What are the characteristics of heat treatment indexes of Q235B steel plate?

The heat treatment strength of Q235B steel plate is a very important physical property index value. The insufficient or uneven strength of Q235B steel plate after heat treatment will reduce the wear resistance and fatigue limit of Q235B steel plate, resulting in the invalidity of Q235B steel plate in the morning, which seriously reduces the service life of Q235B steel plate. What are the reasons for the insufficient or uneven strength of Q235B steel plate?

1) The cross section of Q235B steel plate is large, and the cutting performance of Q235B steel plate is poor.

2) In the initial mechanism of Q235B steel plate, the cementite shrinkage porosity is serious or the mechanism is thick. There are high-purity graphite carbon and cementite shrinkage porosity and agglomeration in the steel.

3) The casting process of Q235B steel plate is wrong, and the spheroidizing annealing is not carried out very well after forging, which makes the spheroidizing mechanism of bearing steel poor.

4) The carburized layer of Q235B steel plate caused by quenching or heat treatment is not removed.

5) The heat treatment temperature of Q235B steel plate is too high, and the amount of residual martensite is too much after heat treatment; or the heat treatment temperature is too low and the heating and heat insulation time is not enough, which makes the change of Q235B steel plate incomplete.

6) The cooling rate of Q235B steel plate after heat treatment and heating is too slow, the temperature of grade classification and isothermal process is too high or the time is too long, and the selection of cooling materials for heat treatment is not good.

7) The water content of alkali bath is too little, or there is too much residue in the cooling material of heat treatment, or the refrigeration material of heat treatment is brittle.

8) After heat treatment and refrigeration, the temperature of cooling material is too high and the refrigeration is not enough.