High reamer steel quality appraisal

high hole expansion steel is based on the core principles of ultra-fine grain strengthening and retained austenite control. By optimizing the chemical composition and heat treatment process, it achieves the synergy of high strength and excellent hole expansion performance. It is widely used in automobile lightweighting, engineering machinery, rail transit and other fields. In automobile manufacturing, it is used for door anti-collision beams, A/B pillars and other safety structural parts; in the field of engineering machinery, it achieves high-strength and lightweight design of hydraulic supports; in rail transit, it meets the fatigue life requirements of high-speed train bogies. Compared with ordinary high-strength steel, high-expansion steel has the characteristics of high energy absorption, low yield-to-strength ratio, and good cold formability. It is a key material for achieving safety and lightweight in modern manufacturing.

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

With the widespread application of high-expansion steel in high-end manufacturing fields, quality dispute cases have gradually increased. The judicial dispute focuses on:

1, performance index dispute: whether the actual hole expansion rate meets the standard, and whether the tensile strength meets the design value;

2, material defects: chemical composition deviation, residual austeni Insufficient body content;

3. Process problems: Improper control of the heat treatment process resulted in coarse grains and excessive surface decarburization depth;

4. Contract performance issues: The delivered steel was inconsistent with the technical agreement.

High-expansion steel quality appraisal is a comprehensive work that requires the use of different technical methods according to specific circumstances.

1. Appearance inspection

First, visually inspect the hole expansion machine tool and the high hole expansion steel processed to observe whether there are deformation, cracks, rust and other abnormalities.

2. Dimensional measurement

uses precision measuring instruments to measure the machining accuracy of the reaming machine tool and the size of the high reaming steel to check whether it meets the requirements of relevant standards.

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The applicant, an automobile manufacturing company, and the respondent, a steel company, signed a "Highly Expanded Steel Procurement Contract", agreeing to purchase 500 tons of highly expanded steel with the grade B180H1 for the production of door anti-collision beams. During the processing, the anti-collision beam's hole expansion and cracking rate exceeded 15%, resulting in batch scrapping. The automobile company believed that the steel had quality defects and demanded compensation for losses. The steel company argued that the problem was caused by improper processing techniques, and both parties took the matter to court.

Identification and analysis results:

The quality analysis expert group discussed and comprehensively analyzed the relevant information, contract technical agreements, on-site investigation case materials and other data on "highly expanded steel", and made the following quality analysis opinions:

The manganese content of the highly expanded steel involved in the case is only 1.3% (contract requirements) 1.5%-2.0%), resulting in insufficient hardenability; the retained austenite content is only 3% (standard ≥5%), which cannot effectively alleviate stress concentration during hole expansion. The grain size is coarse (grain size 6, standard ≥ 8), the plastic deformation ability is reduced; the depth of the surface decarburization layer is 0.08mm (standard ≤ 0.05mm), and the local strength is reduced.

The steel company failed to control the manganese content and retained austenite proportion according to the contract. The grains were coarse and the decarburization exceeded the standard, which was the main reason for the problems of high-expansion steel.

High-expansion steel quality appraisal report should include the following content:

1. The purpose and basis of the appraisal.

2. Model, specification, manufacturer and other information of the equipment being identified.

3. Identification method.

4. Identification results (including whether there are quality problems, causes of problems, etc.).