What are the key points of stainless steel welding process?

What are the key points of stainless steel welding process?

Stainless steel welding applies to stainless steel electrodes for manual arc welding, the chromium content of such deposited metal should be greater than 10.50% and the iron content should exceed any other element. Deposited metal: the weld metal formed by completely melting the filler metal.

A. Stainless steel welding main parameters

Stainless steel welding including welding current, tungsten diameter, chord length, arc working voltage, welding rate, maintenance cyclone, nozzle diameter, etc.

(1) The size of the welding current is the main condition that determines the weld formation. Usually, the decision is based on the raw material, thickness and appearance of the weld seam of the welded part.

(2) The welding diameter of stainless steel is determined based on the welding current. The higher the current, the larger the diameter.

(3) The chord length of the welding arc and arc welding film is about 0.5 to 3 mm, and the corresponding arc working voltage is 8 to 10 V.

(4) The welding speed of stainless steel welding: In the selection, the current size, the sensitivity of the raw material of the welded parts, the welding position and the actual method of operation should be fully considered.

B. The stainless steel plate flux-cored wire welding points and common problems

(1) Select the characteristic welding switch power source, AC welding selected reverse rotation. It can be welded with ordinary CO2 buzzer, but the working pressure of the wire feeder should be slightly adjusted.

(2) Maintenance steam is generally CO2 steam with gas pressure of 20~25L/min.

(3) The distance between the stainless steel welding nozzle and the product workpiece should be 15~25mm.

(4) Dry extension length: 15mm for general welding current below 250A, 20~25mm for above 250A.

C. Stainless steel welding process points:

(1) stainless steel welding. Austenitic stainless steel has excellent welding properties, almost all fusion welding methods can be used for welding of austenitic stainless steel.

(2) stainless steel welding generally does not require preheating and post-heating before welding. In order to prevent thermal cracking, heat-affected zone grain growth and carbide precipitation, to ensure the plastic toughness and corrosion resistance of the welded joint, should control the lower interlayer temperature. Usually, no stress relief heat treatment after welding.

(3) stainless steel welding specifications. Usually, welding does not use a large heat input. In the electrode arc welding process, a small diameter welding rod should be used for fast multi-pass welding. For more demanding welds, even the method of pouring cold water should be used to accelerate cooling. For pure austenitic and austenitic stainless steel, due to its high sensitivity to thermal cracking, welding heat input should be strictly controlled to prevent severe growth of weld grains and the occurrence of weld thermal cracking.

D. The welding of ordinary ferritic stainless steel can be used for ordinary welding methods. When using the same material welding, the following stainless steel welding measures should be taken:

1. Warm up. Generally at about 100 ℃ ~ 150 ℃. When the chromium content increases, the preheating temperature will also increase accordingly.

2. Stainless steel welding should use a smaller heat input. When welding, the welding torch (torch) shall not swing, welding should be discontinuous. Interlayer temperature should be controlled at 150 ℃ or more, but not too high.

3. Stainless steel post-weld heat treatment temperature should be 750 ℃ ~ 850 ℃, and should be rapidly cooled to prevent σ-phase and 475 ℃ embrittlement.