WO2004029314A1 - 機械部品およびその製造方法 - Google Patents
機械部品およびその製造方法 Download PDFInfo
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- WO2004029314A1 WO2004029314A1 PCT/JP2003/011612 JP0311612W WO2004029314A1 WO 2004029314 A1 WO2004029314 A1 WO 2004029314A1 JP 0311612 W JP0311612 W JP 0311612W WO 2004029314 A1 WO2004029314 A1 WO 2004029314A1
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- hardness
- nitriding
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Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/06—Surface hardening
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- 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
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
- C23C8/24—Nitriding
- C23C8/26—Nitriding of ferrous surfaces
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- 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
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/40—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions
- C23C8/42—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions only one element being applied
- C23C8/48—Nitriding
- C23C8/50—Nitriding of ferrous surfaces
Definitions
- the present invention relates to a mechanical component made of steel subjected to a surface hardening treatment by a nitriding treatment and a method of manufacturing the same. And a method of manufacturing the same.
- Machine parts such as gears, bearings, shafts, crankshafts and connecting rods are required to have high levels of wear resistance and fatigue characteristics. Therefore, when manufacturing these mechanical parts, surface hardening is generally performed to increase the strength of the parts such as wear resistance and fatigue characteristics.
- the surface hardening treatment is performed by hot forging a forging material made of steel such as carbon steel for machine structural use and alloy steel, performing heat treatment such as normalizing, and further forming a desired shape required for various machine parts. This is done after machining. After performing this surface hardening treatment, finishing such as bending correction is performed, and the product is manufactured as a mechanical part.
- the surface hardening treatment described above is performed by a nitriding treatment such as a salt bath nitriding treatment or a gas soft nitriding treatment.
- a nitriding treatment such as a salt bath nitriding treatment or a gas soft nitriding treatment.
- this nitriding treatment generates a smaller amount of distortion after the treatment than a surface hardening treatment such as a carburizing treatment, and it is recognized that this nitriding treatment is a particularly useful method.
- the surface hardening treatment is performed by nitriding, the amount of generated strain may not be acceptable, and as a result, the surface hardening Later, it is often necessary to perform straightening.
- the smoothness of the process depends on the surface hardness after surface hardening.
- the softer the surface hardness the higher the bending straightness.
- the softer the surface hardness the lower the component strength, such as the wear resistance and fatigue characteristics, of the mechanical components. Therefore, in order to increase the component strength of the mechanical component, the higher the surface hardness after the surface hardening treatment, the better.
- the present invention has been made in view of this problem, that is, the present invention is to perform a surface hardening treatment by nitriding treatment and to improve both the component strength and the bending straightening property. It is an object of the present invention to provide a mechanical part and a method for manufacturing the same. Disclosure of the invention
- Machine parts made of steel and surface-hardened by nitriding.
- the inner layer has a picker hardness of the surface layer at a reference position corresponding to a depth of 50 from the member surface of the mechanical component and is approximately 40 to 46 OHV, and has a substantially constant hardness not affected by nitriding.
- the Vickers hardness of the part is 190 to 260 HV, and the effective hardened layer depth from the surface of the member whose Vickers hardness is 27 OHV is adjusted to 0.3 mm or more.
- a method for manufacturing a mechanical component according to the present invention for solving the above-described problems includes:
- the Vickers hardness of the surface layer at the reference position corresponding to a depth of 50 / itn from the member surface of the mechanical part in the nitriding treatment is 3400 to 460 HV, substantially not affected by nitriding.
- the Vickers hardness of the inner layer part showing a certain hardness is 190 to 26 OHV, and the effective hardened layer depth from the surface of the member with Vickers hardness of 270 HV is 0.3 mm or more.
- the mechanical component of the present invention is directed to a component made of steel and subjected to a surface hardening process by a nitriding process.
- the nitriding treatment means that, during the treatment, a nitrogen component is diffused from the member surface of the mechanical component toward the inner layer portion, and the surface layer portion of the mechanical component is nitrided, so that the surface of the surface layer portion including the member surface is This is a process for increasing hardness. Therefore, the problem in the present invention is to increase the surface hardness by nitriding treatment and to impart both excellent component strength and bending straightness to a machine component provided as a product after the nitriding treatment. It is.
- the surface hardness of the surface layer of machine parts can be increased by nitriding.
- the mechanical strength of mechanical parts such as wear resistance and fatigue properties increases.
- the bending straightness which indicates the ease of bending straightening performed after nitriding, decreases.
- this decrease in bending straightness causes defects such as microcracks on the surface of the member during the bending straightening process, and as a result, it is not possible to commercialize mechanical parts as good products. This is a factor that causes a reduction in product yield.
