15CrMoG seamless steel pipe and thick-walled large-diameter seamless steel pipe purchase guide

Dear friends, when purchasing 15CrMoG seamless steel pipe or thick-walled large-diameter seamless steel pipe, do you often encounter these problems: Don’t understand the material performance? Can’t understand the specification parameters? Don’t know how to choose due to the large price difference? Don’t worry, I will help you sort out your thoughts!

First, the common pain points of seamless steel pipes

1. Material confusion: What does the "G" in 15CrMoG seamless steel pipe stand for? What is the difference with ordinary 15CrMo seamless steel pipes?

2. Specification selection: How thick is the "thickness" of thick-walled seamless steel pipes? What will be the impact of a larger diameter of seamless steel pipes?

3. Price trap: Why do the quotations of seamless steel pipes with the same nominal value differ by 30% or even more?

4. Quality concerns: How to identify inferior seamless steel pipes? Is ultrasonic flaw detection really reliable?

Second, a practical guide to the purchase of seamless steel pipes

1. Analysis of the material characteristics of seamless steel pipes

15CrMoG is a chromium-molybdenum alloy steel for boilers. "G" means it is dedicated to boilers. Compared with ordinary 15CrMo:

- More stringent control of carbon content (0.12-0.18%)

- Lower phosphorus and sulfur content requirements (≤0.025%)

- High-temperature mechanical properties data must be provided

2. Specification selection tips for seamless steel pipes

Thick-walled large-diameter seamless steel pipes (usually refers to outer diameter ≥219mm, wall thickness ≥20mm) should pay attention to:

- For every 1mm increase in wall thickness, the pressure bearing capacity increases by about 5-8%

- Large-diameter seamless steel pipes are preferably heat-expanded to avoid weld problems

- Common misunderstandings: The thicker the wall thickness of seamless steel pipes, the better. Weight cost and installation difficulty should be considered

3. Four-step method for quality identification of seamless steel pipes

① Look at the surface: The inner and outer walls of high-quality seamless steel pipes are smooth, without cracks or folds

② Dimensions: Measure with a caliper, the tolerance should be within ±1%

③ Check the certificate: Material report and heat treatment record must be provided

④ Test: It is recommended to sample for a water pressure test or ultrasonic test

Suggestions for using and maintaining seamless steel pipes

1. Welding points: 15CrMoG seamless steel pipes need to be preheated to 150-200℃ before welding, and slowly cooled after welding

2. Anti-corrosion measures: Both ends of the seamless steel pipes should be sealed when stored to avoid rust inside the seamless steel pipes

3. Regular inspection: It is recommended to measure the wall thickness of seamless steel pipes every 2 years under high pressure environment