NIOBIUM AND CHROMIUM LOW ALLOY CARBON STEEL FOR HIGH WEAR RESISTANT AUTOMOTIVE CHAIN LINK PLATES

Abstract

Niobium chromium low allow carbon steel for automotive chain link plates has improved wear resistance. In one preferred embodiment, the steel composition includes niobium, chromium, carbon, iron, and any impurities. One preferred composition including these components includes, by weight percentage, approximately 0.25% to 0.75% carbon, approximately 0.20% to 2.0% chromium, approximately 0.26% to 1.5% niobium, and the remaining component of the composition is iron. Trace amounts of impurities may also be present. In another embodiment, a steel composition includes, by weight percentage, approximately 0.25% to 0.75% carbon, approximately 0.2% to 1.0% manganese, approximately 0.05% to 0.60% silicon, approximately 0.26% to 1.5% niobium, approximately 0.20% to 2.0% chromium, up to approximately 0.30% aluminum, up to approximately 0.03% phosphorus, up to approximately 0.03% sulfur, and a remainder of the composition being iron and any other impurities.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The invention pertains to the field of steel compositions. More particularly, the invention pertains to steel compositions for automotive chain link plates.

Description of Related Art

A lot of effort has been put into developing wear resistant chains. One desire is to reduce wear and frictional losses for the next generation of engine timing chains to be used in gasoline direct injection (DI) engines and diesel engines. Current production chains in these types of engines have high wear or chain elongations and friction losses, which result in poor engine fuel efficiency and high emission, or even engine failure due to the malfunction of elongated chains which can cause tooth jump that leads to vehicle safety concerns. The prior art has mainly seen chain pin developments such as vanadium carbide (VC) pins or VC coated pins and stainless steel nitrided (SSN) pin technologies. There is a need in the art for more resistant timing chains for gasoline direct injection and diesel engines.

SUMMARY OF THE INVENTION

An optimum steel composition for automotive chain link plates has improved wear resistance. The composition is preferably low alloy carbon steel with niobium and chromium.

In one embodiment, a steel composition includes, by weight percentage, approximately 0.25-0.75% carbon, approximately 0.20-2.0% chromium, approximately 0.26-1.5% niobium, and the remainder of the composition is iron and any impurities. This composition may also optionally include one or more of the following: approximately 0.2 to 1.0% manganese, approximately 0.05 to 0.60% silicon, up to approximately 0.30% aluminum, up to approximately 0.03% phosphorus, or up to approximately 0.03% sulfur.

In another embodiment, a steel composition includes, by weight percentage, approximately 0.25 to 0.75% carbon, approximately 0.2 to 1.0% manganese, approximately 0.05 to 0.60% silicon, approximately 0.26-1.5% niobium, approximately 0.20 to 2.0% chromium, up to approximately 0.30% aluminum, up to approximately 0.03% phosphorus, up to approximately 0.03% sulfur, and a remainder of the composition being iron and any other impurities.

The compositions described herein are preferably used for automotive chain link plates. The chain links are preferably heat treated to a hardness in the range of HRc 50 to 60, either by oil quenching and tempering or salt bath austempring and/or martempering preferably by salt bath austempering and/or martempering.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a chain link/chain link plate that could be made using the compositions described herein.

FIG. 2 shows an example of a silent chain including chain links that could be made using the compositions described herein.

FIG. 3A shows a top view of an example of a roller chain that could be made using the compositions described herein.

FIG. 3B shows a side view of the roller chain of FIG. 3A.

FIG. 3C shows a section of the roller chain along line 3C-3C of FIG. 3A.

FIG. 4A shows a top view of an example of a bushing chain that could be made using the compositions described herein.

FIG. 4B shows a side view of the bushing chain of FIG. 4A.

FIG. 4C shows a section of the bushing chain along line 4C-4C of FIG. 4A.

DETAILED DESCRIPTION OF THE INVENTION

An optimum steel composition for automotive chain link plates has improved wear resistance. The composition is preferably Nb Cr low alloy carbon steel. The chain link plates made with the compositions are preferably used in silent chains, roller chains or bushing chains.

In one preferred embodiment, the steel composition includes niobium, chromium, carbon, iron, and any impurities. One preferred composition including these components includes, by weight percentage, approximately 0.25%-0.75% carbon, approximately 0.20%-2.0% chromium, approximately 0.26%-1.5% niobium, and the remaining component of the composition is iron. The amount of iron in the composition is the remainder of the weight percentage of the composition not made of other components in the composition. Trace amounts of impurities may also be present.

The composition may also include one or more of the following additional components (by weight percentage): approximately 0.2%-2.0% manganese, approximately 0.05%-0.60% silicon, up to approximately 0.30% aluminum, up to approximately 0.03% phosphorus, and up to approximately 0.03% sulfur. The amount of iron in the composition is the remainder of the weight percentage of the composition not made of other components in the composition.

The chain link plates made using this steel composition are preferably heat treated to a hardness in the range of HRc 50 to 60. In some embodiments, heat treatment occurs either by oil quenching and tempering or salt bath austempring and/or martempering preferably by salt bath austempering and/or martempering. In some embodiments, the hardness is in the range of HRc 52 to 58.

