Spray welding process should be selected under the following conditions:
(1) the surface load of all kinds of carbon steel and low alloy steel workpiece is large, especially the impact load. For the workpiece with the bonding strength between coating and substrate of 350-450n / mm2, the spray welding hardness is HRC150 ≤ 65, the coating thickness is from 0.3 to several millimeters, and the surface roughness of spray welding layer after grinding can reach ra0.4-0.1 μm.
(2) when used in corrosive medium, the coating should be compact without pores;
(3) quenching, carburizing, nitriding and hard chromium plating are used in the original design of workpiece surface, which requires high hardness
(4) the working environment of the workpiece is bad, such as strong abrasive wear, erosion wear, cavitation erosion and so on.
(5) oxygen acetylene flame alloy powder spray welding process is suitable for surface strengthening or repair of various carbon steel and low alloy steel parts, but some characteristics of parts materials should be noted. When the linear expansion coefficient of matrix material is greatly different from that of alloy spray welding layer, it is less than 12 × 10-6 / ℃ greater than 12 × If the content of elements with high affinity to oxygen is more than 3%, such as tungsten and molybdenum, and the total content of aluminum, magnesium, cobalt, titanium, molybdenum and other elements is more than 0.5%, or the sulfur content of steel is more, it will also bring difficulties to spray welding. This is because these materials can easily form dense and stable oxide film by interaction with oxygen, In order to prevent the wetting effect of the molten alloy on the matrix, the liquid alloy will roll down like beads during remelting. Therefore, the adaptability of the spray welding process to the sprayed matrix material should be paid attention to when using the spray welding process.
(6) metal materials that can be spray welded without special treatment:
① Carbon structural steel with carbon content ≤ 0.25%
② The total content of MH, Mo, V, Cr and Ni is less than 3%.
③ 18-8 stainless steel, nickel stainless steel, gray cast steel, malleable iron, ductile iron, low carbon pure iron and red copper.
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