National standard seamless steel pipes

National standard seamless steel pipes are made by piercing steel ingots or solid billets to form rough tubes, and then they are made through hot rolling, cold rolling, or cold drawing. National standard steel pipes hold an important position in China's steel pipe industry. According to incomplete statistics, there are currently about 240 national standard steel pipe production enterprises in China, with approximately 250 sets of seamless steel pipe production units, and the annual production capacity is about 4.5 million tons. In terms of caliber,

The raw material for rolling national standard steel pipes is round billets. The round billets are cut by a cutting machine into billets about 1 meter in length and sent to a furnace for heating via a conveyor belt. The billets are sent into the furnace for heating, with the temperature reaching about 1200 degrees Celsius. The fuel used is hydrogen or acetylene. Controlling the temperature inside the furnace is a crucial issue. After the round billets come out of the furnace, they are pierced by a pressure piercing machine. The most common piercing machine is the cone - roll piercing machine. This type of piercing machine has high production efficiency, good product quality, a large diameter expansion during piercing, and can pierce various types of steel. After piercing, the round billets are then successively processed by three - roll cross - rolling, continuous rolling, or extrusion. After extrusion, the pipes need to be stripped and sized. The sizing machine drills holes in the steel billets by a high - speed rotating cone - shaped drill bit to form steel pipes. The inner diameter of the steel pipe is determined by the outer diameter of the sizing machine's drill bit. After sizing, the national standard steel pipes enter a cooling tower and are cooled by water spraying. After cooling, the steel pipes need to be straightened. After straightening, the steel pipes are sent by a conveyor belt to a metal flaw detector (or a hydrostatic test) for internal flaw detection. If there are problems such as cracks or bubbles inside the steel pipes, they will be detected. After quality inspection, the steel pipes also need to be carefully selected by hand. After quality inspection, the steel pipes are painted with numbers, specifications, production batch numbers, etc., and then hoisted into the warehouse by a crane.

Specifications: The specifications of seamless steel pipes are expressed in millimeters of outer diameter * wall thickness.

Specification table of national standard seamless steel pipes

Implementation standards of national standard seamless steel pipes

In addition, there are also GB/T17396 - 1998 (Hot - rolled seamless steel pipes for hydraulic props), GB3093 - 1986 (High - pressure seamless steel pipes for diesel engines), GB/T3639 - 1983 (Cold - drawn or cold - rolled precision seamless steel pipes), GB/T3094 - 1986 (Cold - drawn seamless special - shaped steel pipes), GB/T8713 - 1988 (Precision inner - diameter seamless steel pipes for hydraulic and pneumatic cylinders), GB13296 - 1991 (Stainless - steel seamless steel pipes for boilers and heat exchangers), GB/T14975 - 1994 (Stainless - steel seamless steel pipes for structural purposes), GB/T14976 - 1994 (Stainless - steel seamless steel pipes for fluid transportation), GB/T5035 - 1993 (Seamless steel pipes for automobile half - axle sleeves), API SPEC5CT - 1999 (Casing and tubing specifications), etc.