Why do some stainless steels have numbers like “4Cr13” and “40Cr13”? If you’ve ever wondered about these codes, you’re not alone. This article clarifies that 4Cr13 and 40Cr13 are essentially the same material but named differently based on the standards from different times. Discover how their carbon and chromium content impact their properties and applications, such as in cutting tools and valve seats. By the end, you’ll understand the nuances between these steel grades and how to read their designations.
“4Cr13” and “40Cr13” refer to the same material, but they are named differently based on the standards used in different time periods.
4Cr13″ is the material grade specified in the GB1220-92 national standard for Stainless Steel Bars. It is a high-hardness, wear-resistant stainless steel often used for cutting tools, nozzles, valve seats, and other applications.
“40Cr13” is the material grade listed in the GBT1220-2007 national standard for Stainless Steel Bars. This standard was issued on May 14, 2007, and went into effect on December 1, 2007, replacing the GB1220-92 standard.
Similarly, the relationship between 1Cr13 and 12Cr13, 2Cr13 and 20Cr13, and 3Cr13 and 30Cr13 is the same as previously described.
4Cr13 reads: four chromium thirteen;
40Cr13 reads: four zero chromium thirteen.
The number “4” in 4Cr13 represents the carbon content, which is 0.4%. This value can be expressed as 4‰, where “4” is the molecular equivalent of 4‰. The carbon content of 4Cr13 falls within a range specified by the national standard, with an average of 0.405% (calculated as the average of 0.36% and 0.45%).
The number “13” in 4Cr13 represents the chromium content, which is 13%. This value is the average of the range specified by the national standard for chromium content in 4Cr13, which is between 12% and 14%.
The number “40” in 40Cr13 represents the carbon content, which is 0.4%. This value can be expressed as 40‰, where “40” is the molecular equivalent of 40‰. The composition comparison table of martensitic stainless steel 40Cr13 is attached for reference.
| Unified numerical code | New grade | Old grade | Chemical composition (mass fraction)/% | ||||||
| C | Si | Mn | P | S | Ni | Cr | |||
| S41010 | 12cr13 | 1Cr13 | 0.08-0.15 | 1 | 1 | 0.04 | 0.03 | （0.6） | 11.5-13.5 |
| S42020 | 20Cr13 | 2Cr13 | 0.16-0.25 | 1 | 1 | 0.04 | 0.03 | （0.6） | 12-14 |
| S42030 | 30Cr13 | 3Cr13 | 0.26-0.35 | 1 | 1 | 0.04 | 0.03 | （0.6） | 12-14 |
| S42040 | 40Cr13 | 4Cr13 | 0.36-0.45 | 0.6 | 0.8 | 0.04 | 0.03 | （0.6） | 12-14 |
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