- the mechanical component of the present invention is subjected to a surface hardening treatment by a nitriding treatment, and a surface portion at a reference position corresponding to a depth of 50 // m from the surface of the member (hereinafter referred to as a surface portion).
- the Vickers hardness of the reference layer is 340 to 46 OHV
- the Vickers hardness of the inner layer part (hereinafter simply referred to as the inner layer part) which shows a substantially constant hardness that is not affected by nitriding is 190.
- the effective hardened layer depth from the surface of the member having a Vickers hardness of 270 HV is adjusted to 0.3 mm or more.
- the Vickers hardness at the surface layer reference position is less than 340 HV, the surface hardness is small, and the component strength cannot be excellent and useful.
- the Vickers hardness at the surface layer reference position exceeds 460 HV, the surface hardness is assumed to be large, and defects such as micro cracks are likely to be induced during the bending straightening process. It cannot be excellent and useful.
- the Vickers hardness of the inner layer portion is less than 190 HV, nitriding is performed, and even when the Vickers hardness at the reference position of the surface layer is within a desired range, the nitriding process is performed from the surface of the member.
- the desired hardness is not provided to a sufficient depth position, and as a result, the surface hardness is reduced and the component strength may not be excellent and useful.
- the nitriding treatment is performed, and even when the Vickers hardness at the reference position of the surface layer is within a desired range, the surface layer imparted by the nitriding treatment is formed. In some cases, the increase in hardness becomes too large, and as a result, the surface hardness is increased, and it may not be possible to make the bend straightening excellent and useful.
- the diffusion concentration of the nitrogen component attenuates in the depth direction and exhibits a substantially constant hardness without the influence of nitriding.
- diffusion of the nitrogen component stops.
- the increase in hardness hardened by the nitriding treatment is attenuated in the depth direction from the member surface to the inner layer.
- the attenuation rate of this attenuation varies arbitrarily depending on the type and content of the constituent elements of the steel used as the material of the mechanical parts, the processing temperature and the processing time in the nitriding treatment, and the like.
- the effective hardening depth from the surface of the member having a Vickers hardness of 27 OHV (hereinafter, also simply referred to as the effective hardening depth) is 0.3 mm or more.
- This condition means that the damping rate in the depth direction from the component surface to the inner layer part, which decreases in the depth direction, and the attenuation rate of the increase in hardness hardened by the nitriding treatment is weakened.
- the surface layer portion of the component can have higher hardness from the member surface to a deeper position. Specifically, if the effective hardening depth from the surface of the member having a Vickers hardness of 270 HV is less than 0.3 mm, the hardness distribution in the depth direction of the surface layer portion of the mechanical part is reduced. However, it becomes too abruptly attenuated in the depth direction, and as a result, the surface hardness cannot be obtained to make the component strength excellent and useful.
- the hardness of the surface layer part reference position, the hardness of the inner layer part, and the effective hardening depth are specified, and the hardness distribution in the depth direction from the member surface of the machine component is optimized, It is possible to make the parts excellent in both part strength and bending straightness.
- various types of steel are used for the mechanical parts. Therefore, in the production method, the amount of nitrogen component flowing into the member surface per hour, the treatment temperature, the treatment time, etc., in the nitriding treatment are adjusted by appropriately adjusting to the composition of the steel as the material.
- Surface layer reference position, inner layer and effective hardening depth In addition to being within the above range, it is possible to make the mechanical parts excellent in both part strength and bending straightness.
- C r [e q.] is 0.72% or more and 1.0% or less
- C [eq.] is 0.65% or more 0.
- the composition of each component is adjusted so that it is 8% or less
- Mn Content of Mn (% by weight);
- T is changed in the range of 500 to 650, On the X plane, ⁇ , (0.3X10 " 3 ) ⁇ 270 (
- An area that can move under the conditions is defined as an area Z. It is characterized by being present in a region z represented by.
- the degree of the surface layer hardened by nitriding is affected by the composition of the steel used as the material for the mechanical parts. Therefore, in order to more reliably set the hardness at the surface layer reference position, the hardness at the inner layer portion, and the effective hardening depth within the range specified above, the inner layer corresponding to the hardness of the surface layer portion before nitriding treatment
- An effective means is to optimize the composition of the steel that effectively contributes to the hardness of the part and the composition of the steel that effectively contributes to nitriding.
- C r [e q.] If its value is less than 0.72%, the Vickers hardness at the reference position of the surface part of the machine part even when nitriding is applied. If the value of Cr [e q.] Exceeds 1.0%, the surface layer will be excessively hardened during nitriding, and the reference position of the surface of the mechanical parts will not be obtained. May not be able to reduce Vickers hardness below 460 HV.
- This C [eq.] Is an indicator of a composition component that effectively increases the hardness in the inner layer. It was found that the components that effectively increase the hardness of the inner layer in the mechanical component were C, Cr, Cu, Ni, Mn, and Si in the order in which the effects were significant.
