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This recommended practice covers five levels of high strength carbon and high strength low-alloy steel plates, bars, and shapes for structural use.

This SAE Recommended Practice covers six levels of high strength carbon and high-strength low-alloy steel plates, bars, and shapes for structural use. The six strength levels are 290, 345, 415, 450, 485, and 550 MPa or 42, 50, 60, 65, 70, and 80 ksi minimum yield point. Different chemical compositions are used to achieve the specified mechanical properties. In some cases there are significant differences in chemical composition for the same strength level, depending on the fabricating requirements. Because the chemical compositions may vary significantly among the producers, despite the required mechanical properties being the same, it is important that the fabricator consult with the producer to determine the relative effects of the producer's composition on the forming, welding, and field service requirements.

Restricted hardenability steels have been in use for some time but the specific restrictions for a particular grade depend upon customer needs and vary from mill to mill. Such steels are desirable to provide more controlled heat treatment response and dimensional control for critical parts. Because of increasing interest in steels with restricted hardenability, the SAE Iron and Steel Technical Committee directed Division 8 to prepare a set of standard steels with restricted hardenability. In general, steels with restricted hardenability (RH steels) will exhibit a hardness range not greater than 5 HRC at the initial position on the end-quench hardenability bar and not greater than 65% of the hardness range for standard H-band steels (see SAE J1268) in the "inflection" region. Generally the restricted hardenability band follows the middle of the corresponding standard H-band. An example of the RH band compared with the standard H-band is given for SAE 4140 in Figure 1.

Restricted hardenability steels have been in use for some time but the specific restrictions for a particular grade depend upon customer needs and vary from mill to mill. Such steels are desirable to provide more controlled heat treatment response and dimensional control for critical parts. Because of increasing interest in steels with restricted hardenability, the SAE Iron and Steel Technical Committee directed Division 8 to prepare a set of standard steels with restricted hardenability. In 1993, the American Society for Testing and Materials (ASTM) adopted the twelve SAE restricted hardenability steels and added ten more. SAE decided to include in SAE J1868 the additional 10 steels. In general, steels with restricted hardenability (RH steels) will exhibit a hardness range not greater than 5 HRC at the initial position on the end-quench hardenability bar and not greater than 65% of the hardness range for standard H-band steels (see SAE J1268) in the "inflection" region.

This document describes the processing and fabrication of carbon and alloy steels. The basic steelmaking process including iron ore reduction, the uses of fluxes, and the various melting furnaces are briefly described. The various types of steels: killed, rimmed, semikilled, and capped are described in terms of their melting and microstructural differences and their end product use. This document also provides a list of the commonly specified elements used to alloy elemental iron into steel. Each element's structural benefits and effects are also included. A list of the AISI Steel Products Manuals is included and describes the various finished shapes in which steel is produced.

Supplementary to the heat or cast analysis, a product analysis may be made on steel in the semifinished or finished form. For definitions and methods of sampling steel for product chemical analysis, refer to SAE J408. A product analysis is a chemical analysis of the semifinished or finished steel to determine conformance to the specification requirements. The range of the specified chemical composition is normally expanded to take into account deviations associated with analytical reproducibility and the heterogeneity of the steel. Individual determinations may vary from the specified heat or cast analysis ranges or limits to the extent shown in Tables 1 through 5. The several determinations of any element in a heat or cast may not vary both above and below the specified range except for lead. Tables 1 through 5 provide permissible limits for various steel forms and composition types.

H steels and their corresponding minimum and maximum hardenability limits are shown for all of the carbon and alloy steels for which there are sufficient hardenability data and for grades that can use the standard end quench test. As hardenability data are accumulated for other grades, this SAE Standard will be revised to include such grades.

All carbon and alloy H-band steels are shown, along with their corresponding minimum and maximum hardenability limits, for which sufficient hardenability data have been established and for grades which use the standard end-quench test. As hardenability data are accumulated for other grades, this SAE Standard will be revised to include such grades.

In 1941, the SAE Iron and Steel Division in collaboration with the American Iron and Steel Institute made a major change in the method of expressing composition ranges for the SAE steels. The plan, as now applied, is based in general on narrower ladle analysis ranges plus certain product (check) analysis allowances on individual samples, in place of the fixed ranges and limits without tolerances formerly provided for carbon and other elements in SAE steels (reference J408). To avoid the possibility of confusion and conflict between SAE and AISI steel designations, all proposed changes in compositions, additions, or deletions of numbers will be coordinated between the two organizations. The compositions in this SAE Standard may apply to open hearth and basic oxygen, or electric furnace steels. Grades shown in Tables 1A and 1B with prefix letter E are normally made by the electric furnace process with maximum limits of 0.035% phosphorus and 0.040% sulfur.