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Zirconium Increased Strength

Jul 13, 2017

Zirconium is a corrosion-resistant metal material, it is a very lively chemical properties of the elements, are generally used in the chemical industry, Zirconium at high temperatures and the atmosphere easily react with a variety of gases. In the zirconium welding, the weld and heat affected area is easily air oxygen, hydrogen, Zirconium nitrogen and other elements of pollution, resulting in hard and brittle compounds, and produce brittle needle-like organization, so that the joint hardness, strength, Plasticity decreased,Zirconium corrosion resistance also dropped significantly. Therefore, the molten bath, weld and heat affected zone should be adequately protected to completely isolate the air when the zirconium is welded. The welding of zirconium material is generally welded with tungsten inert gas shielded arc welding method. Other welding methods include: electron beam welding, plasma arc welding and resistance welding. Zirconium Its welding performance and titanium welding is relatively close, due to the thermal expansion coefficient of zirconia and elastic modulus is small, so the welding deformation and weld residual stress is relatively small, it is recommended at 1100 ° F (594 ℃) under the weld stress relief time 1 hour / inch thickness. Zirconium In the case of pollution, the weld is not prone to crystal cracks and cold cracks. Zirconium at high temperature is generally easy to react with the atmosphere, at 200 ℃ began to absorb oxygen, 300 ℃ absorption of hydrogen, Zirconium 400 ℃ absorption of nitrogen, the higher the temperature the more intense the intensity of reaction. Another major problem with zircon welding is that the weld is easily softened and the welds are misaligned. The root bead is easy to burn. Therefore, Zirconium when welding zirconium, the welds should be properly fixed and double-sided welds should be used as much as possible. Zirconium In addition to titanium, niobium, silver, vanadium, zirconium and other metals can not be directly welded.

Zirconium and zirconium alloy used TIG welding welding wire is generally the same with the base material, zirconium wire selection should be in line with ASME standard SFA-5.24 in the relevant provisions and requirements, the wire by the appearance of inspection: its appearance must be smooth, Round, Zirconium do not allow the existence of burr, wrinkles, overlapping, cracks, pores and other defects, Zirconium if necessary, Zirconium micro-microscopic inspection, does not allow segregation, slag and other defects.

Zirconium pipe before cutting should check the material and specifications, and do material marking the transplant work should be used non-corrosive marker, is strictly prohibited to make steel, zirconium cutting should use mechanical methods, if the use of plasma or wheel cutting, Zirconium cutting pipe Rotation, so that it is always in the best position, the use of plasma cutting should take measures to protect the inner and outer surface of the tube to prevent the surface was spark burns, and mechanical removal of pollution. Always clean up the dirt on the tool, before each use should be clean, without any debris. Zirconium pipe, whether with mechanical processing or sawing, Zirconium should also use the file to repair the incision, and then use stainless steel brush or electric stainless steel wire wheel and other tools to further processing, so that the groove surface smooth, burr, pits, sand, etc. defect. Zirconium Pipe, pipe group on the process, do not allow strong group, is strictly prohibited hammering or scratching the material surface.

Zircon weld can be liquid penetration testing, X-ray test, there should be no cracks, undercut, not penetration and excessive stomatal existence.

Exposed to the air in the zirconium, at different temperatures, the surface will form ZrO or Zr2O3 or ZrO2 and other oxide film, which presents a different surface color, such as the surface of the oxide film is very thin, Zirconium with a stainless steel wire brush can be removed on the performance Has little effect. Zirconium From dark blue to white or white powder, it indicates that the weld metal is heavily polluted and that the weld metal and the adjacent base metal must be completely shoveled.

Another way to test whether the weld is contaminated is to measure the surface hardness of the weld. Zirconium When the hardness of the weld than the base metal hardness 30HB (5HRB), regardless of the surface color of the weld, that the weld has been seriously polluted.