- the constant term indicating the degree is a measured value based on the measurement result, as described above.
- C [e q.] Has such a meaning, if the value is less than 0.65%, the Vickers hardness of the inner layer of the mechanical part may not be able to be increased to more than 190 HV. If the value of C, [e q.] Exceeds 0.86%, the hardness of the inner layer becomes excessively high, and the Vickers hardness may not be reduced to 260 HV or less.
- Mn Content of Mn (% by weight);
- T is changed in the range of 500 to 650, in on the X-plane ⁇ , of (0.3X10- 3) ⁇ 270
- the area that can move under the conditions is area ⁇ . It exists in the area ⁇ represented by.
- x 0
- the nitriding treatment is a treatment in which a nitrogen component is diffused from the surface of the member in the depth direction, and the surface layer is cured by nitriding. Therefore, the diffusion concentration of the nitrogen component at a certain depth position from the member surface is closely correlated with the hardness hardened by nitriding at the certain depth position, and can be approximately replaced. is there. Therefore, first, C (X) in the equation (2) is replaced with a hardness distribution H '(X) in the depth direction X from the member surface after the nitriding treatment.
- H'0 the hardness of the inner layer of the mechanical component
- H '0 C [e q.] X 2 54 + 33.8
- H '0 is used together with C [e q.]
- C 1 in equation (2) is H ′ 1 indicating the hardness of the mechanical part at the reference position of the surface layer. In other words, since the exact hardness of the surface of the mechanical part cannot be measured, H ′ 1 is represented as the surface of the mechanical part.
- H'1 Cr [eq.] X392 + 65.8, and H, 1 together with Cr [e ⁇ .] Based on the actual measurement value.
- a formula approximating the formula ⁇ ⁇ is a formula 1.
- D in equation (2) is the diffusion coefficient in metals and alloys.
- activation energy Q gas constant R of 1 mo 1 and temperature in degrees Celsius T
- D D 0 X e X p (-Q / (RX (T + 27 3))
- the material of the mechanical component is steel, and the content of the main component Fe is at least 50% by weight.
- the diffusion constant D is assumed to be the case where N diffuses as a diffusion element in pure Fe.
- Equation ⁇ ⁇ that is not in Equation is a correction diffusion coefficient for correcting the diffusion coefficient D used in Equation 1. Therefore, the corrected diffusion coefficient was set to (—1.47 X Si 1 ⁇ 0.918 XMn + 0.998).
- This corrected diffusion coefficient ⁇ is to incorporate into H '(x) the effect of constituent elements other than Fe contained in steel on the diffusion of ⁇ .
- This ⁇ is also a measured value based on the result of the detailed hardness measurement. It should be noted here that Si and ⁇ , especially Si, contained in the steel are component elements that suppress the diffusion of N. In other words, as the content of Si and Mn increases, the intensity decreases sharply.
- the Si content it is preferable to adjust the contents of Si and Mn so that the range of H is in the range of 0.3 to 1.6.
- H '(X) t is with a processing time of nitriding treatment, as its value is typically in the range of 3. 6 X 1 0 3 ⁇ 1 8 X 1 0 3 seconds.
- T is a processing temperature of the nitriding treatment, and the value is generally in a range of 500 to 600 ° C.
- H '(x) as described above.
- This H '(X) is a function that, when uniquely determining the composition of steel used as a material for machine parts, uses the values of t and T relating to the processing conditions of nitriding as arbitrary variables.
- the definition of the region of H (X) in the region Z means that the content of C r [e q.], C [e q.] And Si contained in H ′ (X),
- the requirements for the steel composition of the machine component material, such as the Mn content have been optimized within the range of general nitriding treatment conditions. In this way, by optimizing the steel composition of the material, it is possible to more reliably impart excellent component strength and bending straightness to machine components.
- the range of Cr [eq.] And C [eq.] Contained in steel used as the material of machine parts is adjusted to the same range as described above, and the nitriding conditions are set as follows. By setting the following range, it is possible to more reliably impart excellent component strength and bending straightness to the machine component.
- the nitriding conditions in the process of gas soft or salt bath nitriding, the nitriding time 3. 6 X 1 0 3 ⁇ 1 8 X 1 0 3 seconds, nitrogen The chemical treatment temperature is set to 500 to 600C.
- the nitriding condition is a condition in a commonly used gas soft nitriding or salt bath nitriding treatment.
- the nitriding temperature is lower than 500 ° C.
- the diffusion of the nitrogen component is excessively weakened, and the machine component is provided with a profile having a desired surface hardness in the depth direction by the nitriding treatment. May not be possible.
