy with fine grains, high and uniform mechanical properties and increased corrosion resistance. Thanks to the addition of nickel in the production of deformed semi-finished products, the appearance of such a negative phenomenon as a stitch structure is eliminated.
Recommendations for improving the properties of copper-zinc alloys taking into account foreign experience. The properties of brasses, along with the purity of the initial components of the alloys, methods and modes of melting and casting, are greatly influenced by the modes of their processing and the preparation of the charge.
To reduce the formation of porosity and bubbles in sheets (strips) and tapes made of brass grades L70, L68, L63 and L60: avoid contamination of the charge with phosphorus; waste in the form of chips containing oil, emulsion, etc. is subjected to oxidative firing before melting; add copper oxide to the melt in an amount of 0.1-1.0 kg per 100 kg of charge; pay special attention to optimal casting and hot rolling conditions; anneal hot-rolled strips before cold rolling.
To increase the resistance of brasses L68 and L70 to corrosion cracking, it is necessary to pay great attention to the selection of cold rolling and annealing conditions. The total reduction during the last cold rolling should be more than 50%, the optimal annealing temperature is 260-280°C.
To increase the resistance of two-phase brass to dezincification (and this is possible if the proportion β -phase in the structure of the alloy is about 30%) it is necessary to carry out heat treatment in the temperature range 400-700°C (depending on the composition of the alloy).
To prevent dezincification of L63 brasses and to obtain a high-quality surface during bright annealing (in bell-type and shaft furnaces), the recrystallization annealing temperature is maintained within 450-470°C. At this temperature, within 1-4 hours, a strip (tape) is obtained with a grain size of 0.035-0.045 mm, a tensile strength of 33-35 kgf/mm 2 and a relative elongation of 50%.
The need for heat treatment.
Heat treatment of steel parts is carried out in cases where it is necessary either to increase the strength, hardness, wear resistance or elasticity of a part or tool, or, conversely, to make the metal softer and easier to machine.
Depending on the heating temperatures and the method of subsequent cooling, the following types of heat treatment are distinguished: hardening, tempering and annealing. In amateur practice, you can use the table below to determine the temperature of a hot part by color.
Heat color: steel |
Heating temperature "C |
Dark brown (visible in the dark) |
530-580 |
Brown-red |
580-650 |
Dark red |
650-730 |
Dark cherry red |
730-770 |
Cherry red |
770-800 |
Light cherry red |
800-830 |
Light red |
830-900 |
Orange |
900-1050 |
Dark yellow |
1050-1150 |
Light yellow |
1150-1250 |
Bright white |
1250-1350 |
Hardening gives the steel part greater hardness and wear resistance. To do this, the part is heated to a certain temperature, held for some time so that the entire volume of the material warms up, and then quickly cooled in oil (structural and tool steels) or water (carbon steels). Typically, parts made from structural steels are heated to 880-900° C (light red incandescent color), those from instrumental steels are heated to 750-760° C (dark cherry red color), and those from stainless steel are heated to 1050-1100° C ( color dark yellow). The parts are heated slowly at first (to about 500°C), and then quickly. This is necessary to ensure that internal stresses do not arise in the part, which can lead to cracks and deformation of the material.
In repair practice, they mainly use cooling in one medium (oil or water), leaving the part in it until it cools completely. However, this cooling method is unsuitable for parts with complex shapes, in which large internal stresses arise during such cooling. Parts of complex shape are first cooled in water to 300-400 ° C, and then quickly transferred to oil, where they are left until completely cooled. The residence time of the part in water is determined at the rate of 1 s for every 5-6 mm of the part’s cross-section. In each individual case, this time is selected empirically depending on the shape and mass of the part.
The quality of hardening largely depends on the amount of coolant. It is important that during the cooling process of the part, the temperature of the coolant remains almost unchanged, and for this its mass must be 30-50 times greater than the mass of the part being hardened. In addition, before immersing a hot part, the liquid must be thoroughly mixed to equalize its temperature throughout the entire volume.
During the cooling process, a layer of gases forms around the part, which impedes heat exchange between the part and the coolant. For more intense cooling, the part must be constantly moved in the liquid in all directions.
Small parts made of low-carbon steel (grades “3O”, “35”, “40”) are slightly heated, sprinkled with potassium iron sulfide (yellow blood salt) and again placed on the fire. As soon as the coating melts, the part is lowered into the cooling medium. Potassium iron sulfide melts at a temperature of about 850° C, which corresponds to the quenching temperature of these steel grades.
Tempering of hardened parts.
Tempering of hardened parts reduces their fragility, increases toughness and relieves internal stress. Depending on the heating temperature, low, medium and high tempering are distinguished.
Low Vacation used mainly in the processing of measuring and cutting tools. The hardened part is heated to a temperature of 150-250 ° C (temperature color is light yellow), maintained at this temperature, and then cooled in air. As a result of this treatment, the material, while losing its brittleness, retains high hardness and, in addition, the internal stresses that arise during hardening are significantly reduced.
Average holiday used in cases where they want to give the part spring properties and sufficiently high strength with medium hardness. To do this, the part is heated to 300-500 ° C and then slowly cooled.
