JPWO2014199423A1 - Steel member and method for manufacturing steel member - Google Patents

Abstract

At least part of the steel material to be treated has a carbon concentration higher than that of the material to be treated and 1.0 wt. % Or less, and the carbon concentration of the outermost surface layer is the highest among the plurality of layers. A step of spraying powder containing carbon on at least a part of the steel material to be treated to form a first layer having a carbon concentration higher than that of the material to be treated; and at least a part of the first layer. A step of spraying a powder containing carbon to form a second layer having a carbon concentration higher than that of the first layer, and including a plurality of the first layer and the second layer. The carbon concentration of the layer of 1.0 wt. % Or less.

Description

  The present invention relates to a steel member and a manufacturing method thereof.

  Since mechanical parts such as drive parts, gears, and bearings are used in an environment where a high load is constantly applied, high mechanical strength such as hardness and fatigue strength is required. For such machine parts, steel for machine structure such as carbon steel, chrome steel, chrome molybdenum steel, nickel chrome molybdenum steel is used.

  Mechanical structural steel has high surface fatigue resistance, and the material itself may be required to have a contradictory nature between the outside and the inside to ensure toughness in order to ensure the impact resistance of the parts. As a material, for example, a material having a relatively low carbon concentration and high toughness such as low alloy steel (such as SCM415 defined in JIS-G4104) is used as a base material, and the carbon concentration is increased by dissolving carbon on the material surface. Carburizing treatment and carbonitriding treatment are often performed to increase hardness and fatigue resistance.

  However, when carbon is simply diffused, the carbon concentration distribution of the surface hardened layer has a slope, and it is difficult to form a thick structure having the necessary carbon concentration. Further, if the surface hardened layer is to be thickened, the surface is excessively carburized (over carburized), and the surface hardened layer becomes brittle. For example, in Patent Document 1, a hard coating of high carbon steel or high carbon low alloy steel is formed on the surface of a base material, and then the base material and the hard coating are diffusion-bonded by heat treatment to ensure a desired strength. A technique is disclosed.

JP-A-11-222663

  However, the thing of patent document 1 has the subject that the carbon concentration difference of the base material which is a to-be-processed material, and the coating film of high carbon steel is large, and it is easy to peel between a base material and a coating film.

  An object of the present invention is to make it difficult for the material to be treated and the surface hardened layer to peel off.

  In order to achieve the above object, for example, the configuration described in the claims is adopted.

  According to the present invention, the material to be treated and the surface hardened layer can be made difficult to peel off.

It is an example of the block diagram of a steel member. It is an example of the block diagram of a steel member. It is an example of process drawing explaining the formation method of the 1st layer and the 2nd layer to to-be-processed material. It is an example of the schematic diagram of the steel member shown in the 2nd Example. It is an example of the schematic diagram which shows the cross section of the steel member shown in the 2nd Example. It is an example of process drawing explaining the formation method of the steel member shown in the 2nd example.

  The steel member of the present invention includes a plurality of layers (high carbon steel layers) having a higher carbon concentration than the material to be treated on the surface of the material to be treated (steel member). All high carbon steel layers have a carbon concentration of 1.0 wt. %, And the layer closest to the surface has the highest carbon concentration.

  An embodiment of the present invention is shown in FIG. At least a part of the material to be processed 101 has a carbon concentration higher than that of the material to be processed and 1.0 wt. The steel member 100 is formed by sequentially laminating the first layer 102 and the second layer 103, which are high-carbon steel layers that are not more than%. The carbon concentration of the second layer is set higher than that of the first layer.

  Another embodiment is shown in FIG. In the present embodiment, the carbon concentration is higher than that of the second layer and the carbon concentration is 1.0 wt. The third layer 104 which is not more than% is stacked.

  Low carbon steel and low carbon alloy steel are mentioned as an example of the material to be surface treated. Examples include highly tough materials such as chrome steel, chrome molybdenum steel, chrome molybdenum nickel steel, chrome manganese steel, and chrome nickel steel (stainless steel). Stipulated in

  Each of the plurality of high carbon steel layers coated on the material to be treated has a carbon concentration higher than that of the material to be treated, and 1.0 wt. % Or less is required. It can be set as the layer excellent in fatigue strength by making carbon concentration of each layer higher than a processed material. Further, the carbon concentration of each layer is set to 1.0 wt. By setting the ratio to not more than%, it is possible to prevent excessive precipitation of reticulated cementite at the grain boundaries, so that surface embrittlement can be reduced and a layer having a long fatigue life can be obtained. The high carbon steel layer includes at least a first layer and a second layer, and if necessary, further forms one or more layers thereon, and the carbon concentration increases from the material to be processed toward the outermost surface layer. ing.

