# US 9,752,636 B2 · Helical compression spring and method for manufacturing same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,752,636 B2 - Document ID: US9752636B2 - Status: Granted - Kind: B2 - Application number: 14/427,106 - Filed: 2013-09-05 - Published: 2015-09-10 - Granted: 2017-09-05 - Earliest claimed: 2012-09-14 - Assignees: NHK Spring Co., Ltd. - Applicants: Nhk Spring Co., Ltd. - Inventors: Yuitirou Ono; Tohru Shiraishi; Yoshiki Ono; Keita Takahashi - Web page: https://patentgrep.com/patent/US9752636B2 ## CPC - F16F 1/021: {characterised by their composition, e.g. comprising materials providing for particular spring properties (composition and manufacture of clock or watch springs G04B1/145)} - B21F 3/02: helically - B21F 35/00: Making springs from wire - B24C 1/10: for compacting surfaces, e.g. shot-peening (for deforming sheet metal, tubes or profiles B21D31/06; as a metallurgical treatment C21D7/00, C22F1/00) - C21D 1/06: Surface hardening - C21D 6/002: {containing Cr (C21D6/004 takes precedence)} - C21D 6/004: {containing Cr and Ni} - C21D 6/005: {containing Mn} - C21D 6/008: {containing Si} - C21D 7/06: by shot-peening or the like - C21D 8/06: during manufacturing of rods or wires - C21D 9/02: for springs - C22C 38/02: containing silicon - C22C 38/04: containing manganese - C22C 38/08: containing nickel {(C22C38/105 takes precedence)} - C22C 38/12: containing tungsten, tantalum, molybdenum, vanadium, or niobium - C22C 38/18: containing chromium - C22C 38/22: with molybdenum or tungsten - C22C 38/24: with vanadium - C22C 38/34: with more than 1.5% by weight of silicon - C22C 38/46: with vanadium - C23C 8/02: Pretreatment of the material to be coated (C23C8/04 takes precedence) - C23C 8/22: of ferrous surfaces - C23C 8/80: After-treatment - F16F 1/06: with turns lying in cylindrical surfaces - F16F 2224/0216: bimetallic - F16F 2226/00: Manufacturing; Treatments - F16F 2236/04: Compression - F16F 2238/026: wound- or coil-like - F16F: SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION - B21F: WORKING OR PROCESSING OF METAL WIRE (rolling of metal wire B21B1/16; by drawing, auxiliary operations used in connection with metal-working without essentially removing material B21C) - B24C: ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL - C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B) - C22C: ALLOYS (treatment of alloys C21D, C22F) - C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04) ## Abstract The coil spring includes steel wire material containing 0.45 to 0.80 weight % of C, 0.15 to 2.50 weight % of Si, 0.3 to 1.0 weight % of Mn and iron and inevitable impurities as the remainder, and having a circle equivalent diameter of 2.5 mm to 10 mm, in which internal hardness at a freely selected cross section of the wire material is in a range of 570 to 700 Hv, C-condensed layer which exceeds average concentration of C contained in the steel wire material exists at surface layer part, and in an approximate maximum principal stress direction generated when a compressive load is loaded on spring of inner diameter side of the coil spring of the wire material, unloaded compressive residual stress at a depth of 0.2 mm and 0.4 min from surface of the wire material is not less than 200 MPa and not less than 60 MPa, respectively. ## Claims ### Claim 1 A compression coil spring, comprising a steel wire material consisting of 0.45 to 0.80 weight % of C, 0.15 to 2.50 weight % of Si, 0.3 to 1.0 weight % of Mn and iron and inevitable impurities as the remainder, and having a circle equivalent diameter of 2.5 mm to 10 mm, wherein an internal hardness at a freely selected cross section of the wire material is in a range of 570 to 700 Hv, a C-condensed layer that exceeds an average concentration of C contained in the steel wire material exists at surface layer part, and in an approximate maximum principal stress direction generated when the coil spring is compressed and a compressive load is loaded on an inner diameter side of the coil spring, an unloaded compressive residual stress at a depth of 0.2 mm and 0.4 mm from surface of the wire material is not less than 200 MPa and not less than 60 MPa, respectively. ### Claim 2 (depends on 1) The compression coil spring according to claim 1, wherein in an approximate maximum principal stress direction generated when the coil spring is compressed and a compressive load is loaded on an inner diameter side of the coil spring, an unloaded maximum compressive residual stress is not less than 900 MPa. ### Claim 3 (depends on 1) The compression coil spring according to claim 1, wherein