Some knowledge about seamless steel pipes

1.Definition of seamless steel pipes

Seamless steel pipes,as the name suggests,are steel pipes with no joints along their cross-sectional edges.They are made by punching a solid round steel bar,and have no welding seams on their surface.Seamless steel pipes are usually made by rolling the steel billet directly,which has high strength and pressure resistance,and are widely used in fluid transportation and mechanical manufacturing in high-pressure and high-temperature environments.

The raw materials for the manufacture of seamless steel pipes include carbon structural steel,low-alloy structural steel,alloy structural steel,acid-resistant stainless steel,etc.According to different production methods,seamless steel pipes can be divided into hot-rolled seamless steel pipes,cold-rolled seamless steel pipes,cold-drawn seamless steel pipes,and extruded seamless steel pipes.The specifications of seamless steel pipes are expressed by the outer diameter and wall thickness,and their outer diameter and wall thickness range is wide,which can meet the needs of different fields.

2.Production methods of seamless steel pipes

The production methods of seamless steel pipes mainly include hot rolling,cold rolling,cold drawing,and extrusion.

Hot-rolled seamless steel pipes

Hot-rolled seamless steel pipes are usually produced on automatic rolling mills.First,the solid billet is inspected and surface defects are removed before it is cut into the required length and the end face is centered on the punching machine.Then,the billet is sent to the heating furnace for heating,and is punched on the piercing machine.During the piercing process,the billet rotates and moves forward under the action of the rollers and the punch,and the internal cavity of the billet gradually forms,called the hollow pipe.The hollow pipe is then sent to the automatic rolling mill for further rolling,and finally the wall thickness is evened by the finishing machine and the diameter is determined by the calibrating machine to meet the specifications.Hot-rolled seamless steel pipes are usually delivered in the hot-rolled or heat-treated

Cold-rolled seamless steel pipes are usually produced on two-roll mills.The pipes are rolled in a ring-shaped die made up of a variable-diameter circular hole and a stationary conical head.The production process of cold-rolled seamless steel pipes is more complicated than that of hot-rolled pipes and requires several processes,including pipe blank preparation,acid washing and lubrication,cold rolling,heat treatment,straightening,finishing,and inspection.Cold-rolled seamless steel pipes have higher dimensional accuracy and better surface quality.

Cold-drawn seamless steel pipes are usually produced on single-chain or double-chain cold-drawing machines.During the cold-drawing process,the steel pipe is gradually reduced in diameter and wall thickness to achieve the desired size and accuracy.Cold-drawn seamless steel pipes have high dimensional accuracy and surface quality,making them suitable for manufacturing precision mechanical parts and hydraulic equipment,among other applications.

Cold-drawn or cold-rolled precision seamless steel tubes are used to manufacture mechanical structures and hydraulic equipment,which can greatly save machining time and improve material utilization and product quality.Seamless steel tubes are used to manufacture high-precision structural steel tubes for automobiles,tractors,aviation,etc.,which can improve the stability and safety of machinery.

Extruded seamless steel pipe

The extruded seamless steel pipe is to place the heated tube blank in the closed extrusion cylinder,and the perforating rod and the extrusion rod move together to extrude the extruded part from the smaller die hole.This method can produce steel pipes with smaller diameters and higher dimensional accuracy.

Three,the type of seamless steel pipe

Seamless steel pipes can be divided into many types according to their use,shape and material.

Classification by use

General purpose Seamless steel pipe:used for conveying fluid,structural parts,such as conveying water,gas pipes and structural parts.

Special seamless steel pipe:used for boiler,geological exploration,bearing,acid resistance and other special purposes.Such as seamless steel pipes for boilers,seamless steel pipes for geology and seamless steel pipes for petroleum.

Classification by shape

Round seamless steel pipe:the most common one,used for a variety of fluid transport and structural parts.

Shaped seamless steel pipe:including square,oval,triangle,hexagonal,melon seed,star and other complex shapes,for special purposes.

Classification by material

Ordinary carbon structural steel pipe:used for general fluid transport and structural parts.

Low alloy steel pipe:with high strength and toughness,it is used for fluid transport in high pressure and high temperature environments.

Alloy structure steel pipe:with excellent mechanical properties and corrosion resistance,used in the manufacture of precision mechanical parts and hydraulic equipment.

Stainless acid-resistant steel pipe:with excellent corrosion resistance,used to transport corrosive fluids.

