The difference between hot rolled and cold rolled seamless steel pipe

Date:2024-04-16Tags:Seamless steel pipe, SSAW steel pipe, casing and tubing

Seamless steel pipe is a kind of metal pipe, which is characterized by smooth inner and outer surfaces of the pipe wall, no obvious welded joints, and a seamless state as a whole. This kind of pipe is widely used in petroleum, natural gas, chemical industry, electric power, aerospace and other fields. Cold rolling and hot rolling are two commonly used processing technologies in steel pipe production, and they are suitable for the production of steel pipes of different types and requirements. Among them, the hot-rolled seamless pipe is divided into general steel pipe, low and medium pressure boiler steel pipe, high pressure boiler steel pipe, alloy steel pipe, stainless steel pipe, petroleum cracking pipe, geological steel pipe and other steel pipes.Seamless steel pipe, SSAW steel pipe, casing and tubing all require cold rolling and hot rolling manufacturing processes. Cold-rolled seamless steel pipes and hot-rolled seamless steel pipes are two common steel pipe manufacturing processes. They are different in manufacturing methods, performance characteristics and There are obvious differences in the applicable fields.

Seamless Steel Pipe

1.Different production Process

Hot-Rolled Seamless Steel Pipes
These are produced by heating steel billets to high temperatures and rolling them into the desired shape. The process involves extensive deformation at elevated temperatures, resulting in the initial shaping and sizing of the pipe.

Cold-Rolled Seamless Steel Pipes
These pipes undergo further processing at room temperature, involving either cold drawing or cold rolling. The absence of heating in the final stages enables precise control over the pipe's dimensions and surface quality, achieved through plastic deformation.


2.Different performance features:

Cold rolled seamless steel pipe:

Smooth internal and external surfaces: Due to processing at room temperature, the surface of cold-rolled seamless steel pipes is usually smooth.

High dimensional accuracy: The cold rolling process can make the dimensional accuracy of steel pipes higher, which is suitable for occasions with strict dimensional requirements.

Relatively high strength and hardness: Cold-rolled steel pipes usually have high strength and hardness and are suitable for some fields that require high material strength.


Hot rolled seamless steel pipe:

Larger surface roughness: Due to high-temperature processing, the surface roughness of hot-rolled seamless steel pipes is usually large.

Good toughness and ductility: Hot-rolled seamless steel pipes usually have good toughness and ductility, and are suitable for some occasions that require high material toughness.


3.Different applicable fields:

Cold-rolled seamless steel pipe: Cold-rolled seamless steel pipe is often used in the manufacturing of mechanical structures, automotive parts, pressure vessels and other fields that require high dimensional accuracy and surface quality. Due to its smooth surface and high dimensional accuracy, it is suitable for occasions requiring high-precision pipes.

Precision machinery and equipment
Automotive and aerospace industries
Hydraulic systems
Instrumentation and high-pressure pipelines

Hot-rolled seamless steel pipe: Hot-rolled seamless steel pipe is often used in the manufacturing of fluid transportation, petrochemical, natural gas pipelines and other fields that require high strength and wear resistance. Because of its good toughness and ductility, it is suitable for applications requiring high strength and wear resistance.

Transportation pipelines
Structural supports
Large machinery components
Low- and medium-pressure piping systems


4.Size Differences

Hot-Rolled Pipes
Typically larger, with outer diameters exceeding 32 mm and wall thicknesses ranging from 2.5 mm to 75 mm.

Cold-Rolled Pipes
These are generally smaller, with outer diameters as small as 6 mm and wall thicknesses as thin as 0.25 mm. Thin-walled versions can achieve diameters of 5 mm and wall thicknesses below 0.25 mm.


5.Different corrosion resistance properties

There are also differences in the corrosion resistance of hot-rolled seamless pipes and cold-rolled seamless pipes. Due to the presence of defects and oxide layers on the surface of hot-rolled seamless steel pipes, their corrosion resistance is relatively poor. Cold-rolled seamless steel pipes have been processed through multiple processes, resulting in higher surface smoothness and better corrosion resistance. Therefore, cold-rolled seamless steel pipes are usually used where corrosion resistance is required, such as in chemical, petroleum and other industries.


6.Different advantages and disadvantages


Cold-rolled seamless pipe refers to steel plates or steel strips that are processed into various types of steel by cold drawing, cold bending, cold drawing and other cold processing at room temperature.

Advantages:

Fast forming speed, high output, no damage to the coating, can be made into a variety of cross-sectional forms to meet the needs of use conditions; cold rolling can cause steel to produce greater plastic deformation, thereby increasing the yield strength of steel points.

Disadvantages:

1. Although there is no thermoplastic compression during the forming process, there is still residual stress in the cross section, which is bound to affect the overall and local buckling characteristics of the steel;

2. The style of cold-rolled steel is generally open-section, which makes the free torsional stiffness of the cross section low. It is easy to twist when bending, and it is easy to bend and torsional buckling when under pressure, and the torsion resistance is poor;

3. The wall thickness of the cold-rolled steel plate is small, there is no thickening phenomenon at the corners of the plate joint, and the ability to withstand local concentrated loads is weak.

Hot-rolled seamless pipe is relative to cold-rolled seamless pipe. Cold-rolled seamless pipe is rolled below the recrystallization temperature, and hot-rolled seamless pipe is rolled above the recrystallization temperature.

Advantages:

It can destroy the casting structure of the steel ingot, refine the steel grains, eliminate microstructural defects, make the steel structure dense, and improve mechanical properties. This improvement is mainly reflected in the rolling direction, so that the steel is no longer isotropic to a certain extent; bubbles, cracks, looseness, etc. formed during casting can also be welded under high temperature and high pressure.



To sum up, there are obvious differences between cold-rolled seamless steel pipes and hot-rolled seamless steel pipes in manufacturing methods, performance characteristics and applicable fields. Choosing the type of steel pipe that suits your needs can effectively improve the material's performance and economic benefits.

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