an average crystal particle diameter (an interface of a direction angle difference of not less than 5° is defined as the particle interface) measured by an SEM/EBSD method is not more than 2.0 μm. ### Claim 4 (depends on 1) The compression coil spring according to claim 1, wherein a hardness of the C-condensed layer is not less than 50 HV higher than the internal hardness. ### Claim 5 (depends on 1) The compression coil spring according to claim 1, wherein a maximum C concentration in the C-condensed layer is 0.7 to 0.9 weight %, and a thickness of the C condensed layer is 0.01 to 0.1 mm. ### Claim 6 (depends on 1) The compression coil spring according to claim 1, wherein a surface roughness (maximum height) is not more than 20 μm. ### Claim 7 A compression coil spring, comprising a steel wire material consisting of 0.45 to 0.80 weight % of C, 0.15 to 2.50 weight % of Si, 0.3 to 1.0 weight % of Mn and iron and inevitable impurities as the remainder, and having a circle equivalent diameter of 1.5 mm to 3 mm, wherein an internal hardness at a freely selected cross section of the wire material is in a range of 570 to 700 Hv, a C-condensed layer that exceeds an average concentration of C contained in the steel wire material exists at surface layer part, and in an approximate maximum principal stress direction generated when the coil spring is compressed and a compressive load is loaded on an inner diameter side of the coil spring, an unloaded compressive residual stress at a depth of 0.15 mm and 0.3 mm from surface of the wire material is not less than 300 MPa and not less than 50 MPa, respectively. ### Claim 8 (depends on 7) The compression coil spring according to claim 7, wherein in an approximate maximum principal stress direction generated when the coil spring is compressed and a compressive load is loaded on an inner diameter side of the coil spring, an unloaded maximum compressive residual stress is not less than 900 MPa. ### Claim 9 (depends on 7) The compression coil spring according to claim 7, wherein an average crystal particle diameter (an interface of a direction angle difference of not less than 5° is defined as the particle interface) measured by a SEM/EBSD method is not more than 2.0 μm. ### Claim 10 (depends on 7) The compression coil spring according to claim 7, wherein a hardness of the C-condensed layer is not less than 50 HV higher than the internal hardness. ### Claim 11 (depends on 7) The compression coil spring according to claim 7, wherein a maximum C concentration in the C-condensed layer is 0.7 to 0.9 weight %, and a thickness of the C condensed layer is 0.01 to 0.1 mm. ### Claim 12 (depends on 7) The compression coil spring according to claim 7, wherein a surface roughness (maximum height) is not more than 20 μm. ### Claim 13 A compression coil spring, comprising a steel wire material comprising 0.45 to 0.80 weight % of C, 0.15 to 2.50 weight % of Si, 0.3 to 1.0 weight % of Mn, 0.005 to 1.34 weight % of at least one of Cr, B, Ni, Ti, Cu, Nb, V, Mo, and W, and iron and inevitable impurities as the remainder, and having a circle equivalent diameter of 2.5 mm to 10 mm, wherein an internal hardness at a freely selected cross section of the wire material is in a range of 570 to 700 Hv, a C-condensed layer that exceeds an average concentration of C contained in the steel wire material exists at surface layer part, and in an approximate maximum principal stress direction generated when the coil spring is compressed and a compressive load is loaded on an inner diameter side of the coil spring, when defining a depth from a surface of the wire material at which a value of an unloaded compressive residual stress is zero as a crossing point, and when defining a value of an integral from the surface to the crossing point in a residual stress distribution curve having a vertical axis of residual stress and a horizontal axis of wire radius as I−σR, the I−σR is not less than 160 MPa·mm. ### Claim 14 (depends on 13) The compression coil spring according to claim 13, wherein Cr is contained 0.5 to 2.0 weight %. ### Claim 15 (depends on 13) A method for production of compression coil spring according to claim 13, comprising processes performed in the following order: a coiling process in which steel wire material is hot-formed by a coil spring forming apparatus, a quenching process in which a coil which is coiled and cut off and is still at an austenite temperature range is quenched as it is, a tempering process in which the coil is thermally refined, a shotpeening process in which compressive residual stress is imparted to wire material