FLAT FORM SPRING, IN PARTICULAR DISC OR WAVE SPRING

Abstract

A flat form spring, in particular a disc spring or corrugated spring, includes a spring body made of a low-alloy steel which has a carbon content of more than 0.35% by weight and at most 0.75% by weight. The steel contains between 0.3 wt. % and 0.9 wt. % manganese (Mn) as an alloying element. The steel also contains chromium (Cr) as an alloying element with a weight proportion of between 0.3 wt. % and 1.5 wt. %. The steel further contains between 0.1% and 0.6% by weight of molybdenum (Mo) as an alloying element. In addition, the steel contains more than 0.4 wt. % and up to 8 wt. % nickel (Ni) as an alloying element. A flatform spring made in this way has an improved strength compared to conventional flatform springs without a loss of toughness compared to a spring made of conventional spring steels.

Claims

1. A flat form spring comprising: a spring body made of a low-alloy steel which has a carbon content of more than 0.35% by weight and not more than 0.75% by weight, wherein the low-alloy steel contains between 0.3% and 0.9% by weight of manganese as an alloying element, wherein the low-alloy steel contains between 0.3% and 1.5% by weight of chromium as the alloying element, wherein the low-alloy steel contains between 0.1% and 0.6% by weight of molybdenum as the alloying element, and wherein the low-alloy steel contains more than 0.1% by weight and up to 8% by weight of nickel as the alloying element.

2. The flat form spring according to claim 1, wherein the low-alloy steel contains between 0.4% and 0.7% by weight of chromium as the alloying element.

3. The flat form spring according to claim 1, wherein the flat form spring is a disc spring or a corrugated spring.

4. The flat form spring according to claim 1, wherein a weight proportion of the low-alloy steel not formed by the alloying element is formed by iron, carbon, and fusion-related impurities.

5. The flat form spring according to claim 1, wherein a weight percentage of the alloying element of the low-alloy steel is not more than 5% by weight.

6. The flat form spring according to claim 1, wherein a weight percentage of the alloying element of the low-alloy steel is not more than 3.7% by weight.

7. The flat form spring according to claim 1, wherein the flatform spring contains at least one of vanadium, titanium, tungsten, and Niobium as the alloying element.

8. The flat form spring according to claim 1, wherein: the low-alloy steel contains at least one of vanadium, titanium, tungsten, and niobium as the alloying element, a first qualified sum of a weight proportion in % by weight of the at least one of the vanadium, the titanium, the tungsten, and the niobium and of the chromium in the low-alloy steel is formed by a sum of the weight proportion of the chromium and three times the weight proportion of the at least one of the vanadium, the titanium, the tungsten, and the niobium, when the alloying element is present in the low-alloy steel, and the first qualified sum is between 0.3% and 1.5% by weight.

9. The flat form spring according to claim 8, wherein the first qualified sum is between 0.4% and 0.7% by weight.

10. The flat form spring according to claim 1, wherein the low-alloy steel contains between 0.1% and 0.3% by weight of molybdenum as the alloying element.

11. The flat form spring according to claim 1, wherein low-alloy steel contains between 0.4% and 2% by weight of nickel as the alloying element.

12. The flat form spring according to claim 1, wherein low-alloy steel contains between 0.5% and 1% by weight of nickel the alloying element.

13. The flat form spring according to claim 1, wherein the low-alloy steel contains not more than 0.3% by weight of silicon as the alloying element.

14. The flat form spring according to claim 1, wherein the low-alloy steel contains vanadium, and/or titanium, and/or tungsten, and/or Niobium in each case with a weight proportion (x) of 0<x<0.2% by weight.

15. The flat form spring according to claim 1, wherein the low-alloy steel contains vanadium, and/or titanium, and/or tungsten, and/or Niobium, in each case with a weight proportion (x) of 0<x<0.1% by weight.

16. The flat form spring according to claim 1, wherein: a second qualified sum is calculated from weight percentages in % by weight of the alloying element silicon, manganese, chromium, nickel, tungsten, vanadium, titanium, niobium, and molybdenum as follows:
S2=Si+Mn+Cr+Ni+W+(V+Ti+NbMo)*3), and the second qualified sum is less than 3% by weight.

17. The flat form spring according to claim 10, wherein the second qualified sum is less than 2% by weight.

18. The flat form spring according to claim 1, wherein the low-alloy steel is quenched and tempered or bainitic quenched and tempered.

