Heat treatment of brass, explaining in detail the annealing temperatures of different grades of brass pipes, rods, and wires as well as the mechanical properties and applications after annealing
Brass is a binary copper-zinc alloy, also known as ordinary brass. According to the structure, it can be divided into single brass and two-phase brass. Single brass is also called α brass, and the Cu content is between 62.4%-100% (wt). Two-phase brass is (α+β) brass, the Cu content is between 56.6%-62.4% (wt), and the solid solubility of Zn in Cu increases as the temperature decreases. Except for aluminum-containing brass, brass generally does not have the strengthening effect of heat treatment. Therefore, annealing is often used to improve its cold working (stamping, drawing, machining) performance. The mechanical properties and cold deformation properties of brass semi-finished products after annealing mainly depend on the grain size. The general rule is that the grain size is small and the hardness is high. In addition, the cold deformation is large and the hardness is high (cold work hardening); the annealing temperature is low and the hardness is high.
After annealing after cold deformation, at the same temperature, the hardness will be low for a long time; at the same time, the hardness will be low for a high temperature.
Brass with low zinc content has little cold work hardening effect, and its grains need to be refined to obtain higher hardness.
Brass containing more than 20% Zn (wt) has residual stress after cold deformation. In humid atmosphere (especially atmosphere containing ammonia and ammonium salts), mercury and mercury salt solvents, it is easy to cause stress corrosion and cracking. It must be Perform stress relief annealing.
The intermediate annealing temperature (℃) during the cold working process of brass generally needs to be appropriately reduced as the effective size (mm) decreases, as listed below:
H96:
560-600 (>5mm) 540-580 (1-5mm)
500-540 (0.5-1mm) 450-500 (<0.5mm)
H90:
650-700 (>5mm) 620-680 (1-5mm)
560-620 (0.5-1mm) 450-560 (<0.5mm)
H80:
650-700 (>5mm) 580-650 (1-5mm)
540-600 (0.5-1mm), 500-560 (<0.5mm)
H68:
580-650 (>5mm) 540-600 (1-5mm)
500-560 (0.5-1mm) 440-500 (<0.5)
H62, H59:
650-700 (>5mm) 600-660 (1-5mm
520-600 (0.5-1mm) 460-530 (<0.5mm)
HFe59-1-1:
600-650 (>5mm) 520-620 (1-5mm)
450-550 (0.5-1mm) 420-480 (<0.5mm)
HSn70-1:
600-750 (>5mm) 560-620 (1-5mm)
520-580 (0.5-1mm) 450-500 (<0.5mm)
HSn62-1:
600-650 (>5mm) 550-630 (1-5mm)
520-580 (0.5-1mm) 500-550 (<0.5mm)
HSn63-3：
600-650 (>5mm) 540-620 (1-5mm)
520-600 (0.5-1mm) 480-540 (<0.5mm)
HSn59-1:
600-650 (>5mm) 580-630 (1-5mm)
550-600 (0.5-1mm) 480-550 (<0.5mm)
Depending on the three states of pipes and bars before annealing: "hard, drawn semi-hard, and soft", the annealing temperature (°C) needs to be gradually increased, as listed below:
Pipe material:
H96 soft 550-600
H80 soft 480-550
H68, H62 hard 340-380 drawn semi-hard 400-450
HPb59-1, HSn70-1 drawn semi-hard 420-450
H60 round rectangular waveguide hard 200-250
Bar:
H96 soft 550-620
H90, H80, H70 drawn semi-hard 250-300 soft 650-720
H68 drawn semi-hard 350-400 soft 500-550
H62, HSn62-1 drawn semi-hard 400-450
H59-1, HFe59-1-1 drawn semi-hard 350-400
HMn58-2 drawn semi-hard 320-370
Recrystallization annealing of brass wire requires gradually increasing the annealing temperature (°C) according to the three relatively "hard, semi-hard, and soft" states before annealing. Different wire diameters also need to be adjusted accordingly, as listed below:
H96, H90, H80:
Wire diameter 0.3-0.6 soft 390-410
Wire diameter 0.3-6.0 Hard 160-180 Soft 390-410
H68:
Wire diameter 0.3-6.0 Hard 160-180 Semi-hard 350-370 Soft 460-480
H62:
Wire diameter 0.3-1.0 Hard 160-180 Semi-hard 160-180 Soft 390-410
Wire diameter 1.1-4.9 Hard 160-180 Semi-hard 240-260 Soft 390-410
Wire diameter 5.0-6.0 Hard 160-180 Semi-hard 260-280 Soft 390-410
HPb59-1:
Wire diameter 0.3-6.0 Hard 160-250 Semi-hard 330-350 Soft 390-430
When major elements such as Al, Ni, Fe, Sn, Si, Mn, and Pb are integrated into the α phase and β phase, the relative amounts of the α and β phases can change. Brass containing more than 3% Al (wt) can be aged and strengthened.
For example, the heat treatment strengthening process of HAl59-3.2 is 800℃ solid solution and 350-450℃ aging.