And finally, high holiday subjected to parts in which it is necessary to completely remove all internal stresses. In this case, the heating temperature is even higher - 500-600 ° C.
Heat treatment (hardening and tempering) of simple shaped parts (rollers, axles, chisels, punches) is often done at one time. The part heated to a high temperature is dipped into the coolant for some time, then removed. Tempering occurs due to the heat retained inside the part.
A small area of the part is quickly cleaned with an abrasive block and the color of the tarnish on it is monitored. When the color corresponding to the required tempering temperature appears (220° C - light yellow, 240° C - dark yellow, 314° C - light blue, 330° C - gray), the part is again immersed in the liquid, now until completely cooling. When tempering small parts (as during hardening), some blank is heated and the part to be tempered is placed on it. In this case, the color of the tarnish is observed on the part itself.
Annealing of steel parts.
To facilitate mechanical or plastic processing of a steel part, its hardness is reduced by annealing. The so-called complete annealing consists in the fact that the part or workpiece is heated to a temperature of 900 ° C, maintained at this temperature for some time necessary to heat it throughout its entire volume, and then slowly (usually together with the furnace) cooled to room temperature.
Internal stresses that arise in the part during machining are removed by low-temperature annealing, in which the part is heated to a temperature of 500-600 ° C and then cooled along with the furnace. To relieve internal stresses and slightly reduce the hardness of steel, incomplete annealing is used - heating to 750-760 ° C and subsequent slow (also together with the furnace) cooling.
Annealing is also used when hardening is unsuccessful or when it is necessary to overheat a tool for processing another metal (for example, if a copper drill needs to be overheated to drill cast iron). During annealing, the part is heated to a temperature slightly below the temperature required for hardening, and then gradually cooled in air. As a result, the hardened part again becomes soft and amenable to machining.
Annealing and hardening of duralumin.
Annealing of duralumin is carried out to reduce its hardness. The part or workpiece is heated to approximately 360° C, as during hardening, held for some time, and then cooled in air.
The hardness of annealed duralumin is almost half that of hardened duralumin.
The approximate heating temperature of a duralumin part can be determined as follows. At a temperature of 350-360° C, a wooden splinter, which is passed along the hot surface of the part, becomes charred and leaves a dark mark. The temperature of the part can be determined quite accurately using a small (about the size of a match head) piece of copper foil, which is placed on its surface. At a temperature of 400° C, a small greenish flame appears above the foil.
Annealed duralumin has low hardness; it can be stamped and bent twice without fear of cracks.
Hardening. Duralumin can be hardened. When hardening, parts made of this metal are heated to 360-400 ° C, held for some time, then immersed in water at room temperature and left there until completely cooled. Immediately after this, duralumin becomes soft and flexible, easily bent and forged. It acquires increased hardness after three to four days. Its hardness (and at the same time fragility) increases so much that it cannot withstand bending at a small angle.
Duralumin acquires its highest strength after aging. Aging at room temperatures is called natural, and at elevated temperatures it is called artificial. The strength and hardness of freshly hardened duralumin, left at room temperature, increases over time, reaching its highest level after five to seven days. This process is called duralumin aging
Annealing of honey and brass.Annealing of copper. Copper is also subjected to heat treatment. In this case, copper can be made either softer or harder. However, unlike steel, copper is hardened by slow cooling in air, and copper becomes soft by rapid cooling in water. If a copper wire or tube is heated red hot (600°) over a fire and then quickly immersed in water, the copper will become very soft. After giving the desired shape, the product can again be heated over a fire to 400 ° C and allowed to cool in air. The wire or tube will then become solid.
If it is necessary to bend the tube, it is tightly filled with sand to avoid flattening and cracking.
Annealing brass increases its ductility. After annealing, brass becomes soft, easily bends, knocks out and stretches well. For annealing, it is heated to 500 ° C and allowed to cool in air at room temperature.
Blueing and "blueing" of steel.
Blueing. After bluing, steel parts acquire a black or dark blue color of various shades, they retain a metallic luster, and a persistent oxide film forms on their surface; protecting parts from corrosion. Before bluing, the product is carefully ground and polished. Its surface is degreased by washing in alkalis, after which the product is heated to 60-70° C. Then it is placed in an oven and heated to 320-325° C. An even coloring of the surface of the product is obtained only when it is heated evenly. The product treated in this way is quickly wiped with a cloth soaked in hemp oil. After lubrication, the product is slightly warmed up again and wiped dry.
"Blueing" of steel. Steel parts can be given a beautiful blue color. For this, two solutions are made: 140 g of hyposulfite per 1 liter of water and 35 g of lead acetate (“lead sugar”) also per 1 liter of water. Before use, the solutions are mixed and heated to a boil. The products are pre-cleaned, polished to a shine, then immersed in boiling liquid and kept until the desired color is obtained. Then the part is washed in hot water and dried, after which it is lightly wiped with a rag moistened with castor or clean machine oil. Parts treated in this way are less susceptible to corrosion.
Graaver 04-03-2010 20:17
I'll start from far away...
I have been making sports medals for more than ten years, but there are questions that I constantly encounter, and I have never found out the final answers to them.. can anyone help? here is one of them..
