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A Practical Guide to SAE J404: Chemical Compositions of Alloy Steels
Understanding SAE J404: Scope and Grade List Maintenance
SAE J404, revised in January 2009, defines the chemical composition ranges for SAE alloy steels as cast or heat analysis. The standard dates back to 1941 when SAE and AISI adopted narrower ladle analysis ranges with product (check) analysis allowances, replacing fixed limits without tolerances.
The standard is maintained by the ISTC Division 1 through industry surveys. To be added, a new grade must meet standard SAE grade ranges, have a minimum production of 225 tonnes per year, and be endorsed by at least two users or producers. Grades that fall out of use are deleted by consensus and archived in SAE J1249.
Related SAE standards include J408 (sampling methods), J409 (check analysis variations), J1081 (potential standard steels), and J1268/J1868 (hardenability bands). The SAE AMS Index provides cross-references to aerospace and government specifications.
Chemical Composition Limits and Grade Designations
Table 1 in J404 lists cast or heat chemical ranges for each SAE grade. These limits are subject to permissible variations in product analysis as defined in SAE J409. The standard emphasizes that small quantities of unspecified elements like Cu, Ni, Cr, Mo may be present as incidental elements up to defined maximums.
Key designations and footnotes:
- Prefix E: Electric furnace steel with maximum phosphorus 0.025% and sulfur 0.025% (e.g., E4340, E52100).
- B grades: Boron addition of 0.0005% to 0.003% (e.g., 50B46, 51B60) for enhanced hardenability.
- Silicon: Other ranges permitted by agreement (Footnote 4).
- Lead: Lead additions (0.15-0.35%) for improved machinability (optional).
The table below summarizes selected grades from SAE J404. Always refer to the latest standard for complete data.
| SAE Grade | C (%) | Mn (%) | Cr (%) | Mo (%) | Ni (%) | Si (%) | Notes |
|---|---|---|---|---|---|---|---|
| 4118 | 0.18–0.23 | 0.70–0.90 | 0.40–0.60 | 0.08–0.15 | — | 0.15–0.35 | Low-alloy case-hardening |
| 4130 | 0.28–0.33 | 0.40–0.60 | 0.80–1.10 | 0.15–0.25 | — | 0.15–0.35 | General-purpose structural |
| 4140 | 0.38–0.43 | 0.75–1.00 | 0.80–1.10 | 0.15–0.25 | — | 0.15–0.35 | Quench and tempering |
| 4340 | 0.38–0.43 | 0.60–0.80 | 0.70–0.90 | 0.20–0.30 | 1.65–2.00 | 0.15–0.35 | High-strength alloy |
| 8620 | 0.18–0.23 | 0.70–0.90 | 0.40–0.60 | 0.15–0.25 | 0.40–0.70 | 0.15–0.35 | Carburizing grade |
| 52100 | 0.93–1.05 | 0.25–0.45 | 1.35–1.60 | — | — | 0.15–0.35 | Bearing steel |
🔍 Design Insight: For applications demanding consistent heat treatment response, consider specifying H-steels per SAE J1268 and J1868. These restrict hardenability bands, providing tighter process control. The chemical composition limits in J404 serve as the foundation for these hardenability specifications. Additionally, using electric furnace steels (E prefix) can offer lower phosphorus and sulfur for improved toughness.
⚠️ Common Mistake: Confusing cast (heat) analysis with product (check) analysis. The composition limits in J404 are for heat analysis. When verifying incoming material, use SAE J409 to determine allowable variations from the specified heat limits. Ignoring these tolerances can lead to incorrect material rejection.
Frequently Asked Questions on Alloy Steel Composition Selection
Q1: How are new steel grades added to or removed from SAE J404?
A1: The technical committee conducts industry surveys. A new grade must meet standard SAE range requirements, have a minimum production of 225 tonnes/year, and obtain endorsement from at least two users or producers. Grades that no longer meet usage criteria are deleted by consensus and archived in SAE J1249.
Q2: What does the prefix ‘E’ signify in grades like E4340?
A2: The prefix ‘E’ indicates the steel is normally produced by the electric furnace process, with maximum limits of 0.025% phosphorus and 0.025% sulfur. This provides tighter control of residual elements compared to standard open-hearth or basic oxygen steels.
Q3: What is the difference between heat analysis and product analysis?
A3: Heat analysis (ladle or cast analysis) is taken during steelmaking and represents the intended composition of the entire heat. Product analysis (check analysis) is performed on the final product and may differ within allowances defined in SAE J409. It is essential to use the correct tolerances when evaluating test results.
Q4: How do boron-treated grades (B grades) enhance hardenability?
A4: Boron is added in very small amounts (0.0005% to 0.003%) and significantly increases hardenability, especially in low-carbon steels. This allows deeper hardening during heat treatment without the need for higher-cost alloy additions.