In one preferred embodiment, the composition includes the following percentages (wt %) of materials:

C	Mn	Si	Nb	Cr	Al	P	S
0.25-0.75%	0.2-1.0%	0.05-0.60%	0.26-1.5%	0.20-2.0%	0.30%	0.03%	0.03%
					max	max	max

The percentages of aluminum, phosphorus, and sulfur are preferably maximum amounts of each of these materials. Phosphorus and sulfur are impurities in steel and are preferred to be zero or as close to zero as possible. Aluminum is also an impurity, and should be kept as low as possible except in special applications. The remainder of the steel composition is composed of iron and any other impurities.

Steel compositions always have impurities and inclusions including, but not limited to, Sulfides (MnS), Alumina, and Silicate. There are industry standards to evaluate the inclusions. One of the most common is ASTM E45. This standard or other industry standards are used to control the amount of the impurities to an acceptable level.

The amount of iron in the composition is the remainder of the weight percentage of the composition not made of other components in the composition. The chain link plates of this steel composition are heat treated to a hardness of HRc 50-60. In some preferred embodiments, heat treatment uses either oil quenching and tempering or salt bath austempering and/or martempering by salt bath. In some embodiments, the hardness is in the range of HRc 52 to 58.

The steel composition for the chain links described herein fill the gap to further improve the wear resistance of the chains. The composition includes carbon, niobium, chromium, and iron. The steel of the composition preferably has a range of carbon from 0.25% to 0.75 wt %, which makes the steel hardenable after heat treatment. In some preferred embodiments, the carbon weight percentage ranges from 0.5-0.6%.

The composition also preferably includes a range of chromium from 0.2%-2.0 wt %, which improves the hardenability of the steel and makes the steel suitable for either oil quenching and tempering or austempering and martempering as hardening options. In some preferred embodiments, the chromium weight percentage ranges from 0.4%-0.6%.

The composition also preferably includes a weight percentage of niobium in the range of 0.26% to 1.5 wt %. In some preferred embodiments, the niobium content, by weight percentage, is between approximately 0.26% and 0.8%. In other embodiments, the niobium weight percentage in the composition is between 0.5% and 1.5%. In other embodiments, the niobium content, by weight percentage, is between 0.5% and 0.8%.

The niobium content in the steel composition not only inhibits the grain growth of the steel and results in a fine grained high strength steel, the niobium also forms nanoscale Niobium Carbide particles after heat treatment. Increased Niobium content results in more Niobium Carbide precipitation, with proper heat treatment. These particles are particularly prevalent if an austempering or martempering process is used for heat treatment, because of the limited solubility of niobium in steel (1.5% max in austerilized iron) and the reduced solubility with reductions of temperature during heat treatment. When the carbides distribute uniformly in the steel matrix in sub-micrometer and nanometer scale particles, the wear resistance of the steel increases greatly without negative impact on its fatigue properties, which are highly desired for the silent chain links. As a result, the wear resistance of the link plates are significantly improved.

The composition may also include one or more of the following additional components (by weight percentage): approximately 0.2%-2.0% manganese, approximately 0.05%-0.60% silicon, up to approximately 0.30% aluminum, up to approximately 0.03% phosphorus, and up to approximately 0.03% sulfur. The amount of iron in the composition is the remainder of the weight percentage of the composition not made of other components in the composition.

In one preferred embodiment, the composition includes the following percentages (wt %) of materials:

C	Mn	Si	Nb	Cr	Al	P	S
0.25-0.75%	0.2-1.0%	0.05-0.60%	0.26-1.5%	0.20-2.0%	0.30%	0.03%	0.03%
					max	max	max

In some of these embodiments, the carbon weight percentage ranges from 0.5%-0.6%, the chromium weight percentage ranges from 0.4%-0.6%, and/or the niobium content, by weight percentage, ranges from 0.26% and 0.8%. In other embodiments, the niobium content, by weight percentage, is greater than 0.5%. In other embodiments, the niobium content, by weight percentage, is between 0.5% and 0.8%. The amount of iron in the composition is the remainder of the weight percentage of the composition not made of other components in the composition.

FIG. 1 shows an example of a chain link plate 1 that can be made using the compositions described herein. FIG. 2 shows an example of a silent chain 10 including chain links 1 made using the compositions described herein. The chain includes guide or outside links A and inside links B, as well as pins 2. Any component of the silent chain 10 may be made of the compositions described herein.

FIGS. 3A-3C show an example of a roller chain 20 with bushings 35 that can be made using the compositions described herein. The roller chain 20 includes guide links 30, bushing links 31, rollers 32, pins, 33, 34 and bushings 35. Any component of the roller chain 20 may be made of the compositions described herein.

FIGS. 4A-4C show an example of a bushing chain 25 with bushings 45 that can be made using the compositions described herein. The bushing chain 25 includes guide links 40, bushing links 41, pins 43, and bushings 45. Any component of the bushing chain 25 may be made of the compositions described herein.

