Thread rolling die and method of making same

Abstract

A thread rolling die includes a thread rolling region comprising a working surface including a thread form. The thread rolling region of the thread rolling die comprises a sintered cemented carbide material having a hardness in the range of 78 HRA to 89 HRA. In certain embodiments, the thread rolling die may further include at least one non-cemented carbide piece metallurgically bonded to the thread rolling region in an area of the thread rolling region that does not prevent a workpiece from contacting the working surface, and wherein the non-cemented carbide piece comprises at least one of a metallic region and a metal matrix composite region. Methods of forming a thread rolling die as embodied herein are also disclosed.

Claims

1. A thread rolling die comprising: a thread rolling region comprising a working surface including a thread form, wherein the thread rolling region comprises a sintered cemented carbide material having a hardness in the range of 78 HRA to 89 HRA, a non-working region comprising one of a layered and a gradient structure comprising at least two different grades of sintered cemented carbide materials, wherein each of the sintered cemented carbide materials in the thread rolling region and non-working region individually comprise hard particles of at least one carbide dispersed in a continuous binder comprising at least one of cobalt, a cobalt alloy, nickel, a nickel alloy, iron, and an iron alloy.

2. The thread rolling die of claim 1, wherein the sintered cemented carbide material of the thread rolling region has a compressive yield strength of at least 400,000 psi.

3. The thread rolling die of claim 1, wherein the sintered cemented carbide material of the thread rolling region has a Young's modulus of at least 5010.sup.6 psi.

4. The thread rolling die of claim 1, wherein the sintered cemented carbide material of the thread rolling region has an abrasion wear volume no greater than 30 mm.sup.3 evaluated according to ASTM 065-04.

5. The thread rolling die of claim 1, wherein the sintered cemented carbide material of the thread rolling region has a compressive yield strength of at least 400,000 psi; a Young's modulus of at least 5010.sup.6 psi; and an abrasion wear volume no greater than 30 mm.sup.3 evaluated according to ASTM G65-04.

6. The thread rolling die of claim 1, wherein the Young's modulus of the sintered cemented carbide material of the thread rolling region is in the range of 5010.sup.6 psi to 8010.sup.6 psi.

7. The thread rolling die of claim 1, wherein the abrasion wear volume of the sintered cemented carbide material of the thread rolling region is in the range of 5 mm.sup.3 to 30 mm.sup.3 evaluated according to ASTM G65-04.

8. The thread rolling die of claim 1, wherein the sintered cemented carbide material of the thread rolling region has a fracture toughness of at least 15 ksi-in.sup.1/2.

9. The thread rolling die of claim 1, wherein the sintered cemented carbide material of the thread rolling region has a transverse rupture strength of at least 300 ksi.

10. The thread rolling die of claim 1, wherein the sintered cemented carbide material of the thread rolling region has a compressive yield strength of at least 400,000 psi; a Young's modulus in the range of 5010.sup.6 psi to 8010.sup.6 psi; an abrasion wear volume in the range of 5 mm.sup.3 to 30 mm.sup.3 evaluated according to ASTM G65-04; a fracture toughness of at least 15 ksi-in.sup.1/2; and a transverse rupture strength of at least 300 ksi.

11. The thread rolling die of claim 1, wherein the thread rolling die is selected from the group consisting of a flat thread rolling die and a cylindrical thread rolling die.

12. The thread rolling die of claim 1, wherein the sintered cemented carbide materials of the thread rolling region and non-working region individually comprise hard particles of at least one carbide of a metal selected from Groups IVB, VB, and VIB of the Periodic Table dispersed in a continuous binder comprising at least one of cobalt, a cobalt alloy, nickel, a nickel alloy, iron, and an iron alloy.

13. The thread rolling die of claim 12, wherein the sintered cemented carbide material of the thread rolling region and non-working region individually comprise 60 weight percent up to 98 weight percent of the hard particles and 2 weight percent to 40 weight percent of the continuous binder.

14. The thread rolling die of claim 12, wherein the binder of the sintered cemented carbide materials of the thread rolling region and non-working region individually further comprise at least one additive individually selected from tungsten, chromium, titanium, vanadium, niobium and carbon in a concentration up to the solubility limit of the additive in the binder.

15. The thread rolling die of claim 12, wherein the binder of the sintered cemented carbide materials of the thread rolling region and non-working region further comprise up to 5% by weight of at least one additive individually selected from silicon, boron, aluminum copper, ruthenium, and manganese.

16. The thread rolling die of claim 12, wherein the hard particles have an average grain size in the range of 0.3 m to 20 m.

17. The thread rolling die of claim 1, wherein at least the working surface of the thread rolling region comprises a hybrid cemented carbide.

18. The thread rolling die of claim 17, wherein a dispersed phase of the hybrid cemented carbide has a contiguity ratio of less than 0.48.

19. The thread rolling die of claim 1, wherein the thread rolling region comprises one of a layered and a gradient structure comprising different grades of sintered cemented carbide materials.

