Selection of welding materialsAustenitic A102 and J507 are recommended for welding of the same type of rare earth wear resistant alloy steel. Austenitic A102 and J507 are recommended for welding of rare earth wear resistant alloy steel and q235-a dissimilar steel.A102 welding rod bottom welding layer, the rest of the welding electrode J507 welding rod welding, generally choose 3.2 welding rod bottom, the remaining welding electrode recommended to choose 4.0 welding rod.Welding electrode should be uniform before welding, A102 welding rod and J507 welding rod drying temperature is generally about 150℃, or according to the provisions of the electrode manual, such as welding welder should keep a certain distance from the incubator, with the welding, welding rod can not repeatedly drying.
Preheat before weldingRare earth wear-resisting alloy steel has a large tendency of hardening, and it is easy to produce hardened tissues and cold cracks in welding. Therefore, it is necessary to preheat before welding, and the preheating temperature is generally controlled within the range of 200 ~ 250℃.The preheating heat source adopts oxyacetylene flame, and the micro carbon flame is used when heating. According to the thickness and diameter of the pipe wall, one or several welding distances can be used to move back and forth along the pipe to evenly heat.The heating width is within the range of 3 wall thickness on both sides of the groove, generally within the range of 50 ~ 100mm, and the minimum is no less than 50mm. The heating temperature can be measured with a temperature measuring pen.
The tack weldingThe number of welding spots is generally from 3 to 6. The length of welding spot is 10 ~ 30mm, and the height is 2 ~ 4mm. The welding specification for positioning welding is the same as that for formal welding.4. Number of welding layersThe welding adopts multi-layer and multi-pass welding.5. Interlayer temperatureDuring welding, the interlayer temperature shall be strictly controlled within the range of 200 ~ 250℃, and the interlayer temperature shall not be too high.6. Post weld heat treatmentIn order to reduce the cooling speed after welding and prevent quenching and cracking, after cooling to 250 ~ 300℃ after welding, immediately wrap the welded joint with asbestos cloth for self-cooling.7. Key points for welding7.1 working environmentOn-site welding, rain, relative humidity is greater than or equal to 90%, welding is prohibited.7.2 welding current selectionWelding current should be reduced appropriately according to the conventional welding specification, and the welding speed should not be too fast. It is generally recommended to control the current of A102 electrode and J507 electrode during welding at 90 ~ 150A, and the current of vertical welding and overhead welding should be correspondingly reduced.7.3 operation pointsWhen applying welding, should be two people butt welding, keep the two solder joints in a symmetrical position, the electrode shall not swing, and the use of short arc welding, narrow welding, multi-layer welding, generally each layer thickness should be equal to the electrode diameter.After welding each seam of each layer, hammer strike with a pneumatic shovel or hammer to reduce the welding stress.When welding, the temperature between layers should be strictly controlled. After welding, in order to reduce the cooling speed and prevent quenching and cracking, asbestos cloth should be used for insulation.
