First, what is the significance of determining the length of cold-drawn steel pipes?
In the field of precision machinery manufacturing, the processing quality of cold-drawn steel pipes directly determines the performance stability of the final product. An unreasonable length determination can easily lead to material waste or insufficient subsequent processing allowance. Improper selection of cutting methods can cause problems such as cut deformation and precision deviation, thus affecting the clamping and positioning effect and the finished product qualification rate. Currently, some enterprises have problems such as relying on experience for length calculation and blindly matching cutting parameters during the processing of cold-drawn steel pipes, resulting in low material utilization and high production losses. Therefore, mastering scientific length determination methods and precise cutting and selection techniques is of great practical significance for improving the economy and accuracy of cold-drawn steel pipe processing.

Second, what is the calculation method for determining the length of cold-drawn steel pipes?
Determining the length of cold-drawn steel pipes needs to consider three core objectives: “meeting subsequent processing needs,” “maximizing material utilization,” and “adapting to the pace of mass production,” avoiding cost waste or quality risks caused by considering only one dimension. Specifically, it can be accurately calculated in the following three steps.
2.1 Basic Length Calculation: The basic length calculation uses the design length of the finished product as the core benchmark, overlaying the machining allowance for all processes and the cutting edge loss, to ensure that subsequent processing can fully cover the requirements for defect correction and precision improvement. The core calculation formula is: Cutting Length L = Finished Product Design Length L₀ + Total End Face Allowance of Subsequent Processes ΔL₁ + Cutting Edge Allowance ΔL₂. The determination of each parameter needs to be combined with the characteristics of cold-drawn steel pipe and processing precision requirements:
2.1.1. Finished Product Design Length L₀: Strictly follow the drawing requirements, accurately extract the actual effective length of the final component, and avoid subsequent assembly problems due to dimensional deviations.
2.1.2. Total End Face Allowance of Subsequent Processes ΔL₁: Covers the end face machining allowance for roughing, semi-finishing, and finishing processes, and needs to be adapted according to the precision level. For high-precision parts of IT6-IT7 grade, ΔL₁ is typically 0.2-0.3mm; for parts of ordinary precision, ΔL₁ can be simplified to 0.1-0.2mm to ensure that minor defects on the blank end face and clamping errors can be corrected.
2.1.3. Cutting allowance ΔL₂: Cold-drawn steel pipes have a smooth surface and stable dimensions, resulting in minimal cutting deformation. Therefore, ΔL₂ can be controlled within 0.5-1.0mm. If subsequent heat treatment is required, the upper limit can be appropriately used to allow for minor deformation; if direct machining is required, the lower limit can be used to reduce material waste.
2.2 Batch production optimization: Improving material utilization. In mass production, layout optimization should be performed based on the standard length specifications of cold-drawn steel pipes (commonly 6m, 9m, 12m). Integer programming should be used to determine the number of single long pipes to be cut, maximizing material utilization and reducing short waste.
Optimization Logic: First, calculate the maximum number of cold-drawn steel pipes that can be cut from a single length (rounded to the nearest integer). Then, calculate the remaining material length. If the remaining material length is ≥ 80% of the single-piece cutting length, it can be consolidated into raw materials for small-batch orders. If the remaining material is too short, adjust the single-piece cutting length appropriately to improve overall utilization.
2.3 Special Working Condition Compensation: Addressing Deformation Risks
If the cold-drawn steel pipe requires heat treatment processes such as tempering and quenching, and the material has a strong hardening tendency, an additional 0.1-0.2mm of heat treatment length deformation compensation should be reserved. The compensation amount needs to be determined through preliminary tests to obtain actual deformation data, avoiding insufficient finished dimensions due to length shrinkage after heat treatment.
Furthermore, for parts with extremely high bending requirements, a straightening allowance of 0.05-0.1mm can be reserved when determining the length to ensure that subsequent processing requirements are still met after straightening.

Third, what are the cutting selection techniques for cold-drawn steel pipes?
