G24Mn6+QT2 and seamless steel pipe welding technology

Welding technology of large cast steel joint G24Mn6+QT2 and seamless steel pipe is a very important process in mechanical construction. The correct choice of welding process, correct welding parameters and correct welding methods, facilities and consumables can ensure that the welded joint meets the design requirements and ensure the safe and reliable operation of the equipment. Therefore, it is necessary to understand and master the welding technology of this kind of welding combination under the premise of ensuring the welding quality.
    
The welding combination of large cast steel joint G24Mn6+QT2 and seamless steel pipe is widely used. Under normal circumstances, it can be welded using manual SMAW or semi-automatic MAG welding process.
    
When the manual shielded metal arc welding process is used for butt welding of large cast steel joint G24Mn6+QT2 and seamless steel pipe, use No. E6013 low hydrogen electrode, and the welding process parameters are as follows: arc voltage: 31~35V; welding current: 100~140A; welding speed: 0.6~1.2m/min. When the electrical stick-out is about 15mm, the polarity should be used in reverse, that is, the negative pole is connected to the plate, and the positive pole is connected to the electrode. In order to largely eliminate the penetration, reduce deformation and reduce welding defects, the welding should be made from the back to the front, using a V-shaped groove and multilayer welding.
    
When using semi-automatic MAG welding process, the following welding parameters should be used: welding current: ≥170A; welding voltage: 25~32V; welding speed: 0.5~1.1m/min. The wire should be 1.0~1.2mm low hydrogen welding wire and the welding layer should also be built according to V-shaped groove welding method.
    
In order to ensure the welding quality of large cast steel joint G24Mn6+QT2 and seamless steel pipe, it is necessary to strictly control the welding process parameters, take full account of the base material's preheating mechanical properties and cooling conditions, strengthen the welding monitoring and inspection, and repair the welding defects in time. In addition, the protective measures of welding slag and cleaning should also be done in time, so as to ensure the quality of welding joint.

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