20. The thread rolling die of claim 1, further comprising at least one non-cemented carbide piece metallurgically bonded to the thread rolling region on a side of the thread rolling region opposite the working surface of the thread rollin region.

21. The thread rolling die of claim 20, wherein the at least one non-cemented carbide piece comprises at least one of a metal or metal alloy region and a metal matrix composite region.

22. The thread rolling die of claim 21, wherein the metal or metal alloy region of the non-cemented carbide piece comprises at least one of nickel, a nickel alloy, cobalt, a cobalt alloy, iron, an iron alloy, titanium, a titanium alloy, copper, a copper alloy, aluminum, and an aluminum alloy.

23. The thread rolling die of claim 21, wherein the metal matrix composite of the non-cemented carbide piece comprises at least one of hard particles and metallic particles bound together by a matrix metal, and wherein a melting temperature of the matrix metal is less than a melting temperature of any of the hard particles and the metallic particles of the metal matrix composite.

24. The thread rolling die of claim 23, wherein the hard particles of the metal matrix composite comprise at least one carbide of a metal selected from Groups IVB, VB, and VIB of the Periodic Table.

25. The thread rolling die of claim 23, wherein the hard particles of the metal matrix composite comprise particles of at least one of carbides, oxides, nitrides, borides and silicides.

26. The thread rolling die of claim 23, wherein the metallic particles of the metal matrix composite comprise grains of at least one of tungsten, a tungsten alloy, tantalum, a tantalum alloy, molybdenum, a molybdenum alloy, niobium, a niobium alloy, titanium, a titanium alloy, nickel, a nickel alloy, cobalt, a cobalt alloy, iron and an iron alloy.

27. The thread rolling die of claim 20, wherein the at least one non-cemented carbide piece is machinable.

28. The thread rolling die of claim 23, wherein the matrix metal comprises at least one of nickel, a nickel alloy, cobalt, a cobalt alloy, iron, an iron alloy, copper, a copper alloy, aluminum, an aluminum alloy, titanium, a titanium alloy, a bronze, and a brass.

29. The thread rolling die of claim 23, wherein the matrix metal comprises a bronze consisting essentially of 78 weight percent copper, 10 weight percent nickel, 6 weight percent manganese, 6 weight percent tin, and incidental impurities.

30. The thread rolling die of claim 1, wherein the thread form comprises at least one of V-type threads, Acme threads, Knuckle threads, and Buttress threads.

31. A thread rolling die, comprising: a non-working region, and a thread rolling region comprising a working surface including a thread form, wherein the non-working region and the working surface of the thread rolling region individually comprise a sintered cemented carbide material, wherein the sintered cemented carbide material comprises hard particles of at least one carbide of a metal selected from Groups IVB, VB, and VIS of the Periodic Table dispersed in a continuous binder comprising at least one of cobalt, a cobalt alloy, nickel, a nickel alloy, iron, and an iron alloy; and at least one non-cemented carbide piece metallurgically bonded to the thread rolling region in an area of the thread rolling region that does not prevent a workpiece from contacting the working surface, wherein the non-cemented carbide piece comprises a composite material including metal or metallic alloy grains, particles, and/or powder dispersed in a continuous metal or metallic alloy matrix composite.

32. The thread rolling die of claim 31, wherein the sintered cemented carbide of the working surface has a compressive yield strength of at least 400,000 psi, a Young's modulus in the range of 5010.sup.6 psi to 8010.sup.6 psi, an abrasion wear volume in the range of 5 mm.sup.3 to 30 mm.sup.3 evaluated according to ASTM 065-04, a hardness in the range of 78 HRA to 89 HRA, a fracture toughness of at least 15 ksi-in.sup.1/2, and a transverse rupture strength of at least 300 ksi.

33. The thread rolling die of claim 20, wherein the at least one non-cemented carbide piece metallurgically bonded to the thread rolling region comprises threads or other features to mechanically attach the thread rolling die to a thread rolling machine.

34. The thread rolling die of claim 31, wherein the at least one non-cemented carbide piece metallurgically bonded to the thread rolling region comprises threads or other features to mechanically attach the thread rolling die to a thread rolling machine.

35. The thread rolling die of claim 1, wherein the sintered cemented carbide material of the thread rolling region has at least one mechanical property or characteristic that differs from the sintered cemented carbide materials of the nonworking region.

36. The thread rolling die of claim 35, wherein the sintered cemented carbide materials of the non-working region have a hardness less than a hardness of the sintered cemented carbide material of the thread rolling region.

37. The thread rolling die of claim 1, wherein one of the at least two different grades of sintered cemented carbide materials of the non-working region have at least one mechanical property or characteristic that differs from the other of the at least two different grades of sintered cemented carbide materials of the non-working region.

38. The thread rolling die of claim 37, wherein the at least one characteristic comprises at least one of average hard particle size, hard particle composition, hard particle concentration, binder phase composition, and binder phase concentration.

39. The thread rolling die of claim 37, wherein the at least one mechanical property comprises at least one of compressive yield strength, Young's modulus, hardness, toughness, wear resistance, and transverse rupture strength.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The features and advantages of articles and methods described herein may be better understood by reference to the accompanying drawings in which:

(2) FIGS. 1A and 1B are schematic representations showing certain aspects of a conventional thread rolling process;

(3) FIGS. 2A and 2B are schematic representations of the microstructural flow lines of the workpiece material in a thread form region of a workpiece formed by r thread cutting and thread rolling, respectively;

(4) FIG. 3 is a schematic representation of one non-limiting embodiment of a circular thread rolling die according to the present disclosure, wherein the die includes a non-cemented carbide region and a sintered cemented carbide working surface having a hardness in the range of 78 HRA to 89 HRA (Rockwell Hardness Scale A);

(5) FIG. 4 is a schematic representation of one non-limiting embodiment of a flat thread rolling die according to the present disclosure, wherein the die includes a non-cemented carbide region and a sintered cemented carbide working surface having a hardness in the range of 78 HRA to 89 HRA;

(6) FIG. 5 is a schematic representation of an additional non-limiting embodiment of a flat thread rolling die according to the present disclosure, wherein the die includes two non-cemented carbide regions and a sintered cemented carbide working surface having a hardness in the range of 78 HRA to 89 HRA;

(7) FIG. 6 is a schematic representation an additional non-limiting embodiment of a circular thread rolling die according to the present disclosure, wherein the die includes a sintered cemented carbide region having a layered or gradient construction and a sintered cemented carbide working surface; and

(8) FIG. 7 is photograph of one non-limiting embodiment of a circular thread rolling die according to the present disclosure comprising a sintered cemented carbide material having a hardness in the range of 78 HRA to 89 HRA.

(9) The reader will appreciate the foregoing details, as well as others, upon considering the following detailed description of certain non-limiting embodiments according to the present disclosure.

DETAILED DESCRIPTION OF CERTAIN NON-LIMITING EMBODIMENTS

(10) In the present description of non-limiting embodiments, other than in the operating examples or where otherwise indicated, all numbers expressing quantities or characteristics are to be understood as being modified in all instances by the term about. Accordingly, unless indicated to the contrary, any numerical parameters set forth in the following description are approximations that may vary depending on the desired properties one seeks to obtain in the articles and methods according to the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter described in the present description should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

(11) Any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein is only incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.

(12) One non-limiting embodiment of a circular thread rolling die 10 according to the present disclosure is depicted in FIG. 3. Non-limiting embodiments of a flat thread rolling die 30 according to the present disclosure are depicted in FIGS. 4 and 5. It will be understood that although the specific embodiments of novel and inventive thread rolling dies depicted and described herein are circular or flat thread rolling dies, the present invention also encompasses additional thread rolling die configurations, whether known now or hereinafter to a person of ordinary skill in the art. Each of thread rolling dies 10, 30 include a thread rolling region 12 comprising a working surface 14, which is the surface of the thread rolling die that contacts a workpiece and forms threads thereon. As such, the working surface 14 includes a thread form 16. The thread rolling region 12 of each of dies 10, 30 comprises a sintered cemented carbide material. According to certain embodiments, the sintered cemented carbide has a hardness in the range of 78 HRA to 89 HRA.

(13) In a non-limiting embodiment, the sintered cemented carbide material of the thread rolling region 12 may have a compressive yield strength of at least 400,000 psi. In another non-limiting embodiment, the sintered cemented carbide material of the thread rolling region 12 may have a Young's modulus of at least 5010.sup.6 psi. A non-limiting embodiment of the thread rolling die 10 comprises a sintered cemented carbide thread rolling region 12, wherein the sintered cemented carbide material has a Young's modulus in the range of 5010.sup.6 psi to 8010.sup.6 psi. In still another non-limiting embodiment, the sintered cemented carbide material of the thread rolling region 12 may have an abrasion wear volume no greater than 30 mm.sup.3 as evaluated according to ASTM G65-04. In one non-limiting embodiment, the sintered cemented carbide material of the thread rolling region 12 has an abrasion wear volume in the range of 5 mm.sup.3 to 30 mm.sup.3 as evaluated according to ASTM G65-04.

(14) According to one non-limiting embodiment of a thread rolling die 10, 30 according to the present disclosure, the sintered cemented carbide material of the thread rolling region 12 may have a combination of properties including a compressive yield strength of at least 400,000 psi; a Young's modulus of at least 5010.sup.6 psi; and an abrasion wear volume no greater than 30 mm.sup.3 evaluated according to ASTM G65-04. In another non-limiting embodiment, the sintered cemented carbide material of the thread rolling region 12 may have a fracture toughness of at least 15 ksi.Math.in.sup.1/2. In still another non-limiting embodiment, the sintered cemented carbide material of the thread rolling region 12 may have a transverse rupture strength of at least 300 ksi.

(15) According to certain other non-limiting embodiments, the sintered cemented carbide material of the thread rolling region 12 of thread rolling dies 10, 30 has one or more of a compressive yield strength of at least 400,000 psi; a Young's modulus in the range of 5010.sup.6 psi to 8010.sup.6 psi; an abrasion wear volume in the range of 5 mm.sup.3 to 30 mm.sup.3 as evaluated according to ASTM G65-04; a hardness in the range of 78 HRA to 89 HRA; a fracture toughness of at least 15 ksi.Math.in.sup.1/2; and a transverse rupture strength of at least 300 ksi.

(16) According to certain non-limiting embodiments according to the present disclosure, the thread form 16 of the working surface 14 of thread rolling dies 10, 30 may include one of V-type threads, Acme threads, Knuckle threads, and Buttress threads. It will be understood, however, that such thread form patterns are not exhaustive and that any suitable thread form known now or here hereafter to a person skilled in the art may be included on a thread rolling die according to the present disclosure.

(17) In certain non-limiting embodiments, sintered cemented carbide included in the thread rolling region and, optionally, sintered cemented carbide material included in other regions of the thread rolling dies according to the present disclosure are made using conventional powder metallurgy techniques. Such techniques include, for example: mechanically or isostatically pressing a blend of metal powders to form a green part having a desired shape and size; optionally, heat treating or presintering the green part at a temperature in the range of 400 C. to 1200 C. to provide a brown part; optionally, machining the part in the green or brown state to impart certain desired shape features; and heating the part at a sintering temperature, for example, in the range of 1350 C. to 1600 C. Other techniques and sequences of steps for providing sintered cemented carbide material will be evident to those having ordinary skill in the art. In appropriate circumstances, one or more of such other techniques may be used to provide sintered cemented carbide material included in thread rolling dies according to the present disclosure, and it will become evident to those having ordinary skill, upon reading the present disclosure, how to adapt such one or more techniques for use in providing the present thread rolling dies.

(18) In certain non-limiting embodiments of thread rolling dies according to the present disclosure, sintered cemented carbide material included in the thread rolling dies according to the present disclosure may be finish-machined using operations such, for example, turning, milling, grinding, and electro-discharge machining. Also, in certain non-limiting embodiments of thread rolling dies according to the present disclosure, finish-machined material included in the thread rolling dies may be coated with materials providing wear resistance and/or other advantageous characteristics. Such coatings may be applied using conventional coating techniques such as, for example, chemical vapor deposition (CVD) and/or physical vapor deposition (PVD). Non-limiting examples of wear resistant materials that may be provided as a coating on all or a region of cemented carbide materials included in thread rolling dies according to the present disclosure include Al.sub.2O.sub.3, TiC, Ti(C,N), either in single layers or in combinations of multiple layers. Other possible materials that may be provided as coatings on cemented carbide materials, either as a single-layer or as part of a multiple-layer coating, included in thread rolling dies according to the present disclosure will be known to those having ordinary skill and are encompassed herein.

(19) In certain non-limiting embodiments, cemented carbide material included in the thread rolling region of thread rolling dies according to the present disclosure includes a discontinuous, dispersed phase and a continuous binder phase. The discontinuous, dispersed phase includes hard particles of a carbide compound of at least one metal selected from Groups IVB, a Group VB, or a Group VIB of the Periodic Table. Such metals include, for example, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, and tungsten. The continuous binder phase comprises one or more of cobalt, a cobalt alloy, nickel, a nickel alloy, iron, and an iron alloy. In certain non-limiting embodiments, the sintered cemented carbide material included in the thread rolling region comprises 60 weight percent up to 98 weight percent of the dispersed phase and 2 weight percent to 40 weight percent of the continuous binder phase. According to certain non-limiting embodiment, hard carbide particles of the dispersed phase have an average grain size in the range of 0.3 m to 20 m.

(20) In a non-limiting embodiment, the continuous binder phase of sintered cemented carbide material included in the thread rolling region of a thread rolling die according to the present disclosure comprises at least one additive selected from tungsten, chromium, titanium, vanadium, niobium and carbon in a concentration up to the solubility limit of the additive in the continuous binder phase. In certain non-limiting embodiments, the continuous binder phase of sintered cemented carbide material in the thread rolling region comprises at least one additive selected from silicon, boron, aluminum copper, ruthenium, and manganese in a total concentration of up to 5% by weight, based on the total weight of the continuous binder phase.

(21) In certain non-limiting embodiments of thread rolling dies according to the present disclosure, the working surface of the thread rolling region comprises sintered cemented carbide material having a surface hardness in the range of 78 HRA to 89 HRA. Grades of sintered cemented having this particular surface hardness include, but are not limited to, grades including a dispersed, discontinuous phase including tungsten carbide particles and a continuous binder phase comprising cobalt. Various commercially available powder blends used to produce grades of sintered cemented carbide materials are known to those of ordinary skill and may be obtained from various sources such as, for example, ATI Engineered Products, Grant, Ala., USA. Non-limiting examples of commercially available cemented carbide grades that may be used in various embodiments of thread rolling dies according to the present disclosure include ATI Firth Grades FL10, FL15, FL20, FL25, FL30, FL35, H20, H25, ND20, ND25, ND30, H71, R52, and R61. The various cemented carbide grades typically differ in one or more of carbide particle composition, carbide particle grain size, binder phase volume fraction, and binder phase composition, and these variations influence the final physical and mechanical properties of the sintered cemented carbide material.

(22) FIGS. 3-6 schematically illustrate certain non-limiting embodiments of thread rolling dies according to the present disclosure. Each of thread rolling dies 10, 30, 40 includes a thread rolling region 12, 42 comprising a working surface 14, 44 which, in turn, includes a thread form 16 (not shown in FIG. 6). Each of thread rolling dies 10, 30, 40 also includes a non-working region 18 that supports the thread rolling region 12. With reference to the thread rolling die 40 of FIG. 6, in certain embodiments, the non-working region 18 comprises the same sintered cemented carbide material as the thread rolling region 42 or may comprise one or more layers, such as layers 46, 48, 50, and 52, of other grades of cemented carbide material. In certain other non-limiting die embodiments, the non-working region 18 may comprise at least one cemented carbide material that differs in at least one characteristic from sintered cemented carbide material included in the thread rolling region of the die. The at least one characteristic that differs may be selected from, for example, composition and a physical or mechanical property. Physical and/or mechanical properties that may differ include, but are not limited to, compressive yield strength, Young's modulus, hardness, toughness, wear resistance, and transverse rupture strength. In certain embodiments of a thread rolling die according to the present disclosure, the die may include different grades of cemented carbide material in different regions of the thread rolling die, selected to provide desired properties such as, for example, compressive yield strength, Young's modulus, hardness, toughness, wear resistance, and transverse rupture strength, in particular regions of the die.

(23) Again referring to the schematic illustration of FIG. 6, a non-limiting example of a circular thread rolling die according to the present disclosure may include several regions of different grades of sintered cemented carbide material. Thread rolling die 40 comprises a thread rolling region 42 that includes a working surface 44. The thread rolling region 42 may comprise a cemented carbide grade having mechanical properties suitable for forming threads on workpieces for which the die 40 is intended. In a non-limiting embodiment, the working surface 44 of the thread rolling region 42 has a surface hardness in the range of 78 HRA to 89 HRA, a compressive yield strength greater than 400,000 psi, a stiffness (Young's modulus) greater than 5010.sup.6 psi, and a wear volume (as evaluated by ASTM G65-04) of less than 30 mm.sup.3. The non-working region 18 includes a second layer 46 of sintered cemented carbide material adjacent to the thread rolling region 44. The non-working region 18 also includes subsequent layers 48, 50, and 52 having at least one mechanical property or characteristic that differs from the cemented carbide material of the thread rolling region 44 and from one another. Examples of characteristics that may differ between the several layers 46, 48, 50, 52 and the thread rolling region 44 may be one or more of average hard particle size, hard particle composition, hard particle concentration, binder phase composition, and binder phase concentration. Physical and/or mechanical properties that may differ between the several layers 46, 48, 50, 52 and the thread rolling region include, but are not limited to, compressive yield strength, Young's modulus, hardness, toughness, wear resistance, and transverse rupture strength.

(24) In a non-limiting embodiment of thread rolling die 40, the second layer 46 may comprise a cemented carbide grade with hardness less than the hardness of the working surface 44 layer in order to better transfer stresses experienced during the thread rolling operation, and minimize cracking of the sintered cemented carbide material at the working surface 44 and in the thread rolling region 42. Sintered cemented carbide layers 48, 50, 52 progressively decrease in hardness in order to transfer stresses from the relatively harder working surface 44, and thus avoid cracking of the sintered cemented carbide at the working surface 44 and in the thread rolling region 42. In is noted that in the non-limiting embodiment of a circular thread rolling die depicted in FIG. 6, the innermost layer 52 defines a mounting hole 54, which facilitates mounting the thread rolling die to a thread rolling machine (not shown). The innermost layer 52 comprises cemented carbide material having reduced hardness relative to the cemented carbide material of the thread rolling region 42, and this arrangement may better absorb stresses generated during the thread rolling operation and increase the service life of the thread rolling die 40. It will be apparent to those having ordinary skill, upon reading the present disclosure, that a mechanical property other than or in addition to hardness may be varied among the layers of the multi-layer cemented carbide thread rolling die illustrated in FIG. 6. Variation of such other mechanical properties among the layers of a multi-layer thread rolling die such a die 40 are also encompassed within the scope of embodiments of this disclosure.

(25) In a non-limiting embodiment of a thread rolling die comprising a plurality of different grades of cemented carbide arranged in a layered fashion as depicted in FIG. 6, the desired thickness of the thread rolling region 42, the second layer 46, and subsequent layers 48, 50, 52 may be determined by a person of ordinary skill in the art to provide and/or optimize desired properties. A non-limiting example of a minimum thickness range for the thread rolling region 42 may be from 10 mm to 12 mm. Further, while FIG. 6 depicts a thread rolling die comprising five discrete layers 42, 46, 48, 50, 52 of different sintered cemented carbide materials, it is recognized that a thread rolling die of this disclosure may comprise more or less than five layers and/or grades of sintered cemented carbide material depending on the final properties desired. In yet another non-limiting embodiment, instead of comprising discrete layers 42, 46, 48, 50, 52 of sintered cemented carbide material, the layers may be so thin as to provide a substantially continuous gradient of the desired one or more properties from the working surface 44 of the thread rolling region 42 to the innermost layer 52, providing greater stress transferring efficiencies. It will be understood that the foregoing description of possible arrangements and characteristics of thread rolling dies according to the present disclosure including a multi-layered or gradient structure of cemented carbide materials may be applied to circular thread rolling dies, flat thread rolling dies, and thread rolling dies having other configurations.

(26) Certain non-limiting methods for producing articles comprising areas of sintered ceramic carbide materials having differing properties is described in U.S. Pat. No. 6,511,265, which is hereby incorporated by reference herein in its entirety. One such method includes placing a first metallurgical powder blend comprising hard particles and binder particles into a first region of a void of a mold. The mold may be, for example, a dry-bag rubber mold. A second metallurgical powder blend having a different composition comprising hard particles and binder particles is placed into a second region of the void of the mold. Depending on the number of regions of different cemented carbide materials desired in the thread rolling die, the mold may be partitioned into additional regions in which particular metallurgical powder blends are disposed. The mold may be segregated into such regions, for example, by placing physical partitions in the void of the mold to define the several regions. In certain embodiments the physical partition may be a fugitive partition, such as paper, that the partition decomposes and dissipates during the subsequent sintering step. The metallurgical powder blends are chosen to achieve the desired properties in the corresponding regions of the thread rolling die as described above. In certain embodiments, a portion of at least the first region and the second region and any other adjacent regions partitioned in the void of the mold are brought into contact with each other, and the materials within the mold are then isostatically compressed to densify the metallurgical powder blends and form a green compact of consolidated powders. The compact is then sintered to further densify the compact and to form an autogenous bond between the first, second, and, if present, any other regions. The sintered compact provides a blank that may be machined to particular desired thread rolling die geometry. Such geometries are known to those having ordinary skill in the art and are not specifically described herein.

(27) In one non-limiting embodiment of a thread rolling die having a construction as depicted in FIG. 6, one or more of the sintered cemented carbide thread rolling region 42, second layer 46, and additional layers 48, 50, 52 may be comprised of hybrid cemented carbide material. As known to those having ordinary skill, a hybrid cemented carbide comprises a discontinuous phase of a first cemented carbide grade dispersed throughout and embedded in a continuous binder phase of a second cemented carbide grade. As such, a hybrid cemented carbide may be thought of as a composite of different cemented carbides.

(28) In one non-limiting embodiment of a thread rolling die according to the present disclosure, the thread rolling die includes a hybrid cemented carbide in which the binder concentration of the dispersed phase of the hybrid cemented carbide is 2 to 15 weight percent of the dispersed phase, and the binder concentration of the continuous binder phase of the hybrid cemented carbide is 6 to 30 weight percent of the continuous binder phase.

(29) Hybrid cemented carbides included in certain non-limiting embodiments of articles according to the present disclosure may have relatively low contiguity ratios, thereby improving certain properties of the hybrid cemented carbides relative to other cemented carbides. Non-limiting examples of hybrid cemented carbides that may be used in embodiments of thread rolling dies according to the present disclosure are described in U.S. Pat. No. 7,384,443, which is hereby incorporated by reference herein in its entirety. Certain embodiments of hybrid cemented carbide composites that may be included in articles herein have a contiguity ratio of the dispersed phase that is no greater than 0.48. In some embodiments, the contiguity ratio of the dispersed phase of the hybrid cemented carbide may be less than 0.4, or less than 0.2. Methods of forming hybrid cemented carbides having relatively low contiguity ratios include, for example: partially or fully sintering granules of the dispersed grade of cemented carbide; blending these presintered granules with the unsintered or green second grade of cemented carbide powder; compacting the blend; and sintering the blend. Details of such a method are detailed in the incorporated U.S. Pat. No. 7,384,443 and, therefore, will be known to those having ordinary skill. A metallographic technique for measuring contiguity ratios is also detailed in the incorporated U.S. Pat. No. 7,384,443 and will be known to those having ordinary skill.

(30) Referring now to FIGS. 3-5, according to another aspect of the present disclosure, a thread rolling die 10, 30 according to the present disclosure may include one or more non-cemented carbide regions in non-working regions 18 of the thread rolling die. The non-working regions 18 comprising non-cemented carbide materials may be metallurgically bonded to the thread rolling region 12, which do comprise cemented carbide material, and are positioned so as not to prevent the working surface 14 from contacting the workpiece that is to be threaded. In one non-limiting embodiment, the non-cemented carbide materials in non-working regions comprise at least one of a metal or metal alloy, and a metal matrix composite. In certain non-limiting embodiments, a non-cemented carbide material in the non-working region 18 included in thread rolling die 10,30 may be a solid metallic material selected from iron, iron alloys, nickel, nickel alloys, cobalt, cobalt alloys, copper, copper alloys, aluminum, aluminum alloys, titanium, titanium alloys, tungsten, and tungsten alloys.

(31) In yet another non-limiting embodiment of a thread rolling die according to the present disclosure, the metal matrix composite of the non-cemented carbide piece comprises at least one of hard particles and metallic particles bound together by a metallic matrix material, wherein the melting temperature of the metallic matrix material is less than a melting temperature of the hard particles and/or the metallic particles of the metal matrix composite.

(32) In certain other non-limiting embodiments, a non-cemented carbide piece included in a non-working region 18 of a thread rolling die 10, 30 is a composite material including metal or metallic alloy grains, particles, and/or powder dispersed in a continuous metal or metallic alloy matrix composite. In certain non-limiting embodiments, a non-cemented carbide piece in a non-working region 18 comprises a composite material including particles or grains of a metallic material selected from tungsten, a tungsten alloy, tantalum, a tantalum alloy, molybdenum, a molybdenum alloy, niobium, a niobium alloy, titanium, a titanium alloy, nickel, a nickel alloy, cobalt, a cobalt alloy, iron, and an iron alloy. In one particular non-limiting embodiment, a non-cemented carbide piece in a non-working region 18 included in a thread rolling die 10, 30 according to the present disclosure comprises tungsten grains dispersed in a matrix of a metal or a metallic alloy.

(33) Another non-limiting embodiment of a thread rolling die according to the present disclosure includes a metal matrix composite piece comprising hard particles. A non-limiting embodiment includes a non-cemented carbide piece comprising hard particles of at least one carbide of a metal selected from Groups IVB, VB, and VIB of the Periodic Table. In one non-limiting embodiment, the hard particles of the metal matrix composite comprise particles of at least one of carbides, oxides, nitrides, borides and silicides.

(34) According to one non-limiting embodiment, the metal matrix material includes at least one of copper, a copper alloy, aluminum, an aluminum alloy, iron, an iron alloy, nickel, a nickel alloy, cobalt, a cobalt alloy, titanium, a titanium alloy, a bronze alloy, and a brass alloy. In one non-limiting embodiment, the metal matrix material is a bronze alloy consisting essentially of 78 weight percent copper, 10 weight percent nickel, 6 weight percent manganese, 6 weight percent tin, and incidental impurities. In another non-limiting embodiment, the metal matrix material consists essentially of 53 weight percent copper, 24 weight percent manganese, 15 weight percent nickel, 8 weight percent zinc, and incidental impurities. In non-limiting embodiments, the metal matrix material may include up to 10 weight percent of an element that will reduce the melting point of the metal matrix material, such as, but not limited to, at least one of boron, silicon, and chromium.

(35) In certain embodiments, a non-cemented carbide piece included in a thread rolling die 10, 30 may be machined to include threads or other features so that the thread rolling die 10, 30 may be mechanically attached to a thread rolling machine (not shown).

(36) As depicted in FIGS. 3 and 4, in a non-limiting embodiment, at least one non-cemented carbide piece in a non-working region 18 may be metallurgically bonded to the thread rolling region 12 on an opposite side 56 of the thread rolling region 12, i.e., opposite the working surface 14 of the thread rolling region 12. In other embodiments, as depicted in FIG. 5, at least one non-cemented carbide piece in a non-working region 18 may be metallurgically bonded to the thread rolling region 12 on an adjacent side 58 of the thread rolling region 12, i.e., laterally adjacent to the working surface 14 of the thread rolling region 12. It is recognized that a non-cemented carbide piece can be metallurgically bonded to the sintered cemented carbide thread rolling region 12 at any position that does not prevent the working surface 14 containing the thread form 16 to contact the workpiece.

(37) According to one aspect of the present disclosure, a non-limiting method for forming a sintered cemented carbide thread rolling die that comprises a non-cemented carbide piece or region includes providing a sintered cemented carbide thread rolling region or sintered cemented carbide thread rolling die. Optionally, one or more non-cemented carbide pieces comprising a metal or metal alloy, as disclosed hereinabove may be placed adjacent to a non-working area of the sintered cemented carbide thread rolling region or sintered cemented carbide thread rolling die in a void of a mold. The space between the sintered ceramic thread rolling region or thread rolling die and the optional solid metal or metal alloy pieces defines an unoccupied space. A plurality of inorganic particles are added to at least a portion of the unoccupied space. The inorganic particles may comprise one or more of hard particles, metal grains, particles, and powders The remaining void space between the plurality of inorganic particles and the sintered cemented carbide thread rolling region or thread rolling die and the optional solid metallic pieces defines a remainder space. The remainder space is at least partially filled by infiltration with a molten metal or metal alloy matrix material that has a lower melting temperature than any of the inorganic particles which, together with the inorganic particles, forms a metal matrix composite material. Upon cooling, the metal of the metal matrix composite material bonds together the inorganic particles and the sintered cemented carbide thread rolling die and, if present, any non-cemented carbide metal or metal alloy pieces. Upon removal from the mold, the sintered cemented carbide thread rolling die with a non-cemented carbide piece comprising at least one of a metal or metal alloy region and a metal matrix composite region may be machined and finished to a desired shape. This infiltration process is disclosed in U.S. patent application Ser. No. 12/196,815, which is hereby incorporated herein by reference in its entirety.

(38) Still another non-limiting embodiment of a thread rolling die encompassed by this disclosure comprises a thread rolling region comprising a working surface having a thread form, wherein at least the working surface of the thread rolling region comprises a sintered cemented carbide material, and at least one non-cemented carbide piece is metallurgically bonded to the thread rolling region in an area of the thread rolling region that does not prevent access of a workpiece to the working surface. The non-cemented carbide piece comprises at least one of a metallic region and a metal matrix composite region. The non-cemented carbide piece may be machinable in order to facilitate, for example, mounting of the sintered ceramic thread rolling die to a thread rolling machine.

(39) In a non-limiting embodiment, the sintered cemented carbide of the thread rolling region has a compressive yield strength of at least 400,000 psi, a Young's modulus in the range of 5010.sup.6 psi to 8010.sup.6 psi, an abrasion wear volume in the range of 5 mm.sup.3 to 30 mm.sup.3 evaluated according to ASTM G65-04, a hardness in the range of 78 HRA to 89 HRA, a fracture toughness of at least 15 ksi.Math.in.sup.1/2, and a transverse rupture strength of at least 300 ksi.

EXAMPLE 1

(40) FIG. 7 is a photograph of a thread rolling die made of sintered cemented carbide as embodied in this disclosure. The die consists of a cylindrical sintered cemented carbide ring with the desired thread form on the working surface of the die. A sintered cemented carbide cylindrical part was first made using conventional powder metallurgy techniques by compacting Firth Grade ND-25 metallurgical powder (obtained from ATI Engineered Products, Grant, Ala.) in a hydraulic press using a pressure of 20,000 psi to form a cylindrical blank. High temperature sintering of the cylindrical blank was carried out at 1350 C. in an over-pressure furnace to provide a sintered cemented carbide material including 25% by weight of a continuous binder phase of cobalt and 75% by weight of dispersed tungsten carbide particles. The cylindrical cemented carbide material blank was machined to provide the desired thread form illustrated in FIG. 7 using conventional machine tools and machining practices.

(41) The properties of the thread rolling die illustrated in FIG. 7 include a hardness of 83.0 HRA, a compressive strength of 450,000 psi, a Young's Modulus of 6810.sup.6 psi, and a wear volume of 23 mm.sup.3 as measured by ASTM G65-04.

EXAMPLE 2

(42) A circular sintered cemented carbide thread rolling die is prepared as described in Example 1 and is placed in a graphite mold. Powdered tungsten is added to the mold to cover the thread rolling die. An infiltrant powder blend consisting essentially of 78 weight percent copper, 10 weight percent nickel, 6 weight percent manganese, 6 weight percent tin, and incidental impurities is placed in a funnel positioned above the graphite mold. The assembly is placed in a vacuum furnace at a temperature of 1350 C., which is greater than the melting point of the infiltrant powder blend. The molten material formed on melting the infiltrant powder blend infiltrates the space between the tungsten powder and the thread rolling die. As the molten material cools and solidifies, it binds tungsten carbide particles formed from the powdered tungsten to the die and forms a non-cemented carbide non-working portion. Subsequently, the rolling die is machined to form a sintered ceramic thread rolling die comprising a non-cemented carbide non-working region 18 as schematically depicted in FIG. 3. The non-cemented carbide non-working region is machined to facilitate mounting of the thread rolling die onto a thread rolling machine.

(43) It will be understood that the present description illustrates those aspects of the invention relevant to a clear understanding of thread rolling dies according to the present disclosure. Certain aspects that would be apparent to those of ordinary skill in the art and that, therefore, would not facilitate a better understanding of the subject matter herein have not been presented in order to simplify the present description. Although only a limited number of embodiments are necessarily described herein, one of ordinary skill in the art will, upon considering the foregoing description, recognize that many modifications and variations may be employed. All such variations and modifications are intended to be covered by the foregoing description and the following claims.