To increase ductility, when pressing, the brass workpiece must be annealed... and this is where the fun begins...
At the moment I am using this recipe for annealing L63 brass (derived experimentally):
Heating in an oven to t=560 C, holding for 1.5-2 hours, cooling in air..
With the same parameters (brand of brass, maintenance mode), the output results are completely different.
In one case, all the “chicks and puffs” ... the brass becomes “soft”, is easily deformed and has an even, mirror-smooth surface (corresponding to the “mirror” of the stamp).
In another version, everything seems to be the same.. “soft” (plastic), only where there should be a “mirror”, a light, barely noticeable “orange peel cellulite” appears.. it seems like a trifle, but it’s terribly unpleasant
The question is...
Has anyone encountered a similar problem and how was it solved?
Interested in temperature, holding time when heating and cooling time (method) ..
Also, is it possible to “cure” brass blanks “infected with cellulite” (incorrect maintenance)?
With all respect, Andrew.
Ress75 04-03-2010 20:47
In jewelry techniques, there is such a technique: it’s called p.. (I don’t remember longer). The point is repeated annealing (6 times) of silver, etc. The metal begins to grind from the inside of the product and with each cycle locally the surface of the product swells - such a desert relief appears with orange peel. In general, it’s beautiful. Then there’s natural bleaching, etc. Maybe something similar will come out here?
YUZON 04-03-2010 21:45
Exactly the whole L 63? or maybe PM
Graaver 04-03-2010 22:08
quote: Is the brass from the same batch, or different supplies?
Exactly the whole L 63? or maybe PM
Party one..
Sometimes they cut three sheets (even if we assume that the sheets are different, all the blanks are brought in one bag, this is about 900 pieces, 300 pieces per sheet), I anneal... part is normal, part is “cellulite” (i.e. one batch after maintenance is all normal, other problem)..
True, I admit that the holding time in the oven is different..
Problems with temperature differences are excluded.. the oven allows you to keep the temperature "+"_"-" 1 degree C
Without annealing there is no “cellulite”, but it’s also oh so difficult to push through such a workpiece..
If anyone has encountered this, is there a guaranteed recipe?
To be “soft” and without “cellulite”...?
Graaver 04-03-2010 22:19
Does anyone know under what conditions (exceeding what parameters) this nasty thing happens?
sm special 04-03-2010 23:35
Perhaps “Googling” a query about annealing defects in brass might clarify something...
YUZON 05-03-2010 11:53
You can also try:
There is no need to make a long shutter speed, according to the process: loading at t=600 C, warming up at about 1 mm/min. Once the temperature has leveled off, cool it in air or with water.
IMHO: When exposed to an oxidizing atmosphere for a long time, zinc begins to oxidize and “scratch” the surface.
And sometimes the sheet rollers are to blame (they can’t handle their technical process)
Graaver 05-03-2010 14:41
When experimenting with t=600 C, I was guaranteed to get “cellulite”, although the exposure time was long..
There will be an opportunity to experiment again in the near future..
I'll try to reduce the time the pieces spend in the oven..
Nestor74 05-03-2010 16:39
2Graaver
After the holidays, I’ll check with my friends (the guys work a lot with brass - souvenirs, award paraphernalia), maybe they can tell me something, I’ll write back if by then this question is still relevant.
YUZON 05-03-2010 16:50
quote: I'll try to reduce the time the pieces spend in the oven..
In terms of time: the less, the better. as long as the oven gets back to normal.
Do not ship in a tight pack.
Boule 05-03-2010 17:28
you can, your 5 kopecks: straight into the water, without exposure to air
Boule 05-03-2010 17:29
simple hardening of copper alloys is exactly the opposite of hardening of steels - ductility increases
Graaver 05-03-2010 20:12
quote: after the holidays, I’ll check with my friends (the guys work a lot with brass - souvenirs, award paraphernalia), maybe they can tell me something, I’ll write back if by then this question is still relevant.
Any advice is relevant!
And practical experience is especially important!
quote: load at 600 and switch the oven to t=560.
Do not ship in a tight pack.
I tried cooling in water.. but again, the exposure of the blanks in the oven was significant, and everything in the batch was as “tight” as possible..
This was probably the reason for the failure...
Graaver 12-03-2010 19:52
What I least expected happened...
The story in short is this...
I ordered two sheets of brass and sent them to production without checking..
It turned out that one sheet, as ordered, was brass (L63), and the second was bronze (brand unknown, has a pleasant pink tint)..
Bronze doesn't suit me technically. characteristics.
Therefore, the whole party, in order not to be wasted, moves to a flea market.
Maybe someone will need it?!!
Here is a photo of blanks and a “test” medal made from this material.
Graaver 13-03-2010 09:27
I conducted an experiment with a new batch... “minimum required” holding time in the oven + “loose” loading + cooling in water.”.
The experiment was a success... there is no “cellulite”!
Many thanks to the one-tent campers “Bul” and “YUZON” for their practical advice!!!
I apologize for being intrusive..
Is it possible to “restore” brass after improper maintenance?
With all respect, Andrew.
