At present, the most widely used Alloy tempered steels are ..

Alloy tempered steel is widely used in the manufacture of various important parts of automobiles

Alloy tempered steel

Alloy tempered steel is widely used in the manufacture of various important parts of automobiles, tractors, machine tools and other machines, such as gears, axles, connecting rods, bolts and so on.Most of the tempering and tempering parts bear a variety of working loads, the stress situation is relatively complex, the requirements of high comprehensive mechanical properties, that is, with high strength and good plasticity.

(1) medium carbon: the carbon mass fraction is generally between 0.25% and 0.50%, with a majority of 0.4%;

(2) add the elements Cr, Mn, Ni, Si to improve the hardenability: these alloy elements can not only improve the hardenability, but also form the alloy ferrite, improve the strength of steel.For example, the performance of 40Cr steel after tempering is much higher than that of 45 steel.

(3) add elements to prevent the second type of tempering brittleness: alloy tempered steel containing Ni, Cr and Mn, the second type of tempering brittleness is easy to occur when tempering at high temperature and cooling slowly.Adding Mo and W to steel can prevent the second type of tempering brittleness, and its appropriate content: the mass fraction of Mo is 0.15% ~ 0.30%, or the mass fraction of W is 0.8% ~ 1.2%.

At present, the most widely used alloy tempered steel is 4140,4340,8620, their basic information is as follows

Heat Treatment of SAE 4140 Alloy tempered steel

ASTM 4140 Steel Annealing

Slowly heat to 800～8500 ºC, keep enough time, ensure heat thoroughly. then cooling in furnace to 480 ºC, then cool in air. After annealing, the hardness 92 HBS Max.

AISI 4140 Steel Hardening & Quenching

4140 Steel is usually used at 18-22 HRc, If needs, AISI 4140 alloy steel can be hardened or Quenching by cold work. Quenching medium: oil

Tempering Of ASTM 4140 Alloy tempered steel

/ ℃ tempering temperature: 205 ~ 649°C.

After tempering hardness HRC: 18-25 HRC.

Heat Treatment of SAE 8620 Alloy Steel

Annealing of 8620 Alloy tempered steel

Slowly heated to 850 ℃ and allow enough times, let the steel to be thoroughly heated, Then cool slowly in the furnace. The 8620 alloy steel will get MAX 250 HB （Brinell hardness）.