Method for the production of drop forge parts containing ti, zr, hf
The invention relates to a method for the production of drop forge parts essentially comprising titanium, zirconium, hafnium or a corresponding alloy, enabling rigidity thereof to be increased.
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This application is a national stage of PCT/EP2004/012952 filed Nov. 16, 2004 and based upon DE 103 55 892.6 filed on Nov. 29, 2003 under the International Convention.
BACKGROUND OF THE INVENTION1. Field of the Invention
The invention concerns a process for production of drop forged parts, which are essentially comprised of titanium, zirconium, hafnium or a corresponding alloy. Besides this, the invention concerns drop forged parts of this type.
Titanium, in particular, is an interesting light metal, since it is almost 50% lighter than steel. For this reason Ti, Zr and Hf components are interesting in the manufacture of motor vehicles, particularly if unsprung or rotating, for example, oscillating masses are to be reduced. In this connection drop forged parts (of bar stock, wires), in particular forged connecting rods, crankshafts and camshafts or valve parts can be mentioned. Titanium however exhibits, in comparison to metallic materials, a comparatively low modulus of elasticity (abbreviated: E-modulus in GPa; Materials Properties Handbook: Titanium Alloys, Editors: Boyer, Welsch, Collings, ASM International, Materials Park, OH 44073-002). Thus, the E-modulus of titanium alloy is approximately 90 GPa, that of steel is approximately 210 GPa, that of Al-alloys is approximately 70 GPa and that of Mg-alloys is approximately 30-40 GPa.
Drop forged moving titanium parts of motors, such as, for example, connecting rods, crankshafts, camshafts and/or valve parts, can as a result tolerate only low loads.
2. Description of Related Art
In the state of the art, coating processes for components are described, which lead to a hardening of the titanium alloy. DE 36 15 425 concerns a time and labor intensive plasma coating process for improving abrasion resistance of surface layers of titanium alloy machine components.
SUMMARY OF THE INVENTIONIt is the task of the present invention to provide a process for production of drop forge parts, which are comprised essentially of Ti, Zr, Hf or a corresponding alloy, in which a higher E-modulus of the drop forge parts is achieved.
The task is solved by a process, in which materials containing 80 wt. % or more Ti and/or Zr and/or Hf, or alloys thereof, during deformation, are heated 5-15K above the α/β phase boundary (transition temperature) and subsequently are cooled. Preferably, the heating takes place over a period of approximately 20-60 minutes. Thereby it is achieved, that the E-modulus and rigidity of the employed Ti, Zr, Hf materials is increased in and during the manufacture of drop forge parts.
With the aid of the inventive process the oscillating mass in a motor, in particular connecting rods, crankshafts and camshafts and/or valves, can be reduced up to 35% or more, in comparison with steel components. Advantages are achieved with respect to improved motor dynamics, lower noise emissions, dispensing of the Lancester counter-weight as well as savings in fuel.
BRIEF DESCRIPTION OF THE DRAWINGSDescription of the figures:
α/β web arrangement (microstructure) of a Ti connecting rod of Ti Al 6 Fe2 Si forged at 975° C. (white α- and grey β-lamella).
α/β web arrangement (microstructure) of a Ti connecting rod forged at 990° C. of Ti Al 6 Fe2 Si with isolated white α islands.
α/β web arrangement (microstructure) of a Ti connecting rod of Ti Al 6 Fe2 Si deformed at 975° C. and then relaxation treated at 650° C. (white α- and grey β-lamella).
DETAILED DESCRIPTION OF THE INVENTIONAs the Ti, Zr, Hf materials, suited for purposes of the invention are titanium as such, zirconium as such, hafnium as such; preferred however are alloys containing up to 80 wt. % or more Ti and/or Zr and/or Hf, preferably 90 wt. %. Particularly preferred are however titanium alloys with 80 wt. % titanium, preferably 90 wt. % titanium. Zr and Hf can be contained as minor components in the range of 1-20 wt. %, preferably 5-15 wt. %. Likewise, incidental amounts of conventional metals can be contained, such as Al, Si, Mg, Se, Ni, Co, Mo, V or other light and heavy metals. Further preferred alloys for employment in motor vehicle construction include Ti Al 6 V 4 or Ti Al 6 Fe2 Si.
In accordance with the invention, α/β-Ti-alloys or, as the case may be, α/β-Ti containing materials are employed which have both a high strength, cubic space-centered β-phase as well as hexagonal α-phase with high E-modulus. In the so-called high temperature deformation, more β-phases are produced and in the low temperature deformation, more α-phases are produced. In accordance with the invention, deformation occurs in the α/β zone, and namely, with heating 5-15° C., preferably 8-10-12° C. above the α/β phase boundary (transition temperature). With pure titanium, for example at 882.5° C., α-Ti transitions into β-Ti (so-called α/β phase boundary limit), that is, the heating should inventively occur at 887-897° C. For Ti Al 6 V 4 or Ti Al 6 Fe2 Si, the corresponding preferred heating value is 975° C.±15° C.
The duration of heating in the indicated temperature range is at least to twenty minutes to forty-five minutes or longer, preferably however not longer than one hour.
Thereby, during heating, the α-low temperature phase is replaced by the β-high temperature phase in such a manner, that an α/β microstructure, or as the case may be, an inventive composite, is produced (
Claims
1-10. (canceled)
11. A process for production of a drop forged part made of a metal alloy containing 80 wt. % or more Ti and/or Zr and/or Hf, wherein the drop forged part during deforming is heated 5-15 K above the α/β phase boundary to form β phases and is subsequently cooled.
12. A process according to claim 11, wherein said drop forged part is a moving part of a motor.
13. A process according to claim 11, wherein said drop forged part is a connecting rod, crankshaft, camshaft or a valve.
14. A process according to claim 11, wherein the material is heated for 20-60 minutes.
15. A process according to claim 11, wherein the relaxation thermal treatment occurs at 600-700° C. after cooling.
16. A process according to claim 11, wherein the E-modulus and the rigidity of the Ti and/or Zr and/or Hf containing materials, or alloys thereof, are increased.
17. A process according to claim 11, wherein the alloy is a titanium alloy containing 1-20 wt. % Zr and/or Hf and optionally incidental amounts of other light or heavy metals.
18. A process according to claim 11, wherein the alloy is a titanium alloy containing 5-15 wt. % Zr and/or Hf and optionally incidental amounts of other light or heavy metals.
19. A process according to claim 11, wherein the alloy is a titanium alloy containing 90 wt. % titanium.
20. A process according to claim 11, wherein the alloy is a titanium alloy selected from Ti Al 6 V 4 and Ti Al 6 Fe2 Si.
21. A process according to claim 11, wherein an α/β micro structure or composite material is formed.
22. A process according to claim 11, wherein the drop forge part after forging is slowly cooled in air.
23. A drop forged part made of a metal alloy containing 80 wt. % or more Ti and/or Zr and/or Hf, made by a process comprising:
- heating, during deforming, 5-15 K above the α/β phase boundary to form β phases; and
- subsequently cooling.
24. A drop forged part as in claim 23, wherein said part is a connecting rod, a crankshaft, a camshaft or a valve part.
25. A drop forged part made of a metal alloy containing 80 wt. % or more Ti and/or Zr and/or Hf, made by a process comprising:
- heating, during deforming, 5-15 K above the α/β phase boundary to form β phases; and
- subsequently cooling in such a manner that the E-modulus is increased.
Type: Application
Filed: Nov 16, 2004
Publication Date: Mar 29, 2007
Applicant:
Inventor: Andreas Barth (Leinfelden-Echterdingen)
Application Number: 10/580,896
International Classification: C22C 14/00 (20060101); C22C 16/00 (20060101);