surface, and a setting process, wherein the coil spring forming apparatus comprises a feed roller continuously supplying the steel wire material, a coiling part coiling the steel wire material in a coil shape, and a cutting means for cutting the steel wire material which is continuously supplied from upstream after the steel wire material is coiled at a predetermined number of winding, the coiling part comprises a wire guide for introducing the steel wire material supplied by the feed roller to an appropriate position in processing part, a coiling tool including a coiling pin or coiling roller for processing the steel wire material supplied via the wire guide into a coil shape, and a pitch tool for imparting pitch, the coil spring forming apparatus further comprises a heating means in which the steel wire material is heated up to an austenite temperature region within 2.5 seconds between exit of the feed roller and the coiling tool, and wherein a carburizing process is performed in which hydrocarbons gas is directly sprayed to surface of the steel wire material between heating process and before quenching. ### Claim 16 (depends on 15) The method for production of compression coil spring according to claim 15, wherein the heating means is a high-frequency heating, and a high-frequency heating coil is arranged so as to be coaxial with the steel wire material on a route of passing of the steel wire material in the wire guide, or on a route of passing of the steel wire material in a space between end of steel wire material exit side of the wire guide and the coiling tool. ### Claim 17 (depends on 15) The method for production of compression coil spring according to claim 15, wherein surface temperature of the steel wire material when spraying the hydrocarbons gas is at 850 to 1150° C., and dynamic pressure of the hydrocarbons gas on the surface part of the steel wire material is 0.1 to 5.0 kPa. ### Claim 18 (depends on 13) A method for production of compression coil spring according to claim 13, comprising processes performed in the following order: a carburizing process in which C-condensed layer is formed on surface of steel wire material, a coiling process in which the steel wire material is hot-formed by a coil spring forming apparatus, a quenching process in which a coil which is coiled and cut off and is still at an austenite temperature range is quenched as it is, a tempering process in which the coil is thermally refined, a shotpeening process in which compressive residual stress is imparted to wire material surface, and a setting process, wherein a means for forming the C-condensed layer in the carburizing process is a method in which hydrocarbons gas is directly sprayed to surface of the steel wire material which is heated, the coil spring forming apparatus which is used in the coiling process comprises a feed roller continuously supplying the steel wire material, a coiling part coiling the steel wire material in a coil shape, and a cutting means for cutting the steel wire material which is continuously supplied from upstream after the steel wire material is coiled at a predetermined number of winding, the coiling part comprises a wire guide for introducing the steel wire material supplied by the feed roller to an appropriate position in processing part, a coiling tool including a coiling pin or coiling roller for processing the steel wire material supplied via the wire guide into a coil shape, and a pitch tool for imparting pitch, the coil spring forming apparatus further comprises a heating means in which the steel wire material is heated up to an austenite temperature region within 2.5 seconds between exit of the feed roller and the coiling tool, the heating means is a high-frequency heating, and a high-frequency heating coil is arranged so as to be coaxial with the steel wire material on a route of passing of the steel wire material in the wire guide, or on a route of passing of the steel wire material in a space between end of steel wire material exit side of the wire guide and the coiling tool, and wherein the carburizing process and the coiling process are continuous each other in which the steel wire material is not cut therebetween. ### Claim 19 (depends on 18) The method for production of compression coil spring according to claim 18, wherein surface temperature of the steel wire material when spraying the hydrocarbons gas is at 850 to 1150° C., and dynamic pressure of the hydrocarbons gas on the surface part of the steel wire material is 0.1 to 5.0 kPa. ### Claim 20 (depends on 13) A method for production of compression coil