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Application of Open Arc Welding in Casting Rolls Repair

Author: ShiXiaoMing
Tutor: ChenJunMei
School: Shanghai Jiaotong University
Course: Materials Engineering
Keywords: casting roll open arc welding 400N-O flux cored wire microstructure hardness wear resistance
CLC: TG455
Type: Master's thesis
Year: 2011
Downloads: 110
Quote: 0
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Abstract

In the whole casting process, the casting roll is the core component of casting equipment. After being used for a period of time, the body of the casting roll could be bent down. In addition, there will be different degrees of mesh cracks, oxidation corrosion, wear and tear and other damages on the roller surface, thus having direct impact on the working efficiency, production costs and the slab quality. As a result, this would seriously constrain the productive capacity of the whole production line. The traditional submerged arc welding (SAW) method still cannot make breakthroughs on the life-time of the casting roll. Therefore, it is inevitable to apply new repair methods to prolong the life-time of the casting roll.That Open Arc Welding,(OAW) is a new welding method developed by British Welding Alloys Co., Ltd. in 1994, before which the company developed the 400-series ultra-low carbon nitrogen flux cored wire. The following article explores the surfacing layer microstructure, hardness, wear resistance of the welding arc after the casting roll is repaired. The article also makes a comparison on the using capacity of the rolling table after repair between the submerged arc welding and the open arc welding. During this research, we designed the experimental methods for the arc 21CrMoV5.11 Surfacing pilot program under three different heat inputs. The fundamental test results showed that: under the three different heat inputs, the dilution rate of the first layer of deposited metal was relatively low, and the base material has no dilution impact on the second and the third-deposited metal.The structure of the deposited metal is characterized by uniform and fine low-carbon martensite and dispersed nitrides. The addition of the N elements into the welding wire inhibits the growth of ferrite. The replacement of C with N, together with alloy Cr, V, Ti has resulted in a stable nitride. A high degree of the dispersion of nitride is able to improve the high-temperature bending capacity, the hardness and capacity of the deposited material, especially the anti-fatigue strength and the wear resistance. In the high temperature, the reaction of nitrogen with chromium forms the nitride, thus eliminating areas with low chromium, and improving corrosion resistance and high temperature corrosion resistance of the lap weld zone.The hardness of the cladding layer is distributed in a uniform method. Because of the dilution of the base metal, the first layer of deposited metal is relatively harder than the second and the third layer. There is no obvious difference on the hardness of the third layers of the three sample pieces. The hardness of the same layer of the deposited metal increases gradually increased with the line energy in terms of the threesample pieces, but, there is little change on a whole method. Amongst the three different heat inputs, the deposited layer with the line energy of 38KJ/cm has the best wear resistance, with an average weight loss ratio of 2.1918. Organizational factors have a significant impact on the wear resistance. When there is a certain amount of nitride on the martensitic matrixt, the highly dispersed nitride is able to inhibit the crack propagation in the wearing process.The technology of this research has been applied in the casting roll deposited welding repair projects taken by the Stainless Steel Division of Shanghai NO.1 steel Electromechanical Co., Ltd . Compared with the traditional Submerged arc welding repair, the open arc welding equipment that is simple and easy to operate; with simple process. It is mature and reliable, with continuous high-speed surfacing. In addition, the dilution rate of the welding table is low, with strong corrosion resistance of the rolling surface, and good wear resistance. The average life-time is twice to three times longer than traditional submerged arc with low repairing cost.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Welding, metal cutting and metal bonding > Welding process > Surfacing and repair welding
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