- the nitriding temperature exceeds 650 ° C, on the contrary, the diffusion of the nitrogen component becomes excessively high, and the surface hardness may become too hard than desired. Then a nitridation processing time but, 3. 6 X 1 0 3 sec, i.e. when less than an hour, making it possible to impart profiles of at nitriding process to a desired surface hardness in the depth direction to the machine parts It may not be possible.
- the nitriding time is longer than 18 ⁇ 10 3 seconds, that is, 5 hours, the surface hardness may be too hard than desired.
- the range of the nitriding time and the temperature of the nitriding process are set based on such contents, it can be said that the ranges are general ranges from the viewpoint of the working efficiency in manufacturing and the like. Based on these reasons, the main nitriding treatment conditions are set, and as a result, it is possible to more reliably impart excellent component strength and bending straightness to machine components.
- the content of Fe in weight% is 90% or more, and C: 0.35 to 0.5% and Si: 0.01, respectively. ⁇ 0.3%, Mn: 0.6 ⁇ : L. 8%, Cu: 0.01 ⁇ 0.5%, Ni: 0.01 ⁇ 0.5%, Cr: 0. . 0 1 ⁇ 0 5%, A 1 : 0. 00 1 ⁇ 0 0 1 0/0, N:. 0. 00 5 ⁇ 0.
- the mechanical component of the present invention is made of steel. Therefore, as described above, Fe is a main component. Specifically, the content of Fe is weight. It is 90% or more at / 0 . Therefore, it is a component element other than F e, first, C is a weight 0/0, is contained 0.3 5 to 0.5%. C is effective to effectively increase the hardness of the mechanical part at the reference position in the inner layer and the surface layer. By containing 0 ; 35% or more, the effect is remarkable. can do. On the other hand, if the content exceeds 0.5%, In some cases, the result is excessive, and the hardness of the surface layer of the machine component cannot be made as desired.
- the machinability may be reduced when machining a forged material made of steel into a desired shape of a mechanical part.
- S i is the weight. /.
- the content is between 0.01 and 0.3%. Since Si is used as a deoxidizing element when smelting steel, its content is required to be at least 0.01% or more. However, as described above, Si is a component element that suppresses the diffusion of N in the nitriding treatment. Therefore, in order to ensure that a desired hardness profile is imparted to the mechanical parts, the content is preferably set to 0.3% or less in the present invention. Next, 0.6 to 1.8% of Mn is contained by weight.
- Mn is effective for effectively increasing the hardness of the mechanical part at the reference position in the inner layer and the surface layer, and the effect is remarkable by containing 0.6% or more. can do.
- the content exceeds 1.8%, bainite may be generated during operations such as hot forging and normalizing before nitriding.
- Mn is a component element that suppresses the diffusion of N during nitriding, although not as much as Si. In this sense, it is desirable that the content of Mn be 1.8% or less.
- both Cu and Ni are contained in a weight percentage of 0.01 to 0.5%. Both Cu and Ni are contained as inevitable impurities in an amount of 0.01% or more, but both elements are effective in effectively increasing the hardness of the inner layer of mechanical parts. However, from an economic point of view, if the content exceeds 0.5%, it becomes uneconomical and the cost of machine parts increases, so their content is set to 0.5% or less.
- Cr is the weight. At / 0 , it is contained in the range of 0.01 to 0.5%. Cr is effective in effectively increasing the hardness of the mechanical part at the reference position in the inner layer and the surface. Therefore, by setting the content to 0.1% or more, the effect can be remarkable.
- a 1 is 0.001 to 0.01% Contained.
- A1 is used as a deoxidizing element when smelting steel like Si, so its content is required to be at least 0.001% or more. However, A1 may excessively increase the hardness of the mechanical component at the surface reference position, so its content is preferably set to 0.01% or less.
- N is contained in 0.005 to 0.0255% by weight in terms of% by weight. N forms nitrides with A 1 and effectively suppresses the grain growth of steel components during hot forging and the like. Therefore, the content is preferably 0.005% or more, but if the content exceeds 0.025%, the effect is saturated, so that 0.025% as the upper limit is sufficient. .
- the above Pb, S, Ca, and Bi are component elements effective for enhancing machinability when machining a forged material made of steel or the like into a desired shape of a machine component.
- the machinability is secured
- the contents of Pb, S, Ca, and Bi are respectively. If the contents exceed the above upper limits, the strength of parts such as hot workability and fatigue properties of mechanical parts may decrease.
- Pb is 0.30% or less
- S is 0.20% or less
- C is 0.20% or less
- Ti, Zr, and Mg are elements that have an effect of finely dispersing MnS and the like by the oxides formed when the steel is melted. In addition to this effect, the machinability during machining is improved, and for example, after heat treatment such as normalizing performed after hot forging.
- the requirements for the mechanical component of the present invention for imparting both component strength and bending straightness have been described above.
