GB/T 5612-2025 Designation of cast irons
1 Scope
This document outlines the classification and designation of cast irons.
This document is applicable to various cast iron materials and castings.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
4 Classification and codes of cast irons
4.1 Classification of cast irons
Based on the morphological characteristics of graphite particles in the metallographic structure of cast iron and the existing forms of carbon within cast iron, cast iron is classified into five major categories: gray cast iron, ductile (spheroidal graphite) cast iron, compacted graphite iron (CGI), malleable cast iron, and white cast iron.
4.2 Codes of cast irons
4.2.1 The basic code for each type of cast iron shall be represented by the initial uppercase Latin letter of its Chinese pinyin abbreviation. The codes for gray cast iron, ductile (spheroidal graphite) cast iron, malleable cast iron, and white cast iron are denoted as HT, QT, KT, and BT, respectively. When two types of cast iron share the same initial letter in their codes, the code for the specific type shall be formed by appending the second lowercase letter of its Chinese pinyin abbreviation after the initial uppercase letter. For example, compacted graphite iron (CGI) is denoted as RuT.
4.2.2 Codes for cast irons with special properties may be composed of the basic cast iron code followed by the initial uppercase Latin letter(s) of the Chinese pinyin abbreviation(s) representing the special property. For instance, HTM denotes wear-resistant gray cast iron, HTR represents heat-resistant gray cast iron, and HTS signifies corrosion-resistant gray cast iron.
4.2.3 Codes for cast irons produced by special processes may be formed by combining the basic cast iron code with the initial uppercase Latin letter(s) of the Chinese pinyin abbreviation(s) representing one or two key words in the name of the special process. For example, QTD denotes austempered ductile iron (ADI), and HTLZ represents continuously cast gray cast iron.
4.2.4 The designations of various types of cast iron are shown in 6.2.
Contents
Foreword
1 Scope
2 Normative references
3 Terms and definitions
4 Classification and codes of cast irons
5 Designation of cast irons
6 Designation example of cast irons
Annex A (Informative) Comparison of cast iron designation with ISO cast iron designation
Bibliography