spring according to claim 13, comprising processes performed in the following order: a coiling process in which steel wire material is hot-formed by a coil spring forming apparatus, a heating and quenching process in which a coil is heated up to an austenite temperature range within 20 seconds and then quenched, a tempering process in which the coil is thermally refined, a shotpeening process in which compressive residual stress is imparted to wire material surface, and a setting process, wherein a heating means in the heating and quenching process is a high-frequency heating, and wherein a carburizing process is performed in which hydrocarbons gas is directly sprayed to surface of the steel wire material between heating process and before quenching. ### Claim 21 (depends on 20) The method for production of compression coil spring according to claim 20, wherein surface temperature of the steel wire material when spraying the hydrocarbons gas is at 850 to 1150° C., and dynamic pressure of the hydrocarbons gas on the surface part of the steel wire material is 0.1 to 5.0 kPa. ### Claim 22 (depends on 13) The compression coil spring according to claim 13, wherein in an approximate maximum principal stress direction generated when the coil spring is compressed and a compressive load is loaded on an inner diameter side of the coil spring, an unloaded maximum compressive residual stress is not less than 900 MPa. ### Claim 23 (depends on 13) The compression coil spring according to claim 13, wherein an average crystal particle diameter (an interface of a direction angle difference of not less than 5° is defined as the particle interface) measured by an SEM/EBSD method is not more than 2.0 μm. ### Claim 24 (depends on 13) The compression coil spring according to claim 13, wherein a hardness of the C-condensed layer is not less than 50 HV higher than the internal hardness. ### Claim 25 (depends on 13) The compression coil spring according to claim 13, wherein a maximum C concentration in the C-condensed layer is 0.7 to 0.9 weight %, and a thickness of the C condensed layer is 0.01 to 0.1 mm. ### Claim 26 (depends on 13) The compression coil spring according to claim 13, wherein a surface roughness (maximum height) is not more than 20 μm. ### Claim 27 A compression coil spring, comprising a steel wire material comprising 0.45 to 0.80 weight % of C, 0.15 to 2.50 weight % of Si, 0.3 to 1.0 weight % of Mn, 0.5 to 2.0 weight % of Cr, and iron and inevitable impurities as the remainder, and having a circle equivalent diameter of 2.5 mm to 10 mm, wherein an internal hardness at a freely selected cross section of the wire material is in a range of 570 to 700 Hv, a C-condensed layer that exceeds an average concentration of C contained in the steel wire material exists at surface layer part, and in an approximate maximum principal stress direction generated when the coil spring is compressed and a compressive load is loaded on an inner diameter side of the coil spring, when defining a depth from a surface of the wire material at which value of an unloaded compressive residual stress is zero as a crossing point, and when defining a value of an integral from the surface to the crossing point in a residual stress distribution curve having a vertical axis of residual stress and a horizontal axis of wire radius as L−σz, the L−σz is not less than 160 MPa·mm. ### Claim 28 (depends on 27) The compression coil spring according to claim 27, wherein in an approximate maximum principal stress direction generated when the coil spring is compressed and a compressive load is loaded on an inner diameter side of the coil spring, an unloaded maximum compressive residual stress is not less than 900 MPa. ### Claim 29 (depends on 27) The compression coil spring according to claim 27, wherein an average crystal particle diameter (an interface of a direction angle difference of not less than 5° is defined as the particle interface) measured by a SEM/EBSD method is not more than 2.0 μm. ### Claim 30 (depends on 27) The compression coil spring according to claim 27, wherein a hardness of the C-condensed layer is not less than 50 HV higher than the internal hardness. ### Claim 31 (depends on 27) The compression coil spring according to claim 27, wherein a maximum C concentration in the C-condensed layer is 0.7 to 0.9 weight %, and thickness of the C condensed layer is 0.01 to 0.1 mm. ### Claim 32 (depends on 27) The compression coil spring according to claim 27, wherein a surface roughness maximum height) is not more than 20 μm. ### Claim 33 A compression coil spring, comprising a steel wire