1. Cutting pain points: What are the “hard bones” of large-diameter seamless steel pipes?
Large-diameter seamless steel pipes (usually refers to outer diameter ≥ 219mm) are prone to three major pitfalls when cutting due to their large diameter and wall thickness (10-100mm):
(1) Poor cutting quality of large-diameter seamless steel pipes: ordinary tools are prone to burrs, skewed bevels, and even cracks in the pipe wall;
(2) Low cutting efficiency of large-diameter seamless steel pipes: manual cutting or non-professional equipment is time-consuming and labor-intensive, and a 10mm wall thick steel pipe may take several hours;
(3) Material waste of large-diameter seamless steel pipes: cutting deviation exceeding ±2mm may cause subsequent welding or assembly to be scrapped.
2. Selection of professional tools for cutting large-diameter seamless steel pipes: Choosing the right “weapon” will get you twice the result with half the effort
- The applicable scenarios of CNC steel pipe cutting machines are batch cutting and high-precision requirements. The advantages of CNC steel pipe cutting machines are error ≤±0.5mm, automatic feeding, and labor-saving. The safety tips of CNC steel pipe cutting machines are that the steel pipes need to be fixed to avoid vibration.
- The applicable scenarios of plasma cutting machines are carbon steel/stainless steel with a thickness of ≤50mm. The advantage of plasma cutting machines is fast cutting speed (100-300mm/min). The safety tips of plasma cutting machines are to wear arc-proof masks and insulating gloves
- The applicable scenarios of grinding wheel cutting machines are temporary operations and small batch cutting. The advantage of grinding wheel cutting machines is low equipment cost. The safety tips of grinding wheel cutting machines are that a cooling system needs to be installed to prevent overheating of pipes.
3. Four-step standardized cutting process of large-diameter seamless steel pipe cutting: zero mistakes from marking to completion
▶ Step 1: Accurately mark the cutting line on the large-diameter seamless steel pipe
- Use an oily marker to draw a circle along the circumference of the large-diameter seamless steel pipe, or use a magnetic scriber to assist, and the error is controlled within ±1mm;
- If a bevel is required (such as for welding), use an angle ruler to mark the 30°-45° inclined line in advance.
▶ Step 2: Adjust the cutting machine parameters
- Carbon steel (Q345B): When the wall thickness is 20mm, the plasma cutting current is adjusted to 200A and the speed is set to 150mm/min;
- Stainless steel (304): Use a CNC pipe cutting machine with a speed of 800rpm and a feed rate of 0.1mm/r to prevent sticking.
▶ Step 3: Smooth cutting of large-diameter seamless steel pipes
- After starting the equipment, advance at a uniform speed along the marked line (if your hands are shaking? You can stick tape on both sides of the large-diameter seamless steel pipe as a guide);
- If there are abnormal sparks (such as splashing) during the cutting process, immediately stop and check the blade wear.
▶ Step 4: Fine finishing of the incision of large-diameter seamless steel pipes
- Use 120-grit sandpaper to grind burrs, or use a portable beveling machine to blunt (R0.5-R1mm);
- If welding is required, wipe the incision oil with acetone to avoid pore defects.
4. A guide to avoiding pitfalls when cutting large-diameter seamless steel pipes: details that 90% of people will ignore
Fix large-diameter seamless steel pipes: Clamp with a V-shaped bracket or chuck. Cutting in mid-air can easily cause deformation of the pipe diameter;
Temperature control: Spray water for cooling when cutting stainless steel (≤60℃) to prevent intergranular corrosion;
Batch quality inspection: Use a vernier caliper to spot-check the verticality of the cut every 10 pipes cut (≤1°).
Finally, a reminder: Cutting large-diameter steel pipes may seem like “rough work”, but it is actually a combination of precision and experience. Newbies can practice with scraps first, and then start formal operations after becoming proficient – efficient cutting starts with choosing the right method!
Post time: Jun-20-2025