High-strength steel welding is a common and extremely complex technology in the welding industry. What are the application and development status of high-strength steel welding technology in engineering? Next, please see the detailed introduction below, I hope it will help you!

First, the application and development of high-strength steel

With the development of modern science and technology, the demand for various new materials and new technologies is becoming more and more urgent. High-strength steel is one of them. Regarding the definition of high-strength steel, there is no international standard. High strength steel.

Taking high-strength steel bars as an example, the specifications for the strength grades or grades of steel bars in different countries in the world are different, but they can be roughly divided into 3 groups of 300MPa (low), 400MPa (medium) and 500MPa (high), considering the specific conditions of each country. , is divided into weldable and non-weldable or seismic and non-seismic. In terms of strength grade, the actual amount of 335MPa steel bars in my country is about 60%, and the main strength is low strength grade; the main strength grade of Japan and the United States is 400MPa (420MPa), which is classified as a medium strength grade; Europe, Britain, Australia and New Zealand The main strength grade is 500MPa, which is classified as a high-strength grade. Especially in the UK and European norms, the trend of high reinforcement is becoming more and more pronounced. The strength grade in the original British standard was 460MPa, and in Europe it was 450MPa. In the process of standard integration, the European Community adopted the British standard and unified it to 500MPa, which improved the application strength of steel bars.

Due to the substantial improvement in the strength of high-strength steel, the use of high-strength steel can reduce the amount of steel in the process of engineering construction, so as to ensure that the quality of the project and the mechanical properties of the structure remain unchanged, which not only saves money, but also reduces the weight of the structure itself. , because the weight is reduced, it can save energy, improve the carrying capacity and work efficiency for vehicles, ships, construction machinery and other operating structures; because the welding workload is reduced, it creates conditions for field construction and hoisting; Good function, can greatly improve the durability of the equipment, prolong its service life, because of the reduction of steel consumption, the reduction of welding workload, the reduction of welding material use, the overall reduction of carbon dioxide emissions, environmental protection, haze Management has an active effect.

2. Welding of high-strength steel

Whether steel can play its role depends on whether it can be welded and formed. Only welded and formed steel can serve citizens. Therefore, welding is a key part of steel to realize its value, because high-strength steel is in the smelting process in order to achieve various goals. China Plus has added certain special elements to improve the yield strength and other functional goals of the steel. Because of the addition of other elements, the carbon equivalent is increased, the hardenability of the steel is enhanced, and the weldability is decreased. The probability of defects such as pores and cracks in the joints is greatly increased; and the welding of high-strength steels should select appropriate welding materials, equip corresponding welding equipment, and we should formulate corresponding welding processes to ensure the quality of welded joints and base metal function, to satisfy According to our engineering quality requirements, the welding of high-strength steel should include the following aspects:

1. Select suitable welding consumables

Welding consumables are selected according to the appropriate criteria for the chemical composition and mechanical function of the weld metal and the base metal, and also to meet the appropriate criteria for the change point and material under the crystalline phase of the deposited metal of the welding material.

2. Control welding process parameters

① Controlling line energy (J/cm): The greater the welding line energy, the longer the weld metal stays at high temperature (11000C), and the grains grow and become brittle, resulting in a decrease in weld resistance. Therefore, selecting a smaller line energy under the condition of ensuring welding penetration can reduce the probability of welding defects, reduce welding deformation, and improve the function of welding joints;

② Adopt the methods of preheating before welding, heat preservation between welding layers, and heat preservation after welding;

③ Control the high temperature stay time tH and t8/5 (800~500 ℃ cooling time) to prevent grain growth; prevent the agglomeration and growth of the second phase particles and uneven dissolution and separation; obtain a high-resistance arrangement.

3. Select suitable welding equipment

It is also an important part to select suitable welding equipment according to the functional characteristics of the base metal and welding material. The production of any new process requires matching equipment. In recent years, new welding equipment has been widely used in my country's production field. , such as two welding, argon arc welding, submerged arc welding, electroslag welding, friction welding, laser welding and plasma welding and other welding equipment has been widely used in various fields, rather than the single hand arc welding method. The welding of special steel should select suitable welding equipment according to the composition and function.

4. Post-weld heat treatment

Because special steel has high strength, high hardness, poor resistance and other functional characteristics, and because the welding process is a process of rapid heating and rapid cooling, heat treatment after welding can greatly improve the structure of welded joints and improve performance, such as T92 after welding. Generally, heat treatment is adopted, and the final temperature of martensite transformation of T92 steel is about 1000C. It is determined that the post-weld heat treatment is carried out 1h after the welding joint is cooled to room temperature. The heat treatment constant temperature is (760±10) 0C, the constant temperature is 1h (tube wall thickness <12.5mm) or 2h (tube wall thickness>12.5mm), and the heat treatment temperature is 1500C/h to ensure that the weld martensite is fully tempered Tempered martensite is formed.

5. Strengthen the inspection and repair of welds

After the welding is completed, non-destructive testing should be carried out immediately. Now, ultrasonic and X-ray flaw detection are generally used. After defects are found, they should be repaired in time until they reach the qualified stop.