Abstract
Crack sensitivity of low welding crack cracking steel plates for pressurized vessels used in Anshan is a process improvement project. The research includes the characteristics of common steel plates, the preparatory work before operation and the welding process of low welding crack cracking steel plates. After welding, the surface observation and nondestructive testing of crack sensitivity of steel plates were carried out. The results are compared and analyzed with relevant national standards. For the purpose of enabling our pressurized vessels to meet the national requirements and ensuring safe and reliable use, the improvement project of crack sensitivity of low welding crack cracking steel plates is in good effect and has high practical value.
1 Introduction
As an important component of the pressure vessels in AnshanSteel,the quality of welding seams of low welding crack cracking steel plate directly affects the safety of pressure vessels. Because of this, the pressure vessel working environment often requires excellent surface quality and nondestructive testing to ensure the crack sensitivity of steel plate is qualified. Therefore, it is of great significance to study the characteristics of common steel plates, the preparatory work before operation and the welding process of low welding crack cracking steel plates, and to analyze the effect of crack sensitivity of steel plates when it is used in pressure vessels.
2 The characteristics of common steel plates
Steel plates used for pressure vessels are usually divided into common steel plates, low temperature steel plates and alloy steel plates according to their functions in the pressure vessels. Common steel plates are quenched and tempered, have good weldability, their performance changes in a certain range when temperature changes, and their mechanical properties are worse when temperature increases. After heat treatment and forming, low welding crack cracking steel plates are able to reduce the weld shrinkage tendency, improve the mechanical properties and ensure better forming characteristics.
3 The preparatory work before operation
The properties of materials used for pressure vessels are closely related to the safety of the vessels. Therefore, it is necessary to select qualified materials that meet the requirements of the national standards before operation. The surface of the steel plate must be smooth and the welding quality of the surface is reliable. The joint gap of the steel plate must be within the acceptable range to ensure correct welding.
4 The welding process of low welding crack cracking steel plates
The welding process of low welding crack cracking steel plates is complex and strict. Generally, argon arc welding is adopted and the heat input should be as low as possible. Before welding, the surface must be preheated, in order to reduce the weld shrinkage and prevent cracking. During welding, it is important to select the welding parameters reasonably and maintain the hydrogen content below 5ml/100g, in order to prevent hydrogen embrittlement. The amount of re-welding should be as little as possible and the welding track should be neat.
5 Nondestructive testing of crack sensitivity
After welding of low welding crack cracking steel plates, surface inspection and nondestructive testing are necessary to check the crack sensitivity of steel plates. Common nondestructive testing methods include ultrasonic testing, magnetic particle testing and penetrant testing. These methods can detect cracks in welded joints and find surface defects. In addition, internal defects can also be seen through radiography and other methods.
6 Results and analysis
After welding of low welding crack cracking steel plates, the surface inspection and nondestructive testing meet the requirements of relevant national standards and are qualified. The results of surface observation and nondestructive testing are compared and analyzed with relevant national standards, and the conclusion is that the crack sensitivity of the steel plates is qualified.
7 Conclusion
The process improvement project of crack sensitivity of low welding crack cracking steel plates for pressurized vessels used in Anshan is in good effect. By applying the project, the quality of welding seams of low welding crack cracking steel plates is improved, and the reliability of pressure vessels is effectively ensured. The project has high practical value.