In preferred embodiments, the compositions described herein are used to make silent chain inside links B, which articulate with the pins 2 and have issues with wear. While it is not necessary to also use the steel compositions described herein for the guide links A, the compositions may also be used for the guide links A.

In other embodiments, the compositions described herein are used to make bushings 35, 45 in a roller chain 20 or a bushing chain 25. The compositions may also or alternatively be used to make the links 30, 31, 40, 41, the rollers 32, and/or other components of these types of chains.

The chain link plates made using the steel compositions described herein are preferably heat treated to a hardness in the range of HRc 50 to 60. In some embodiments, the composition is heat treated either by oil quenching and tempering or salt bath austempring and/or martempering preferably by salt bath austempering and/or martempering. In some embodiments, the hardness of the chain link plates is in the range of HRc 52 to 58.

In some embodiments, chain link plates made with the composition described herein are used in combination with advanced pin technologies including, but not limited to, VC pins or SSN pins.

In some embodiments, the composition does not include tungsten (W). In some embodiments, the composition does not include any molybdenum (Mo). In some embodiments, the composition does not include titanium (Ti), Nickel (Ni), and/or boron (B).

The chain link plate compositions described herein create a more wear resistant chain. Due to the improved wear resistance of the steel compositions described herein, it is unnecessary to coat the chain link plates made with the compositions. This eliminates both the cost and time associated with expensive coating processes.

Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.

Claims

1.-10. (canceled)

11. A chain link comprising a steel composition comprising, by weight percentage, approximately 0.25% to 0.75% carbon, approximately 0.26% to 1.5% niobium, approximately 0.20% to 2.0% chromium, iron and any impurities.

12. The chain link of claim 11, wherein the chain link has a hardness of HRc 50 to 60.

13. The chain link of claim 12, wherein the chain link has a hardness of HRc 52 to 58.

14. The chain link of claim 11, wherein the weight percentage of carbon in the composition ranges from approximately 0.5% to 0.6%.

15. The chain link of claim 11, wherein the weight percentage of chromium in the composition ranges from approximately 0.4% to 0.6%.

16. The chain link of claim 11, wherein the weight percentage of niobium in the composition is greater than 0.5%.

17. The chain link of claim 11, wherein the weight percentage of niobium in the composition ranges from approximately 0.26% to 0.8%.

18. The chain link of claim 11, wherein the composition further comprises, by weight percentage, approximately 0.2% to 1.0% manganese.

19. The chain link of claim 11, wherein the composition further comprises, by weight percentage, approximately 0.05% to 0.60% silicon.

20. The chain link of claim 11, wherein the composition further comprises at least one impurity, by weight percentage, selected from the group consisting of:

a) up to approximately 0.3% aluminum;

b) up to approximately 0.03% phosphorus;

c) up to approximately 0.03% sulfur; and

d) any combination of up to approximately 0.3% aluminum, up to approximately 0.03% phosphorus and up to approximately 0.03% sulfur.

21. The chain link of claim 11, wherein the composition further comprises approximately 0.2% to 1.0% manganese and approximately 0.05% to 0.60% silicon.

22.-36. (canceled)

37. A chain link comprising a composition comprising, by weight percentage, approximately 0.25% to 0.75% carbon, approximately 0.2% to 1.0% manganese, approximately 0.05% to 0.60% silicon, approximately 0.26% to 1.5% niobium, approximately 0.20% to 2.0% chromium, up to approximately 0.30% aluminum, up to approximately 0.03% phosphorus, up to approximately 0.03% sulfur, and a remainder of the composition being iron and any other impurities.

38. The chain link of claim 37, wherein the chain link has a hardness of HRc 50 to 60.

39. The chain link of claim 38, wherein the chain link has a hardness of HRc 52 to 58.

40. A chain that includes a plurality of links, each link comprising a steel composition comprising, by weight percentage, approximately 0.25% to 0.75% carbon, approximately 0.2% to 1.0% manganese, approximately 0.05% to 0.60% silicon, approximately 0.26% to 1.5% niobium, approximately 0.20% to 2.0% chromium, up to approximately 0.30% aluminum, up to approximately 0.03% phosphorus, up to approximately 0.03% sulfur, and a remainder of the composition being iron and any other impurities.

41. The chain of claim 40, wherein the links have a hardness of HRc 50 to 60.

42. The chain of claim 41, wherein the links have a hardness of HRc 52 to 58.

43. A method of producing a chain link, comprising the step of heat treating a steel composition comprising by weight percentage, approximately 0.25% to 0.75% carbon, approximately 0.2% to 1.0% manganese, approximately 0.05 to 0.60% silicon, approximately 0.26% to 1.5% niobium, approximately 0.20 to 2.0% chromium, up to approximately 0.30% aluminum, up to approximately 0.03% phosphorus, up to approximately 0.03% sulfur, and a remainder of the composition being iron and any other impurities, to a hardness of HRc 50 to 60.

44. The method of claim 43, wherein the heat treating step uses a method selected from the group consisting of oil quenching and tempering, salt bath austempering, and salt bath martempering.