[Chemical composition deviation] quality objection analysis
Case Overview
A manufacturing company purchased a batch of 316L from a supplier, but the inter-company inspection found that the nickel content of this batch of 316L did not meet the standard, so the customer complained to the supplier and raised a quality objection.
Case Study
After receiving the complaint, the supplier immediately arranged personnel for the customer to understand the situation. After preliminary confirmation, it was found that the quality objection raised by the customer was 316L stainless steel imported from North America, the specification was 20×2000×6000mm, and the quantity was one piece. Because the price of 316L is higher, the amount involved in the quality objection is relatively large.
The customer provided two pieces of data to the supplier’s personnel, one is the quality assurance certificate for this batch of 316L stainless steel, which shows that this batch of 316L stainless steel is in accordance with the ASTM standard, and the nickel content is 10.09%; the other is the customer’s test report, showing nickel The content is only 9.81%, which is inconsistent with the warranty. The most important thing is that the test report shows that the nickel content does not meet the ASTM standard.
People in the stainless steel industry know that most of the existing 316L is produced in accordance with American standards, but due to cost considerations, steel mills generally keep the nickel content of their products as low as possible.
my country’s national standard GBT4237-2007 stipulates that the nickel content of 316L is 10-14%, the American standard ASTM A240 stipulates that the nickel content of 316L is 10-14%, and the Japanese standard JIS G4304 stipulates that the nickel content of 316L is 12 ~ 15%. Therefore, there is a 2% difference in nickel content between the national standard and the Japanese standard. The 316L purchased by the customer is in accordance with the American standard, so the nickel content should reach the 10% standard, and the customer’s test result is 9.81%, which is obviously not up to the standard.
However, considering that various elements may have uneven distribution (segregation) during crystallization in the steelmaking process, the chemical composition of the finished product is allowed to have a certain deviation.
Since the complainant did not have the latest relevant American standards on hand, he referred to the “GBT 222-2006 Permissible Deviation of Chemical Composition of Finished Steel” standard.
The standard stipulates that when the nickel content in the steel is greater than 5%, the allowable lower deviation of the nickel content is 0.1%, that is, the minimum nickel content of 316L should not be less than 9.9%. Judging from this standard, the batch of 316L steel plates is still unqualified.
Process Result
Because the batch of 316L steel plates is imported steel plates, the processing procedures are cumbersome. For the sake of insurance, the customer complainant proposed to take samples again, and then go to the local qualified quality inspection department for testing, and then process them after the results are available.
After the inspection by the quality inspection department, the nickel content of this batch of 316L steel grade is 10.03%, which has reached the lower limit specified by the American Standard and is a qualified product.
The customer complaint officer sent the report to the customer to inform the customer that the steel plate can be used safely.
The result of this quality objection was perfect. Both the company and the customers are quite satisfied.