特殊材质焊管焊前预热与焊后热处理的必要性,不锈钢焊管需要热处理吗

对于特殊材质的焊管，焊前焊后都要进行热处理，这对焊接质量至关重要，特殊材质的焊管焊前预热不仅可以减缓焊后冷却速度，还有助于氢从焊缝金属中扩散逸出，避免产生氢致开裂。同时降低了焊缝和热影响区的淬硬程度，提高了焊接接头的抗裂性能。

For welded pipes of special materials, heat treatment shall be carried out before and after welding, which is very important to the welding quality. Preheating before welding of welded pipes of special materials can not only slow down the cooling rate after welding, but also help the diffusion and escape of hydrogen from the weld metal to avoid hydrogen induced cracking. At the same time, the hardening degree of weld and heat affected zone is reduced and the crack resistance of welded joint is improved.

还能降低焊接应力，均匀地局部预热或整体预热，降低焊接区域焊件间的温差，这样一方面降低了焊接应力，另一方面降低了焊接应变速率，有利于避免焊接裂纹。它可以降低焊接结构的拘束度，尤其是对降低角接接头的约束程度尤为明显，随着预热温度的升高，裂纹发生率降低。

It can also reduce the welding stress, uniformly preheat locally or as a whole, and reduce the temperature difference between weldments in the welding area. On the one hand, it reduces the welding stress, on the other hand, it reduces the welding strain rate, which is conducive to avoiding welding cracks. It can reduce the restraint degree of welded structure, especially for the corner joint. With the increase of preheating temperature, the incidence of crack decreases.

特殊材质的焊管预热温度和层间温度的选择不仅与钢和焊条的化学成分有关，还与焊接结构的刚度、焊接方法、环境温度等有关。应综合考虑这些因素后确定，此外，钢材厚度方向和焊缝区预热温度的均匀性对降低焊接应力有重要影响。

The selection of preheating temperature and interlayer temperature of welded pipe with special materials is not only related to the chemical composition of steel and electrode, but also related to the stiffness of welding structure, welding method, ambient temperature, etc. In addition, the thickness direction of steel and the uniformity of preheating temperature in the weld zone have an important impact on reducing welding stress.

而特殊材质的焊管焊后热处理有三个目的，即消氢、消除焊接应力、改善焊缝组织和综合性能，焊后消氢处理的主要作用是加速焊缝和热影响中氢的逸出，对防止低合金钢焊接裂纹极其有效。

The post weld heat treatment of welded pipes with special materials has three purposes, namely hydrogen elimination, elimination of welding stress and improvement of weld microstructure and comprehensive properties. The main function of post weld hydrogen elimination treatment is to accelerate the escape of hydrogen in weld and heat effect, which is extremely effective in preventing welding cracks of low alloy steel.

去应力热处理是降低焊接工件在高温下的屈服强度，从而松弛焊接应力，常见的方法有两种:一种是整体高温回火，一种是局部高温回火。热处理后改善了焊接接头的金相组织，提高了焊接接头的塑性和韧性，从而提高了焊接接头的综合力学性能。

Stress relief heat treatment is to reduce the yield strength of welded workpiece at high temperature, so as to relax the welding stress. There are two common methods: one is overall high-temperature tempering, and the other is local high-temperature tempering. After heat treatment, the metallographic structure of the welded joint is improved, the plasticity and toughness of the welded joint are improved, and the comprehensive mechanical properties of the welded joint are improved.

以上就是小编为大家讲述的关于《特殊材质的焊管焊前预热与焊后热处理的必要性》的全部内容，希望对大家有所帮助！

The above is what Xiaobian told you about the necessity of pre welding preheating and post welding heat treatment of welded pipes of special materials. I hope it will be helpful to you!

合金钢为什么需要焊前预热和焊后热处理？

合金钢具有良好的抗高温氧化及组织稳定性，较高的高温强度。但它的可焊性较差，淬硬倾向大，焊接过程中焊缝及热影响区可能出现如下一些问题： （1）焊后在焊缝及热影响区出现硬而脆的淬硬组织，若再的较大内应力存在，就会出现冷裂纹，韧性、塑性降低。 （2）具有出现弧坑裂纹的倾向。 （3）某些合金元素，具有焊接再热裂纹倾向，尤以含钒、含硼的钢种为甚。 为了避免和消除上述缺陷，合金钢需要焊前预热，焊后热处理。 焊前预热的主目的是改善材料的可焊性。在加热并保持一定温度的过程中可以降低焊接接头区域的温差，使热影响区的淬硬倾向减弱。在焊接过程中有利于氢气的逸出，降低焊缝中的氢含量，防止冷裂纹的产生，改善焊接接头的塑性及韧性。 后热处理的方法一般是高温回火，其主要目地是： （1）消除或减少在焊接过程中所产生的内应力，防止焊缝和热影响区产生裂纹。 （2）改善焊缝和热影响区的机械性能，即提高其塑性及韧性，改善硬脆倾向。 （3）改善焊缝和热影响区的金相组织。 一般碳素钢的焊接性能好，焊接时可不必预热与热处理。但对于含碳量高、刚度大的焊件，由于焊后残余应力大，也需预热及热处理，如壁厚于30mm的碳钢管。

为什么焊接前要预热，焊接后要热处理

焊前预热是为了防止出现裂纹。
焊后热处理是为了消除焊接应力。