As we all know, the sand making machine is composed of many parts as a large-scale mechanical sand device. The parts of the sand making machine will also need to be repaired due to the time of use. The repair of the sand making machine parts is not only chrome plating but also iron plating. The essence of the iron plating process is the precipitation of iron from a hot electrolyte at high current densities. In this way, the plating speed can be increased by about 9 times compared with that of chrome plating, and the thickness of the plating layer can be up to 3-5 mm. The iron coated layer has a hardness of Hb = 180-200 and can be subsequently carburized; the hardness after carburizing can be increased to Hb = 500-600. When repairing parts with severe wear, the surface can be iron-plated and then chrome-plated. At this time, the hardness of the coated layer can reach Hb=700-800. The process of iron plating is as follows: (1) Machining the parts (turning , grinding) to eliminate scratches, wear, ovality, conicity, etc.; (2) Mount the part on the fixture and isolate it from the place where iron plating is not required (3) Caustic soda at a concentration of 100 g/l The electrolyte is degreased in the solution, and its working specifications are as follows: electrolytic density is 3-10 amps/dm2, voltage is 7-10 volts, temperature is 30-80°; time is 10-15 minutes; (4) first Washing in hot water and then in cold water (5) Electrolyte pickling removes the part that needs to be iron-plated to eliminate the oxide film, exposing the surface, so that the plating layer adheres well to the base metal. The composition of the solution is as follows: concentrated sulfuric acid is 100- 150 g / liter, sodium oxide is 20-50 g / liter. The working specifications are as follows: current density is 5-7 amps/dm2, temperature is 15-25°, time is 3-5 minutes (6) washing in cold water (7) plating with chloride electrolyte and sulphate electrolyte iron. Chloride electrolytes have found a wide range of applications, resulting in smoother and thicker deposits with higher current densities. When the current density is 10-30 A/m 2 , the plating speed is in the range of 0.12-0.32 mm/hr; the current efficiency is 85-98%. Electrolytic iron has a high brittleness and needle-like structure (the needles are arranged perpendicular to the iron-plated surface). In order to obtain a fine-grained structure and eliminate the brittleness of the precipitate, the part must be tempered and allowed to stand at a temperature of 300-500 deg; for 30 minutes and then slowly cooled in air. The strength limit of the annealed coating is increased by 55-60%, the yield point is increased by 15%, and the Brinell hardness is increased by 45%.
Why are you going to repair the parts of the sand making machine? First of all, there are many parts of the sand making machine, which can be repaired in some simple parts. The replacement part is expensive, so we choose to repair the parts of the sand making machine and repair the parts of the sand making machine explained today. Method.