The cutting of cold-drawn steel pipes requires selecting a suitable cutting method based on wall thickness, precision requirements, and production batch size. Simultaneously, optimizing equipment parameters and standardizing post-processing procedures are crucial to ensure the quality of the cut and lay the foundation for subsequent processing.
3.1 Selection of Cutting Methods for Cold-Drawn Steel Pipes: The core selection logic for cutting methods is as follows: wall thickness determines cutting difficulty, precision requirements determine cutting precision, and batch size determines cutting efficiency. Specific suitable solutions are as follows:
3.1.1. Thin-walled cold-drawn steel pipes (wall thickness ≤ 4mm): Laser cutting or plasma cutting is preferred. These methods result in a very small heat-affected zone (≤ 0.2mm), high cut flatness (perpendicularity deviation ≤ 0.1mm/m), no significant deformation, and can significantly reduce subsequent processing allowances. They are especially suitable for high-precision component blanks (such as precision hydraulic component sleeves). Laser cutting offers higher precision and is suitable for small-batch, high-precision production; plasma cutting offers higher efficiency and is suitable for large-batch processing of thin-walled pipes.
3.1.2. Thick-walled cold-drawn steel pipes (wall thickness > 4mm): High-precision sawing should be used for cutting, balancing efficiency and cost. Flame cutting should be avoided due to its large heat-affected zone (>1mm), which easily leads to oxidation and deformation of the cut, increasing the difficulty of subsequent processing. Manual precision sawing is suitable for small-batch production, while fully automatic CNC sawing is suitable for large-batch production, improving cutting consistency.
3.2 Optimization of cutting equipment parameters for cold-drawn steel pipes: Improving cut quality. Different cutting methods require targeted adjustment of equipment parameters to avoid cut defects caused by improper parameters:
3.2.1. Laser cutting parameters: Power increases with wall thickness; cutting speed is controlled at 1-3m/min; compressed air is used for slag removal to avoid slag buildup on the cut and improve surface finish.
3.2.2. CNC sawing parameters: Use a carbide saw blade (suitable for carbon steel/alloy steel), speed 300-500 r/min, feed rate 0.1-0.3 mm/r; before cutting, use a V-clamp for precise positioning and clamping, with rubber pads placed at the contact points between the clamp and the cold-drawn steel pipe to prevent damage to the pipe surface and to avoid rotational deviation during cutting.
3.3 Post-cutting processing specifications for cold-drawn steel pipes: Ensuring compatibility with subsequent processing.
After cutting, the end face must be treated immediately to avoid affecting subsequent clamping and processing accuracy. Specific procedures:
3.3.1. Burr and slag removal: Grind the cut surface with an angle grinder or file to ensure the end face is free of sharp edges, burrs, and slag, preventing scratches on the clamp or affecting positioning accuracy during clamping.
3.3.2. High-precision end face grinding: For high-precision component blanks of IT6 grade and above, the end face needs to be further ground using a surface grinder to ensure a flatness error ≤0.05mm and a perpendicularity deviation between the end face and the axis of the cold-drawn steel pipe ≤0.1mm/m.
3.4. Rust prevention treatment of cold-drawn steel pipes: After treatment, promptly clean the iron filings from the end face and apply rust-preventive oil or spray rust-preventive primer to prevent rusting at the cut.
3.5 Full-process quality control of cold-drawn steel pipes: reducing scrap rate
3.5.1. Dimensional sampling inspection: Randomly select 3-5 pieces from each batch to check the cutting length accuracy, with deviation controlled within ±0.1mm; if the deviation exceeds the limit, adjust the equipment positioning parameters promptly.
3.5.2. Cut quality inspection: Visually inspect or use a magnifying glass to check the cut for defects such as cracks, delamination, and excessive oxide scale; for products with high precision requirements, use a roughness tester to check the surface roughness of the cut to ensure compliance.
3.5.3. Equipment Calibration: Before starting work each day, check the positioning accuracy of the cutting equipment and the wear condition of the saw blade/laser head. Perform precise calibration regularly to avoid batch quality problems caused by equipment deviations.
3.5.4. Raw Material Management: After cutting, raw materials are classified and labeled according to specifications and batches, and stacked in layers to prevent damage and deformation.