Patent Application
20190002998
The present disclosure relates generally to methods of forming alloy steels and to devices and materials formed by such methods. More specifically, embodiments of the present disclosure provide for methods of forming steels with enhanced structural properties.
There has been a long-felt but unmet need to provide alloy steels with enhanced structural properties and to provide lightweight materials with desired strength characteristics and material properties.
Embodiments of the present disclosure contemplate steel alloy materials and methods of making the same. In various embodiments, induction-hardenable ferrous metals are provided that contain at least one of the following alloy elements: carbon, manganese, tungsten, nickel, molybdenum, chromium, phosphorous, niobium, vanadium, aluminum, titanium, nitrogen, and/or boron. In some embodiments, induction-hardenable steels are provided that contain about 0.50 to 0.75 percent carbon by weight, about 0.2 to 1.7 percent manganese by weight, about 0.1 to 1.0 percent tungsten by weight, about 0.1 to 3 percent nickel by weight, up to about 0.5 percent molybdenum by weight, up to about 1.5 percent chromium by weight, up to 0.02 percent phosphorous by weight, up to about 0.025 percent niobium by weight, up to about 0.2 percent vanadium by weight, up to about 0.1 percent aluminum by weight, up to about 0.05 percent titanium by weight, up to about 0.02 percent nitrogen by weight, about 0.0005 to 0.003 percent boron by weight, and the balance iron with the usual impurities in conventional amounts.
In some embodiments, steel alloys are provided comprising austenite grains smaller than about 20 μm in diameter. The steel alloys are transformed to martensite with some retained austenite by rapid heating and quenching at rates that are attainable with induction heating and quenching. The small austenite grain size of embodiments of the present disclosure, along with control of alloy additions at austenite grain boundaries enables production of materials and components with enhanced ductility, notched fracture and fatigue strengths at increased carbon and hardness levels. The provision of such materials in accordance with methods and systems of the present disclosure results in the production of lighter and stronger components.
Devices and methods of the present disclosure contemplate controlling an amount of manganese, nickel, tungsten, molybdenum, chromium, phosphorous, niobium, vanadium, aluminum, titanium, nitrogen, and/or boron and obtaining relatively small austenite grain sizes over a workable range of induction heating rates and peak temperatures for the manufacture of parts with high hardness. The small austenite grain sizes of embodiments of the present disclosure, and favorable effects of elemental additions provide for ductile trans-granular fracture at hardness in excess of 595 HV (55 HRC) and up to 835 HV (65 HRC). By reducing or preventing inter-granular fracture, lighter, stronger parts and materials are achieved by embodiments of the present disclosure. Such parts and materials may be provided, for example, for use with highly stressed automotive driveline parts including, but not limited to, drive-shafts, axles and gears.
In one embodiment, a method of forming a steel alloy is provided comprising the steps of: providing a carbon steel; adding an alloy addition wherein the one alloy addition comprises not more than approximately 2.0 weight percent of the combined carbon steel and the alloy addition; austenitizing the carbon steel and the at least one alloy addition for at least approximately 1,000 seconds at a temperature of at least 900 degrees Celsius; quenching the carbon steel and the at least one alloy addition; tempering the carbon steel and the at least one alloy addition at a temperature of not more than approximately 250 degrees Celsius; performing a second austenitizing step; and further quenching and tempering the carbon steel and the at least one alloy addition at a temperature of not more than approximately 250 degrees Celsius.
In one embodiment, a steel alloy is provided that is formed by a method comprising the steps of: providing a carbon steel; adding an alloy addition wherein the one alloy addition comprises not more than approximately 2.0 weight percent of the combined carbon steel and the alloy addition; austenitizing the carbon steel and the at least one alloy addition for at least approximately 1,000 seconds at a temperature of at least 900 degrees Celsius; quenching the carbon steel and the at least one alloy addition; tempering the carbon steel and the at least one alloy addition at a temperature of not more than approximately 250 degrees Celsius; performing a second austenitizing step; and further quenching and tempering the carbon steel and the at least one alloy addition at a temperature of not more than approximately 250 degrees Celsius. The resultant steel alloy comprises a hardness of at least approximately 650 HVeq and a torsional fatigue strength of at least approximately 650×105 MPa.
The Summary is neither intended nor should it be construed as being representative of the full extent and scope of the present disclosure. The present disclosure is set forth in various levels of detail in the Summary as well as in the attached drawings and the Detailed Description and no limitation as to the scope of the present disclosure is intended by either the inclusion or non-inclusion of elements, components, etc. in this Summary. Additional aspects of the present disclosure will become more readily apparent from the Detailed Description, particularly when taken together with the drawings.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the disclosure and together with the general description of the disclosure given above and the detailed description of the drawings given below, serve to explain the principles of these inventions.
