Using Oxygen-Acetylene Flame Spraying Technology to Repair Large Machine Tool Guideway

       Large machine tool guide rails often have defects such as strain during use, which affects the normal use of the machine tool. In the past, methods such as welding or glue repair were used to repair the strained machine guide rails, but the phenomenon of glue stirring often occurred during use. , it is difficult to achieve the expected effect. The use of oxygen-acetylene flame spraying process method can achieve on-site repair of large machine tool guide rails.



    1) Selection of thermal spraying process

    The guide rails of the large-scale machine tool to be repaired are seriously scratched. For example, the longitudinal guide rails, horizontal guide rails and vertical guide rails of the T68 boring machine have serious strains, while the guide rails of the B2152 planer are seriously strained within a range of about 5m long. Spraying methods suitable for general guide rail repairs such as plasma spraying, arc spraying, oxygen-acetylene spraying and spray welding. Considering the situation of on-site repair in the workshop, plasma spraying is difficult and generally difficult to achieve; the arc spraying equipment has poor spraying adaptability for the strained part of the guide rail, and it is difficult to take advantage of the high deposition rate of arc spraying; for large-area strains, use Oxygen-acetylene spray welding will cause large deformation and even cracking of the guide rail, so it should not be used. Oxy-acetylene flame spraying technology is selected for the on-site repair of large machine tool guide rails because of the characteristics of simple process operation, small equipment investment, wide and flexible application, fast repair speed and good economy.

    2) Selection of spraying materials

    The material of the machine tool guide rail is gray cast iron, and the depth of its strain is large. The choice of spraying material should first consider that the coating will not fall off during use. Therefore, three materials of low carbon steel wire, 2CrB and T8 were selected for the thickness and bonding strength test of the coating. Under the condition of the same sample pretreatment process, the three materials were sprayed with 1mm, 2mm and 3mm thick coatings respectively to carry out the coating bond strength tensile test. The results show that the 2CrB coating has the best bonding performance and still has a high bonding strength when the coating thickness is 3 mm. At the same time, considering the performance of the machine tool guide rail, the hardness of the coating is required to match the hardness of the matrix, which is slightly higher than that of the matrix cast iron, that is, the HRC is about 30, and the coating has good wear resistance and corrosion resistance. From the comprehensive consideration of coating performance, spraying technology and economy, 2CrB was selected as the spraying material for repairing machine tool guide rails.

    3) Selection of pretreatment process

    In the repair process of machine tool guides, the pretreatment process is very important. Otherwise, the coating will peel off. To this end, the effect of pretreatment process on the bonding strength of coatings was tested.

    In the test, a standard sample of φ40mm is used, the material is Q235, the total thickness of the coating is 1.2mm, the bottom layer material is Ni/AI powder, the coating thickness is 0.1mm, and the working layer material is 2CrB. The selected pretreatment schemes are: Nickel brushing + spraying Ni/AI; nickel brushing; sandblasting + spraying Ni/AI. The sprayed sample is made of E-7 glue to stick to the unsprayed sample. The test process is carried out according to the GB8642-88 standard, and the test results are shown in Table 4-6.

    It can be seen from the strength test results that the pretreatment method of nickel brushing + spraying Ni/AI bottom layer has the best bonding strength among the selected schemes, and is also suitable for on-site repair of machine tool guideways.