What is Cold-Rolled Seamless Steel Pipe?
Cold-rolled
seamless steel pipe & tube is a high-precision, high-performance steel tube made from hot-rolled seamless steel tubes or extruded tubes, precision rolled at room temperature or below recrystallization temperature using a cold rolling mill.
How is it manufactured?
Understanding its manufacturing process is key to understanding its characteristics:
1. Billet Preparation:
Hot-rolled seamless tubes are used as the base tube.
2. Pickling: Removing the iron oxide scale from the surface of the hot-rolled tube.
3. Cold Rolling: Rolling the base tube at room temperature using a cold rolling mill. This is the core process, using immense pressure to induce plastic deformation in the steel tube, reducing its outer diameter, thinning its wall thickness, and lengthening its length.
4. Heat Treatment: Eliminating the work-hardening internal stress generated during cold rolling, restoring the material's plasticity and toughness.
5. Straightening & Finishing: Straightening the steel tube and performing necessary cutting and polishing.
6. Inspection and Warehousing: Strict dimensional, surface, and performance testing is conducted.
Core characteristics of cold-rolled seamless steel pipes:
1. High precision: Outer diameter tolerance can be controlled within ±0.05mm, and inner wall smoothness reaches Ra≤0.8μm, suitable for precision mechanical parts.
2. High strength: The cold work hardening effect increases its tensile strength by 10%-30% compared to hot-rolled pipes. For example, the tensile strength of 20# carbon steel cold-rolled pipe can reach over 500MPa.
3. Thin-wall advantage: Minimum wall thickness can reach 0.5mm (such as ultra-thin tubes for medical devices), while hot-rolled pipes are usually no less than 3mm.
Cold working of steel pipes:
The main cold working methods for steel pipes are
cold drawing and cold rolling. In recent years, with the development of science and technology, a cold spinning method has also been developed. This method can produce large-diameter, high-precision cold-rolled pipes and variable cross-section cold-rolled pipes. The raw materials for cold-worked steel pipes can be hot-rolled seamless steel pipes or welded pipes. The common characteristics of cold-working steel pipes are high dimensional accuracy and good surface roughness, enabling the production of extremely thin-walled pipes (0.05~0.01mm) and extremely fine capillary tubes (0.3~0.1mm in diameter).
Material:
Cold-rolled seamless steel pipes are mainly made of carbon steel, alloy steel, and stainless steel. Carbon steel offers high strength, good wear resistance, and low cost, making it a cost-effective material. Alloy steel incorporates alloying elements such as chromium and molybdenum to improve its corrosion resistance and high-temperature resistance. Stainless steel offers good corrosion resistance and aesthetic appeal.
Specifications:
Cold-rolled seamless steel pipe specifications are generally marked according to outer diameter and wall thickness. Their dimensions are widely ranged, with outer diameters ranging from a few millimeters to several hundred millimeters, and wall thicknesses can be adjusted according to requirements. This flexibility allows them to meet the application needs of various industries. Common outer diameters include φ6mm, φ8mm, φ10mm, φ12mm, φ14mm, φ16mm, φ18mm, and φ20mm, with wall thicknesses typically ranging from 0.5mm, 0.8mm, 1.0mm, 1.2mm, 1.5mm, 2.0mm, 2.5mm, and 3.0mm. Custom thicknesses are also available upon request.
Wall Thickness:
The wall thickness of cold-rolled seamless steel pipes significantly impacts their mechanical properties and service life. Thicker walls allow for greater pressure resistance and strength, but also increase weight and cost. Due to the precise control of the cold-rolling process, wall thickness deviations are minimal, which is particularly important in high-precision applications. Generally, different applications require different wall thicknesses, which must be selected based on specific circumstances.
Mechanical Properties:
The mechanical properties of cold-rolled seamless steel pipes include tensile strength, yield strength, and elongation. Generally, tensile strength is required to be above 400MPa, yield strength above 240MPa, and elongation above 15%. These indicators ensure the durability and safety of the pipe during use.
Quality Inspection: In terms of quality control, cold-rolled seamless pipes require rigorous testing. Common testing items include dimensional measurement, surface defect inspection, and mechanical property testing. Dimensional measurement mainly focuses on whether the outer diameter, wall thickness, and length meet standards; surface defect inspection involves visually inspecting or using instruments to check for cracks, scratches, and other problems; mechanical property testing includes tensile tests and hardness tests to ensure that the strength, plasticity, and toughness of the pipe meet the usage requirements.
Application Areas of Cold-Rolled Seamless Steel Pipes:
Cold-rolled seamless steel pipes are mainly used in machinery manufacturing, automobiles, hydraulic equipment, aerospace, and petrochemical industries, offering advantages such as high precision, high strength, and lightweight.
1. Automobile Manufacturing: In the automotive industry, cold-rolled seamless steel pipes are commonly used to manufacture components such as drive shafts and hydraulic cylinders. These components have high requirements for the strength, toughness, and corrosion resistance of the materials.
2. Machinery Manufacturing: In the machinery manufacturing sector, it is used to produce high-precision bearings or structural components. Due to the high surface finish of cold-rolled seamless steel pipes, subsequent processing such as plating or spraying achieves better adhesion. For example, cold-rolled
precision seamless pipes play a crucial role in high-precision transmission components such as hydraulic systems, lubrication systems, and machine tool guideways.
3. Aerospace: In the aerospace sector, cold-rolled precision seamless steel pipes are widely used in manufacturing key components for aircraft, rockets, and other aircraft. Their high precision and excellent mechanical properties ensure the safety and reliability of aircraft.
4. Petrochemical Industry: The petrochemical industry has high requirements for the corrosion resistance and high-temperature, high-pressure performance of materials, and cold-rolled precision seamless steel pipes are ideal materials that meet these requirements. They are widely used in the manufacture of chemical pipelines, equipment, and containers.
Market Price:
The market price of cold-rolled seamless steel pipes is affected by various factors, such as material, specifications, wall thickness, and industry demand. Taking carbon steel as an example, the general market price is around 4,000-5,000 yuan per ton, while alloy steel and stainless steel are relatively more expensive. Of course, prices will fluctuate depending on changes in the market environment.
Read more: Cold Drawn Seamless Steel Tubing