It should be understood that the drawings are not necessarily to scale. In certain instances, details that are not necessary for an understanding of the disclosure or that render other details difficult to perceive may have been omitted. It should be understood, of course, that the disclosure is not necessarily limited to the particular embodiments illustrated herein.
It is known that alloy elements tend to segregate to prior austenite grain boundaries (“PAGB”) during conventional austenitizing and tempering methods. Embodiments of the present disclosure contemplate the provision of shorter austenitizing times to provide different effects on PAGB segregation and mobility and to obtain enhanced material characteristics. In various embodiments, shorter austenitizing times are achieved through induction hardening methods. Embodiments of the present disclosure further contemplate the provision of various alloy and impurity elements to alter prior austenite grain size (“PAGS”) and affect grain boundary strength during short austenitizing times. Certain embodiments contemplate the provision of various alloy additions with 0.55% carbon steels. Molybdenum, phosphorous, chromium, nickel, manganese, silicon, antimony, tin, and arsenic are elements known to segregate to PAGB during temper embrittlement at about 450-600° C. Carbon, phosphorous, molybdenum, manganese, silicon, nickel and cobalt are known to segregate to PAGB during quench embrittlement. Low carbon alloys such as boron, manganese, carbon, chromium, molybdenum, and nickel, for example segregate to PAGB in austenitic steels. These alloy additions are contemplated for use with embodiments and methods of the present disclosure.
At relatively long austenitizing times, elements segregate into PAGB at varying ratios. Carbon and substitutional alloys affect PAGB at these relatively long austenitzing times. Applicant has found that substitutional elements can affect PAGS with relatively short austenitizing times as well.
In various embodiments of the present disclosure, alloy additions were provided in combination with a steel comprising 0.55% carbon, 0.008% nitrogen, and 0.015% sulfur. The alloy additions include at least one of manganese, silicon, chromium, nickel, molybdenum, tungsten, niobium, vanadium, titanium, aluminum, phosphourous, and boron. A composed alloy is treated by austenitizing the material at 900° C. and 1150° C., quenching the alloy, and tempering the alloy at approximately 175° C. In various embodiments, the tempered materials are then processed on a GLEEBLE™ device with austenitizing times of 2 seconds, 10 seconds, or 1000 seconds at 850° C., 950° C., and 1050° C., respectively, and quenched and tempered at approximately 175° C.
Various steels as shown in
Methods according to embodiments of the present disclosure limit an inter-granular crack initiation in alloy steels. In various embodiments of the present disclosure, alloys are provided comprising enhanced fatigue strength at higher harnesses.
While various embodiments of the disclosed device have been described in detail, it is apparent that modifications and alterations of those embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and alterations are within the scope and spirit of the present disclosure, as set forth in the following claims. Further, the invention(s) described herein are capable of other embodiments and of being practiced or of being carried out in various ways. In addition, it is to be understood that the phraseology and terminology used herein is for the purposes of description and should not be regarded as limiting. The use of “including,” “comprising,” or “adding” and variations thereof herein are meant to encompass the items listed thereafter and equivalents thereof, as well as, additional items.
The foregoing discussion has been presented for purposes of illustration and description. The foregoing is not intended to limit the disclosure to the form or forms disclosed herein. In the foregoing description for example, various features of the disclosure have been identified. It should be appreciated that these features may be combined together into a single embodiment or in various other combinations as appropriate. The dimensions of the component pieces may also vary, yet still be within the scope of the disclosure. Moreover, though the description has included description of one or more embodiments and certain variations and modifications, other variations and modifications are within the scope of the disclosure, e.g. as may be within the skill and knowledge of those in the art, after understanding the present disclosure. It is intended to obtain rights which include alternative embodiments to the extent permitted, including alternate, interchangeable and/or equivalent structures, functions, ranges or steps to those claimed, whether or not such alternate, interchangeable and/or equivalent structures, functions, ranges or steps are disclosed herein, and without intending to publicly dedicate any patentable subject matter.
The present disclosure, in various embodiments, includes components, methods, processes, systems and/or apparatus substantially as depicted and described herein, including various embodiments, subcombinations, and subsets thereof. Those of skill in the art will understand how to make and use the devices of the disclosure after understanding the present disclosure. The present disclosure, in various embodiments, includes providing devices and processes in the absence of items not depicted and/or described herein or in various embodiments hereof, including in the absence of such items as may have been used in previous devices or processes, e.g., for improving performance, achieving ease and/or reducing cost of implementation. Rather, as the following claims reflect, inventive aspects lie in less than all features of any single foregoing disclosed embodiment.
This U.S. Non-Provisional patent application claims the benefit of priority from U.S. Provisional Patent Application Ser. No. 62/526,704, filed Jun. 29, 2017, the entire disclosure of which is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62526704 | Jun 2017 | US |
