Analysis of the production process of 40Cr thick-walled steel pipes from material selection to finished products

Dear friends, as an "old steel" who has been working in the steel pipe industry for many years, I know that the production process of 40Cr thick-walled steel pipe is a "mystery" for many buyers and engineers. Today I will use the most down-to-earth way to take you to understand the birth process of this "steel warrior".

First, common pain points of 40Cr thick-walled steel pipes in production

1. Difficult material selection: Improper control of the alloy composition of 40Cr steel will lead to poor subsequent heat treatment effects and substandard strength

2. Uneven wall thickness: The most feared thing about thick-walled steel pipes is that the wall thickness deviation of 40Cr thick-walled steel pipes is large, affecting mechanical properties and service life

3. Internal stress problem: The internal stress generated during the cooling process will cause the 40Cr thick-walled steel pipe to deform or even crack

4. Surface defects: Common pitting, cracks, and other problems seriously affect the appearance and quality of 40Cr thick-walled steel pipes

Second, the entire production process of 40Cr thick-walled steel pipes

1. Raw material preparation

- Select 40Cr round steel billets, strictly control the carbon content at 0.37-0.44%, and the chromium content at 0.80-1.10%

- Use a spectrometer for component detection to ensure that the material meets the standard

- Shot blasting the billet surface to remove oxide scale and impurities

2. Heating and perforation

- Use a step-beam heating furnace to heat to 1200-1250℃

- Use a piercing machine for hot piercing to form a hollow tube

- Key control points: heating uniformity, piercing temperature, and speed

3. Rolling forming

- Use a three-roller oblique rolling mill for hot rolling, gradually reducing the wall and increasing the diameter

- Real-time monitoring of wall thickness during rolling, and control of the deviation within ±5%

- Use an online thickness gauge and laser measurement system to ensure dimensional accuracy

4. Heat treatment process

- Normalizing treatment: heating to 850-880℃, air cooling after insulation

- Quenching and tempering treatment: quenching (830-850℃ oil quenching) + high temperature tempering (500-650℃)

- Hardness is controlled at HRC28-32 to ensure comprehensive mechanical properties

5. Finishing and inspection

- Straightening machine for straightness correction

- Ultrasonic flaw detection to detect internal defects

- Water pressure test to verify pressure bearing capacity

- Finally, anti-rust treatment and packaging are carried out

Third, practical suggestions for 40Cr thick-walled steel pipes

1. Procurement tips: Require suppliers to provide complete material reports and heat treatment records

2. Precautions for use: Preheat to 150-200℃ before welding, and cool slowly after welding

3. Storage suggestions: Store in a dry environment and avoid contact with corrosive substances