In the case of no bending equipment or single small batch production, the number of elbows is small, and the production of bending die is not economic. In this case, manual bending is used. The main processes of manual bending are sand-filling, scribing, heating and bending.
(1) In order to prevent deformation of steel pipe section, the following main methods are adopted when bending the pipe manually by sand filling: The pipe is filled with fillers (quartz sand, rosin and low melting point alloy, etc.). For larger diameter steel pipes, sand is generally used. Before sand filling, one end of the steel pipe is plugged with a conical wooden plug, and an outlet hole is opened on the wooden plug to allow the air inside the pipe to escape freely when heated and expanded. After sand loading, the other end of the pipe is also plugged with a wooden plug. The sand loaded into the steel pipe should be clean, dry and tight.
For large diameter steel pipe, when it is inconvenient to use the cork, the steel plug plate can be used.
(2) The heating length of the steel pipe is determined by marking
(3) Heating heating can be used charcoal, coke, gas or heavy oil as fuel. Heating should be slow and uniform. The heating temperature of ordinary carbon steel is generally about 1050℃. Cold bending for stainless steel and alloy steel pipe.
(4) The heated steel pipe can be bent on the manual bending device.
Have a core pipe bending
The core bending pipe is to bend the pipe back along the die by using the mandrel on the bender. The function of the mandrel is to prevent deformation of the section of the pipe when it is bent. Mandrel in the form of round head type, pointed head type, spoon type, unidirectional joint type, universal joint type and flexible shaft type.
The quality of a core bend depends on the shape, size and position of the mandrel.
No core pipe bending
Coreless bending pipe is to control the deformation of the steel tube section by using the reverse deformation method on the bender. It makes the steel tube enter the bending deformation area before giving a certain amount of reverse deformation in advance, so that the outer side of the steel tube protruding outwardly to offset or reduce the deformation of the steel tube section during bending, so as to ensure the quality of the bending pipe.
Coreless elbow is widely used. When the bending radius of the steel pipe is greater than 1.5 times of the pipe diameter, coreless bending pipe is generally used. Only for the steel pipe with larger diameter and thinner wall thickness can the core bend be used.
In addition, the method of bending pipe also has the top pressure elbow, medium frequency elbow, flame elbow and extrusion elbow.
Steel pipe is divided into two kinds: seamless steel pipe and seam steel pipe.
(1) seamless steel pipe
Seamless steel pipe is divided into hot rolled pipe, cold drawn pipe, extrusion pipe and so on. According to the shape of the section, it can be divided into two kinds: circular and special-shaped steel pipes, which are square, oval, triangle, star and so on. According to different uses, there are thick walls and thin wall pipes, plates and gold pieces are mostly thin wall pipes.
(2) Steel pipe with seam
Seam steel pipe is also known as welded steel pipe, welded with steel belt, galvanized and not galvanized into two kinds. The former is called white iron pipe, the latter is called black iron pipe.
Steel pipe specifications are expressed as outer diameter and wall thickness in the metric system and inner diameter in inches in the imperial system.
The size marking method of steel pipe is: outer diameter × wall thickness × length, such as pipe D60×10×6000
Connection mode of sheet metal parts:
Custom Sheet Metal Fabrication are composed of many parts, which must be connected in a certain way to form a complete product. The common connection methods are welding, riveting, thread connection and expansion. The connection between the steel pipes also adopts the above methods. About welding, riveting, thread connection
Expansion joint is a method of sealing and fastening by deformation of steel pipe and tube plate. It can use the methods such as mechanical, explosions and hydraulic, to expand the diameter of the steel pipe, steel tube plastic deformation, the tube plate hole wall produce elastic deformation, using the tube plate hole wall of the rebound in steel radial pressure, make steel tube to tubesheet joint has enough expanded joint strength (pulled off force), ensure the joint work (mechanical) steel tube will not be pulled out from the pipe hole. At the same time, it should have good sealing strength (pressure resistance) to ensure that the medium in the equipment will not leak out from the joint under the working pressure.