As the foundation and key component of modern industry and major engineering equipment, steel casting has gradually developed towards large-scale, complex, precision, high strength, toughness, and high corrosion resistance with the development of material technology and manufacturing processes. The international standard for steel casting, as a technical standard document guiding the standardized production of steel casting enterprises, has also absorbed the achievements of advanced materials and manufacturing processes, forming a complete technical standard system, Can meet the needs of different industries and service environments for steel castings. The international standard for steel castings is not only the basic basis for ensuring the production, quality control, and inspection of steel castings, but also provides a judgment basis for international trade and acceptance of steel castings.
1. International standard system for steel casting
The International Organization for Standardization’s Technical Committee on Steel Casting (ISO/TC17/SC11) has issued 21 international standards and is currently revising 4 international standards (ISO4991, ISO4993, ISO11970, and ISO16468). The current international standard classification for steel castings is shown in Table 1, which includes 9 material standards for steel castings, 8 standards for chemical composition, surface quality, and internal quality testing methods for steel castings, 4 basic standards for welding process specifications for steel casting, and general technical conditions for delivery acceptance. These standards regulate the chemical composition and mechanical properties of steel castings, and informative appendices related to material properties in the standards are available for reference by designers, Helps designers select materials for use. At the same time, it will further promote the research, manufacturing, and promotion of steel casting in China, provide technical basis for scientific research, product design, and standardized production of enterprises, facilitate technical cooperation, product evaluation, and academic exchange among enterprises of various countries, establish a stable production and operation order, and promote international technological exchange and trade development, which will play an important role.
| Classification | Standard number | Standard name |
| Cast steel materials | ISO 4991:2015 | Steel castings for pressure purposes |
| Cast steel materials | ISO 9477:2023 | High strength cast steels for general engineering and structural purposes |
| Cast steel materials | ISO 10679:2019 | Steels — Cast tool steels |
| Cast steel materials | ISO 11972:2023 | Corrosion-resistant cast steels for general applications |
| Cast steel materials | ISO 11973:2023 | Heat-resistant cast steels and alloys for general applications |
| Cast steel materials | ISO 13521:2023 | Austenitic manganese steel castings |
| Cast steel materials | ISO 13583-2:2023 | Centrifugally cast steel and alloy products — Part 2：Heat-resistant materials |
| Cast steel materials | ISO 14737:2021 | Carbon and low alloy cast steels for general applications |
| Cast steel materials | ISO 19960:2023 | Cast steels and alloys with special physical properties |
| Test method | ISO 4986:2010 | Steel and iron castings — Magnetic particle testing |
| Test method | ISO 4987:2010 | Steel and iron castings — Liquid penetrant testing |
| Test method | ISO 4992-1:2020 | Steel castings — Ultrasonic testing — Part 1：Steel castings for general purposes |
| Test method | ISO 4992-2:2020 | Steel castings — Ultrasonic testing — Part 2：Steel castings for highly stressed components |
| Test method | ISO 4993:2015 | Steel and iron castings — Radiographic testing |
| Test method | ISO 11971:2010 | Steel and iron castings — Visual testing of surface quality |
| Test method | ISO 13520:2023 | Determination of ferrite content in austenitic stainless steel castings |
| Test method | ISO 19959:2010 | Steels, nickel alloys and cobalt alloys investment castings — Visual testing of surface quality |
| Basic universal | ISO 4990:2023 | Steel castings — General technical delivery requirements |
| Basic universal | ISO 11970:2016 | Specification and qualification of welding procedures for production welding of steel castings |
| Basic universal | ISO 13583-1:2023 | Centrifugally cast steel and alloy products — Part 1：General testing and tolerances |
| Basic universal | ISO 16468:2015 | Investment castings (steel，nickel alloys and cobalt alloys) — General technical requirements |
The ISO standard system for steel castings is mainly classified based on material chemical composition, main characteristics, uses, and testing methods. The ISO technical standard system for steel castings is similar to the technical standard system for steel casting in China. In terms of basic standards such as digital imaging, metallographic inspection, and casting repair welding, China has made pioneering work, such as GB/T 43409 “Metallographic Inspection of Carbon Steel and Low Alloy Steel Casting for General Engineering and Structural Purposes”, GB/T 39638 “X-ray Digital Imaging Inspection of Castings”, GB/T 38222 “Metallographic Inspection of Medium and High Strength Stainless Steel Casting for Engineering Structures”, and GB/T 13925 “Metallographic Inspection of Cast High Manganese Steel”, These standards stipulate the organization and inspection methods of steel casting materials, which is a significant difference between China’s standard system and the ISO standard system for steel casting. China places more emphasis on the development of basic general standards and digital imaging standards, solves the problem of missing industry development standards, guides the application of new technologies in the steel casting industry, and lays the foundation for China to lead the revision of international standards in the future.
