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How to weld tractor cast iron
When using the welding method to repair the tractor's iron castings, in addition to selecting the appropriate welding method according to the actual situation, the following points should also be noted: 1. Preparation of welds Welds and all surrounding harmful impurities such as rust must be welded before welding. , oil, paint, etc. completely removed; weld repair crack if the weldment wall thickness is less than 25 mm, it should drill a diameter of about 4 mm crack stop; some weldments but also according to the wall thickness and process requirements choose groove Type and so on. Second, the choice of welding rod and its diameter Different types of cast iron should use its corresponding electrode; its diameter is mainly determined by the thickness of the weldment welding repair; in order to prevent the production of white mouth and fire-fighting organizations, reduce heat-affected zone At present, many small diameter electrodes are used. Third, the choice of power polarity In DC arc welding, in order to avoid excessive penetration, weldment overheating and burn through, use reverse polarity connection, that is, the weldment - then the cathode, the electrode is connected to the anode. Fourth, the choice of current strength When the current is too large, the depth of penetration increases, and the weld metal components and impurities diffuse into the weld pool to change the performance of the weld; current is too small will affect the stability of the arc, easy to produce slag inclusions, pores and other defects; current intensity The selection should be based on cracks or defects in the spatial conduction of the weldment, while also considering the weld number and diameter. Fifth, the welding operation points to reduce cracks should try to avoid local overheating of the welding area, long cracks should be intermittent, sub-jump welding; In order to reduce the penetration, should choose a small current, fine electrode, and try to use short solitary welding; Welding rods with good plasticity, such as nickel-based electrodes and copper-iron electrodes, should be tapped quickly with a round-headed hammer to remove loosening stress and remove cracks and pores; each small wave should not be straddled at the same time. On both sides of the day, this facilitates the free contraction of the unwelded portion and avoids that the arc stays on both sides of the groove for too long; the welding layer should cope with the underlying layer to anneal the underlying layer and change its processing performance.