Cold-drawn seamless steel pipe is a precision cold-drawn seamless steel pipe with high dimensional accuracy and good surface finish for mechanical structure and hydraulic equipment. Selecting precise seamless steel pipe to manufacture mechanical structure or hydraulic equipment can greatly save machining time, improve material utilization rate and improve product quality.
In order to obtain seamless steel pipes with smaller size and better quality, cold rolling, cold drawing or both methods must be adopted. Cold rolling is usually carried out on a two-high mill, and seamless steel pipes are rolled in an annular pass formed by a variable cross-section circular groove and a fixed conical plug. Cold drawing is usually carried out on 0.5~100T single-chain or double-chain cold drawing machine.
2. The cold-drawn seamless steel pipe is a product that has emerged in recent years, mainly because the inner hole and outer wall dimensions have strict tolerance and roughness.
Features of cold-drawn (rolled) seamless steel pipe:
1. Smaller outer diameter. 2. High precision can be used for small batch production 3. High precision of cold drawn (rolled) products and good surface quality. 4. The cross area of seamless steel pipe is more complex. 5. The performance of seamless steel pipe is superior, and the metal is relatively dense.Seamless steel pipes for structures(GB/T8162-2008) are seamless steel pipes for general structures and mechanical structures. It is a kind of seamless steel pipe classified according to its different uses. The scope of use includes all kinds of structural seamless steel pipes used in general structures and mechanical structures, as well as a large number of industries such as construction, machinery, transportation, aviation, oil exploitation, etc.
Main differences between annealing and normalizing:
1. The cooling rate of normalizing is slightly faster than that of annealing, and the degree of supercooling is higher 2. The microstructure obtained after normalizing is finer, and the strength and hardness are higher than that of annealing.
Selection of annealing and normalizing:
1. Normalizing is usually used instead of annealing for low-carbon seamless steel pipes with carbon content less than 0.25%. because
For faster cooling rate, it can prevent the low-carbon seamless steel pipe from segregating along the grain boundary and migrating for three times of carburization To improve the cold deformation performance of the stamping parts; Normalizing can improve the hardness of steel
Machinability of carbon seamless steel pipe; When there is no other heat treatment process, normalizing can To refine the grain and improve the strength of low-carbon seamless steel pipe.
2. Medium-carbon cold-drawn seamless steel pipe with carbon content between 0.25 and 0.5% can also be replaced by normalizing
Replace annealing, although the hardness of cold-drawn seamless steel pipe of medium carbon steel close to the upper limit of carbon content is slightly higher after normalizing High, but it can still be cut, and the normalizing cost is low and the productivity is high.3. The cold-drawn seamless steel pipe with carbon content between 0.5 and 0.75% has high carbon content,
The hardness after normalizing is significantly higher than that of annealing, so it is difficult to carry out cutting, so generally Use complete annealing to reduce hardness and improve machinability.
4. High carbon or tool steel with carbon content ＞ 0.75% of cold-drawn seamless steel pipe generally adopts ball Chemical annealing is used as a preliminary heat treatment. If there is network secondary cementite, it should be carried out first Fire elimination. Annealing is to heat the cold-drawn seamless steel pipe to a proper temperature and keep it for a certain time,Heat treatment process with slow cooling. Slow cooling is the main feature of annealing, and annealing and cold drawing are not Generally, the seam steel pipe is cooled to below 550 ℃ in the furnace. Annealing is widely used Extensive heat treatment is often used as preparation in the manufacturing process of tooling or mechanical parts The heat treatment is arranged after casting, forging and welding and before cutting (rough) to eliminate the previous process.Some defects caused by the process, and prepare for the subsequent process.
Annealing purpose: ① reduce the hardness of cold-drawn seamless steel pipe to facilitate machining; ② Eliminate various types Stress to prevent deformation of cold-drawn seamless steel pipe; ③ Refine coarse grains and improve internal structure Prepare for final heat treatment.
Post time: Jan-11-2023