- the mechanical parts to which the present invention is applied are not particularly limited, and can be applied to known mechanical parts such as gears, bearings, shafts, crankshafts, and connecting ports.
- the crankshaft is the limited one.
- Crankshafts are used at high-speed rotation, and are mechanical parts that need to reliably control eccentricity by bending correction. Therefore, when it is applied to the mechanical component of the present invention, which is capable of improving both the component strength and the bending correction property, the usefulness thereof can be enhanced.
- FIG. 1 is a schematic side view showing one embodiment of a mechanical component of the present invention.
- FIG. 2 is a cross-sectional view taken along line II-II of FIG.
- FIG. 3 is a diagram showing measurement results of the present example together with a hardness profile based on a theoretical formula.
- FIG. 1 is a schematic side view showing a fillet part of a main part of a crankshaft which is an embodiment of a mechanical part.
- FIG. 2 is a schematic cross-sectional view when a cross-section is taken along line ⁇ - ⁇ of the fillet portion in FIG.
- the fillet part 1 is referred to as a mechanical part 1 in the drawing.
- the crankshaft is formed by assembling them. Even if it is regarded as a mechanical part of the invention, it does not depart from the spirit of the invention.
- the fillet portion 1 is made of steel and subjected to nitriding. Then, as shown in FIG. 2, the surface layer 2 has a surface hardness increased by nitriding by nitriding, and the inner layer 3 has a substantially constant hardness that is not affected by nitriding.
- the surface layer portion 2 has such a shape that the hardness decreases in the depth direction from the member surface 4 to the inner layer portion 3.
- the Vickers hardness of the inner layer 3 is 190 to 260 HV, and the Vickers hardness of the inner layer 3 at the reference position corresponding to a depth of 50 ⁇ m from the surface of the member in the surface layer 2 is 340 to HV.
- the effective hardened layer depth from the surface 4 of the member having a Vickers hardness of 470 HV and a Vickers hardness of 270 HV is adjusted to 0.3 mm or more.
- the mechanical component 1 can have excellent component strength such as wear resistance and fatigue characteristics. At the same time, it is possible to improve the bending straightening property at the time of bending straightening performed after nitriding.
- a steel adjusted to a predetermined composition is melted so as to have the composition of the steel used as the material of the machine parts, and the material is forged by hot forging. Then, the forged material made of the steel is tempered by heat treatment such as normalizing, quenching, and tempering, and then machined according to the shape of a desired mechanical part.
- the surface is hardened by nitriding to improve the strength of the parts.
- a bending correction process is performed to correct the bending to a desired allowable range, including the bending caused by the distortion generated in the nitriding process.
- the machine parts are provided as products.
- a mechanical part consists of two or more types of components and they are manufactured individually, the components are regarded as mechanical parts, and after being manufactured according to the above-mentioned manufacturing flow, By incorporating them, a mechanical part having a desired shape is obtained.
- the mechanical parts of the present invention cover well-known mechanical parts such as gears, bearings, shafts, crankshafts, and connecting rods. It may be considered a mechanical part of the invention.
- the above-mentioned manufacturing method is an example, and may be a non-heat-treated one in which heat-treatment by heat treatment performed after hot forging is omitted. What is important is that at least the surface hardening treatment is performed by nitriding treatment, and then the finishing is performed by bending straightening treatment, and any manufacturing method that can be used as a manufacturing method according to the present invention can be applied to machine parts. It is. Further, as the nitriding treatment, a known treatment such as a salt bath nitriding treatment or a gas soft nitriding treatment can be used.
- the depth of the surface layer in the machine component can be reduced. It is possible to make the hardness distribution desired. Examples performed to confirm the effects of the present invention will be described below.
- Table 1 also shows the chromium equivalent Cr [eq.] And the carbon equivalent C [eq.] Of the steel used as the material for each test sample. ] Using the values of Cr [eq.] And C [eq.], The surface of the member in the theoretical formula H '(X) Table 1 also shows the value of Vickers hardness (HV) at a depth x of 0.3 mm from, that is, the calculation result of H (0.3 X 10 3 ).
- HV Vickers hardness
- the cross-sectional hardness of the test specimen was measured with a Vickers hardness tester at a depth of 0.1 mm at a load of 2.9 kN for a time of 15 seconds.
- the Vickers hardness at a position 50 m from the surface of the member and the hardness of the surface of the member are measured here.
- the Vickers hardness at a depth of 0.3 mm from the surface of the member (hereinafter referred to as the effective hardening depth position), the fatigue strength as an index of the fatigue characteristics, and the indentation of the bending straightness index are shown. See Figure 2.
- the cross-sectional hardness measurement, fatigue property measurement, and bending straightness measurement performed here were performed using individual specimens manufactured under the same conditions.
