In addition to the hardenability properties, high strength and ductility are also required in tempered steels. In order to achieve a sufficient level of hardness, tempered steels contain relatively high carbon content. Since the hardness depth is the most important criterion for thick-section parts, these parts are manufactured from alloyed tempered steels.

Part dimensions and strength values are at the forefront in the selection of tempered steels. Unalloyed tempered steels can only be efficient in small cross-section parts. For thick-section parts, homogeneity of hardness distribution depends on the alloying of the steel. The variation of the hardness distribution according to the material alloys can be observed with the results of the Jominy test. Jominy test in simple terms; Islah steels, which express the hardening values in the distances from the cooled end by cooling only one end of a bar-shaped material heated to the hardening temperature, can be hardened by flame and induction, or they can be hardened by flame and induction after curing. In the selection of the material to be heat treated in this way, besides the chemical composition, the hardness value to be obtained on the surface and the hardening depth are taken into consideration. While the depth of hardness can be 3-4 mm in unalloyed steels, this depth reaches 10-12 mm in alloyed steels.

In addition, it is more appropriate to use high-carbon-low-manganese Cf quality steels, as high manganese cracking hazard during induction hardening will occur. In addition, the decrease in the risk of cracking is closely related to the small grain structure of the material.

Breeding steels are collected in 4 main groups according to their chemical composition.

1. Unalloyed tempered steels
2. Manganese alloy tempered steels
3. Chromium alloy tempered steels
4. Chromium-molybdenum alloy tempered steels

In unalloyed steels, the curing strength increases with the amount of carbon. The lowest yield limit up to 16 mm diameter is between 370 N/mmz (%C:0.25) to 570 N/mm* (%C:0.50). It is 50-80 N/mm2 lower for sizes between 16-40 mm diameter.

Since manganese increases hardenability in manganese alloyed tempered steels, the yield limit in 30 Mn 4 and 40 Mn 4 steels shows its properties in C60 steel. In chromium alloyed steels, the chromium element greatly increases the hardenability and has a positive effect on plasticity. For example, in 40 Cr 4 steel, the minimum yield is 700 N/mm2 in the 16-40 mm diameter range.

Molybdenum increases hardenability more strongly than chrome. It also increases the temper strength and reduces the possibility of temper brittleness.