What should be paid attention to when selecting welding rods?
Release time: 2023-02-03
1. Chromium stainless steel has corrosion resistance (oxidizing acid, organic acid, cavitation), heat resistance and wear resistance. It is usually used for equipment and materials such as power stations, chemical industry and petroleum. The weldability of chromium stainless steel is poor, so attention should be paid to the welding process, heat treatment conditions and the selection of appropriate welding electrodes.
2. Chromium-13 stainless steel has high hardenability after welding and is easy to crack. If the same type of chromium stainless steel electrode (G202, G207) is used for welding, preheating above 300 ℃ and slow cooling treatment around 700 ℃ after welding must be carried out. If the weldment cannot be subject to post-weld heat treatment, chrome-nickel stainless steel electrode shall be selected.
3. Chromium-17 stainless steel, in order to improve the corrosion resistance and weldability, appropriate amount of stable elements such as Ti, Nb, Mo, etc. are added, and the weldability is better than that of Chromium-13 stainless steel. When the same type of chromium stainless steel electrode (G302, G307) is used, preheating above 200 ℃ and tempering treatment around 800 ℃ after welding shall be carried out. If the weldment cannot be heat treated, chrome-nickel stainless steel electrode shall be selected.
4. Chromium-nickel stainless steel electrode has good corrosion resistance and oxidation resistance, and is widely used in chemical industry, fertilizer, petroleum, hospital machinery manufacturing.
5. When Cr-Ni stainless steel is welded, carbide is precipitated by repeated heating, which reduces corrosion resistance and mechanical properties.
6. The welding rod shall be kept dry during use. The titanium-calcium type shall be dried at 150 ℃ for 1 hour, and the low-hydrogen type shall be dried at 200-250 ℃ for 1 hour (the drying shall not be repeated for many times, otherwise the coating is easy to crack and peel off) to prevent the coating of the welding rod from sticking oil and other dirt, so as not to increase the carbon content of the weld and affect the quality of the weldment.
7. In order to prevent intergranular corrosion caused by heating, the welding current should not be too large, about 20% less than that of carbon steel electrode, the arc should not be too long, the interlayer cooling should be fast, and the narrow weld bead should be preferred.
8. Chromium-nickel stainless steel coating includes titanium-calcium type and low-hydrogen type. Titanium-calcium type can be used for AC and DC welding, but the penetration depth is shallow during AC welding, and it is easy to turn red, so DC power supply should be used as far as possible. Diameter 4.0 and below can be used for all-position weldments, and diameter 5.0 and above can be used for flat welding and flat fillet welding.
Scientists and archaeologists have confirmed that brazing is one of the oldest methods of connecting materials. Back to 1500-2000 BC, ancient brazing was first used to make jewelry and handicrafts, but it was found in metals such as gold and silver that welding existed in natural form and produced new metals, and then alloys were derived.Learn more