Fourth,the application field of seamless steel pipe

Seamless steel pipe has become an indispensable material in industrial manufacturing due to its excellent performance and wide application fields.

Machine building

Cold-drawn or cold-rolled precision seamless steel pipes are used to manufacture mechanical structures and hydraulic equipment,which can greatly save machining hours and improve material utilization and product quality.Seamless steel pipes are used to manufacture high-precision structural steel pipes for automobiles,tractors,aviation,etc.,to improve the stability and safety of machinery.

Geological drilling

Seamless steel pipe for geological drilling is an important tool for core drilling in geological department,including drill pipe,drill collar,core pipe and so on.The seamless steel pipe has high strength and corrosion resistance,which can meet the complex environment of geological drilling.

shipbuilding

Marine carbon steel seamless steel pipes are used to manufacture pressure piping,boilers and superheaters of ships to ensure the safe operation of ships.Seamless steel pipe can withstand high pressure and high temperature environment to ensure the stability and safety of the ship.

Boiler making

Low and medium pressure boilers and high pressure boilers with seamless steel pipes for the manufacture of boiler superheated steam pipe,boiling water pipe,etc.,to withstand high temperature and high pressure environment.Seamless steel pipe has excellent high temperature and high pressure resistance to ensure the safe operation of the boiler.

Petrochemical industry

Seamless steel tubes for oil drilling and oil cracking are used in furnace tubes and heat exchangers in oil drilling and precision plants to withstand high pressure and corrosive environments.Seamless steel pipe has excellent corrosion resistance and high pressure resistance,ensuring the safe operation of oil drilling and chemical production.

Fluid transport

Seamless steel pipes for fluid transportation are widely used to transport water,oil,gas and other fluids to ensure the safe transportation of fluids.Seamless steel pipe has excellent fluid transport performance to ensure the safe,stable and efficient transport of fluids.

Fifth,seamless steel pipe common problems and solutions

In the process of production and use of seamless steel pipes,some problems are often encountered,such as folding,size aberration,marking,bucket grain and concave.These problems will affect the quality and performance of seamless steel pipes,so corresponding measures need to be taken to prevent and solve.

enfold

Folding refers to the folding of the inner and outer surfaces of the steel pipe in a straight or spiral direction,which appears locally or in a long way on the steel pipe.The main causes of folding are folding or inclusion on the surface of pipe material,serious scratches and cracks.The main way to prevent and eliminate folding is to strictly control the quality of hot rolling perforation and ensure that the surface quality of pipe material is good.

Dimensional overshoot

Dimensional overdifference includes wall thickness overdifference,wall thickness inhomogeneity,diameter overdifference,elliptic eccentricity,etc.The main reasons for the size overdifference are improper selection of drawing die,unreasonable design and manufacture of internal and external die or serious wear.The main methods to prevent and solve the size overdeviation are the correct design and selection of the drawing die and the correct execution of the heat treatment system.

paddle

The scratch refers to the longitudinal straight line scratch on the surface of the steel pipe,the length of the scratch is different,the width is different.The main reasons for the row are the surface of the drawing die is not smooth,and the excessive part of the hammer head is angular.The main way to prevent and solve the row is to improve the surface quality of the drawing die and rinse the steel pipe after pickling.

Pipe pattern

The bucket pattern refers to the uneven ring wave or the same arrangement of the wave one by one on the surface of the steel pipe along the length direction,and appears locally or consistently on the inner and outer surfaces of the steel pipe.The main reasons for the pipe lines are uneven performance after heat treatment,cleaning after pickling and so on.The main way to prevent and solve the dueling pattern is to heat treat,acid wash,phosphating and saponification according to the requirements of the operating procedures.

concave

Concave refers to the longitudinal steel pipe,pipe wall inward strip depression,its length is irregular.The main reasons for the dimple are too large reduction when drawing thin wall steel pipe with or without mandrel,and the edge of the hammer head.The main way to prevent and solve the concave is to choose the appropriate drawing process,and the end of the hammer head should be free from edges and wrinkles.

Conclusion

As an important industrial material,seamless steel pipe plays an important role in various fields.Understanding the definition,production methods,types,application areas and common problems and solutions of seamless steel pipes helps us to better use and maintain seamless steel pipes,improve production efficiency and product quality.I hope this article can provide you with some useful knowledge of seamless steel pipes,so that you have a deeper understanding of seamless steel pipes.