Which of the following designations is not typically associated with a grade of steel?

The designation SAE 74XX is not typically associated with a grade of steel. When analyzing steel grades, the SAE (Society of Automotive Engineers) designations usually follow a numbering system that indicates the chemical composition and characteristics of the steel. For example, in the SAE system:

• The first two digits indicate the major alloying element or elements, with the second digit often signifying the specific type of steel or the range of carbon content.
• The last two digits signify the approximate carbon content of the steel in hundredths of a percent.

In the case of SAE grades like 43XX, 13XX, and 10XX, these designations accurately reflect specific classifications within the broader family of steel types; they include varying amounts of elements like chromium and manganese along with carbon content. However, SAE 74XX does not fit within the established alloying categorization and is not commonly recognized in the same manner as the others, making it the odd one out in the context of steel grades. Understanding the numbering system and its significance provides insight into the properties and applications of different grades of steel.