Causes and solutions of cracks after flange welding
Cracks appear after flange welding causes
Table of Contents
In the production of container equipment, stainless steel flange and barrel welding when the flange neck will appear cracks, and not in the weld place, what is going on? Why would such a situation occur? First of all, we first analyze the reasons why thermal cracking will occur.
Thermal cracking is in the weld cooling process, the high-temperature stage of the crack, mainly occurs in the weld metal, a small amount in the near seam area. It can be divided into crystallization (solidification) cracks, liquefaction cracks and multilateralization cracks. Crystallization cracking is the most common one and is mainly found in the welds of carbon steels containing more impurity elements (S, P, Si and C), single-phase austenitic stainless steels, aluminum and its alloys, and other welded structures. The main influencing factors are the degree of weld tensile stress, low melting point eutectic (chemical composition of the weld metal), and overheating of the welded joint (process).
Measures to avoid thermal cracking in welding
From the photo, 304 stainless steel material plasticity, if it is forged flange, welding process requirements are relatively lenient, generally will not cause cracks. If it is a casting, it will be easy to appear such a situation. So, in practice, how do we avoid the phenomenon of cracking in the workpiece? The measures to reduce the tendency of thermal cracking are
1) Reduce the content of impurity elements such as S and P in the material.
2) Properly increase the Mn/S ratio, which can replace the Fe-FeS low melting point eutectic Fe, the formation of MnS with a melting point of 1620 Co, thereby improving the crack resistance of the weld.
- WC=0.10~0.12%, WMn=2.5% has worked before.
- WC=0.13~0.20%, WMn=1.8% or less has a role.
- WC = 0.21 ~ 0.23%, WMn beneficial impact range more narrow.
3) The use of appropriate welding methods and processes, control the line energy input to reduce the weld overheating.
4) The addition of Ti, Mo, Nb or rare earth elements in the weld material to inhibit the development of columnar grains, refine the grain, and significantly improve performance.
Source: China Custom Flanges Manufacturer – Yaang Pipe Industry (www.epowermetals.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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