Knowledge presentation straight seam steel 16Mn due to the low carbon content, reduce hardening tendency, cold cracking tends to decrease. But as the intensity level increases, the thickness increase, still has a certain tendency to cold cracking. Because often using cellulose electrodes, self-shielded flux cored wire and other high hydrogen content of welding consumables, line energy is small, the cooling speed, will increase the sensitivity to cold cracking, need to be taken in the field of welding welding necessary measures, such as welding before preheating. HAZ embrittlement is often caused by broken straight seam steel 16Mn, induced root cause of catastrophic accidents. Partial embrittlement has two main areas, namely HAZ coarse grain zone embrittlement is due to over-grown grains overheated zone and the formation of undesirable tissue caused by the multi-layer welding CGHAZ another critical embrittlement, reheating CGHAZ that is, before the weld bead by subsequent two-phase region caused. This is done by adding a certain amount in the steel Ti, Nb micro alloying elements and control weld cooling rate to obtain a suitable t8 / 5 to improve toughness. With 16Mn straight seam steel pipe to reduce the carbon content, super-thick-walled seamless steel tubes, welded reduced susceptibility to hydrogen-induced cracking, in order to avoid cracking process to produce the required measures to reduce, special thick-walled seamless steel tubes, welded heat affected zone reduce performance extent of the damage. However, due to the welding straight seam steel 16Mn through a series of complex non-equilibrium physical and chemical processes, thick-walled seamless steel pipe, which may cause a defect in the welding area, or the joint performance degradation, mainly weld cracking problems and weld heat affected District embrittlement problem. 16mn seamless change of manganese is divided into A, B, C, D four and so on. Where A, B grade steel usually called 16Mn. 16Mn pipe joints, said the current law: Q345B seamless, texture similar to this is Q345C, Q345D, Q345E, quality rating symbols ABCDE respectively are not required impact test impact test temperature of +20 degrees 0 degrees -20 degrees 40 degrees Category: ABCD represents quality level according to the quality level is divided into A, B, C, D four levels, from A to D denote quality from low to high. Different quality level requirements are as follows: A-- offer S, P, C, Mn, Si chemical composition and fu, fy, δ5 (δ10), according to the buyer needs to provide 1800 cold bend test, 20g thick-walled seamless steel pipe, but no impact energy provision, carbon content and manganese content is not as terms of delivery. B-- offer S, P, C, Mn, Si chemical composition and fu, fy, δ5 (δ10), cold-formed 180 'test. Also provides + 200C impact energy when Ak≥27J, C-- except with the Class B requirements, like, but also provides impact energy when 00C Ak≥27J. D ---- except with the Class B requirements, like, but also provides impact energy when -200C Ak≥27J E-- except with the Class B requirements, like, but also provide -400C impact energy Ak≥27J. Thick-walled seamless steel pipe industry _ _ virtue thick-walled seamless Co., Ltd. Liaocheng by virtue of Industry. Liaocheng virtue Pipe Co., Ltd. (www.meidegc.com) (www.meidegc.com) (www.mdwfg.com) (www.mdggc.com) strong, credible, Liaocheng in Shandong steel industry has accumulated a a large number of loyal customers. The company better work attitude and constantly improving innovative ideas will lead virtue of Industry and you work into the brilliant, for a better future!