Steel pipe quality appraisal

steel pipe is based on the core principles of metallurgical forming and process strengthening. By optimizing the continuous casting and rolling process, heat treatment parameters and surface treatment technology, it achieves the synergy of strength, toughness and corrosion resistance. It is widely used in fields such as oil and gas transportation, building structures, machinery manufacturing and marine engineering. In long-distance pipelines, it is used for high-pressure natural gas transportation; in the construction field, it meets the load-bearing requirements of super-high-rise steel structures; in offshore platforms, it ensures the seawater corrosion resistance and fatigue resistance of pile foundation pipes. Compared with ordinary pipes, steel pipes have the characteristics of high dimensional accuracy, diverse forming processes, and long service life. They are the core materials of modern industry and infrastructure.

Zhongke Testing is a product quality appraisal service organization registered with the court. It can provide steel pipe quality appraisal services. It has a professional appraisal team and advanced instruments and equipment to provide fair and accurate appraisal results for steel pipe quality appraisal.

As engineering safety standards improve, cases of steel pipe quality disputes have increased significantly. The judicial dispute focuses on:

1, performance index dispute: yield strength is not up to standard, low temperature impact energy is insufficient;

2, material defects: carbon equivalent exceeds standard, non-metallic inclusions exceed standard Standard;

3, process problems: out-of-control hot rolling temperature caused banding structure, and welds were not fused;

4, contract performance disputes: material substitution, anti-corrosion coating type did not match the technical agreement.

Steel pipe quality appraisal requires a variety of technical means, mainly including:

1. Appearance inspection: Check whether there are cracks, pits, scratches, rust and other defects on the surface of the steel pipe.

2. Dimensional measurement: Measure the outer diameter, inner diameter, wall thickness, length and other geometric dimensions of the steel pipe, and compare them with standard requirements.

3. Material analysis: Determine the specific material and alloy composition of the steel pipe through spectrometer or chemical analysis.

4. Mechanical property test: Conduct tensile test, bending test, impact test, etc. to measure the mechanical properties such as yield strength, tensile strength, elongation, impact toughness, etc. of the steel pipe.

The applicant, an oil and gas company, and the respondent, a steel pipe factory, signed an "X80 Line Pipe Procurement Contract", agreeing that the yield strength is ≥555MPa. A pipe explosion occurred during construction, and the manufacturer argued that it was due to improper welding by a third party.

identification analysis results:

The quality analysis expert group conducted relevant data on "steel pipes", contract technical agreements, on-site inspection case materials and other data. After discussion and comprehensive technical analysis, the following quality analysis opinions were made:

The pipe body yield strength of the steel pipe involved is only 510MPa, and the carbon equivalent is 0.48% (agreement ≤ 0.43%); the weld heat affected zone hardness HV 280 (standard ≤ 245), banded structure rating 4 (standard ≤ 2); UT testing shows that the base material has a Φ3.5mm delamination defect.

The appraisal conclusion determined that material composition and rolling process defects were the main causes of the pipe explosion.

steel pipe quality appraisal report mainly includes the following contents:

1, purpose of appraisal (such as pipe burst attribution, performance verification) and reference standards;

2, specifications of the steel pipe involved, heat number, usage record;

3. Testing methods and equipment list;

4, analysis of the correlation between test data and failure;