- the machinability in machining and the like when producing test specimens was evaluated.
- the evaluation of the machinability was performed as follows. In the same manner as above, a steel having the chemical composition shown in Table 1 was melted, and a rod-shaped forging material having a diameter of 40 mm produced by hot forging was heated and held at 880 ° C for 60 minutes. A normalizing material that had been subjected to a normalizing process to be cooled to room temperature was prepared. Then, a cut test using a carbide tool was performed on this normalized material to evaluate the machinability.
- the cutting test was performed at a cutting speed of 200 m / min, a feed rate of 2 mm / rotation, a cutting width of 2 mm, and a cutting time until the wear width of the lateral flank of the carbide tool became 0.2 mm. It was to be measured.
- the baking corresponding to Assuming that the cutting time of the normalized material is 100, Table 2 shows the normalized cutting time of the normalized material corresponding to the other test specimens with this value as the machining efficiency indicating the machinability.
- the products of Examples 1 to 10 Vickers hardness of the inner layer is from 190 to 26 OHV, and Vickers hardness at the effective hardening depth position is at least 270 HV.
- the parts having a fatigue strength of 40 OMPa or more as an index of the fatigue characteristics and an indentation of 2 mm or more as an index of the bending straightness were considered to have a component strength and It is defined as a machine part with excellent bending straightness.
- the remainder other than those indicated is substantially Fe.
- the hardness of the inner layer was less than 190 HV, and the hardness at the reference position of the surface layer was 365 HV, but the hardness at the effective hardening depth was 2 HV. It was less than 7 OHV.
- the surface hardness at the surface layer could not be sufficiently secured, and the fatigue strength was much lower than that of the actual product, that is, the component strength could not be sufficiently secured.
- the C [eq.] Force is lower than that of the working product due to the content of C.
- the processing conditions (processing temperature and processing time) of the nitriding treatment are within a general range.
- the hardness at the reference position of the surface layer and the hardness at the effective hardening depth position are determined. It can be said that it is desirable to set C [eq.] To 0.65 or more in order to increase the hardness of the inner layer, which is required to ensure the strength of parts, as required. . Further, regarding the C content, it is desirable that the content be, for example, 0.35% by weight / 0 or more (see Example 2).
- the hardness of the inner layer portion was less than 190 HV, and the hardness at the reference position of the surface layer portion and the effective hardening depth position was the desired value.
- the hardness attenuation rate is high toward the inner layer, and as a result, the surface hardness in the surface layer cannot be sufficiently secured, and the fatigue strength is much higher than that of the actual product. It has been reduced.
- the thickness of the inner layer required to ensure sufficient component strength was confirmed. It can be said that it is desirable to set C [e q.] To 0.65 or more in order to actually increase it.
- Comparative product 3 the hardness of the reference position of the surface layer and the hardness of the inner layer were the desired ones, but the hardness at the effective hardening depth position was less than 270 HV, and the decay rate of the hardness toward the inner layer As a result, the surface hardness at the surface layer could not be sufficiently secured, and the fatigue strength was much lower than that of the actual product. Furthermore, from the viewpoint of the steel composition of the comparative product 3, since the content of Si is excessively large as compared with that of the actual product, the decay rate of the hardness toward the inner layer is reduced. It can be said that it has become excessively large. Therefore, in order to surely increase the hardness at the effective hardening depth required to secure sufficient component strength, the content of Si should be, for example, 0.3% by weight or less ( See 2).
- the hardness of the inner layer portion of the comparative product 12 was as desired, but the hardness at the surface layer reference position and the effective hardening depth position was smaller than desired. As a result, the surface hardness of the surface layer could not be sufficiently secured, and the fatigue strength was much lower than that of the actual product. Further, from the viewpoint of the steel composition of the comparative product 12, in order to surely increase the surface hardness required for sufficiently securing the component strength, the value of Cr [e q. It is desirable to make the above.
- Example 2 The hardness of the inner layer and the hardness at the effective hardening depth position were as desired for the comparative products 6 and 7, but the hardness at the reference position of the surface layer was 46 OHV. It exceeded it. As a result, the surface hardness became too large, and the amount of indentation was much lower than that of the actual product, that is, sufficient bending straightening could not be secured. Furthermore, from the viewpoint of steel composition, it can be said that the surface hardness of the surface of the comparative product 7 was too high because Cr [eq.] Was larger than that of the actual product.
- the content of A1 is, for example, 0.01 weight. / 0 or less (see Example 3)
- the product of Comparative Example 2 is excellent in both the component strength and the bending straightness, like the actual product. However, since the content of C is high, the machinability is suppressed. Therefore, when it is necessary to improve both machinability and component strength and bending straightness, the content of C is set to, for example, 0.5 weight. / 0 or less (see Example 3)
- the content of C is set to, for example, 0.5 weight. / 0 or less (see Example 3)
- at least one of Pb, S, Ca, Bi, Ti, Zr and Mg is contained as a steel composition as an element for enhancing machinability. . As a result, the examples 5 to 10 had higher machinability than the others.
