GB/T 40281-2021Determination of content of nonmetallic inclusions in steel—Extremum analytical method (English PDF)

Foreword

This document is in accordance with the provisions of GB/T 1.1-2020 "Guidelines for Standardization Work Part 1: Structure and Drafting Rules of Standardization Documents" Drafting.

Introduction

The presence of large non-metallic oxide inclusions in steel will cause the decline of the metal's mechanical properties, resulting in unqualified performance. Non-metallic inclusions The test method standards such as GB/T 10561 adopt the comparative method to assess the level. The level and the length of non-metallic inclusions increase exponentially.

Continuous data is difficult to correlate with the fatigue life of parts, and the detected non-metallic inclusions are accidental and the data is discrete. Some research sheets Obviously, the extreme value analysis method applies statistical principles, increases the number of inspections for non-metallic inclusions, and performs statistical analysis on the data, which can be reflected to the greatest extent.

Reflect the distribution of non-metallic inclusions and reduce chance. The extreme value of non-metallic inclusions analyzed by the extreme value analysis method can better reflect the The overall state of the existing non-metallic inclusions is continuously comparable in value, which can establish a correlation with the life of the part.

The extreme value analysis method allows the tester to analyze the maximum value of the endogenous non-metallic inclusions or the second phase in the steel. Under normal circumstances, measurable The largest oxidized inclusion in the tapped sample. If necessary, the maximum value of multiple types of inclusions can also be determined.

Measure the maximum value of oxides, sulfides, silicates, point-shaped non-metallic inclusions, titanium carbonitride and other inclusions. Extreme value analysis method is also available It is used to determine the characteristics of other microstructures, such as the extreme value of the graphite ball size in ductile cast iron, and the maximum value of carbides in tool steel and bearing steel. Large particle size and maximum diameter of crystal grains.

The distribution characteristics of foreign inclusions in steel are not easy to predict, and other non-destructive testing methods, such as ultrasonic flaw detection, should be used to determine.

1 Scope

This document specifies the sample preparation, inclusion inspection, extreme value calculation, extreme value graph drawing, and data for the extreme value analysis method of non-metallic inclusions in steel Effectiveness analysis, difference evaluation and test report, etc.

This document is applicable to the extreme value analysis of non-metallic inclusions in steel, steel ingots and continuous casting slabs. The characteristic values of other microstructures can also be referred to use. This document is not applicable to the extreme value analysis of foreign non-metallic inclusions.

2 Normative references

The contents of the following documents constitute the indispensable clauses of this document through normative references in the text. Among them, dated quotations Only the version corresponding to that date is applicable to this document; for undated reference documents, the latest version (including all amendments) is applicable to this document.

GB/T 10561 Standard Determination of Non-metallic Inclusions in Steel Grading Chart Microscopic Inspection Method

GB/T 13298 Metal Microstructure Inspection Method

GB/T 30067 Metallographic Terms

3 Terms and definitions

The following terms and definitions defined in GB/T 30067 apply to this document.