What are the key points for confirming the specifications of cold-drawn steel pipes

Cold-drawn steel pipes are widely used in machinery manufacturing, automotive parts, hydraulic systems, and other fields due to their high precision and good surface quality. However, incorrect specification selection can easily lead to problems such as inability to assemble and substandard performance, resulting in wasted costs and delays in the construction period. The core solution is to "first clarify the requirements, then accurately verify the specifications, and finally verify the compatibility." The following six key confirmation points must be implemented one by one.

First, what are the core dimensional specifications of cold-drawn steel pipes?
Dimensions are the basis for selecting cold-drawn steel pipes. It is necessary to clarify and verify the three core parameters: outer diameter, inner diameter (or wall thickness), and length, to avoid compatibility failures due to tolerance deviations.
(a) Outer diameter and inner diameter (wall thickness) of cold-drawn steel pipes: First, clarify the nominal dimensions required by the design drawings, focusing on verifying the tolerance grade—common tolerance grades for cold-drawn steel pipes are H8 and H9 (outer diameter). It is necessary to confirm whether it is a precision grade or a standard grade.
(b) Length Specifications of Cold-Drawn Steel Pipes: The length of cold-drawn steel pipes is determined based on the actual application scenario, and is divided into fixed length, non-fixed length, or customized length. Note: For fixed-length purchases, it is necessary to confirm whether cutting allowance is included; for customized cold-drawn steel pipes, the length tolerance requirements must be clearly defined to avoid assembly interference or material waste due to length deviations.

Second, what are the material and mechanical properties of cold-drawn steel pipes?
The material of cold-drawn steel pipes directly determines their mechanical properties and applicable scenarios. Buying the wrong material can easily lead to insufficient strength, poor corrosion resistance, and other problems. It is necessary to confirm the material grade, heat treatment state, and performance parameters.
(a)Material Grade of Cold-Drawn Steel Pipes: Clearly define the core components and grade. Common cold-drawn steel pipe materials include 20# and 45# carbon steel, 20Cr and 40Cr alloy structural steel, and 304 and 316L stainless steel. When purchasing, it is necessary to request material certificates from suppliers and verify whether the chemical composition meets the standards to avoid "inferior products being passed off as superior ones." 
(b)Heat Treatment State of Cold-Drawn Steel Pipes: Common states for cold-drawn steel pipes are "cold-drawn state," "annealed state," and "quenched and tempered state." This needs to be confirmed based on processing requirements and operating conditions.
(c) Mechanical Properties of Cold-Drawn Steel Pipes: Key parameters include tensile strength, yield strength, and elongation, which must match design requirements. Sampling testing can be requested during procurement to avoid performance defects affecting safe use.

Third, What are the Surface Quality and Precision Requirements of Cold-Drawn Steel Pipes?
The surface quality and dimensional accuracy of cold-drawn steel pipes directly affect assembly sealing and motion stability. The following indicators need to be carefully checked to avoid failure due to surface defects or precision deviations.
(a) Surface Roughness: Confirmed based on the application scenario. For conventional cold-drawn steel pipes, the surface roughness Ra ≤ 1.6 μm; for precision hydraulic steel pipes, Ra ≤ 0.8 μm; and for mirror finishes, Ra ≤ 0.4 μm. The surface must be checked for defects such as oxide scale, cracks, scratches, and dents, especially on the inner wall. Impurities or burrs may scratch seals and affect the cleanliness of the hydraulic system.
(b) Geometric Accuracy: Focus on verifying the roundness, cylindricity, and straightness of the cold-drawn steel pipe. For standard cold-drawn steel pipes, roundness ≤ 0.05 mm/m and straightness ≤ 1 mm/m; for precision applications, roundness ≤ 0.02 mm/m and straightness ≤ 0.3 mm/m.

Fourth, How to Match the Application and Working Condition of Cold-Drawn Steel Pipes?
Different working conditions place vastly different requirements on cold-drawn steel pipes. Additional requirements must be clearly defined based on the actual application to avoid mismatched specifications and working conditions.
(a) Pressure Conditions: For cold-drawn steel pipes subjected to pressure, the pressure resistance rating must be confirmed. Select the appropriate wall thickness and material based on the working pressure. If necessary, request a hydrostatic test report from the supplier.
(b) Corrosive Environments: If used in humid, acidic, alkaline, or high-temperature corrosive environments, the corrosion resistance of the cold-drawn steel pipe material must be confirmed to prevent premature pipe failure due to corrosion.
(c) Processing Requirements: If subsequent processing such as welding, bending, and tapping of the cold-drawn steel pipes is required, the material processing performance of the cold-drawn steel pipes must be confirmed. Annealed pipes should be selected for bending to avoid breakage due to insufficient plasticity in the cold-drawn state.

Fifth, what are the supplier qualifications and inspection conditions for cold-drawn steel pipes?
There are cases of "non-standard cold-drawn steel pipes masquerading as national standards" in the market. Supplier qualification review and arrival inspection are necessary to ensure specifications meet requirements.
(a) Supplier Qualifications: Prioritize manufacturers with production qualifications and good reputations. Require them to provide business licenses, production licenses, product qualification certificates, quality assurance certificates, etc., clearly defining quality assurance clauses.
(b) Arrival Inspection: Upon arrival, samples must be taken to verify specifications. The outer diameter, wall thickness, and length of the cold-drawn steel pipes should be measured using calipers and micrometers. The surface quality of the cold-drawn steel pipes should be tested using a roughness tester, and the straightness should be tested using a ruler and dial indicator. For critical operating conditions, a third-party testing agency can be commissioned to test the material and mechanical properties of the cold-drawn steel pipes to ensure consistency with procurement requirements. 

Sixth, what details should be paid attention to in the procurement communication of cold-drawn steel pipes?
During procurement communication, the vague requirements for cold-drawn steel pipes need to be clarified to avoid purchasing the wrong product due to unclear expression.
(a) Clarify the standard: Specify the applicable standard. Different standards for cold-drawn steel pipes have different specifications and performance requirements. Avoid deviations caused by defaulting to inconsistent standards.
(b) Specify the unit: Standardize the unit of measurement for cold-drawn steel pipes to avoid specification errors due to confusion in units.
(c) Allow for processing allowance: If the cold-drawn steel pipes require subsequent processing, the supplier must be clearly informed to allow for a processing allowance to avoid insufficient dimensions after processing.