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AISI/SAE Steel Grade Decoder — Composition, Machinability & Heat Treatment

Decode Any Common Steel Grade for Alloy Chemistry, Properties, and Applications

Free steel grade decoder covering 29 AISI/SAE grades across five families: Carbon, Free-Machining, Alloy, Stainless, and Tool Steel. See alloy composition, machinability rating, heat treatment response, weldability, and applications for each grade.

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Includes composition bar chart, quick-compare mode (2-3 grades side by side), and family filter pills. Designed for machinists, engineers, and purchasing agents decoding grade callouts.

Pro Tip: The first two digits tell you the alloy family (10xx = plain carbon, 41xx = chrome-moly, 43xx = nickel-chrome-moly) and the last two digits are carbon content in hundredths of a percent. A 4140 is chrome-moly with 0.40% carbon. Learn this pattern and you can make educated guesses about any grade.

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AISI/SAE Steel Grade Decoder
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How It Works

  1. Select or Search

    Choose a grade or type a number to search. Organized by family: Carbon, Free-Machining, Alloy, Stainless, and Tool Steel.

  2. Review Composition

    See full alloy chemistry with composition bar chart for visual comparison.

  3. Check Machinability

    Rating shown as percentage relative to AISI 1212 baseline (100%).

  4. Review Heat Treatment

    Notes on heat treatment response and weldability for process planning.

  5. Compare Grades

    Select 2-3 grades for side-by-side comparison table.

Built For

  • Machinists looking up unfamiliar grade callouts before setting speeds and feeds
  • Purchasing agents verifying material certs match specified grades
  • Manufacturing engineers selecting grades based on machinability and properties
  • Tool and die makers choosing tool steel grades for specific applications
  • Welding engineers evaluating weldability and preheat requirements
  • Students learning the AISI/SAE numbering system

Features & Capabilities

29 Steel Grades

Carbon (1018, 1045, 1095), Free-Machining (1215, 12L14), Alloy (4130, 4140, 4340, 8620), Stainless (303, 304, 316, 17-4PH), Tool (A2, D2, O1, S7, H13, M2), and more.

Composition Bar Chart

Visual chart showing percentage of each alloying element (C, Mn, Cr, Mo, Ni, V, W, Si).

Machinability Rating

Percentage relative to AISI 1212 = 100%. Free-machining steels: 125-170%. Stainless/tool steels: 30-60%.

Quick Compare Mode

View 2-3 grades side by side comparing composition, machinability, hardness, and applications.

Family Filter Pills

Color-coded filters for Carbon, Free-Machining, Alloy, Stainless, and Tool Steel families.

PDF Export

Export grade data as branded PDF for material requisitions or training documentation.

Frequently Asked Questions

First two digits = alloy family (10xx plain carbon, 41xx chrome-moly, 43xx nickel-chrome-moly). Last two digits = nominal carbon content in hundredths of a percent. 4140 = chrome-moly with 0.40% carbon.
4340 adds approximately 1.8% nickel to the chrome-moly base, adding toughness and deeper hardenability. 4340 is for critical high-strength applications; 4140 is the general-purpose workhorse.
12L14 contains lead and sulfur that act as chip breakers and internal lubricants. Rates around 170% vs 70% for plain 1018. Tradeoff: poor weldability and environmental concerns with lead.
303 stainless is the free-machining grade, rating about 55-60% vs 36% for 304. Contains sulfur additions that improve chip breaking. Tradeoff: reduced corrosion resistance and poor weldability.
Disclaimer: Data compiled from AISI/SAE standards, ASM Metals Handbook, and industry references. Actual composition varies by manufacturer and heat lot — always verify against the material test report.

Learn More

Machinist

Understanding AISI/SAE Steel Grade Numbers for the Machine Shop

What AISI and SAE steel grade numbers mean, how the 4-digit system works, and how to pick the right grade for machining, welding, and heat treatment.

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