Butt welding elbows are harder after welding and are prone to cracks

Butt welding elbows are harder after welding, and are prone to cracks. If the same type of stainless steel stamping elbow is used for welding, preheating above 300 ° C and slow cooling around 700 ° C after welding must be performed. If the weldment cannot be heat-treated after welding, the stainless steel stamped elbow electrode should be used.

Butt welding elbows are subjected to repeated heating to precipitate carbides, reducing corrosion resistance and mechanical properties. In order to prevent the corrosion between the eyes due to heating, the welding current should not be too large, about 20% less than the carbon steel electrode, the arc should not be too long, the interlayer cooling is fast, and the narrow weld bead is suitable.

Butt welding elbows, in order to improve corrosion resistance and weldability, appropriately increase the appropriate amount of stability elements Ti, Nb, Mo, etc. Weldability is better than stainless steel stamping elbows. Butt welding elbow electrode has good corrosion resistance and oxidation resistance, and is widely used in chemical, fertilizer, petroleum, medical machinery manufacturing.

The electrode should be kept dry when using. The titanium calcium type should be dried at 150 ℃ for 1 hour, and the low hydrogen type should be dried at 200-250 ℃ for 1 hour (can not be repeatedly dried, otherwise the coating will be easy to crack and peel) Stick oil and other dirt to avoid increasing the carbon content of the weld and affecting the quality of the weldment. When using the same type of chromium stainless steel electrode, it should be preheated above 200 ℃ and tempered at about 800 ℃ after welding. If the weldment cannot be heat-treated, the chromium-nickel stainless steel electrode should be used.

The determination principle of the heating temperature of the stainless steel elbow is that the material is above the austenitizing temperature, and the main compressive stress of the inner wall of the elbow is less than the limit of the material at this temperature when it is pushed. The higher the austenitizing temperature of the material, the higher the heating temperature; the higher the high temperature yield limit of the material, the higher the heating temperature. The temperature measurement method is a combination of a fixed far infrared thermometer and a manual far infrared thermometer, which is directly controlled by the shape of the induction ring and the relative position of the induction ring and the core rod head. The shape of the induction coil is the main factor, and the relative position of the induction coil and the mandrel head is the secondary factor. The heating temperature is high. The wall thickness of the stainless steel elbow increases. The effect of the propulsion speed on the geometry of the elbow is promoted. As an important process parameter, the hydraulic system flow control directly controls the elongation of the outer wall of the elbow. Elongation.