2. Research and analysis of international standards for steel casting
2.1 Material standards for steel casting
There are 9 current international standards for steel casting materials, as shown in Table 2. Among them, the international standard project ISO 4991 led by China for revision is currently in the DIS stage. According to the development of steel casting technology, ISO/TC17/SC11 timely updates the standards for steel casting materials, incorporates new and commonly used grades into international standard documents, defines the chemical composition range of materials, and strictly limits harmful elements, greatly improving the performance of steel casting materials to meet the needs of industrial development.
| Default | Standard name | Changes from the previous version |
| ISO 4991:2015[11] | Pressure bearing steel castings | a) All tables have updated the grades: “G240 and G280” to “GP240GH and GP280GH”; Delete “GX2CrNiN18-10 and GX5CrNi19-9”; Add “GX10CrMoV9-1, GX2CrNiN19-11, and GX5CrNiNb19-1”; b) Changes have been made to the P, S, and V content components in Table 1; c) Table D.1 in Appendix D provides the corresponding relationship between the approximate cast steel grades of UNS and ISO standards. |
| ISO 9477:2023[2] | High strength cast steel for general engineering and structural purposes | a) Added Chapter 3 Terminology and Definitions; b) In Chapter 6 (formerly Chapter 5), the requirement for silicon content was removed. |
| ISO 10679:2019[3] | Casting tool steel | a) Added grades to Tables 1, 2, and Appendix A; b) If available, the UNS number has been added to Appendix A. |
| ISO 11972:2023[4] | General purpose corrosion-resistant cast steel | a) Added Chapter 3 Terminology and Definitions; b) Changed the format of the header for “Table 1 Chemical Composition” (representation of mass fraction%); c) Chapter 8 “General Delivery Conditions Requirements” has been added, and the specific requirements should comply with the requirements of ISO 4990. |
| ISO 11973:2023[5] | General purpose heat-resistant cast steel and alloys | a) Added Chapter 3 Terminology and Definitions; b) Chapter 4 “General Delivery Conditions Requirements” has been added, and the specific requirements should comply with the requirements of ISO 4990; c) Appendix A has added a corresponding relationship to “ISO casting grades similar to UNS casting grades”; d) Added the maximum operating temperature for general purpose heat-resistant cast steel and alloys. |
| ISO 13521:2023[6] | Austenitic manganese steel castings | a) Updated according to the latest changes in ISO guidelines; b) Revised normative reference documents; c) Revised Chapter 5 Heat Treatment Technical Requirements. |
| ISO 13583-2:2023[7] | Centrifuge cast steel and alloy castings Part 2: Heat resistant materials | a) Updated normative reference documents; b) Updated according to the latest changes in ISO guidelines. |
| ISO 14737:2021[8] | General purpose cast carbon steel and low alloy | a) Insert new comments in the scope; Renumber Attachment B’s previous Note 1 as Note 2; b) Add Chapter 3 “Terms and Definitions”; c) Footnote “a” has been added to GE200, GS200, GE240, and GS240 in Table 1 to limit the content of chromium, molybdenum, nickel, vanadium, and copper, consistent with EN 10293; d) The thickness correction values of G10MnMoV6-3 in Table 2, t; e) Correction of tempering temperature range for G25NiCrMo2-2. |
| ISO 19960:2023[9] | Special physical properties alloy cast steel | a) Changed the unit in Table 2 (changed from “N/mm2” to “MPa”); b) Change the grade “GX5Ni36S” to “GX5NiS36” in Table 4. |
2.2 Testing Method Standards
The current international standard for testing steel casting includes 8 items, as shown in Table 3. At present, the international standard ISO 4993 is being revised and the project is in the FDIS stage. The standard system for testing methods for steel castings is mainly classified based on non-destructive testing techniques, metallographic methods, and magnetic methods.
