Equivalent Grades of Steels

Introduction:

Steels are widely used in the industry and covered by different Standards Development Organizations (SDOs). By time, many of the existing plants need to replace equipment or part of equipment following different standard specification either due to limitation in supply of the original specifications or possibly due to update in company specifications where the old standard organization are no more in use or endorsed. Certainly, some other causes can be added to the aforementioned cases.

There are many different standards for steel grades, depending on the country or region where they are used. Some of the most common ones are ASTM (USA), JIS (Japan), EN (Europe), DIN (Germany), ISO (International), SAE, BS (UK), AFNOR (France), UNI (Italy), GB (China). Each standard has its own system of naming and classifying steel alloys based on their chemical composition, mechanical properties, and applications.?

In this article, I will explore the challenge and proposed approaches to identify the optimized alternative selection between different standards in addition to suggested resources and references can be consulted and used for the selection.

This article is intended to be used as an exploration and discussion starter requesting positive participations and comments to enrich the discussion and to correct any possible mistakes in the followed approach.

Challenges

There is not always a one-to-one correspondence between steel grades from different standards. Sometimes, one standard may have several equivalent grades in another standard, or vice versa. Sometimes, there may be no exact equivalent at all, but only a similar or comparable grade.

One of the big challenges is the limited access to get full material speciation between the different comparable standards, although many manufacturers, suppliers and many pen references are available, but that should be handled carefully as it might include incorrect or incomplete information. ?

There is no direct equivalent grades can be defined between different standards as it usually there is some difference wither in one of the mechanical properties or one or more of the elements in the chemical compositions. At best, one can be able to group comparable or close match steel grades.

Comparison based on mechanical properties can match in some properties while not matching in others, tensile strength can match while yield strength and hardness are not.

Comparison based on chemical composition, can be in some cases misleading as presence of minor impurities or different range of one or more of the alloying elements can have tangible impact either in mechanical properties or corrosion resistance of the material in specific applications.

Method of fabrication in many cases has significant impact on the material usage, for example forged steel due to grain flow the direction of the shape of the forged component increases its strength and toughness as compared to casting of similar (close match) chemical composition.

?Questions and quires on comparison basis

Many questions raised and reported by John E. Bringas in his book "Handbook of comparative world steel standards" shows how the comparison and looking for equivalent grade is a challenging process.

Should mechanical properties or chemical composition be the main criteria? If mechanical properties are compared, which property should be the first criteria for comparison, that is, yield strength, tensile strength, elongation, impact strength, or hardness, etc.? Once having selected a primary criteria, say tensile strength, should there be a secondary criteria for ranking the comparative steels within this group, for example, yield strength, hardness, etc.?

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When mechanical properties or chemical compositions vary with section thickness for a given steel grade, which section thickness data should be selected as the criteria for comparison?

When two steels have the same minimum tensile strength values, but have different yield strength values, are they no longer similar?

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Should comparisons be based on the data's minimum values, maximum values, or average values of their min/max ranges? Should alloy steels and stainless steels be compared on their mechanical properties when they are generally selected for use based on their alloying elements' abilities to provide satisfactory service in their intended applications?

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Is it reasonable to compare steels based only on their chemical compositions, regardless of their product form? That is, should forging steels be compared to steel plates or tubes because they have similar chemical compositions and is this type of comparative data useful in engineering practice?

Suggested Resources for material comparisons:

1. ?Handbook of comparative world steel standards, ASTM DA67A, John E. Bringas.

That is a good reference provides comparative tables based on chemical composition and mechanical properties with consideration of eh product form (structural steel plates, pressure vessel plates, forgings, casting, etc.)

2. TEMA (Tubular Exchanger Manufacturer Association)

Table D-4 includes a cross-reference of materials produced to common international. material specifications. Material. groupings are presented based on similarity of material chemistry and alloying elements.

The table presented with the following alert: "Information presented in this table shall not be considered as permissible allowable substitutions between materials listed. This table serves as a guideline only in locating similar materials for more detailed consideration".

3. ? https://www.totalmateria.com/

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4. MakeItFrom.com: Material Properties Database

That’s a good website that can do comparison between different materials with huge database including chemical composition and mechanical properties in graphical form.

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Please feel free to adjust or add more specifics as needed!

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