On-line process for improving performance of welding heat affected zone

Abstract

The invention relates to an on-line process for improving performance of a welding heat affected zone. According to the technical scheme, the process comprises the following steps of: blowing compressed gas at a welding joint which is 20 to 50mm away from a welding arc along with the forward movement of the welding arc in the welding process of steel for 2 to 10 seconds; immediately covering the welding joint by using heat preservation cotton along with the departure of the compressed gas and slowly cooling to room temperature; and continuously performing welding, blowing and slow cooling processes respectively until the entire welding joint is cooled to the room temperature, wherein the compressed gas is air, the pressure of the compressed gas is between 0.5 and 1.0MPa, and the flow rate of the compressed gas is between 5 and 10L/min; and the welding joint is one of welding joints which are formed by a manual arc welding method, a submerged arc welding method, a gas shielded welding method and a tungsten electrode argon arc welding method. The on-line process has the characteristics of simple process, convenience of operation, no need of arranging special equipment and low cost; and by the process, cracks of the welding heat affected zone can be reduced or eliminated, and the performance of the welding heat affected zone can be obviously improved.

Description

technical field [0001] The invention belongs to the technical field of welding. In particular, it relates to an in-line process for improving the performance of the welding heat-affected zone. Background technique [0002] With the rapid development of the global economy, the construction of large-scale equipment and various heavy rails is advancing by leaps and bounds, and the demand for high-carbon steel and high-carbon high-alloy steel is increasing day by day. High-carbon high-manganese steel can maintain austenite metastable state through water toughening treatment, obtain high toughness, and has strong work hardening characteristics. When impacted or cold deformed, the surface of the workpiece hardens quickly, and its The hardness can reach 450-500HB; at the same time, the deep layer still maintains the original state and has good toughness. This kind of cast steel with the characteristics of "soft inside and rigid outside" has been widely used, such as railway frogs...

AI Technical Summary

Problems solved by technology

At the same time, the thermal conductivity of high-carbon steel is worse than that of low-carbon steel, and the carbon content is higher than that of medium-carbon steel, which has a tendency to be quenched and hardened. During the welding process, when the heat-affected zone is cooled to 200-300 ° C, it is easy to produce martensite In addition, high-carbon steel and high-carbon high-alloy steel have a large linear expansion coefficient, large shrinkage after welding, small thermal conductivity, and uneven temperature distribution, which will generate large welding stress and provide mechanical strength for the generation of cold cracks. Factors that lead to the generation of cold cracks in the welding heat-affected zone

[0004] To reduce the cracks in the welding heat-affected zone of high-carbon steel and high-carbon high-alloy steel, the method to improve the performance is mainly to change the welding process: (1) reduce the welding line energy, which can limit the grain size of the welding heat-affected zone. Reduce the precipitation of carbides and improve the resistance to hot cracks; but in turn, for the control of cold cracks, it is hoped that the line energy should not be too small, otherwise the heat-affected zone will be hardened and the welding stress will increase, which is not conducive to the control of cold cracks. That is, it is contradictory to reduce and control hot cracks and cold cracks by controlling line energy; (2) proper preheating can prevent cold cracks; Generate additional stress, but will promote the generation of cold cracks

That is to say, by adopting or changing the welding process, the performance of the welding heat-affected zone can only be improved to a limited extent, and the stability of the welding heat-affected zone performance cannot be guaranteed.