High strength and ductility are required in addition to the hardenability properties of the steels. In order to obtain sufficient hardness, the correction steels contain relatively high carbon compared to others. Since the hardness depth is the most important criterion for thick section parts, these parts are made of alloyed correction steels.
In the selection of correction steels, part dimensions and strength values are at the forefront. Unalloyed breeding steels can only be efficient in small cross-section parts. For the sections with thick sections, the homogeneity of the hardness distribution depends on the alloy of the steel. The variations of the hardness distribution with respect to material alloys can be observed with Jominy test results. Jominy test with a simple expression; It refers to the hardening values at distances to the cooled end by cooling only one end of a rod-shaped material heated to the hardening temperature.
Correction steels can be hardened by flame and induction, or after curing, they can be hardened by flame and induction. In the selection of the material to be heat treated in this way, besides the chemical composition, the hardness value and the hardening depth to be obtained on the surface are taken into consideration. In unalloyed steels, the hardness depth can be 3 - 4 mm, while in alloy steels this depth reaches 10 - 12 mm. Also, it is more convenient to use high carbon - low manganese Cf quality steels, as they will create a high risk of manganese cracking during induction hardening. In addition, the reduced risk of cracking is closely related to the small grain size of the material.
In Unalloyed Steels, the improvement strength increases with the amount of carbon. The lowest flow limit up to 16 mm diameter is between 370 N / MM'2 (% C: 0.25) to 570 N / MM'2 (% c: 0.50). For sizes between 40 mm diameter, 50-80 N / MM'2 will be lower.
Since manganese increases the setability in Manganese Alloy Correctional steels, the yield limit in 30 MN 4 and 40 MN 4 steels shows the properties in C 60 steel.
Chromium element increases hardenability in chromium alloyed steels and positively affects plasticity. For example, in 40 Cr 4 steel, minimum flow in the diameter range of 16-40 mm is 700 N / MM.
It increases the ability to harden more strongly than molybdenum chrome. It also increases the strength of temper and reduces the possibility of temper brittleness.