Submerged arc welding (including submerged arc surfacing and electroslag surfacing, etc.) is a method of welding in which the arc burns under the flux layer. Its inherent advantages of stable welding quality, high welding productivity, no arc and very little fume make it the main welding method in the fabrication of important steel structures such as pressure vessels, pipe section fabrication and box-shaped beams and columns. Although there have been many new welding methods of high efficiency and quality, the application area of submerged arc welding remains unaffected. From the point of view of the share of the weight of the deposited metal of various fusion welding methods, submerged arc welding accounts for about 10%, and has not changed much over the years.
When the wire is determined (usually depending on the type of steel welded), the matching flux becomes the key material, which directly affects the mechanical properties of the weld metal (especially plasticity and low-temperature toughness), crack resistance, the incidence of welding defects and welding productivity. Wire and flux with a weight ratio of wire: flux = 1.1 to 1.6, depending on the type of welded joint, the type of flux used, welding specification parameters. Compared with molten flux, sintered flux dosage is more economical, about 20% less can be used.
China's use of welding volume fluctuates around 50,000 tons, of which 70% is about molten flux, the rest is non-melting flux. Europe and the United States industrial developed countries to non-melting flux is the main, about 80%, 90% or more, but there are still molten flux production and sales, molten flux this lasting productivity with some of its inherent characteristics.
1)The steel pipe has one longitudinal weld, and the inner and outer welds are welded together by one submerged arc welding.
2) After the overall mechanical expansion treatment, the internal stress of the steel pipe is small and evenly distributed, which can effectively prevent stress corrosion cracking and high dimensional accuracy, which is convenient for on-site welding construction.
3)Adopting the process of pre-welding and then finish welding, the welding process is stable and the quality of the weld is high.
4)The weld seam is easy to realize nondestructive testing in the production process and nondestructive testing review in the field during use.
5)Large range of product specifications, can produce both small diameter, large wall thickness and large diameter, large wall thickness of the steel pipe.
Steel strip or steel plate is bent and deformed into a round, square shape and then welded into a steel pipe with a seam on the surface. The billet used for welded steel pipe is steel plate or strip.
1.According to different welding methods can be divided into electric arc welding pipe, high frequency or low frequency resistance welding pipe, gas welding pipe, furnace welding pipe, Bundy pipe, etc.
Electric welded steel pipe: used in oil drilling and machinery manufacturing, etc.
Furnace welded pipe: can be used as water and gas pipe, etc. Large diameter straight seam welded pipe is used for high pressure oil and gas transmission, etc.; spiral welded pipe is used for oil and gas transmission, pipe piles, bridge piers, etc.
2.According to the shape of the welded seam, it can be divided into straight seam welded pipe and spiral welded pipe.
Longitudinal welded pipe: simple production process, high production efficiency, low cost, faster development.
Spiral welded pipe: generally higher strength than LSAW, can produce larger diameter welded pipe with narrower billet, also can produce different diameter welded pipe with the same width of billet. But compared with the same length of straight seam pipe, the weld length increases by 30~100% and the production speed is lower.
Therefore, most of the smaller diameter welded pipes are straight seam welded, and most of the large diameter welded pipes are spiral welded.
The applications of square welded steel pipe are construction, machinery manufacturing, steel construction projects, shipbuilding, solar power generation support, steel structure engineering, power engineering, power plants, agricultural and chemical machinery, glass curtain walls, automobile chassis, airports, boiler construction, highway railings, housing construction, etc.