What is black pipe

The black pipe is jargon sentence of our pipe industry (non standard industry terms). It refers to the seamless steel pipe and welded steel pipe without galvanization and other permanent coating process.The use of steel tube is made in 1815, a Scottish inventor for conveying the lamp with gas and connected the barrel. In 1836, Britain already has the production patent of seamless steel tube extrusion method, but it was not until 1885 that Manmesmann brother invented the process of the bar steel directly producing seamless steel pipe.In terms of welded pipe, patented in 1923, after a low frequency electric resistance welding method and dc welding method, now has entered into the high frequency induction welding times for small diameter steel pipe. In addition, for large diameter steel tube, using U.O. molding process submerged arc automatic welding production for straight seam pipe, and using spiral submerged arc automatic welding production for the forming of spiral steel pipe.

1 seamless steel tubeThe production method of seamless steel pipe is roughly divided into skew rolling and extrusion method. The former method is to use the slant roller punch the tube billet first, and then extend it with the mill. This method is with fast production speed, but also with higher workability requirements for tube bloom, mainly is suitable for the production of carbon steel and low alloy steel pipe. The latter is use piercing mill punch the tube billet or ingot and then make into a steel tube with the extruder. This method is with lower efficiency than skew rolling method, is suitable for the production of high strength alloy steel pipe. Skew rolling and extrusion method must first heat the pipe billet or steel ingot, and the steel pipe produced is called hot-rolled tube.Sometimes according to the needs, the steel pipe by hot working method should get a cold working again. There are two ways of cold working: one kind is cold drawn method, pulling pipe and making steel tube tapering and elongate; Another method is cold rolling, it applies the hot rolling mill invented by the mannesmann brothers invented in cold working. Cold working of seamless steel pipe can improve the dimension precision and processed finish of steel tube, improve mechanical properties of materials, etc.

2 Welded steel pipeThis method is to make the strip steel rolled into a cylindrical, then weld the steel pipe seam together. With the development of welding technology and the increase of the demand for large diameter steel pipe, welded steel pipe production has experienced an alarming development, the world of welded steel pipe production has reached 75% of steel production. Welded steel pipe can be divided into ERW steel pipe, spiral seam submerged arc welding steel pipe, longitudinal UOE seam submerged arc welding steel pipe and so on.