One only needs some superficial knowledge of some existing cast steel specifications and metallurgy in general to understand that stating what one needs is not a simple matter. All requirements must be clearly stated and not taken for granted. This is best achieved through the use of standards and specifications.

definition
In the specification process of steel castings, three key words need to be understood. These are specifications, standards and codes.

Specification
A specification is a form of standard that specifies a precise set of requirements that a casting is to meet. Some of these requirements may be chemical composition, mechanical properties, restoration procedures or any other requirements necessary to improve the casting quality required for its end use. Specifications for steel castings are sometimes extended or limited by standards and codes.

standard
Criteria can be defined as passing through the country
Specifications, test methods, definitions, or recommended practices approved by an accredited specification authoring body such as ASTM (American Society for Testing and Materials), ISO (International Organization for Standards), or SAE (Society of Automotive Engineers). A standard can be further defined as a document detailing properties, processes, dimensions, material compositions, relationships or concepts. This connotation follows Webster's definition of "something established and established by authority as a measure of quantity, weight, range, value, or quality." As can be seen, there is some overlap between codes and standards, so the two terms are often used interchangeably when referring to steel castings.

code
The term "code" has a much broader meaning than a code or standard, and is best described as a set of rules developed by recognized authorities such as the American Society of Mechanical Engineers (ASME), boiler and pressure vessel codes, or the American Standards Institute ( USASI) Pressure Piping Code. In adopting the rules that make up the various norms, considerations are usually based on health, safety and environmental protection. In addition to writing rules, specification bodies often adopt ASTM material specifications in whole or in part as part of the specification.

what can be specified
As mentioned earlier, a specification is a precise statement of requirements. Therefore, any requirement can be specified or incorporated into the specification. The most common will be listed and discussed in the following paragraphs.

It should be emphasized that ASTM specifications take into account all of these requirements and more, so omissions rarely arise when using ASTM specifications.

Ingredient Limits and Tolerances
Most steel casting specifications take into account the chemical analysis of castings, either directly by specifying the analysis or indirectly by specifying an analysis-related property such as hardness or tensile strength, and leave the choice of composition to the foundry. But no matter how you think about it, composition is important. For example, chromium in the various stainless steel grades of ASTM A351 must be within specified limits for predictable corrosion resistance. Other elements of the same grade, such as carbon, nickel and molybdenum, must also be within a range to maintain the balanced microstructure required for the alloy's mechanical strength and to ensure proper corrosion resistance and performance in different environments.

Carbon and low alloy grades with specific chemical ranges are also found in some ASTM specifications such as A216, A217, A487 and others. Most of the grades found in these codes have been evaluated for weldability and mechanical properties at various elevated temperatures and are approved for use in the ASME Code by the ASME Boiler and Pressure Vessel Committee. Since any change in composition may have some effect on weldability and high temperature performance of castings, other grades whose chemical composition may differ only slightly from the approved grade cannot be used to ASME Code.

A148 (High Strength Steel Castings) covers the structural and engineering grades of high strength steel castings. The only chemical requirements in this specification are sulfur and phosphorus. Additional chemical requirements are avoided since no foundry can cast all steel in many modifications. A148 is available in strength levels from 80 ksi to 175 ksi (552-1207 MPa) tensile strength. The chemical composition selected for each grade should take into account the strength level, the size of the section to be cast, the complexity of the design, the heat treatment method and the end use of the casting.

Tolerances for chemical analysis are relatively new to cast steel specifications, although they have been used in other steel products for some time. If a product analysis tolerance is given, only the amount by which the analysis of a sample taken from a casting may deviate from the specified composition range is specified.

Dimensions, weights and tolerances
Parts made from any metal forming process will vary in size and weight. Tolerance is an expression of expected or acceptable variation. Dimensional tolerances shall be included on any casting drawings. Foundry quotes and acknowledgments often mention weight or weight tolerance changes.

Properties and Performance
Wherever possible, steel castings should be purchased based on performance requirements rather than chemical analysis specifications. Most national codes are written in terms of tensile properties, and in some cases hardness values, impact values, and hardenability ranges. This allows the casting engineer to select the alloy composition that best meets the mechanical properties selection.

The mechanical properties of steel castings can be divided into the following categories:

Tensile properties including tensile strength, yield strength, elongation and area reduction.
Impact properties or toughness, usually by Charpy V-notch impact
The energy absorbed during fracture in the test determines, including ductility and strength, usually expressed in "foot pounds" in US specifications.
fatigue properties. Most fatigue test results are represented by a graph of stress versus number of cycles. This plot is often referred to as the "SN" curve, where S is the stress and N is the number of stress cycles leading to failure. The stress level at which failure does not occur, regardless of the number of cycles, is called the durability limit of the material. For steel, testing for 10 million cycles is considered a sufficient guarantee for reaching the limit of durability.
Hardness and hardenability. Hardness and hardenability should not be confused. Hardness is a commonly specified attribute and is a measure of resistance to indentation during hardness testing. Hardenability is a property that determines the depth and distribution of hardness induced by quenching. The importance of mechanical properties at depths below the surface of a casting for a given design determines the importance an engineer must assign to hardenability. Carbon steels are not as hardenable as low alloy steels and should not be used in applications requiring high hardenability.