The Technique Requirement of 4145H MOD Steel
1. Chemical composition (%)
4145H
Chemical Composition
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Contents
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C
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0.42-0.49
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Si
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0.15-0.35
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Mn
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0.75-1.15
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P
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≤0.025
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S
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≤0.025
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Cr
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0.75-1.25
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Mo
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0.25-0.35
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Cu
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≤0.35
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2. Smelting method: EAF+LF+VD
3.Forging: The forging ratio shall be not less than 3.0. The shape of forgings shall be according to the requirement of the drawing (rough turned forgings). 。
4. Heat treatment: Quenching & Tempering
5. Machining:
According to the drawing, the externality and dimensions must meet the requirement of the drawing. External surface area: Ra 3.2; Internal surface: Ra 6.3—12.5
6. Mechanical properties (according to ASTMA370 and API7)(in 1” depth under the surface, room temperature):
Tensile strength
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≥931N/mm2
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Yield strength
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≥759N/mm2
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Elongation
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≥13%
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Reduction of area
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≥45%
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V type notch, radial, notch direction, radius direction
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40Ft/Lbs (≥54J)
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7. Hardness:
Surface hardness: 285-341HB (respectively measuring one point in 300mm from both sides)
Under surface 1“hardness:285-341HB
8. Ultrasonic test :As per ASTM A388
9. Surface defects
After final heat treatment and machining, the surface defects shall be checked for each stabilizer.
Test methods: Magnetic test or liquid penetrant inspection or other methods.
Acceptance: There shall be free from surface defects such as cracks, scabs, folds etc. Welding repair shall be forbidden.
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