Classification of seamless steel pipes based on different production processes
2013-07-18
Generally, seamless steel pipes are divided into two types based on the production process: hot-rolled seamless pipes and cold-drawn seamless pipes.
Hot-rolled seamless steel pipes are categorized into general steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, geological steel pipes, and other types of steel pipes. Hot-rolled steel pipes are delivered in a hot-rolled state or heat-treated state; the production process for hot-rolled seamless steel pipes is as follows: pipe blank → heating → perforation → three-roll slant rolling, continuous rolling → pipe removal → sizing → cooling → straightening → hydraulic testing → marking → storage. The raw material for rolling seamless steel pipes is round pipe blanks. The round pipe blanks need to be cut to a length of about 1 meter by a cutting machine and then transported by conveyor belt to the furnace for heating. The pipe blank is heated in the furnace to about 1200 degrees Celsius. The fuel for heating the pipe blank is hydrogen or acetylene. Controlling the temperature inside the furnace is crucial; after leaving the furnace, the pipe blank must go through a perforating machine for perforation. A common type of perforating machine is the conical roller perforating machine for steel tubes; this type of machine has high production efficiency and good product quality with a large expansion diameter and can work with various types of steel. After perforation, the pipe blank undergoes three-roll slant rolling and continuous rolling sequentially. After extrusion, it needs to be removed from the tube for sizing. The sizing machine uses a conical drill bit that rotates at high speed to punch holes into the steel blank, forming a steel tube (the inner diameter of the tube is determined by the outer diameter length of the sizing machine's drill bit). After sizing, the tube enters a cooling tower where it is cooled by water spray; once cooled, it must be straightened. After straightening, it is sent via conveyor belt to a metal flaw detector for internal inspection; if there are any issues such as cracks or bubbles inside the tube, they will be detected. After quality inspection, it also undergoes strict manual selection. Once quality inspection is complete, paint is sprayed on with numbers, specifications, production batch numbers etc., and then it is lifted into storage by a crane.
Cold-drawn seamless steel pipes include not only general steel pipes but also low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking tubes and other types of tubes; they also include carbon thin-walled tubes, alloy thin-walled tubes and stainless thin-walled tubes. Cold-rolled products are delivered in heat-treated condition. The production process for cold-drawn seamless steel pipes includes: pipe blank → heating → perforation → heading → annealing → acid cleaning → oil coating → multiple passes of cold drawing → finished tube → heat treatment → straightening → hydraulic testing → marking → storage. The rolling method for cold-drawn seamless steels is more complex than that for hot-rolled steels; their first three steps in production processes are basically similar. The difference starts from step four: after being hollowed out from round pipe blanks they need to be headed and annealed. After annealing they must undergo acid cleaning using specialized acidic liquids. Following acid cleaning comes oil coating before proceeding through multiple passes of cold drawing. After heat treatment they need to be straightened again before being sent via conveyor belt to metal flaw detectors for internal inspection; if there are any issues such as cracks or bubbles inside these tubes they will similarly be identified during this process.
Shenyang Tengfei Iron Corporation
Shenyang Tengfei Steel Pipe Co., Ltd.
Address: No.6 A 3, No.13 Road, Economic and Technological Development Zone, Shenyang City, Liaoning Province
E-mail:tfwelcome@163.com
Focus on us