material comprising 0.45 to 0.80 weight % of C, 0.15 to 2.50 weight % of Si, 0.3 to 1.0 weight % of Mn, 0.005 to 1.34 weight % of at least one of Cr, B, Ni, Ti, Cu, Nb, V, Mo, and W, and iron and inevitable impurities as the remainder, and having a circle equivalent diameter of 1.5 mm to 3 mm, wherein an internal hardness at a freely selected cross section of the wire material is in a range of 570 to 700 Hv, a C-condensed layer that exceeds an average concentration of C contained in the steel wire material exists at surface layer part, and in an approximate maximum principal stress direction generated when the coil spring is compressed and a compressive load is loaded on an inner diameter side of the coil spring, when defining a depth from a surface of the wire material at which a value of an unloaded compressive residual stress is zero as a crossing point, and when defining value of an integral from the surface to the crossing point in a residual stress distribution curve having a vertical axis of residual stress and a horizontal axis of wire radius as I−σR, the I−σR is not less than 130 MPa·mm. ### Claim 34 (depends on 33) The compression coil spring according to claim 33, wherein in an approximate maximum principal stress direction generated when the coil spring is compressed and a compressive load is loaded on an inner diameter side of the coil spring, an unloaded maximum compressive residual stress is not less than 900 MPa. ### Claim 35 (depends on 33) The compression coil spring according to claim 33, wherein an average crystal particle diameter (an interface of a direction angle difference of not less than 5° is defined as the particle interface) measured by a SEM/EBSD method is not more than 2.0 μm. ### Claim 36 (depends on 33) The compression coil spring according to claim 33, wherein a hardness of the C-condensed layer is not less than 50 HV higher than the internal hardness. ### Claim 37 (depends on 33) The compression coil spring according to claim 33, wherein a maximum C concentration in the C-condensed layer is 0.7 to 0.9 weight %, and a thickness of the C condensed layer is 0.01 to 0.1 mm. ### Claim 38 (depends on 33) The compression coil spring according to claim 33, wherein Cr is contained 0.5 to 2.0 weight %. ### Claim 39 (depends on 33) The compression coil spring according to claim 33, wherein a surface roughness (maximum height) is not more than 20 μm. ### Claim 40 A compression coil spring, comprising a steel wire material comprising 0.45 to 0.80 weight % of C, 0.15 to 2.50 weight % of Si, 0.3 to 1.0 weight % of Mn, 0.5 to 2.0 weight % of Cr, and iron and inevitable impurities as the remainder, and having a circle equivalent diameter of 1.5 mm to 3 mm, wherein an internal hardness at a freely selected cross section of the wire material is in a range of 570 to 700 Hv, a C-condensed layer that exceeds an average concentration of C contained in the steel wire material exists at surface layer part, and in an approximate maximum principal stress direction generated when the coil spring is compressed and a compressive load is loaded on an inner diameter side of the coil spring, when defining a depth from a surface of the wire material at which a value of an unloaded compressive residual stress is zero as a crossing point, and when defining a value of an integral from the surface to the crossing point in a residual stress distribution curve having a vertical axis of residual stress and a horizontal axis of wire radius as I−σR, the L−σR is not less than 130 MPa·mm. ### Claim 41 (depends on 40) The compression coil spring according to claim 40, wherein in an approximate maximum principal stress direction generated when the coil spring, an unloaded maximum compressive residual stress is not less than 900 MPa. ### Claim 42 (depends on 40) The compression coil spring according to claim 40, wherein an average crystal particle diameter (an interface of a direction angle difference of not less than 5° is defined as the particle interface) measured by a SEM/EBSD method is not more than 2.0 μm. ### Claim 43 (depends on 40) The compression coil spring according to claim 40, wherein a hardness of the C-condensed layer is not less than 50 HV higher than the internal hardness. ### Claim 44 (depends on 40) The compression coil spring according to claim 40, wherein a maximum C concentration in the C-condensed layer is 0.7 to 0.9 weight %, and a thickness of the C condensed layer is 0.01 to 0.1 mm. ### Claim 45 (depends on 40) The compression coil spring according to claim 40, wherein a surface roughness (maximum height) is not more than 20 μm.