Welding is a process by which two or more metal parts are joined together by melting the interface of the pieces and adding a filler material. The Chinese steel grades used for welding are usually the ones with classification number in the range of 90-970, and the welding material is usually the same grade as the parts that need welding.
The most commonly used welding steels in China include Q235B, 16Mn, 20# and so on. Q235B has low carbon content, good plasticity, toughness, weldability and cold forming performance, as well as good load bearing performance. The strength, toughness, weldability and cold forming properties of 16Mn are equivalent to that of Q235B, which further improves the load bearing performance and fatigue strength. 20# steel is widely used in welding technology because its good performance in both strength and toughness. It is often used for the manufacture of car frames, bridges and other steel structure welded parts.
Besides common carbon structural steel, China also develops welding steel. It has the advantages of not only high strength and ductility, but also high weldability and corrosion resistance. One of the most common types of welding steel is the X80 grade. Its chemical composition is 21.5% C, 0.30% S, 1.20% Mn, 0.028% P and 0.015% Nb, which make it a low-alloy high-strength steel steel.
In welding technology, there are four main types of welding processes used in China. They are gas shielded welding, arc welding, submerged arc welding and tungsten inert gas welding. Gas shielded welding is a traditional welding method which uses acetylene and oxygen as fuel. It works well for welding stainless steel and other types of steel. Arc welding uses an electric arc to generate heat to melt the welded material. But it will create slag and droplets. Submerged arc welding uses a protected electric arc under a flux layer to achieve welding. It has higher efficiency, with less slag and droplets. Lastly, TIG welding is also an arc welding process which uses a tungsten inert gas to generate heat and protect the weld area. It is suitable for welding thin plates and has good welding quality.
To ensure the quality of steel welding, it is important to select an appropriate welding material. In general, the welding materials are usually of the same grade as the parts that need welding, so that they have similar characteristics, such as chemical composition and mechanical strength. In addition, good understanding and strict control of welding parameters such as welding current, voltage and speed are also key to ensure the welding quality.
In conclusion, welding steel plays an important role in Chinas industry and many types of weldable steels are developed. It is necessary to select an appropriate welding material and have a good understanding of welding technology in order to ensure high quality welding.
