Straight seam pipe commonly used knowledge summary

Straight seam pipe refers to weld steel tube and steel tube parallel to the longitudinal. Generally, also known as straight seam welded pipe and straight seam steel pipe [1]. Straight seam pipe is made by high frequency welding machine will be plastic strip rolled steel strip and USES the straight seam welded together. In nominal diameter straight seam pipe specifications, according to the wall thickness can be divided into thin-walled straight seam pipe and thick wall tube two straight. According to the shape can be divided into round, square or shaped tube, etc.

1. The welding

Straight seam pipe generally adopt high-frequency welding, high frequency welding is a kind of induction (or contact pressure welding) welding, it need to weld filler, no welding spatter, narrow welding heat affected zone, weld moulding beauty, weld the advantages of good mechanical performance, thus is widely used in steel production. According to the principle of electromagnetic induction and ac charge in the conductor skin effect and proximity effect and eddy current heating effect, make the edge of the weld steel locally heated to a molten state, the squeezing roller, to realize the joint between the crystal butt weld, so as to achieve the purpose of the welding seam, cooled to form a solid straight seam weld.

2. The weld gap

Will strip into welded pipe unit, the multichannel roll rolling, strip steel rolled up gradually, there is an open space form of round billet, adjust the quantity of the squeezing roller, make the weld gap control in 1 ~ 3 mm, and the joint match on both ends. If clearance is too large, resulting in a decrease of proximity effect, eddy current heat is insufficient, the joint between the weld crystal bad and incomplete fusion or crack generation. Proximity effect such as the gap is too small a result, the welding heat is too big, cause the burning of the weld; Or weld after extrusion, rolling the deep pit formation, affect the surface quality of the weld.

3. The welding temperature

Low carbon steel material, welding temperature control in 1250 ~ 1460 , the wall thickness 3 ~ 5 mm penetration can meet the requirements. Welding temperature is mainly by regulating the high frequency eddy current to control thermal power and welding speed. When the heat input is insufficient, the heated weld edge short of welding temperature, metal organization remains solid, forming not fusion or lack of penetration; When the heat input is too large, weld edge over welding temperature of the heated, burnt or drop, make the weld formation of melt hole.

Welded steel pipe refers to the steel belt or steel plate bending deformation shapes such as round, square before welding, jointed on the surface of steel pipe. Welded steel pipe is made of billet is steel plate or strip.

According to the weld shape classification

Can be divided into straight seam welded pipe and spiral welded pipe

Straight seam welded pipe, simple production technology, high production efficiency, low cost, rapid development.

The strength of the spiral welded pipe, is generally higher than straight seam welded pipe, use a narrow billet production of larger diameter welded pipe, you can also use the same width of billet in the production of different pipe diameter welded pipe. But compared with the same length of straight seam pipe, weld length by 30 ~ 100%, and the production speed is low. As a result, a small diameter welded pipe are mostly with straight seam welding, large diameter welded pipe for the most part adopts spiral welded.

According to the application is divided into general welded pipe, galvanized welded pipe, oxygen blowing metric welded pipe, welded pipe, wire casing, roller tube, deep well pump pipe, auto tube, transformer, electric welding thin wall pipe, welded pipe and spiral welded pipe.

General welded pipe: general welding work for low pressure liquid. Use Q195A, Q215A, Q235A steel manufacturing. Also can be used to other mild steel welding manufacturing. Steel pipe for pressure, bending, flattening and so on experiment, the surface quality is a certain request, usually the delivery length for 4 to 10 m, often required scale (or foot) delivery of the goods. Of the specifications of the welded pipe in nominal diameter (mm or inches) nominal diameter is different from the actual, welded pipe wall thickness by the regulation with ordinary steel pipe and thickening steel pipe, steel pipe and the form of the pipe end points with thread and don't take two.

Galvanized steel pipe: in order to improve the corrosion resistance of steel pipe, galvanized steel pipe (clarinet) commonly. Zinc galvanization steel tube hot dip galvanized and electrical steel, hot dip galvanized zinc coating thickness, electric galvanizing cost is low.

Oxygen tube welding: used for steelmaking oxygen tube, generally with small diameter welding pipe, specifications by 3/8 inch - 2 inch eight. With 8, 10, 15, 20, or Q195 - made of Q235 steel strip. For corrosion protection, some aluminized processing.

Wire casing: are ordinary carbon steel welded steel pipe, used in concrete and various power distribution project, common nominal diameter from 13-76 - mm. Wire set set wall is thinner, mostly for coating or galvanized after use, requirements for cold bending test.

Metric welded pipe, the form of specifications with a seamless tube, expressed in mm outside diameter * wall thickness of welded steel pipe, can use ordinary carbon steel, quality carbon steel or low alloy steel in the tropics, cold welding, or with tropical again after the cold welding method is made. Metric can tube welding points, and thin wall, the common used as a structure, such as transmission shaft, or transmission fluid, thin wall used to make furniture, lamps and lanterns, etc., to ensure that the steel pipe strength and bending test.

Roller tube: used in belt conveyor roller welded steel pipe, Q215, Q235A, B is commonly used in steel and 20 steel manufacture, 63.5 219.0 mm in diameter. Of tube bending, end face to the center line of the vertical, ovality has certain requirements, general water pressure and the flattening test.

Transformer tube: used in the manufacture of transformer radiator pipe and other heat exchanger, using common carbon steel manufacturing, requirement of flattening, flaring, bending, hydraulic test. Steel tube to length or delivery times ruler, steel tube bending has certain requirements.

Special pipe: by ordinary carbon structural steel and 16 mn steel guitar with welded square tube, rectangular pipe, caps, empty plastic steel doors and Windows with steel tube, mainly used for agricultural machinery parts, steel window, door, etc.

Welding thin wall pipe: mainly used for making furniture, toys, lamps, etc. In recent years, with production of stainless steel thin wall pipe application is very wide, senior furniture, decoration, fencing, etc.

Spiral welded pipe, is to put the low carbon carbon structural steel and low alloy steel strip according to certain Angle of helix Angle (called molding) rolled into a tube billet, then pipe seam welding made up, it can use a narrow strip in the production of large diameter steel pipe. Spiral welded pipe is mainly used in oil, natural gas pipeline, its specifications expressed in diameter * wall thickness. Spiral welded pipe with one-side welding and double welding, tube welding shall ensure that the water pressure test, the tensile strength and cold bending properties of the weld in accordance with regulations.

By the end shape classification

Is divided into circular welded pipe and alien (square, flat, etc) welded pipe.