19. The flat form spring according to claim 1, wherein the low-alloy steel is quenched and tempered to a strength of more than 1700 MPa.

20. The flat form spring according to claim 1, wherein a carbon content of the low-alloy steel is more than 0.55% by weight.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The disclosure will now be described with reference to the drawing wherein:

[0027] FIG. 1 shows a schematic sectional view of a flat form spring 1, which is realized as a disc spring according to an exemplary embodiment of the disclosure. Other forms of flatform spring 1 are also conceivable, such as a wave spring not shown in FIG. 1.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0028] The flat shaped spring 1 configured as a disc spring includes a spring body 2 made of a low-alloy steel, which has a carbon content of more than 0.35% by weight and at most 0.75% by weight. The weight proportion of all alloying elements is at most 5 weight %, in a typical variant at most 3.7 weight %.

[0029] In the exemplary embodiment shown in FIG. 1, the steel contains between 0.3 wt. % and 0.9 wt. % manganese (Mn) as an alloying element. In the example exemplary embodiment shown in FIG. 1, the steel also contains chromium (Cr) as an alloying element. Chromium (Cr) is present in a proportion by weight of between 0.3% and 1.5%. In addition, the steel contains between 0.1% and 0.6% by weight of molybdenum (Mo) as an alloying element. Furthermore, the steel contains more than 0.1 wt. % and up to 8 wt. % nickel (Ni) as an alloying element. The weight proportion of the steel not formed by the alloying elements is formed by iron (Fe). In addition to the iron and the alloying elements, the steel may also contain a small amount of impurities, which, however, contribute to the total weight of the steel by not more than 0.1% by weight.

[0030] The weight proportion of all alloying elements of the low-alloy steel is expediently at most 5 wt. %, typically at most 3.7 wt. %. Typically, the carbon content of the steel is more than 0.55% and at most 0.75% by weight.

[0031] Furthermore, the steel may contain at least one of the alloying elements vanadium (V), titanium (Ti), tungsten (W) and niobium (Nb). In this variant, a (first) qualified sum (S1) of the percentage by weight (in % by weight) of these alloying elements (V, Ti, W, and Nb) and of the chromium (Cr) which is also necessarily present in the steel is formed by the sum of the percentage by weight of chromium (Cr) and three times the percentage by weight of the other four said alloying elements (V, Ti, W, and Nb), if these are present in the steel. If one, two or three of the said four alloying elements vanadium (V), titanium (Ti), tungsten (W), and niobium (Nb) are not present in the steel in this variant, they are not taken into account in the calculation of the (first) qualified sum (S1), i.e., their weight proportion is assumed to be 0 wt. %. In this variant, the (first) qualified sum (S1) is between 0.3 wt. % and 1.5 wt. %, typically between 0.4 wt. % and 0.7 wt. %.

[0032] The steel contains typically between 0.1 wt. % and 0.6 wt. % molybdenum (Mo) and/or between 0.5 wt. % and 1 wt. % nickel (Ni) as alloying elements.

[0033] Optionally, the steel may contain at most 0.3 wt. % silicon (Si) as an alloying element.

[0034] Typically, a (second) qualified sum (S2) is calculated from the weight percentages of the alloying elements silicon (Si), manganese (Mn), chromium (Cr), nickel (Ni), tungsten (W), vanadium (V), titanium (Ti), niobium (Nb), and molybdenum (Mb) as follows: S2=Si+Mn+Cr+Ni+W+(V+Ti+NbMo)*3). In this variant, the (second) qualified sum (S2) is less than 3% by weight, typically less than 2% by weight. The remaining or missing parts by weight of the spring body are expediently formed by iron (Fe) and production-related impurities.

[0035] Optionally, the steel can contain cobalt as an alloying element, but at most with some 0.1 wt. %. The steel must be suitably quenched and tempered and typically contains no pearlite. The low-alloy steel is typically for bainitic quenching and tempering. Typically the strength of the steel is more than 1700 MPa. The surface has a surface roughness Ra of less than 0.8 m at least in sections, typically completely. This surface roughness Ra can typically be achieved by polishing the relevant surfaces of the flatform springs.

[0036] The spring properties of the flatform spring presented here can be further improved by introducing suitable residual compressive stresses by shot peening, smooth rolling or deep rolling.

[0037] It is understood that the foregoing description is that of the exemplary embodiments of the disclosure and that various changes and modifications may be made thereto without departing from the spirit and scope of the disclosure as defined in the appended claims.