Standard No.:	TB/T 2478-1993
English Name:	Grading Diagram for Elastic Strip Metallographic Structure
Chinese Name:	弹条金相组织评级图
Chinese Classification:	H24    Metallographic testing method
Professional Classification:	TB    Professional Standard - Railway Transport
Source Content Issued by:	Ministry of Railways
Issued on:	1993-12-18
Implemented on:	1994-7-1
Status:	valid
Target Language:	English
File Format:	PDF
Word Count:	5000 words
Translation Price(USD):	150.0
Delivery:	via email in 1 business day

TB/T 2478-1993 Metallographic grading atlas for spring clips 1 Subject content and applicable scope This standard specifies the technical requirements, inspection methods, and metallographic structure grading atlas for elastic strips metallography. This standard is applicable to the inspection on metallographic structure of 60Si2Mn and 55Si2Mn spring clips in spring-clip type I fasteners. 2 Normative references TB/T 1495.2 Spring-clip type I fasteners 3 Technical requirements 3.1 Martensite The martensite structure in the quenched state shall comply with Grades 1 ~ 4 of the first grading atlas given in this standard, as shown in Table 1. If the martensite morphology is judged by the tempered microstructure, the first grading atlas will apply. 3.2 Residual ferrite The residual ferrite shall be in the form of small particles or lumps, and its area shall not be greater than 2% of the field of view (FOV) area. It shall comply with Grades 1 ~ 2 of the second grading atlas given in this standard, as shown in Table 2. 3.3 Bainite 1 ~ 2 small pieces of bainite are allowed, which shall not be larger than 2% of the field of view area. It shall comply with Grade 1 of the third grading atlas given in this standard, as shown in Table 3. 4 Inspection method 4.1 Sampling position The sampling position shall comply with the requirements specified in 5.3.3 of TB/T 1495.2. 4.2 Assessment methods and results

Contents 1 Subject content and applicable scope 2 Normative references 3 Technical requirements 4 Inspection method 5 Grading atlas of metallographic structure Additional explanation: