The manufacturing process of butt welded seamless elbow is divided into two kinds: hot rolling (extrusion) seamless elbow and cold drawing (rolling). Cold drawing pipe is divided into two types: circular pipe and heteroid pipe.
A brief introduction to welding seamless bend process is as follows:
Cold drawing (rolling) : seamless elbow pipe billet and heating to punch to heading, annealing, pickling and oil (copper) and multichannel time cold drawing (cold rolled) to the pipe billet – heat treatment – straightening, hydrostatic test (NDT) – > tag to put in storage.
Hot rolled seamless elbow (extrusion) : the circular pipe billet – heat – perforated – three-roll skew rolling, rolling or extrusion – pipe – sizing (or reducing) – cooling – straightening to hydrostatic test or inspection – > tag, put in storage
Rolling seamless elbow materials are tubular billet, round pipe embryo through cutting machine cutting the growth degree of billet is about one meter, and the conveyor belt to the heating furnace. Billet heating are fed into the furnace, the temperature is about 1200 degrees Celsius. Fuel for hydrogen or acetylene. Furnace temperature control is a crucial problem. Circular pipe billet after going through pressure punch wear empty. General is one of the more common punch is tapered roller puncher, this kind of punch high production efficiency, product quality is good, large amount of perforated hole enlargement, can wear a variety of pipe fittings.
After perforation, circular pipe billet has been three-roll skew rolling, rolling, or pressing. To take off the pipe sizing. After extruding sizing mill by taper drill bits high-speed steel into embryo punching and forming pipe. Pipe diameter by sizing mill bit length to determine the diameter. Pipe after sizing, into the cooling tower, by water spray cooling, pipe after cooling will be straightening. Pipe fittings by the conveyor belt to the metal detection after straightening machine (or water pressure experiment) for internal inspection. If the steel pipe internal crack, air bubble, will be detected. Seamless elbow after also through strict in quality control manual pick. Seamless elbow after quality inspection, spray paint on the serial number, specification, batch number, etc. Seamless elbow and by crane into the warehouse.
Cold drawing (rolling) seamless steel pipe rolling method is more complicated than the hot-rolled seamless elbow (extrusion). They are in the same production process flow of the first three steps. The difference from the fourth step, circular pipe billet after punch to heading, annealing. After annealing to use special acid pickling liquid. After acid pickling, oil. Then followed by cold drawing through multi-channel time (cold) and billet pipe, special heat treatment. After heat treatment, will be straightening. Steel pipe by the conveyor belt to the metal detection after straightening machine (or water pressure experiment) for internal inspection. If the steel pipe internal crack, air bubble, will be detected. After the quality inspection, the steel pipe shall be selected by hand after the quality inspection. After the quality inspection, the steel pipe shall be sprayed with the number, specification and batch number of the paint and shall be hoisted into the warehouse by crane.