“"Steel grade" and "unified digital code"”

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I recently saw the draft for comments on the new version of 150 on the Internet. In the stainless steel grades, the "unified numerical code" is used. The steel material is represented by a grade and a numerical code. GB/T 17616-1998 "Steel and Alloy Grades Unified Numerical Code System" clearly states that "all those included in* * Standard and industry standard steel and alloy products should be included in both product grades and unified numerical codes, and should be compared with each other. Both representation methods are valid." GB/T 221-2008 "Method for Representation of Steel Product Trademarks" also clearly states: “All included * * Standards and industry standard steel products should be graded according to the grade representation specified in this standard." I have spent a lot of effort to find standards for unified numerical codes, GB∕T 699-1999 "High-quality carbon structural steel" GB∕T 700-2006 "Carbon structural steel" GB∕T 3077-1999 "Alloy structural steel" GB∕T 20878-2007 "Stainless Steel and Heat-Resistant Steel Grades and Chemical Compositions" I only see that these standards match the grades and numerical codes, and there are quite a few that do not, such as low alloy steel, which is also commonly used in our industry. Numerical codes are also divided according to uses, and so are grades, but there are differences in expressions. One day we see two completely different grades, but it is very likely that their chemical composition is the same. To understand the grade, you must also understand the definitions of "steel" and "iron". The more I checked, the more confusing it became, and I really didn’t have the confidence to continue checking. The “source” of expectations is probably gone.