manufacturer astm a106/a53/api 5l gr.b pipe

Time :2012 -8-15 17:50:45 Steel World Text Size: medium and small]

First, preheating

Preheat help reduce the carbon steel heat-affected zone of the highest hardness and prevent cold cracking, which is a major carbon steel welding process measures, preheating can improve joint plastic, reducing the welding residual stresses. Typically, 35 and 45 steel preheating temperature of 150 ~ 250 ℃ then high carbon content or because a large thickness and stiffness, cracking tendency is large, the preheating temperature can be increased to 250 ~ 400 ℃.

If too much solder pieces, the overall preheating of difficulty, can be partially preheated heating locally preheated weld both sides of the range of 150 ~ 200mm.

Second, the electrode

When conditions permit preferred alkaline electrode.

Third, the groove in the form

Try to open the weldment into a U-shaped groove type welding. If the casting defects, dig out the shape of the groove should be smooth, and its aim is to reduce the molten parent metal into the weld metal in proportion to the reduction in the carbon content of the weld to prevent the cracks.

Fourth, the welding parameters

As molten parent metal to the first layer of weld metal in the proportion of up to 30%, so the first layer weld, should maximize the use of a small current, the welding speed is slow, the base material to reduce the depth of penetration.

Five, PWHT

Butt welding member immediately after the best stress relief heat treatment, especially for large thickness weldment, high-rigidity structure part and harsh conditions (dynamic load or impact load) working weldment even more so. Stress relief tempering temperature is 600 ~ 650 ℃. If the post-weld stress relief heat treatment should be carried out immediately after the heat treatment.