What issues should be noted when welding stainless steel fittings

There are many production steps for stainless steel pipe fittings, each with detailed requirements. Welding is a very important step in the production process of stainless steel pipe fittings, which directly affects the quality of stainless steel pipe fittings. So, what are the issues that need to be paid attention to during welding?

1. To prevent eye erosion caused by heating, the welding current should not be too high, about 20% less than that of carbon steel welding rods. The arc should not be too long, and the interlayer should be cooled quickly. Narrow weld beads are recommended.

2. Stainless steel pipe fittings have a high degree of hardening after welding, which facilitates the occurrence of cracks. If the same typical stainless steel pipe fittings are accepted for welding, preheating at 300 ℃ or above and slow cooling treatment around 700 ℃ after welding must be carried out. If the welded parts cannot undergo post weld heat treatment, stainless steel pipe fitting welding rods should be used.

3. Stainless steel fittings, with the addition of appropriate amounts of invariant elements such as Ti, Nb, Mo to improve corrosion resistance and weldability, have better weldability than stainless steel fittings. When accepting typical chromium stainless steel welding rods, preheating at 200 ℃ or above and tempering at around 800 ℃ after welding should be carried out. If the welded parts cannot undergo heat treatment, chromium nickel stainless steel welding rods should be used.

4. Stainless steel pipe welding rods have exquisite corrosion resistance and oxidation resistance, and are widely used in chemical, fertilizer, petroleum, and medical machinery manufacturing.

5. Stainless steel pipe fittings have titanium calcium type and low hydrogen type coating. Titanium calcium type can be used for AC and DC welding, but the melting depth is shallow during AC welding, and it is convenient to turn red. Therefore, DC power supply is generally accepted.

6. Stainless steel fittings have certain corrosion resistance (oxidative acids, organic acids, cavitation), heat resistance, and wear resistance. All materials used for equipment decoration in power plants, chemicals, petroleum and other industries. Stainless steel pipe fittings have poor weldability, and attention should be paid to the welding process and the selection of suitable welding electrodes before heat treatment.

7. When manipulating welding rods, they should be connected and dried. Titanium calcium type should be dried at 150 ℃ for 1 hour, and low hydrogen type should be dried at 200-250 ℃ for 1 hour (multiple drying should not be repeated, otherwise the coating will easily crack and peel off). Beware of oil and other dirt on the coating of the welding rod to avoid increasing the carbon content of the weld and affecting the quality of the welded part.

8. During the welding of stainless steel pipe fittings, carbides are precipitated due to repeated heating, which reduces their corrosion resistance and mechanical properties.

Through analysis, it is not difficult to find that there are still many welding requirements for stainless steel pipe fittings. In order to ensure welding quality, these details must be strictly followed during operation, so as to improve welding quality and bring better use effects.