The standard grain size of brass is expressed in average grain size (mm) (see YS/T 347-2004 "Method for determination of average grain size of copper and copper alloys" for details). Different standard grain sizes adapt to different processing methods:
The standard grain size is 0.015mm, suitable for lightly deformed parts, such as blanking and bending.
The standard grain size is 0.025mm, suitable for light stamping parts, such as embossing and other convex and concave processing.
The standard grain size is 0.035mm, which is suitable for parts requiring high smoothness after stamping.
The standard grain size is 0.050mm, suitable for deep drawing parts, such as deep drawing and bending parts.
The standard grain size is 0.070mm, suitable for thick stamping parts.
The mechanical properties and uses of brass are listed below:
Ordinary brass:
1. H96, annealed, tensile strength 240MPa, elongation 52%, used for waveguides, condenser tubes, heat sinks, and conductive parts.
2. H90, annealed, tensile strength 260MPa, elongation 44%, used for water tank water supply and drainage pipes, resistor caps, medals, worship statues, etc.
3. H80, annealed, tensile strength 310MPa, elongation 52%, used for copper mesh, thin-walled pipes, corrugated pipes, building supplies, etc.
4. H68, annealed, tensile strength 330MPa, elongation 56%, used in various complex cold stamping parts, radiator shells, waveguides, bellows, etc. It is the most widely used brass alloy.
5. H62, annealed, tensile strength 360MPa, elongation 49%, used for various pins, nuts, rivets, washers, waveguides, clamping plates, rings and radiator parts, sugar industry, shipbuilding industry, Parts for paper industry, etc.
Tin Brass:
1. HSn70-1, annealed (cold deformation 50%), tensile strength 350MPa----elongation 60%; tensile strength 700MPa----elongation 4%, used for condenser tubes of seagoing ships.
2. HSn62-1, annealed, (cold deformation 50%), tensile strength 400MPa----elongation 40%; tensile strength 700MPa----elongation 4%, used for ship parts.
3. HSn60-1, annealed, (cold deformation 50%), tensile strength 380MPa----elongation 40%; tensile strength 560MPa----elongation 10%, used for ship welding parts and welding rods.
Lead brass:
1. HPb74-3, annealed (cold deformation 50%), tensile strength 350MPa----elongation 50%; tensile strength 550MPa----elongation 5%, used in automobiles and agricultural machinery requiring good cutting performance of parts.
2. HPb64-2, annealed (cold deformation 50%), tensile strength 350MPa - elongation 55%; tensile strength 600MPa - elongation 5%, used in the watch and automobile industries requiring good cutting performance Component.
3. HPb63-3, annealed (cold deformation 50%), tensile strength 350MPa - elongation 55%; tensile strength 600PMa - elongation 5%, used for watch parts that require excellent cutting performance .
4. HPb60-1, annealed (cold deformation 50%), tensile strength 370MPa----elongation 45%; tensile strength 670MPa----elongation 4%, used for processing with good thermal shock and cutting performance pieces.
Aluminum brass:
1. HAl85-0.5, annealed, tensile strength 350MPa, elongation 60%, used for condenser tubes on seagoing ships.
2. HAl77-2, annealed (cold deformation 50%), tensile strength 400MPa ---- elongation 55%; tensile strength 650MPa ---- elongation 12%, used for condenser tubes on seagoing ships.
3. HAl60-1-1, annealed (cold deformation 50%), tensile strength 450MPa - elongation 45%; tensile strength 750MPa - elongation 8%, used for high-strength parts working in seawater.
4. HAl59-3-2, annealed (cold deformation 50%), tensile strength 380MPa----elongation 50%; tensile strength 650MPa----elongation 15%, used for high strength working at normal temperature Component.
Manganese brass:
1. HMn58-2, annealed (cold deformation 50%), tensile strength 400MPa - elongation 40%; tensile strength 700MPa - elongation 10%, used for shipbuilding and weak current industrial parts.
2. HMn57-3-1, annealed (cold deformation 50%), tensile strength 550MPa - elongation 25%; tensile strength 700MPa - elongation 3%, used for corrosion-resistant parts.
Iron brass:
1. HFe59-1-1, annealed (cold deformation 50%), tensile strength 450MPa - elongation 50%; tensile strength 700MPa - elongation 7%, used under friction and seawater corrosion conditions parts and washers.
2. HFe58-1-1, annealed, tensile strength 450MPa, elongation 10%, used for hot pressing and machined parts with high cutting requirements.
Nickel Brass:
1. HNi65-5, annealed, tensile strength 380MPa, elongation 65%, used for pressure gauge tubes, condenser tubes, etc.
Silicon Brass:
1. HSi80-3, annealed, tensile strength 500MPa, elongation 40%, used for steam pipes and water pipe fittings, and can replace wear-resistant tin bronze.
2. HSi65-1.5-3, annealed, tensile strength 300MPa, elongation 20%, used for neat pipes and water pipe fittings, and can replace wear-resistant tin bronze.
