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US 11,767,572 B1Granted
Alloy steel having excellent hydrogen embrittlement resistance and strength and method of manufacturing same
AssigneesHyundai Motor Company, Kia Corporation
InventorHyun Je Sung
Life of this patent
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Abstract
Disclosed are an alloy steel including boron (B) to provide improved hardenability, cobalt (Co) to provide improve strength, and the method of preparing the alloy steel. In particular, components of the alloy steel composition are appropriately mixed to form 100 vol % of tempered martensite as a constituent structure, thereby exhibiting excellent hydrogen embrittlement resistance and strength.
Claims9
An alloy steel composition, comprising:
- 0.2 wt % to 0.5 wt % of carbon (C),
- 0.1 wt % to 0.5 wt % of silicon (Si),
- 0.6 wt % to 0.9 wt % of manganese (Mn),
- 0.001 wt % to 0.03 wt % of phosphorus (P),
- 0.001 wt % to 0.01 wt % of sulfur (S),
- 0.001 wt % to 0.1 wt % of aluminum (Al),
- 0.001 wt % to 0.3 wt % of copper (Cu),
- 0.6 wt % to 2.5 wt % of chromium (Cr),
- 0.001 wt % to 0.5 wt % of nickel (Ni),
- 0.05 wt % to 1.0 wt % of molybdenum (Mo),
- 0.01 wt % to 0.3 wt % of vanadium (V),
- 0.01 wt % to 0.1 wt % of niobium (Nb),
- 0.01 wt % to 0.1 wt % of titanium (Ti),
- 0.001 wt % to 0.005 wt % of calcium (Ca),
- 0.001 wt % to 0.005 wt % of magnesium (Mg),
- 0.001 wt % to 0.01 wt % of oxygen (O),
- 0.001 wt % to 0.015 wt % of nitrogen (N),
- 0.0113 wt % to 0.0197 wt % of boron (B),
- 0.01 wt % to 0.1 wt % of cobalt (Co), and
- a remainder of iron (Fe) and other unavoidable impurities,
- all the wt % are based on the total weight of the alloy steel composition,
- wherein the alloy steel has a microstructure comprising tempered martensite, and a fraction of the tempered martensite is 100 vol % at a temperature of 15° C. to 25° C. based on an area fraction, and
- the alloy steel satisfies Relation 1 below:
- Notch tensile strength ratio (MPa)×tensile strength (GPa)≥0.75, [Relation 1]
- wherein in the Relation 1, the notch tensile strength ratio is a value obtained by dividing a notch tensile strength in a hydrogen-charged atmosphere by a notch tensile strength in a general ambient atmosphere.
22 more elements
A method of manufacturing an alloy steel, comprising:
- providing an alloy steel slab comprising, based on a total weight thereof, 0.2 wt % to 0.5 wt % of carbon (C), 0.1 wt % to 0.5 wt % of silicon (Si), 0.6 wt % to 0.9 wt % of manganese (Mn), 0.001 wt % to 0.03 wt % of phosphorus (P), 0.001 wt % to 0.01 wt % of sulfur (S), 0.001 wt % to 0.1 wt % of aluminum (Al), 0.001 wt % to 0.3 wt % of copper (Cu), 0.6 wt % to 2.5 wt % of chromium (Cr), 0.001 wt % to 0.5 wt % of nickel (Ni), 0.05 wt % to 1.0 wt % of molybdenum (Mo), 0.01 wt % to 0.3 wt % of vanadium (V), 0.01 wt % to 0.1 wt % of niobium (Nb), 0.01 wt % to 0.1 wt % of titanium (Ti), 0.001 wt % to 0.005 wt % of calcium (Ca), 0.001 wt % to 0.005 wt % of magnesium (Mg), 0.001 wt % to 0.01 wt % of oxygen (O), 0.001 wt % to 0.015 wt % of nitrogen (N), 0.0113 wt % to 0.0197 wt % of boron (B), 0.01 wt % to 0.1 wt % of cobalt (Co), and a remainder of iron (Fe) and other unavoidable impurities, wherein all the wt % are based on the total weight of the alloy steel composition;
- primary heat treating the alloy steel stab;
- manufacturing an alloy steel by secondary heat treating the alloy steel slab at a temperature equal to or higher than an A3 transformation point;
- austenitizing the alloy steel by subjecting the alloy steel to cooling, third heat treating, and maintenance;
- cooling the austenitized alloy steel;
- and
- tempering the cooled alloy steel by fourth heat treating,
- wherein the alloy steel has a microstructure comprising tempered martensite, and a fraction of the tempered martensite is 100 vol % at a temperature of 15° C. to 25° C. based on an area fraction, and
- the alloy steel satisfies Relation 1 below:
- Notch tensile strength ratio (MPa)×tensile strength (GPa)≥0.75 [Relation 1]
- wherein in the Relation 1, the notch tensile strength ratio is a value obtained by dividing a notch tensile strength in a hydrogen-charged atmosphere by a notch tensile strength in a general ambient atmosphere.
8 more elements
Dependencies are inferred from the claim text.