--Enhance customer trust and product competitiveness with hierarchical management

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Ⅰ.The necessity of constructing a quality grading system

      As a core material in the industrial field, the quality of seamless stainless steel tubes directly affects equipment safety and service life. In order to meet the needs of different application scenarios, it is recommended to classify the products into three grades, namely, Grade A (Industrial Premium), Grade B (Standard Supplies), and Grade C (Economical Supplies). Through differentiated quality control standards, it can provide customized protection for high-end customers and also take into account the cost control needs of small and medium-sized enterprises.

Ⅱ.Grading quality control standards and core indicators

 

1.Grade A (Industrial Grade)

 

• Chemical composition testing:

Carbon content ≤ 0.08%, chromium content ≥ 18%, nickel content ≥ 10% (in accordance with ASTM A312/A312M standards), and need to be through the X-ray fluorescence spectrometer (XRF) inspection of the whole batch

 

• Mechanical properties:

Tensile strength ≥520 MPa, yield strength ≥210 MPa, elongation ≥35% (refer to GB/T 14976 standard), 10% samples randomly selected from each batch for tensile test

 

• Surface quality:

Inside and outside walls need to be 100% through the eddy current detection (ET test), allowing the existence of ≤ 0.05 mm longitudinal scratches, but no folding, cracks and other defects

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2. Level B (standard supplies)

• Chemical composition testing:

Carbon content ≤ 0.10%, chromium content ≥ 16%, nickel content ≥ 8%, using spectrometer sampling ratio of not less than 30%.

• Mechanical properties:

Tensile strength ≥ 500 MPa, yield strength ≥ 200 MPa, elongation ≥ 30%, 5% of samples sampled in each batch.

• Surface quality:

The inner wall is allowed to exist ≤ 0.1 mm slight pits, the outer wall needs to be visually inspected and magnetic particle flaw detection (MT), the defect rate ≤ 1‰.

 

3. Class C (affordable)

• Chemical composition testing:

Carbon content ≤ 0.12%, chromium content ≥ 13%, nickel content ≥ 5%, sampling ratio of not less than 10%.

• Mechanical properties:

Tensile strength ≥ 480 MPa, yield strength ≥ 180 MPa, elongation ≥ 25%, sampling ratio of 3%.

• Surface quality:

The outer wall allows the existence of ≤ 0.3 mm local scratches, the inner wall defect rate of ≤ 3 ‰, the use of sampling hydrostatic test to verify sealing.

Ⅲ.Key considerations in the quality control process

1.Calibration and maintenance of testing equipment

 

    Zero calibration of spectrometer and tensile testing machine is required before daily start-up, and the influence of environmental temperature and humidity on testing results is recorded.

Quarterly commission a third-party organization to verify the accuracy of the flaw detection equipment (e.g. ET, UT) to ensure that the error range is ≤±2%.

2.Standardization of personnel operations

 

    Quality inspectors are required to hold ISO 9712 NDT certification and regularly participate in ASTM standard update training.

Introducing two-person review mechanism: A-grade products need to have inspection reports independently signed by two senior technicians.

 

3.Batch traceability and archive management

 

    Each batch of products should be accompanied by a unique QR code to record the melting furnace number, rolling parameters and testing data, with an archive cycle of ≥10 years.

For A-grade products, it is recommended to provide online quality traceability system, so that customers can view the whole production process data in real time.

Ⅳ.Prevention and Response Strategies for Quality Problems

1.Analysis of the causes of common defects

 

• Uneven wall thickness: mostly due to roll wear or temperature control misalignment, need to be sampled every 4 hours to check the mill parameters.

• Intergranular corrosion: can be improved by solution treatment (1050-1100 ℃ water quenching), and increase the intergranular corrosion test (ASTM A262 Practice E)

 

2.Customer Complaint Handling Process

 

       Establish a 24-hour response mechanism, provide free third-party re-inspection services (e.g., SGS, TÜV), and if the quality is indeed a problem, pay or exchange goods according to the terms of the contract.

 

Ⅴ.Extension of the marketing value of graded quality control

1.Enhance trust by presenting data

    Publicize the sample of A-grade product test report on the official website and product brochures with typical cases (e.g., a chemical enterprise adopts A-grade pipe and the equipment life is increased by 40%)

2.Customized services to enhance customer stickiness

    Provide “Quality Upgrade Package” option (e.g. increase the proportion of flaw detection for a fee) for B and C grade customers to meet the temporary high standard demand.

Ⅵ.Conclusion

     Through the graded quality inspection system, enterprises can establish high-end brand image with A-grade products and cover multi-level markets with flexible quality control strategies.