logoxgvb
Joined: 30 Aug 2010
Posts: 1580
Read: 0 topics
Warns: 0/5
Location: hdfttv
|
 Posted: Mon 0:33, 20 Dec 2010 Post subject: air jordans Welding on the Corrosion of metallic m |
|
|
Welding on the Corrosion of metallic materials
Sub-properties, microstructure and chemical composition of major changes will occur, while welding corrosion of materials will have a greater impact. Weld joint area is the most severe stress condition, the corrosion behavior of the most complex and concentrated expression of the region. First,[link widoczny dla zalogowanych], the welding surface defects caused by tumors, such as welding, undercut, incomplete penetration, are the deposited metal and the gap formed between the base metal. Splash also the base metal and the metal particles to form the site of contact between the cracks. In electrolyte solutions (such as NaC1 solution), these gaps tend to occur at the crevice corrosion. Of course, the occurrence of crevice corrosion conditions, including the gap size, the medium state of stagnation and erosion characteristics of various aspects. But the welding surface defects undoubtedly provided a venue for crevice corrosion. Second, carbon steel welding process, non-metallic inclusions generated mostly oxides, nitrides,[link widoczny dla zalogowanych], sulfides. These inclusions will increase the fragility and tendency to hot cracking and reduce the corrosion resistance of the weld and plastic. Which mainly sulfide flux into the coating or, more to form MnS. Mns as the active central debris. Often as \Stainless steel and other materials in the welding process, due to heating and cooling process to bring the heat affected zone change of the phase structure and composition, these materials will increase the tendency to intergranular corrosion. Third, from the corrosion point of view, the weld area is a pair of contact with the battery. Because different metal contacts together, and placed in corrosive media, so that part of the lower electrode potential as anode materials, will produce corrosive solution, so the composition of the uneven weld joint area is caused by selective corrosion of the important factors. Fourth, the welding residual stress is mainly caused by stress corrosion cracking of materials. General steel plate welding,[link widoczny dla zalogowanych], the maximum residual stress close to the base metal yield strength. Stress corrosion cracking and tensile cracks are often the maximum principal stress is vertical. Therefore, the stress is directly caused by the crack maximum principal stress. If the principal stress and minimum principal stress perpendicular to the greater, the earlier the crack occurred. Hardening of austenitic stainless steel is greater. The cold will increase the material yield limit. If using cold plate after welding, welding residual stress can rise to near the yield limit, then stress corrosion may be more dangerous in the state. In addition, the weld geometry of the stress concentration caused by the deviation will increase tendency to stress corrosion and corrosion fatigue. Fifth, the welded joint zone of the change on the occurrence of stress corrosion material. Because of this effect varies in different corrosive environments such as austenitic stainless steel welded joints of the original site of the iron melt body tangled in hydrochloric acid solution, the corrosion will be a priority phase, easily shaped, shelter network cracks. The heat affected zone along the intergranular chromium carbide precipitation and other types of corrosion in the NaCl aqueous environment, the type of stress corrosion of steel resistance Crystal cyberspace was worse. In short, the welding on the corrosion of metallic materials is very complex, this article only describes several common situation. To reduce the welding on the corrosion of metallic materials, in practice the amount of cough rhino weld defects and residual stress control, but more important is reasonable under the corrosive environment when the selection and use of the best welding process. In principle from the electrochemical corrosion of carbon steel welded base material should be collected and dumped the same type of welding filler metals. Different types of carbon steel corrosion in the different nature of the environment and the corrosion mechanism is different,[link widoczny dla zalogowanych], the situation is more complex (not repeat them here.) The stainless steel, we consider is how to eliminate soldering chromium carbide precipitation and intergranular corrosion occurred, and brought the gap phase precipitation decrease corrosion resistance. Solve this problem,[link widoczny dla zalogowanych], by alloying the welding process, welding core mole and medicine through the skin of the ingredients to adjust the weld metal alloy ribs, so that no heat Wedelia ring area and gap-phase chromium carbide precipitation. For example, by reducing the carbon content, and normalizing the time extension and the addition of stable carbide forming elements such as Ti and Mo to avoid intergranular corrosion of the day. Carbide precipitation can be accelerated by adding Ni, delayed clearance phase precipitation. The opposite effect of Mo and Ni. Add N to delay the precipitation of carbides and phase space. The si is able to strongly promote the precipitation of carbides and phase space, it should minimize its content. Through the interaction of alloying elements such rejection, it is possible and the gap relative to chromium carbide does not precipitate in the weld, to obtain better corrosion resistance. Boilers and pressure vessels and other chemical equipment mostly to go through the welding process. Weld metal and heat affected zone corrosion how the dark shadow of a great production safety. Therefore, the full consideration of various factors that could weld corrosion of the material is important. Editor: Guo Xiaodan Received I1999-04-19 \ 1 deep shame on T l 』』
相关的主题文章：
[link widoczny dla zalogowanych]
[link widoczny dla zalogowanych]
[link widoczny dla zalogowanych]
The post has been approved 0 times
|
|