| Default | Standard name | Changes from the previous version |
| ISO 4986:2020[10] | Magnetic particle testing of cast steel and cast iron parts | a) Added the definition of non-linear display (SM) in 6.1.2; b) Add “Calibration (AM) indication” in sections 6.1.3, 6.2.3, 6.2.4, 7.1.3, and Appendix C. |
| ISO 4987:2020[11] | Penetration testing of cast steel and cast iron parts | a) 6.1.2 defines isolated nonlinear displays; b) Changed the definition of aligned linear display in 6.1.3. |
| ISO 4992-1:2020[12] | Ultrasonic testing of steel castings – Part 1: General purpose steel castings | a) Added new definitions for “outer layer” (3.6) and “unmeasurable size” (3.8); b) The general principle requirement of “maximum allowable size of defects” has been added (see 4.3.1); c) Redrawn the “wall thickness zoning” diagram; d) Corrected legend 8 in Figure A.1 for the corresponding sound beam diameters of probes with various sound path and near-field lengths. |
| ISO 4992-2:2020[13] | Ultrasonic testing of steel castings Part 2: High strength steel castings | a) Added new definitions for “outer layer” (3.6) and “unmeasurable size” (3.8); b) The general principle requirement of “maximum allowable size of defects” has been added (see 4.3.1); c) Redrawn the “wall thickness zoning” diagram; d) New addition of “measuring the size of defects in the direction of wall thickness using an oblique probe”; e) Corrected legend 8 in Figure B.1, which corresponds to the sound beam diameter for various sound path and near-field length probes. |
| ISO 4993:2015[14] | Radiographic testing of cast steel and cast iron parts | a) Chapter 12 (Record Retention Requirements) has been deleted; b) Added B.3 (using higher radiation energy to reduce contrast), B.4 (beam hardening), and B.5 (thickness equalization); c) Delete C.3 “Light alloys and copper”. |
| ISO 11971:2020[15] | Visual inspection of surface quality of cast steel and cast iron parts | a) Add Chapter 2 “Normative References” and Chapter 3 “Terms and Definitions”; b) Revisions to Chapter 5 (previously Chapter 3) regarding the use of SCRATA comparators in cast iron castings; c) Move the previous versions of Tables 3 and 4 to a new Appendix A. |
| ISO 13520:2023[16] | Determination of ferrite content in austenitic stainless steel castings | ASTM A799 and BNIF 345 appear as references |
| ISO 19959:2020[17] | Visual inspection of surface quality of investment castings, steel castings, nickel alloy castings, and cobalt alloy castings | a) Added Chapter 3 “Terms and Definitions”; b) Chapter 7 “Test Report” has been added. |
(1) According to commonly used non-destructive testing techniques, ISO 4992-1 “Ultrasonic testing of steel castings – Part 1: General purpose steel castings” and ISO 4992-2 “Ultrasonic testing of steel castings – Part 2: High strength steel castings” are classified by ultrasonic testing, ISO 4993 “Radiographic testing of cast steel and cast iron castings” is classified by radiographic testing, and ISO 4986 “Magnetic particle testing of cast steel and cast iron castings” is classified by magnetic particle testing, ISO 4987 “Penetration Testing of Cast Steel and Iron Castings” is classified by penetration testing. With the development of eddy current testing technology, China should actively propose new international standards for eddy current testing to fill the gap in eddy current testing technology standards.
(2) ISO 11971 “Visual inspection of surface quality of cast steel and iron parts” and ISO 19959 “Visual inspection of surface quality of nickel alloy and cobalt alloy parts of investment casting steel parts” are classified by visual inspection. With the development of foreign trade, there is an increasing demand for product quality, which not only requires superior performance and reliable internal quality, but also increasingly strict requirements for the surface quality of steel casting.
(3) ISO 13520 “Determination of Ferrite Content in Austenitic Stainless Steel Castings” is classified by metallographic, magnetic, and chemical composition methods. This standard specifies the method for determining the ferrite content in austenitic iron chromium nickel alloy castings, and the chemical composition of castings controls the content of the second phase of ferrite within the specified range. This standard specifies the methods for determining the content of ferrite, including chemical composition method, magnetic method, and metallographic method.
In recent years, with the development of detection technology and equipment, X-ray digital imaging technology represented by CT and DR has rapidly developed. Defect automatic recognition technology represented by intelligent detection has been widely applied in large-scale casting enterprises. New technologies such as eddy current testing, acoustic emission testing, infrared testing, and diffraction time difference ultrasonic testing have begun to be promoted and applied.
2.3 Basic General Standards
The current four universal international standards for steel casting foundations are shown in Table 4. Two international standards are currently being revised: ISO 11970 and ISO 16468 are in the CD stage. ISO/TC17/SC11 places great emphasis on the updating speed of basic standards. The revision process will be initiated around 3 years, and the standard age of international standards will be controlled within 5 years to facilitate better communication and cooperation among countries.
| Standard number | Standard name | Changes from the previous version |
| ISO 4990:2023 [18] | General technical conditions for delivery of steel castings | a) Revised the definition of 3.1 heats; b) Added 4.2 ordering information; c) Changed 6.2.3.3 shape, dimensions, and dimensional tolerances; d) Revised the inspection content in A.1.3; e) Changed the component deviation of Table 1 products. |
| ISO 11970:2016 [19] | Specification for welding process flow of steel castings | I have redrawn Figure 1 (welding pit section), Figure 2 (welding joint), and Figure 3 (welding specimen), making the annotations on the drawings clearer and easier to understand. |
| ISO 13583-1:2023 [20] | Centrifuge cast steel and alloy castings – Part 1: General tests and tolerances | a) Updated normative reference documents; b) Updated according to the latest changes in ISO guidelines. |
| ISO 16468:2015 [21] | General technical requirements for investment castings, steel castings, nickel alloy castings, and cobalt alloys | a) Updated normative reference documents; b) Revised the definition of investment castings (see 3.3); c) Removed the definition of the mold shell; d) Revised ultrasonic testing requirements (see 10.6). |