Special shape steel pipe is a kind of economic cross section steel tube including non circular cross section, equal-thickness wall, variable wall thickness, symmetrical section, no-symmetrical section, etc. Such as square, rectangle, conical, trapezoidal, spiral, etc. The special shape steel pipe is more suitable for the particular condition of use. And it can save metal and improve the labor productivity of parts and components manufacturing. It is widely used in aviation, automobile, shipbuilding, mining machinery, agricultural machinery, construction, textile and boiler manufacturing and so on. The method to make special pipe including cold drawing, welding, such as extrusion, hot rolling, cold drawing method has been more widely used.
Special shape seamless steel tube is a general term of cross-section shape steel pipes besides the circular tube.
According to the different size of steel pipe cross section shape, it can be divided into equal wall thickness seamless steel tube (code-named D), unequal wall thickness seamless steel pipe (code-named BD), variable diameter seamless steel tube (code-named BJ).
Special shape seamless steel tube is widely used in all kinds of parts, tools and machinery parts. Compared with those of circular tube section tube, it usually have large moment of inertia and section modulus, have bigger bending torsional capacity, and can greatly reduce the structure weight and save steel.
Special pipe is generally distinguished according to the broken section, and according to the material, it can be divided into special pipe seamless steel pipe, aluminum alloy section tube, plastic tube. And in the following, the special shape steel pipe will be introduced.
Special shape steel pipe can be divided into oval shaped steel tube, triangular shaped steel tube, hexagonal shaped steel tube, the diamond shaped steel tube, octagonal shaped steel tube, semicircle deformed steel circle, not equilateral hexagons five disc shaped steel tube, the plum flower form shaped steel tube, double convex shaped steel tube, double concave shaped steel tube, melon seeds shaped steel tube, the cone shaped steel tube, corrugated shape profiled steel pipe.
The forming method is steel pipe bending forming, what we also called bending. Deformed steel tube bending is divided into two kinds, a kind of real bending, another empty bending.
The advantage of rectangular tube bending is that the real solid curve will be relatively small, and it is more accurate, and the production time and roller accuracy as well as the internal rebound after the steel tube forming, we can ensure accurate.
A certain shortcomings of instant bending is that the main stretch of time will lead to a thin steel tube. The real bending rectangular tube bending, the stretch bending of agricultural products, led to the bending line in the direction of the length of the deformed steel tube length is shorter, and the metal content will decrease for stretch.
Empty rectangular pipe bending production, the outside roller with square and the walls of the profiled steel tube, and the metal bending, bending the time of the individual, steel pipe bending line will produce certain compression, compression effect, so the longitudinal variable length zigzag line, rectangular tube bending of metal, will become the thick air bending, compression or thickening effect.
These two kinds of production methods including two basic ways square and rectangular pipe production of profiled steel pipe forming, according to the requirements of different products, select the appropriate process configuration. It is important to note that when stretched and compressed,it may lead to the deformation of rectangular tube.