Auxiliary swing plate weldment

Overview: Stainless steel welding rod refers to a type of welding rod coated with stainless steel as raw material. It can be divided into chromium stainless steel welding rods and chromium-nickel stainless steel welding rods, which are widely used in chemical industry, fertilizer, petroleum, medical machinery manufacturing and other industries.

Performance requirements:

In addition to meeting the general welding process performance and mechanical properties of the welded joint, stainless steel welding rods must also ensure that the welded joint can meet certain corrosion resistance requirements. For coatings and welding cores, the following requirements are usually considered:

1) Through the transition of various alloy elements through the welding core and coating, the weld metal becomes a structure containing a certain amount of austenite and ferrite to ensure that the weld metal has both good crack resistance and good resistance to cracking. The ability of corresponding media to corrode.

2) Through the welding core or coating, a certain amount of carbide-forming elements (such as niobium, molybdenum, titanium, etc.) can be penetrated into the weld metal to form stable carbides with carbon to prevent the carbonization of chromium at the grain boundaries. things.

3) The increase in carbon will cause intergranular corrosion in the welds of austenitic stainless steel (or ferritic stainless steel). Therefore, the carbon content in the welding core and coating raw materials must be strictly controlled. It is recommended to use low-carbon or ultra-high-carbon welding materials. Low-carbon welding core uses low-carbon or carbon-free iron alloys and metal elements as raw materials for coating.

4) Strictly control the sulfur and phosphorus content in the stainless steel welding core and coating to reduce the risk of hot cracks in the weld.

Classification

According to the GB/T 983-1995 "Stainless Steel Welding Rods" standard, stainless steel welding rods can be divided into two categories: chromium stainless steel welding rods and chromium-nickel stainless steel welding rods.

(1)Chromium stainless steel welding rod

This type of welding rod is mainly composed of Crl3 series stainless steel welding rods and Crl7 series stainless steel welding rods. The welding characteristics of the two series of electrodes are described below:

1)Cr13 series stainless steel electrodes: Welding electrodes such as G202, G207, G217 and other electrodes are Cr13 series stainless steel electrodes with martensitic structure. When using this series of stainless steel electrodes to weld martensitic stainless steel, the weldment should be preheated to above 300°C before welding. , and the weldment must be tempered at 700°C after welding. Only by taking the above process measures can we avoid cracks in the weld and the heat-affected zone due to the greater hardening tendency.

2) Cr17 series stainless steel welding rods: Welding rods such as G302 and G307 are Cr17 series stainless steel welding rods with a ferritic structure. When using this series of stainless steel welding rods to weld ferritic stainless steel, the weldment should be preheated to 200°C before welding, and the welding Finally, the weldment must be tempered 800%. Only by taking the above process measures can we avoid the embrittlement of the weld and the heat-affected zone at 475°C and the occurrence of cracks due to the large hardening tendency.

(2)Chromium-nickel stainless steel welding rod

This type of welding rod has good corrosion resistance and oxidation resistance. However, due to repeated heating during the welding process, the precipitated carbides will reduce the corrosion resistance and mechanical properties. Therefore, when selecting chromium-nickel stainless steel welding rods, welding should be considered. The working temperature of the parts and the type of media, etc.