Improvement of copper bushing soldering process

In some high-power engineering machinery, copper bearings welded by two half-piece copper bushes are often used. However, in the process of machining after welding, the joints of the copper bushings are often not cracked and cracked. Phenomenon, seriously affecting the quality of parts, and sometimes even scrapped.

In the past, when we were welding copper bearings, we usually used oxyacetylene flames for preheating (this kind of preheating method was not heated enough), and then used a certain power of soldering iron to solder two copper bushes (usually with ZQSn6-6). -3) Soldering, but it is often the case that the workpiece is scrapped due to cracking of the copper bearing pad joint.

To this end, we reviewed the relevant information. After repeated trials, we finally found an ideal welding method, which is described below.

Since copper has a large thermal conductivity and heat capacity, the heat input during soldering should also be larger. To this end, the copper bearing bush should be pre-heat treated before welding, that is, using a 2~4kw electric oven, the temperature is adjusted to 150±5°C, and several half-piece copper bushes to be welded are baked in the oven for 3~4h. Then take out and weld, but you must take time to prevent excessive heat dissipation. Atlas air compressor parts welding program:

(1) Wash the joint surface of the two half-piece copper bearing bushes with dilute sulfuric acid or dilute hydrochloric acid for 1~2 times, and apply a few times when the dirt is too much, until the oil, impurities and the like are removed. The surface roughness of the joint surface should be Ra 3.2 μm.

(2) Use a certain power of soldering iron (depending on the size of the part) to uniformly apply the solder wire (or solder, rosin) on the two joint surfaces, the thickness of the tin layer is about 0.05mm.

(3) Evenly apply a thin layer of paraffin (stearic acid) on the tin layer.

(4) Quickly put the two copper bushes together, clamp them with iron pliers or special tools, and push them back and forth several times in the longitudinal direction to make the upper and lower bearing pads adhere to each other accurately.

(5) Since the coefficient of linear expansion of the copper bearing bush is large, the shrinkage rate during cooling is also large, so the weldment should be gently tapped immediately after welding to refine the grain, reduce residual deformation, and prevent the welding surface. Cracking.

(6) After the welded parts are completely cooled, they can be machined.