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冷拔无缝钢管热处理工艺:退火和正火

2018-12-13 14:38:20 常州市星火铝艺制品有限公司 阅读

冷拔无缝钢管热处理工艺:退火和正火.冷拔无缝钢管退火与正火的主要区别: 1、正火的冷却速度比退火稍快,过冷度较大2、正火后所得到的组织比较细,强度和硬度比退火高一些。退火与正火的选择 :

Heat treatment process of cold-drawn seamless steel tube: annealing and normalizing. The main differences between annealing and normalizing of cold-drawn seamless steel tube: 1. The cooling speed of normalizing is slightly faster than annealing, the degree of undercooling is larger 2. The microstructure obtained after normalizing is finer, and the strength and hardness are higher than annealing. Selection of annealing and normalizing:

1、含碳量<0.25%的低碳钢,通常采用正火代替退火。因为较快的冷却速度可以防止低碳钢沿晶界析出游离三次渗碳体,从而提高冲压件的冷变形性能;用正火可以提高钢的硬度,低碳钢的切削钣金加工性能;在没有其它热处理工序时,用正火可以细化晶粒,提高冷拔无缝钢管强度。

1. Low carbon steel with carbon content less than 0.25% is usually normalized instead of annealing. Because the faster cooling speed can prevent the free tertiary cementite from precipitating along the grain boundary of low carbon steel, thus improving the cold deformation performance of stamping parts; normalizing can improve the hardness of steel and the cutting performance of low carbon steel; normalizing can refine grains and improve the strength of cold-drawn seamless steel tube without other heat treatment processes.

2、含碳量在0.25~0.5%之间的中碳钢也可用正火代替退火,虽然接近上限碳量的冷拔无缝钢管正火后硬度偏高,但尚能进行切削钣金加工,而且正火成本低、生产率高。

2. Medium-carbon steel with carbon content between 0.25% and 0.5% can also be normalized instead of annealing. Although the hardness of cold-drawn seamless steel pipe approaching the upper limit of carbon content is higher after normalizing, it can still be machined, and the normalizing cost is low and the productivity is high.

3、含碳量在0.5~0.75%之间的钢,因含碳量较高,正火后的硬度显著高于退火的情况,难以进行切削加工,故一般采用完全退火,降低硬度,改善切削加工性。

3. Steel with carbon content between 0.5% and 0.75% is difficult to be machined because of its high carbon content and its hardness after normalizing is significantly higher than that after annealing. Therefore, complete annealing is generally used to reduce hardness and improve machinability.

4、 含碳量> 0.75%的高碳钢或工具冷拔无缝钢管一般均采用球化退火作为预备热处理,如有网状二次渗碳体存在,则应先进行正火消除。退火是将工件加热到适当温度,保持一定时间,然后缓慢冷却的热处理工艺。缓冷是退火的主要特点,退火件一般随炉冷却至550℃以下时出炉空冷。退火是应用非常广泛的热处理,在工模具或机械零件等的制造过程中,经常作为预备热处理安排在铸锻焊之后,切削(粗)加工之前,用以消除前一道工序所带来的某些缺陷,并为随后的工序做好准备。

4. Spheroidizing annealing is generally used as the preparatory heat treatment for high carbon steel or cold-drawn seamless steel pipes with carbon content of more than 0.75%. If there are reticulated secondary cementite, normalizing should be carried out first. Annealing is a heat treatment process in which the workpiece is heated to an appropriate temperature for a certain period of time and then slowly cooled. Slow cooling is the main feature of annealing. The annealed parts are generally cooled with the furnace to below 550 (?) Annealing is a widely used heat treatment. In the manufacturing process of dies, dies and mechanical parts, it is often arranged as a preparatory heat treatment after casting, forging and welding, before cutting (rough) to eliminate some defects caused by the previous process and prepare for the subsequent process.

退火目的①降低材料硬度,以利于切削加工;②消除各类应力,防止零件变形;③细化粗大晶粒,改善内部组织为最终热处理做好准备。

The purpose of annealing is: (1) to reduce the hardness of materials to facilitate cutting; (2) to eliminate various stresses and prevent deformation of parts; and (3) to refine coarse grains and improve internal structure in preparation for final heat treatment. 



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