Carbon Steel Butt Weld Pipe Fittings

The production process of carbon steel butt welded pipe fittings is to perforate steel ingots or solid round steel into capillaries, and then undergo a series of processes such as hot rolling, cold rolling or cold drawing.Carbon steel butt weld pipe fittings play an important role in my country’s steel pipe industry.

The Classification Of Carbon Steel Butt Weld Pipe Fittings

Carbon steel butt weld fittings are divided into two categories: hot-rolled and cold-rolled (drawn) steel pipes.

Common Problems And Process Measures When Carbon Steel Butt Weld Pipe Fittings 

Problems that easily occur when welding medium carbon steel butt weld pipe fittings are as follows:

Due to its high carbon content, a hard and brittle martensite structure is easily generated in the heat affected zone during welding, so cold cracks are prone to occur. If the welding materials are improperly selected or the welding process is improperly formulated, the weld is also prone to cold cracks.

During welding, after the base metal with higher carbon content melts, carbon will also be brought into the weld, increasing the carbon content in the welding.

Carbon can intensify the effect of sulfur, phosphorus, etc. in the metal that causes hot cracks, so when welding medium carbon steel, the weld is prone to hot cracks.

In addition, the high carbon content in steel also increases the tendency of CO pores in the weld seam.

Process Measures Of Carbon Steel Butt Weld Pipe Fittings

Since medium carbon steel is prone to defects such as cold cracks and hot cracks during welding, some special process measures need to be taken during welding to achieve normal welding.

Various arc welding methods can be used to weld medium carbon steel. Since medium-carbon steel is mostly used to manufacture machine parts and is not a large-scale welded structure, the electrode arc welding method is most commonly used in production.

In order to prevent cold cracks and hot cracks in welded joints, low-hydrogen electrodes are usually used during arc welding. When the carbon content in the steel is low and the joints are not restrictive, ilmenite or titanium-calcium type electrodes can also be used for welding, but strict process measures must be taken to match.

Preheating before welding is the most effective process measure to prevent cracks . Preheating can not only reduce the cooling rate of the joint to prevent the generation of martensite, but also reduce welding stress and accelerate the diffusion and escape of hydrogen.

It is best to have a U-shaped or V-shaped groove on the weldment, which can reduce the proportion of the base metal melting into the weld. If defects on castings are repaired by welding technology, the shape of the groove dug by the shovel should be rounded to reduce the amount of base metal melting into the weld.

Welding should use DC reverse polarity power supply. During multi-layer welding, since the proportion (mass fraction) of the base metal melted into the first layer of weld can reach up to about 30%, it is advisable to use small-diameter electrodes, low current, and slow welding speeds for welding.

After welding, it is best to undergo stress relief heat treatment immediately after welding. Especially for large thickness weldments, large rigid structural parts and weldments working under dynamic load or impact load. The temperature for stress relief tempering is generally 600~650℃.

The Advantage Of Carbon Steel Butt Weld Pipe Fittings

Carbon steel butt weld pipe fittings are generally lower in strength than seamless steel pipes, but their production process is simple, with high production efficiency, a wide variety of specifications, and low equipment investment.

The production process of straight seam welded pipes is simple, with high production efficiency, low cost, and rapid development. . Narrower billets can be used to produce larger diameter welded pipes, and billets of the same width can be used to produce welded pipes of different diameters.

However, compared with straight seam pipes of the same length, the weld length increases by 30~100%, and the production speed is lower.Therefore, welded pipes with smaller diameters mostly use straight seam welding, while welded pipes with large diameters mostly use spiral welding.

Carbon steel remains the most widely used base material in the metal construction industry, ahead of aluminum and stainless steel materials. Carbon steel’s high strength and low cost make it a popular building material.

Among all metal materials, carbon steel has the best weldability. The biggest welding challenge is to minimize the deformation of the material, so choosing the right welding process is crucial.