控制冷却对中碳高钒非调质钢组织性能的影响

 利用Gleeble- 3800热模拟试验机研究了锻后控制冷却对一种胀断连杆用中碳高钒非调质钢37MnSiVS微观组织及硬度的影响。结果表明，冷却速度对试验钢的组织性能具有显著的影响，即随着冷却速度的增加，试验钢中的珠光体体积分数和硬度均逐渐增加；当冷却速度增加到1. 5 ℃/s以上时，组织中开始出现贝氏体组织，硬度不再提高。锻造变形有助于获得细小的组织和较多的铁素体，但使钢的硬度有所降低。试验钢变形后快冷到600 ℃左右进行合适的等温处理，通过大量细小弥散的V(C,N)粒子的析出强化作用，可使试验钢的强度得到显著提高。结果表明，通过控制锻后冷却方式而控制组织及V(C,N)粒子的析出程度可实现对锻件硬度(强度)的差异化控制。

Effect of controlled cooling on microstructure and properties of medium-carbon high-vanadium microalloyed steel

The effect of post- forging controlled cooling on the microstructure and hardness of a kind of medium- carbon high- vanadium microalloyed steel (37MnSiVS) for fracture splitting connecting rod was investigated by Gleeble- 3800 thermal simulator. The results showed that the cooling rate had a significant influence on the microstructure and properties of sample. Both the pearlite content and hardness of tested steel gradually increased with the increase of cooling rate. As the cooling rate was higher than 1. 5 °C/s，the bainite was observed in microstructure and the hardness did not increase any more. The forging deformation is advantageous to the formation of fine microstructure and higher content of ferrite. However，the hardness of steel decreased. The fast cooling to about 600 °C followed by proper isothermal treatment significantly promoted strength of tested steel due to the precipitation strengthening effect of many fine and dispersed V(C,N) particles. The results indicated that the differentiation control of forging hardness (strength) could be realized by adjusting post- forging cooling method，which could control the microstructure and precipitation of V(C,N) particles.