- the component strength may decrease, so it is an effective means to include an element that enhances machinability in the steel composition. It can be said.
- Example 5 containing an element that enhances machinability has a lower fatigue limit. It can be said that it has become higher.
- the comparative products 9 to 11 also have excellent parts strength and bending straightness, as in the actual products.
- the above-mentioned elements for improving the free-cutting property are contained in the steel composition.
- the fatigue limit which is an indicator of component strength, is lower than that of other products. Therefore, when a free-cutting element is contained, for example,? ) Is 0.30 wt ° / 0 or less, S is 0.20 wt% or less. & Is less than 0.01% by weight, B UiO. 30% by weight. /. Below, T UiO. 2% by weight or less, Zi O. 0. 2% by weight or less, Mg: 0.01% by weight. It is desirable to set each value to / 0 or less.
- Comparative Example 4 the bainite was excessively generated because the Mn content in the steel composition was excessively high. As a result, the comparative product 4 could not be a product when it was forged. Therefore, when Mn is contained, its content is desirably, for example, 1.8% by weight or less.
- FIG. 3 shows data on the above equation (1) accompanying claim 2.
- Each data point in Fig. 3 shows the measurement result of a representative test sample among the cross-sectional hardness measurements performed on the test sample.
- each curve (broken line), which is shown to be substantially in line with each data point, complies with Equation (2).
- the expression is an approximate expression that better reflects the actually measured value of the sectional hardness.
- the cross-sectional hardness decreases from the surface of the member toward the inner layer, and , The hardness is substantially constant.
- a region having a depth of 1 mm or more from the member surface is defined as an inner layer portion.
- the curves according to equation (1) shown in the figure are obtained when T corresponding to the nitriding temperature is 600 ° C. and t corresponding to the processing time is 7.2 ⁇ 10 3 seconds.
- the black data points correspond to the actual product and the white data points correspond to the comparative product.
- the region formed by the data points (vertical line region in the figure) in the actual product is included in the region Z defined by using Equation (2).
- the machine component can surely have both excellent component strength and excellent bending straightness. It turns out that it becomes.
- the numerical range of H ′ 1 representing the hardness at the reference position of the surface layer included in the formula (1) is based on Cr [e q.]
- the defined range of the Vickers hardness is as follows. , 348HV or more and 458HV or less.
- the numerical value range of H'0 representing the hardness in the inner layer is based on C [eq.]
- the existence of the measured hardness distribution profile in the area Z defined by the equation (1) makes it possible to further improve both the component strength and the bending straightness. It is.
- the hardness distribution profile in the region Z it is possible to obtain desired component strength and bending straightness.
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Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
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US10/527,318 US20060048860A1 (en) | 2002-09-25 | 2003-09-11 | Machine part and method for manufacturing same |
EP03798399A EP1548141B8 (en) | 2002-09-25 | 2003-09-11 | Machine part and method for manufacturing same |
CN03822868A CN100594249C (zh) | 2002-09-25 | 2003-09-11 | 机械部件及其制造方法 |
Applications Claiming Priority (4)
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JP2002-279833 | 2002-09-25 | ||
JP2002279833 | 2002-09-25 | ||
JP2003-37802 | 2003-02-17 | ||
JP2003037802A JP4230794B2 (ja) | 2002-09-25 | 2003-02-17 | 機械部品およびその製造方法 |
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WO2004029314A1 true WO2004029314A1 (ja) | 2004-04-08 |
