Keywords: Hardening, Quenching Temperature, Tempering Temperature, Coolant, Cross Section, Deformation, Cracking, Carburising, Salt Bath Furnace, Chamber Furnace,

Hardening Temperature Selection / Tempering Temperature Selection

 　　Quenching temperature selection

 　　(1) the same steel parts quenching if the cooling capacity of the coolant (such as water quenching with sodium hydroxide water, oil quenching with diesel fuel) temperature should be taken as the lower limit, and vice versa, take the upper limit.

 　　(2) large cross-sectional area needs to be quenched quenching temperature should be taken as the upper limit, or even slightly higher, such as a small cross-sectional area, the lower limit should be taken.      

The lower limit should be taken.

 　　(3) easy to produce deformation or easy to quench the cracked workpiece should take the lower limit, in order to prevent deformation and cracking of thin pieces of carbon steel Can try quenching oil, spinning speciality factory 3m/m book are used to quench oil. (Whether 45 steel or T10 steel)

 　　(4) only require surface wear without quenching (cold mould) to take the lower limit, carburised workpiece can also be reduced some more.

 　　(5) For workpieces requiring low hardness, the lower limit should be taken.

 　　(6) salt bath furnace speed, uniform, small deformation, decarburisation and short heating time to take the upper limit, box furnace heating time should take the lower limit.

 　　Long heating time should be taken as the lower limit.

 　　(7) Retreating hardened workpiece (large parts must be annealed or tempered at high temperature) should be taken as the lower limit.

 　　(8) The upper limit shall be taken for workpieces requiring high red hardness.

 　　(9) Metallographic organisation of spherical quenching body should be taken as the upper limit, lamellar quenching body should be taken as the intermediate value, and point pearlite should be taken as the lower limit.

body should be taken as the lower limit.

 　　(10) The upper limit shall be taken if the size of the workpiece is required to expand a little. The lower limit shall be taken if the size of the workpiece is required to be reduced a little.

 　　(11) The lower limit should be taken if the 45 steel is within the critical size range for easy quenching and cracking. Subtemperature quenching is preferred.

 　　There are special studies and reports on this issue, but we all use 770-780 ℃ quenching.

 　　Selection of tempering temperature

 　　(1) strong cooling quenched workpiece, tempering to take the upper limit. Group quenching isothermal quenching take the lower limit.

 　　(2) There is a self-tempering phenomenon or the possibility of self-tempering should take the lower limit.

 　　(3) The temperature of the case (closed) is higher than that of the case (closed).

 　　(4) fan and temperature uniformity of the pit-type furnace should take the lower limit, salt furnace tempering should take the lower limit.

 　　(5) The lower limit should be taken for pit-type furnaces with moderate temperatures in the low-temperature tempering oil bath.

 　　(6) The lower limit shall be taken for tempering of workpieces with low hardness measured after hardening. (Carbon steel and low alloy steel, but not high alloy steel).

More Hardening Temperature Selection / Tempering Temperature Selection: www.quenchtank.com/view-57.html