As a special spring steel, 60Si2mna steel has similar characteristics to the same type of steel S5 (also used as cold work die steel) abroad. This steel grade has significant high yield strength, high fatigue limit and good plasticity, and at the same time has the advantages of low cost and simple heat treatment process, which makes it widely used in the manufacture of impact tools, molds and other fields. Especially in the standard parts industry, it is often used to manufacture key components such as cold heading die punches, nut cold heading dies, and cold punching dies.
60Si2mna steel has high strength and toughness, good tempering stability, but the wear resistance is slightly insufficient, and the hardenability is not excellent. Due to its high silicon content, it has a certain tendency to graphitization and a high sensitivity to decarburization. These characteristics make it necessary to pay special attention to prevent these problems during application to ensure optimal performance.
The chemical composition of 60Si2mna conforms to GB T1222-2007 standard, and the content of the components is as follows:
Carbon (c): 056-0.64%
Silicon (Si): 160-2.00%
Manganese (mn): 060-0.90%
Chromium (cr): 0035%
Phosphorus (p): 0030%
Sulfur (s): 030%
Nickel (Ni): 035%
Copper (cu): 025%
60si2mNa spring steel critical point.
ac1≈755℃，ac3≈810℃，ar1≈700℃，ar3≈770℃,ms≈305℃。
Heat treatment process of 60Si2mnA spring steel.
1. Prepare for heat treatment.
1) Conventional spheroidization annealing is not easy to spheroidize the flaky pearlite in steel, so it is rarely used.
2) Rapid spheroidization annealing: heating temperature is 850, oil cold quenching;The isothermal spheroidization temperature was 790 °C, and the heat preservation was 25minQuench to 680 and keep warm for 1h;The furnace is cooled to 500 degrees Celsius. Spherical pearlite can be obtained.
3) Normalizing: heating temperature is 830 860, air cooling, hardness 254hbs.
4) High temperature tempering, the temperature is 640 680, air cooling.
2. Quenching and tempering.
1) Conventional heat treatment process: quenching temperature is 840 870, oil cooling, hardness is 60 62HRC. The tempering temperature is generally 200 350, but the tempering brittle zone of about 300 must be avoided. The tempering temperature ( ) is 100 200 300 400 500 550 600 650, and the hardness (HRC) is 60 58 56 51 43 38 33 29. [Note: 860 oil quenching, tempering 2h.] Tempering should be avoided at this temperature. ]