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Vacuum oil quenching and tempering spring steel wire

Alloy spring steel wire is divided into three categories, alloy spring steel wire, vacuum oil quenching and tempering silicon-manganese spring steel wire, vacuum oil quenching and tempering chromium-silicon alloy spring steel wire for valves, from the current status of alloy spring use in developed countries, vacuum oil quenching and tempering steel wire The proportion is increasing.

Vacuum oil quenching and tempering spring steel wire production process

1.Surface treatment

Remove impurities such as scale on the surface of the wire rod by mechanical peeling and other processes.

2.Brushed

Different passes are drawn according to different specifications and diameters to meet specific wire diameter requirements.

3.Vacuum heat treatment

According to the requirements of the process sheet, check the steel grade, specification and surface quality of the semi-finished vacuum oil-quenched steel wire. Unqualified materials will not be put into production; when the steel wire is hoisted, it should be stable and smooth, and the waste wire should be used as a lead when threading the head. In order to minimize the fouling in the furnace pipes and the furnace mouth, try not to use rusty steel wires, and do not bring in thin iron wires; also try to reduce the dirt on the steel wires, so the steel wires must pass through the decontamination device before entering the furnace.

Heat the steel wire to Ac₃+(150~200)°C (actually rapid heating), and immediately send it to 40~80°C oil for cooling, and calculate according to 6s/mm when cooling. After the martensite structure is obtained, it is sent to a vacuum tempering furnace at 450°C for tempering. Vacuum tempering time is realized by adjusting the line beat according to performance and organization requirements. It can also be heated to 960°C (65Mn), graded in a fluidized furnace at 380°C for 4s, then cooled in 40°C oil for 4-5s to complete the martensitic transformation, and immediately placed in a 450°C lead bath or nitrogen-filled protective furnace After tempering for 20s, the tempered troostite structure can be obtained. At present, most steel wires use vacuum quenching and vacuum tempering. After vacuum oil quenching and tempering, the spring steel wire should be stress relieved and tempered at 340~360°C after cold winding. Manganese steel wire is temper brittle, so it should be cooled with water or oil after stress relief. The steel wire has high σs/σb, small elastic residual deformation, and long fatigue life. It is suitable for valve springs and vehicle suspension springs, but it must prevent aging brittleness.

4.Vacuum oil quenching

When the steel wire is vacuum oil quenched, it should be ensured that the oil surface is ≥ 4cm higher than the steel wire, but the quenching oil cannot overflow the tank, let alone enter the furnace body, to ensure production safety. When the steel wire comes out of the oil tank, try to wipe off the oil attached to the steel wire clean. Always observe the oil level of the quenching oil tank, and it is not enough to add it in time. In order to minimize the quenching oil on the steel wire entering the vacuum tempering furnace, a degreasing device is added.

5.Vacuum tempering

The furnace temperature is set according to the process requirements. The steel wires in the furnace cannot be staggered, and they must be combed smoothly. At the entrance of the lead pot, due to the residual oil on the steel wires, it will catch fire after a long time. It can be extinguished by dry powder fire extinguishing agent. Clear, add new.

6.Water cooling

After the steel wire is vacuum tempered, water cooling should be ensured, and the residual water should be dried to prevent the steel wire from rusting.

7.Apply anti-rust oil

In order to prevent the steel wire from rusting, the steel wire should be evenly coated with a thin layer of anti-rust oil.