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PCT/JP2003/011612 WO2004029314A1 (ja) | 2002-09-25 | 2003-09-11 | 機械部品およびその製造方法 |
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US (1) | US20060048860A1 (ja) |
EP (1) | EP1548141B8 (ja) |
JP (1) | JP4230794B2 (ja) |
CN (1) | CN100594249C (ja) |
WO (1) | WO2004029314A1 (ja) |
Families Citing this family (15)
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JP2007197812A (ja) * | 2005-12-28 | 2007-08-09 | Honda Motor Co Ltd | 軟窒化非調質鋼部材 |
JP4923927B2 (ja) * | 2006-09-29 | 2012-04-25 | 大同特殊鋼株式会社 | クランクシャフトの製造方法 |
JP2008144200A (ja) * | 2006-12-07 | 2008-06-26 | Isuzu Motors Ltd | 軟窒化鋼製品の製造方法 |
JP4821711B2 (ja) * | 2007-06-15 | 2011-11-24 | 住友金属工業株式会社 | 軟窒化用鋼材 |
JP5580517B2 (ja) * | 2008-03-31 | 2014-08-27 | 本田技研工業株式会社 | 軟窒化クランクシャフト用素材の製造方法 |
WO2012163391A1 (en) * | 2011-05-27 | 2012-12-06 | Società Bulloneria Europea S.B.E. Spa | Process for manufacturing engine starting motor shafts |
KR101717390B1 (ko) * | 2013-03-07 | 2017-03-16 | 신닛테츠스미킨 카부시키카이샤 | 비조질형 연질화 부품 |
RU2556261C2 (ru) * | 2013-08-20 | 2015-07-10 | Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Ижевский государственный технический университет имени М.Т. Калашникова" | Способ изготовления мелкоразмерного режущего инструмента из быстрорежущей стали |
WO2016098143A1 (ja) * | 2014-12-18 | 2016-06-23 | 新日鐵住金株式会社 | 窒化部品の製造方法及び窒化用鋼材 |
BR112018003454A2 (ja) * | 2015-09-08 | 2018-09-25 | Nippon Steel & Sumitomo Metal Corporation | A nitriding processing steel part article and a manufacturing method for the same |
BR112019016977A2 (pt) * | 2017-02-20 | 2020-04-07 | Nippon Steel Corp | chapa de aço |
JP7273324B2 (ja) | 2018-10-29 | 2023-05-15 | 日本製鉄株式会社 | 窒化部品粗形材、および窒化部品 |
FR3096419B1 (fr) * | 2019-05-22 | 2021-04-23 | Hydromecanique & Frottement | Organe de guidage, système mécanique comprenant un tel organe de guidage, et procédé de fabrication d’un tel organe de guidage |
CN112853208B (zh) * | 2020-12-31 | 2022-01-07 | 江苏铸鸿锻造有限公司 | 一种热稳定性较高的注塑机螺杆用钢及其制备方法 |
CN115558887B (zh) * | 2022-09-16 | 2024-05-14 | 浙江海马传动科技股份有限公司 | 一种铜钢复合套筒及其制备方法 |
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JPH0718379A (ja) * | 1993-06-30 | 1995-01-20 | Aichi Steel Works Ltd | 耐焼付性及び疲労強度に優れた機械構造用鋼 |
JPH09279295A (ja) * | 1996-04-16 | 1997-10-28 | Nippon Steel Corp | 冷間鍛造性に優れた軟窒化用鋼 |
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JP3239758B2 (ja) * | 1996-06-07 | 2001-12-17 | 住友金属工業株式会社 | 軟窒化用鋼材、軟窒化部品及びその製造方法 |
JPH10219393A (ja) * | 1997-02-04 | 1998-08-18 | Sumitomo Metal Ind Ltd | 軟窒化用鋼材、軟窒化部品及びその製造方法 |
JPH1129838A (ja) * | 1997-07-15 | 1999-02-02 | Sumitomo Metal Ind Ltd | 非調質鋼 |
US6083455A (en) * | 1998-01-05 | 2000-07-04 | Sumitomo Metal Industries, Ltd. | Steels, steel products for nitriding, nitrided steel parts |
JP4556334B2 (ja) * | 2001-02-01 | 2010-10-06 | 大同特殊鋼株式会社 | 軟窒化用非調質鋼熱間鍛造部品 |
-
2003
- 2003-02-17 JP JP2003037802A patent/JP4230794B2/ja not_active Expired - Fee Related
- 2003-09-11 US US10/527,318 patent/US20060048860A1/en not_active Abandoned
- 2003-09-11 WO PCT/JP2003/011612 patent/WO2004029314A1/ja active Application Filing
- 2003-09-11 CN CN03822868A patent/CN100594249C/zh not_active Expired - Fee Related
- 2003-09-11 EP EP03798399A patent/EP1548141B8/en not_active Expired - Fee Related
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0718379A (ja) * | 1993-06-30 | 1995-01-20 | Aichi Steel Works Ltd | 耐焼付性及び疲労強度に優れた機械構造用鋼 |
JPH09279295A (ja) * | 1996-04-16 | 1997-10-28 | Nippon Steel Corp | 冷間鍛造性に優れた軟窒化用鋼 |
Non-Patent Citations (1)
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See also references of EP1548141A4 * |
Also Published As
Publication number | Publication date |
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EP1548141A1 (en) | 2005-06-29 |
EP1548141B1 (en) | 2011-12-21 |
CN1685073A (zh) | 2005-10-19 |
EP1548141B8 (en) | 2012-04-25 |
US20060048860A1 (en) | 2006-03-09 |
CN100594249C (zh) | 2010-03-17 |
JP2004162161A (ja) | 2004-06-10 |
JP4230794B2 (ja) | 2009-02-25 |
EP1548141A4 (en) | 2006-02-08 |
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