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4340 is a highly alloyed steel with high nickel and chromium content which assures deep hardening when oil quenched, with high strength characteristics throughout the section. Used for heavily stressed parts operating under strenuous conditions.
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TYPICAL ANALYSIS |
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AISI 4340 |
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Carbon (C) |
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.38A43 |
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Manganese (Mn) |
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.60/.80 |
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Silicon (Si) |
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.15/.35 |
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Molybdenum (Mo) |
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.20/.30 |
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Chromium (Cr) |
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70/.90 |
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Nickel (Ni) |
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1.65/2.00 |
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Sulphur (S) |
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.040 MAX |
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Phosphorus (P) |
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.035 MAX |
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HEAT TREATMENT |
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Oil Quenched from |
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1550°F(828°C) |
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Temper as shown:
1 Round (center) |
Tensile |
Yield |
BHN |
RC |
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800° |
208,000 |
200,000 |
415 |
44 |
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1000° |
174,000 |
163,000 |
352 |
38 |
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1200° |
142,000 |
124,000 |
285 |
30 |
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4 Round (1/2 radius) |
Tensile |
Yield |
BHN |
RC |
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800° |
193,000 |
184,000 |
401 |
42 |
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1000° |
170,000 |
159,000 |
341 |
37 |
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1200° |
136,000 |
119,000 |
269 |
28 |
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Quench: 1475° to 1550° |
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Anneal: 1475° to 1700° |
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Available in Annealed and Q&T machinable state.
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