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The OnlineMetals Guide to (chromoly) Alloy Steel
Chromoly is an abbreviation for "chromium-molybdenum steel". Chromoly is a range of low alloy steels
used, for example, to produce tubing for bicycle frames and race-car roll cages. It is not as
lightweight as aluminum alloys, but has the advantages of high tensile strength and malleability.
It is also easily welded and is considerably stronger and more durable than standard (1020) steel tubing.
Chromoly contains chromium but it does not have the corrosion resistance of stainless steel.
8620 is a triple-alloy carburizing steel with good toughness and ductility, increased hardness penetration, and
hardneability to a strong, tough, core, with high case-hardness. Weldability is rated as excellent.
| 4130 (Chromoly) Normalized Alloy Steel |
| Minimum Properties |
Ultimate Tensile Strength, psi |
97,200 |
| Yield Strength, psi |
63,100 |
| Elongation |
25.5% |
| Rockwell Hardness |
B92 |
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| 4130 (Chromoly) Annealed Alloy Steel |
| Minimum Properties |
Tensile Strength, psi |
81,200 |
| Yield Strength, psi |
52,200 |
| Elongation |
28.2% |
| Rockwell Hardness |
B82 |
| Chemistry |
Iron (Fe) |
97.3 - 98.22% |
| Carbon (C) |
0.28 - 0.33% |
| Chromium (Cr) |
0.8 - 1.1% |
| Manganese (Mn) |
0.4 - 0.6% |
| Molybdenum (Mo) |
0.15 - 0.25% |
| Phosphorus (P) |
0.035% max |
| Sulphur (S) |
0.04% max |
| Silicon (Si) |
0.15 - 0.35% |
| 4340 (chromoly) Normalized Alloy Steel |
| Minimum Properties |
Ultimate Tensile Strength, psi |
186,000 |
| Yield Strength, psi |
125,000 |
| Elongation |
12.2% |
| Rockwell Hardness |
B100 |
| Chemistry |
Iron (Fe) |
96% |
| Carbon (C) |
0.37 - 0.43% |
| Chromium (Cr) |
0.7 - 0.9% |
| Manganese (Mn) |
0.7% max |
| Molybdenum (Mo) |
0.2 - 0.3% max |
| Nickel (Ni) |
1.83% |
| Phosphorus (P) |
0.035% max |
| Sulphur (S) |
0.04% max |
| Silicon (Si) |
0.23% |
| 8620 (chrome-nickel-moly) Alloy Steel |
| Minimum Properties |
Tensile Strength, psi |
97,000 |
| Yield, psi |
57,000 |
| Brinell Hardness |
201 |
| Elongation |
25% |
| Machinability |
66% |
| Chemistry |
Carbon (C) |
0.18 - 0.23% |
| Manganese (Mn) |
0.7 - 0.9% |
| Phosphorus (P) |
0.35% Max |
| Sulphur (S) |
0.4% Max |
| Silicon (Si) |
0.15 - 0.35% |
| Chromium (Cr) |
0.4 - 0.6% |
| Nickel (Ni) |
0.4 - 0.7% |
| Molybdenum (Mo) |
0.15 - 0.25% max |
At OnlineMetals, we all failed shop class. Multiple times. As a matter of fact, our employment applications
specifically ask to see people's grades for their high school shop classes. If they're too high, they go
into the rejected pile. We're also not engineers, and cannot make any specific recommendations about the suitability
of a given alloy, temper, or shape for your project or application.
All technical data is for comparison purposes only and is NOT FOR DESIGN. It has been compiled
from sources we believe to be accurate but cannot guarantee. This ends the part of the website
that our pointy-headed lawyers made us put in.
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