Test results of welding process Assessment

Test Plan tensile test flexural Test Impact toughness Test Aky (J/CM2)

Tensile strength Δb/mpa fracture part bending angle face curved back bend weld fusion Line heat affected zone (HAZ) The scheme ⅰ550/530 base material 50.

Qualified 84.8 162 135.6 The scheme ⅱ525/520 base material 50.

Qualified 79.4 109.2 96.7 The tensile test results show that the tensile specimens of the two schemes are all broken in the base material, which indicates that the tensile strength of the weld is higher than that of the base material and the bending test is all qualified. According to the results of the impact toughness test in table 5, the impact toughness of the scheme Ⅰ is obviously higher than that of the scheme Ⅱ, it is proved that the scheme Ⅰ the welding heat treatment criterion is ideal, the high-temperature tempering not only achieves the improvement of the joint organization and performance, but also makes the toughness and strength fit properly The results of mechanical properties at room temperature show that the two recommended welding process schemes can be used for site construction. The project Ⅰ uses the welding rod which is close to the base material composition, the weld performance matching, the weld should have the high thermal strength, the weld seam at the high temperature is not easy to destroy. The difficulty is that after welding heat treatment standard is more strict, tempering temperature and heat preservation time and heating and cooling speed control improper but will cause weld performance drop. The solution Ⅱ using austenitic stainless steel welding electrodes, although it can save heat treatment after welding, but because the weld and the base material expansion coefficient, long-term high-temperature work can occur carbon diffusion migration phenomenon, easily lead to weld in the fusion zone damage.

Therefore, from the use of reliability considerations, on-site use of the program Ⅰ welding more secure.

Conclusion It is feasible to weld two kinds of welding schemes for 15CrMo steel thick wall high-pressure pipe.

In order to ensure weld performance matching and high thermal strength, the adoption of the scheme Ⅰ effect is better, the key is to strictly control the heat treatment after welding process.

Although the scheme Ⅱ can save heat treatment after welding, but the possibility of weld damage caused by the transfer and diffusion of carbon at high temperature may not be neglected, so it is only prudent to use the heat treatment after welding. Steel tube Weight Calculation formula: [(outside diameter-wall thickness) * Wall thickness]*0.02466=kg/m (weight per metre)