High-strength bainitic steel

Abstract

A high-strength steel alloy and automotive components produced therefrom, as well as a method for forming a steel alloy, are provided. The high-strength steel alloy includes iron, about 0.24 to about 0.80 weight percent carbon, about 0.40 to about 2.10 weight percent manganese, about 0.20 to about 1.60 weight percent silicon, about 0.05 to about 0.14 weight percent sulfur; about 0.10 to about 12.0 weight percent chromium, about 0.10 to about 2.50 weight percent nickel, and about 0.02 to about 0.07 weight percent aluminum. The steel alloy may also include boron, molybdenum, titanium, niobium, and / or nitrogen. The method includes air quenching a steel alloy component after mold shakeout until the component reaches a temperature in the range of 420 to 530 degrees Celsius.

Description

FIELD[0001]The present disclosure relates generally to steel alloys, and more particularly, to high-strength steel alloys and casting processes for forming them, as well as components made therefrom, such as crankshafts.INTRODUCTION[0002]An engine's crankshaft converts reciprocating linear movement of a piston into rotational movement about a crank axis to provide torque to propel a vehicle, such as but not limited to a train, a boat, a plane, or an automobile. Crankshafts are a vital part of an engine, and are a starting point of engine design. Crankshaft design affects the overall packaging of the engine, and thereby the total mass of the engine. Accordingly, minimizing the size and / or mass of the crankshaft reduces the size and mass of the engine, which has a compounding effect on the overall size, mass and fuel economy of the vehicle.[0003]The crankshaft includes at least one crank pin journal that is offset from the crank axis, to which a reciprocating piston is attached via a ...

AI Technical Summary

Benefits of technology

The patent describes a high-strength steel alloy that is suitable for use in casting crankshafts. The alloy has a medium-low carbon content, fine grain sizes, and a microstructure consisting of bainite and upper bainite. The alloy has good machinability and can be easily heat treated. The ultimate tensile strength of the alloy ranges from 750 to 1100 MPa. The alloy can be combined with other elements such as boron, vanadium, molybdenum, and niobium. The method of forming the alloy involves creating a steel alloy with the desired composition and then casting it in a mold and air quenching it to a temperature of 420 to 530 degrees Celsius. The high-strength steel alloy can be used to create crankshafts for automotive propulsion systems.

Problems solved by technology

Although the forging process is more costly than the casting process, most steel alloys exhibit a high shrinkage while cooling, and do not cast well, because the shrinkage that occurs while the cast product cools forms voids in the final cast product.

This weakens the final cast product and makes it unsuitable for use in an engine.

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