There are many welding methods for cast iron, such as manual arc welding, gas welding, CO2 gas shielded welding, and manual electroslag welding. Manual arc welding is divided into hot welding, semi-hot welding and cold welding; gas welding is divided into hot welding, heating and reducing welding, and not preheating welding. In selecting these welding methods, the selection is mainly based on the size, thickness of the casting, the defect condition of the welding repair site, the complexity of the stiffness, and the post-weld requirements (such as whether processing, compactness, strength, color, etc.).
We often encounter problems such as cracks, perforations, or damaged shapes in automobiles and tractor cylinders that require repair by welding. Due to the HT21-4, the HT21-4 is usually used in cars and tractors. And HT15-32 made of materials, coupled with the complex structure of the cylinder, thin and uneven wall, welding is very easy to produce cracks, so the welding repair work caused great difficulties. According to actual production conditions, production efficiency, and economic factors, manual arc cold welding is used more often. The following two examples are used to describe the process method for welding the cylinder block.
Case 1, Dongfeng windmill cylinder, due to overhaul disassembly, the cylinder surface hit a piece, when we used low-carbon steel plate as a replacement, and manual arc cold welding, with a small 3.2mm cast 308 electrode, welding current I = 100A, short-segment welding, interrupted welding, dispersion welding this process.
This process is based on this cylinder defect located on the surface, without processing, if the original block is made up, the stress is increased, the filling metal is more, and the tensile cracking resistance is poor.
For this workpiece, first carefully clean up the oil impurities near the defect, annealing the low-carbon steel plate without gaps, and only open the half-side groove around the casting, use a small 3.2 diameter cast 308 electrode and 506 carbon steel electrode to cross use (this guarantee The quality also reduces the cost). The solid current is 100 amps, the same as the welding current. The length of each weld does not exceed 20mm. Immediately after welding, the weld is quickly hammered with a small hammer to eliminate stress, reduce cracks, and make the weld dense, if there are tiny pores, Slagging, after hammering, can reduce leakage without affecting the tensile strength of the weld.
After each welding, the weld should be cooled until it can be touched by hand and brushed clean with a wire and then welded again. This is repeated until the weld is completed.
Example 2: The forklift truck cylinder was frozen without cracking due to no antifreeze in winter. The crack length was 50mm, and the middle part protruded 5mm.
At that time, we used pressure iron to flatten and crack holes at both ends of cracks, based on the fact that the cracks were long and the rigidity was large. Using a cast 308 electrode with a diameter of 3.2, using a sand wheel with a bevel, each weld is 10-15mm long, and the weld is hammered with a small hammer, brushed clean with a wire, cooled to about 600°C and then welded for the next section. Afterwards, three blocks of steel plates of 30x50 and 3mrn were used to reinforce the welds in the welds, and the cracks were finally sealed.
Practice shows that the above-mentioned process method is practical and feasible. It is worthy of promotion and reference in the welding repair of cast iron, especially the welding of cylinder block.
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