The tolerance can be minimized to ±0.05 for the Inner and Outer diameter. And lower roughess for both inner and outer surface.

Tube can be process freely, and tube is free for bending and flaring.

Tube can be used for hydraulic lines, It can maintain stability and safety in high-pressure environments.

After galvanizing and black phosphating, the corrosion resistance is significantly improved. These surface treatments form an effective protective layer against corrosion.

Top stainless steel (304L, 316L) and carbon Steel(ST35, E235...) used for the production.


The raw material is usually high-quality round steel billet (such as carbon steel or alloy steel).
The steel billet undergoes preliminary inspection to ensure that its chemical composition and quality meet the requirements, such as checking impurity content, hardness, etc.

Heating: The steel billet is heated in a heating furnace to bring it to a plastic state for subsequent processing.
Piercing: The heated steel billet is punched on a punching machine to form a hollow tube. This process usually uses roller perforation to ensure smooth inner walls and reduce initial defects.

The cold drawn process is the core step in producing cold drawn seamless steel pipes and is divided into the following links:

Pickling and Lubrication:
The capillary tube is pickled to remove the oxide scale on the surface, and then coated with lubricant (such as phosphating solution) to reduce friction during cold drawn.

Annealing or normalizing:
The hardness of cold-drawn steel pipes increases and the plasticity decreases, so heat treatment is required to eliminate internal stress and improve mechanical properties.
After heat treatment, steel pipes have good toughness, strength and workability.

Straightening:
The heat-treated steel pipe may be bent, and it must be adjusted to the specified straightness by a straightening machine.
Cutting:
Cut to a fixed length according to customer requirements, and remove burrs from the nozzle.

In order to enhance the anti-corrosion performance and appearance quality of steel pipes, the following treatments are usually performed:

Pickling and phosphating: further improve surface corrosion resistance.
Galvanizing Adding a protective coating to steel pipes, especially useful where high corrosion resistance is required.

Major Inspection Items: Tensile stength, Yield stength, Elongation, Flattenging, Flaring, Chemical analysis Eddy Current Test 100%, Size and surface checking 100%

The raw material is steel coil, and the material can be selected from carbon steel, stainless steel or alloy steel according to the product requirements.
The steel coil is inspected to ensure that its chemical composition, thickness and surface quality meet the standards, and then it is cut into steel strips of specified width.

Forming: The steel strip is gradually bent into a circle or other required cross-sectional shape, such as a square or rectangle, by a forming machine. The continuity of the steel strip will not be destroyed during this process.
Welding: The seams of the steel pipe are welded together using arc welding to form a long welded steel pipe
Seam Treatment: After welding, the weld will undergo internal and external bead removal treatment to ensure the flatness and uniformity of the welding area.

Sizing: The newly welded steel pipe may be slightly deformed. The outer diameter is adjusted by the shaping equipment to make it close to the target size.
Cutting: The steel pipe is cut into a fixed length of rough pipe for subsequent processing.

Pickling: The steel pipe is pickled to remove the surface oxide scale, residual impurities and oil stains in the heat affected zone of welding, and improve the surface cleanliness.
Lubrication: Lubricant (such as phosphating liquid or saponifying liquid) is applied to the surface of the steel pipe to provide good friction conditions for the cold drawing process and reduce surface damage during drawing.

Cold Drawing: The rough pipe is drawn into the required outer diameter and wall thickness through the drawing die at room temperature. The cold drawing process significantly improves the dimensional accuracy and surface finish of the steel pipe.
Multiple Drawing: Depending on the product specifications, multiple cold drawing may be required. Intermediate heat treatment is required after each cold drawing to soften the steel pipe and restore its plasticity.

After cold drawing, the steel pipe will undergo a heat treatment process (such as annealing and normalizing) to eliminate the internal stress during the cold drawing process and improve the mechanical properties.
Heat treatment can improve the strength, toughness and ductility of the steel pipe, while optimizing the performance of the weld area to make it consistent with the base material.

Straightening: After heat treatment, the steel pipe may bend, which is corrected by a straightening machine to ensure that the straightness of the steel pipe meets the standard.
Cutting: The steel pipe is cut into specific lengths according to customer requirements, and the pipe mouth is processed to remove burrs.

The surface of the cold drawn welded steel pipe can be treated in a variety of ways according to application requirements:
Pickling and phosphating: Provide basic corrosion protection.
Galvanizing: A layer of zinc is plated on the surface of the steel pipe to enhance corrosion resistance
Bright treatment: Improve the surface finish through pickling or polishing, suitable for high-demand decoration or precision application scenarios.

ISO 9001 key requirements for precision steel tube production:
Product quality management (Clause 8: Operation)
In the manufacturing process of precision steel tubes, the following requirements are particularly critical:

Customer demand analysis:
Ensure that the dimensional accuracy (such as inner and outer diameter tolerances), surface finish, mechanical properties (such as tensile strength, yield strength) and specific uses (such as hydraulic, pneumatic, etc.) of precision steel tubes are clearly recorded and meet customer requirements.

Process control:
Ensure that all links from raw material selection, cold drawing, heat treatment to surface treatment (such as galvanizing or phosphating) are carried out in accordance with standardized operating procedures.
Key process parameters (such as drawing speed, heat treatment temperature, welding quality) need to be monitored in real time.

Quality inspection and testing:
Define and implement test methods such as dimensional accuracy, pressure resistance, surface defect detection (such as non-destructive testing), and chemical composition analysis.
Regularly calibrate production equipment to ensure accurate and reliable test results.

ASTM – Seamless carbon steel, stainless steel and alloy steel

Application: Precision seamless steel tubes for machining, automotive parts and high-strength structural applications.

Key requirements:
The steel tubes are manufactured by cold drawing or hot rolling to ensure high dimensional accuracy.
Different heat treatment conditions (such as annealing, normalizing, quenching and tempering) are available to meet specific mechanical property requirements.
Covering a variety of steel grades, such as 1020, 1025, 4130 (low alloy steel), etc.
Test methods: Including tensile test, hardness test and dimensional accuracy test.