(658, 'As welding technology welding structure increasingly to high parameter large scale in the direction of development which the performance of welded structural steel demand higher and higher not only have good mechanical properties and to have good processing properties such as welding Special conditions for the application of steel but also requires a corresponding special properties such as corrosion high temperature low temperature and so on Therefore carbon structural steel have been the original can not meet the requirements further promote alloy structural steel gained rapid development and wide application The quality of welding of steel used to evaluate the performance of one of the key indicators Welding Welding materials And the corresponding welding process welding alloy structural steel of the three basic elements the three are inseparable Therefore if not effectively addressed each of the welding of alloy structural steel and associated welding materials and welding technology issues will directly impede the wide application of such steel br br To continue to improve the welding alloy structural steel the foreign country from the late 60s from the 80 39 s started to develop and produce good micro weld alloy rolled steel and began to research the next generation of ultra fine grain steel The emergence of a new steel Welding of steel brought significant changes br br 1 micro alloy rolled steel Past production of alloy structural steel steel itself focused on the performance relative to the oxidation purification processing forming and heat treatment phase transitions And less consideration of its welding welding technology and welding it to produce much inconvenience In recent decades foreign special attention to start from the fundamental solution metallurgical steel welding issues Metallurgical workers in the past two decades China has also this attention and the measures adopted by metallurgical and low carbon micro alloyed TMCP process measures such as production of several kinds of good toughness good welding steel bridge steel pressure vessel steel etc This alloy structural steel welding development br br Made a new contribution The production of new steel grades have the following characteristics br 1 1 Clean Coal Technology Cleanliness of steel will significantly improve the impact toughness of steel welding Connector The crack resistance and anti HIC 39 s capacity the weldability will be significantly increased the corresponding request has to be clean of weld br br 1 2 Fine Grain Technology Available through the fine grain strengthening low alloy high strength steel to further reduce the carbon content and reduce the solid solution of alloying elements so that the toughness will be further enhanced Wuhan Iron and steel products using these technologies the impact toughness of steel bridges have reached a higher level the steel Charpy impact energy measured under 40 were more than 100J br br 1 3 micro alloy rolled steel requirements of the welding material br 1 3 1 cleanliness of weld metal br 1 Welding clean of raw and auxiliary materials br 2 Welding Metallurgy of reaction clean br 1 3 2 Micro alloy welding material br br Micro alloy rolled steel weld strengthening and toughening of high strength and toughness required match and this requires not only the weld metal to achieve clean technology but also to achieve fine crystallization But Weld is not as fine crystallization plate as can achieve controlled rolling and cooling process it is only through alloying complete the grain is refined The results show that a large number of weld acicular ferrite can significantly improve the weld metal strength and toughness this is because the ferrite is very small needle the average size of about 1 m and the orientation of ferrite needle free large angle grain boundary which has strong anti crack growth so that the weld line that sufficient amount of acicular ferrite is to increase strength and toughness of weld metal key While adding a number of trace elements in the weld heat inhibit austenite grain growth and second to promote the formation of acicular ferrite the weld material point as the mixture of acicular ferrite in the nuclei to improve the acicular ferrite nucleation rate plays an important role ')
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