  Instead of carburizing diffusion, when the layer is coated on the material to be treated to increase the carbon concentration in the direction of the steel member, the difference in carbon concentration between the layers can be reduced by providing multiple layers. Peeling between steel layers, peeling between high carbon steel layers, cracks, and the like can be reduced. Furthermore, the required carbon concentration and layer thickness can be freely adjusted. When the number of layers is three or more, even if there is a large difference in carbon concentration between the outermost surface layer and the material to be processed, the difference in carbon concentration between the layers can be reduced. Further, peeling between layers can be reduced.

  Although the layers are clearly separated in the figure, a slight carbon diffusion occurs from the layer with a high carbon concentration to the layer with a low carbon concentration, so there is a gradual carbon concentration gradient in the film thickness direction between the layers. . In the present invention, a portion where the carbon concentration is inclined is allowed as an interlayer (boundary).

  The alloy composition other than carbon in each layer is not particularly limited, but examples of such steel materials include high carbon steel and high carbon alloy steel. In particular, the first layer, the second layer, and the one or more layers formed as necessary (hereinafter referred to as a plurality of high carbon steel layers) in which the composition of alloy elements other than carbon substantially matches the material to be treated. It is suitable because it is excellent in integrity with the object to be processed and can prevent the generation of local composite compounds. In addition to fatigue resistance, other properties such as corrosion resistance and heat resistance are improved at the same time. It is possible to adjust other alloy elements to achieve this.

  Further, the plurality of high carbon steel layers may be formed with the same thickness on the entire surface of the material to be processed, but each layer has a thickness distribution on the surface of the material to be processed, or a part of the material to be processed. It can also be formed in a limited manner. For example, in the case of mechanical parts, if the shaft is a contact part with a bearing, if it is a gear, it is a tooth tip, and if it is a press roll, it is a part that requires particularly high fatigue strength, such as a contact part with a member. Each layer can be formed in a limited manner. Such a partial process is suitable when individually controlling the characteristics of a location where toughness is desired and a location where fatigue resistance is desired. Also, on the surface of the material to be treated, a distribution is given on the surface of the material to be treated, such as a place where no layer is formed, a place where only the first layer is formed, a place where the first layer and the second layer are formed. It is also possible to form each layer. Similarly, one or more layers formed on the second layer can be partially formed on the material to be processed.

  There are various methods for forming such a plurality of high carbon steel layers. Examples of methods that are excellent in forming speed and adhesion to a material to be processed include a cold spray method, a warm spray method, a plasma spray method, an arc method, and the like. Examples include a thermal spraying method, a flame spraying method, a build-up welding method, and an aerosol deposition method, and a method of sequentially forming each layer as shown in FIG.

  (A) A material 101 to be processed on which a high carbon steel layer is formed is prepared.

  (B) The first layer 102 is formed on the workpiece 101. The material of each layer is supplied in the form of powder, wire, bar, etc. so as to suit each method. In this figure, a method of spraying powder and depositing it on the material to be processed is used. For example, the film is formed by the above method using a powder having a low carbon concentration (first powder). The carbon concentration of this powder is higher than that of the material to be treated, and is 1.0 wt. % Or less. The first powder may be a mixture of carbon and another powder. When the layer is formed, the concentration of carbon contained in the entire layer is higher than that of the material to be processed, and 1.0 wt. % Or less.

  (C) The second layer 102 is formed on the first layer 102. The second layer is formed on the first layer 102 using a powder (second powder) having a higher carbon concentration than the first layer. The second powder may be a mixture of carbon and other powders as in the first split. When the layer is formed, the concentration of carbon contained in the entire layer is higher than that of the first layer, and 1.0 wt. % Or less.

  (D) The steel member 100 in the case of two high carbon steel layers is formed.

  Changing the mixing ratio of a plurality of types of powders having different carbon concentrations is more preferable because the types of raw materials required for layer formation can be reduced even when the high-carbon steel layer is a multilayer. The film formation conditions are appropriately adjusted according to the method used, the material to be processed, and the material of each layer. However, when the temperature of the material to be processed at the time of film formation is room temperature or higher, the film formation efficiency is improved, and the material to be processed for each layer This is suitable because it can increase the adhesion to the substrate and promote interdiffusion at the interface of each layer. However, it is desirable to adjust the film formation temperature according to various conditions such as the heat resistance and oxidation resistance of the material to be processed and the material of each layer. In addition to the formation of the above layers, it is possible to further perform heat treatment such as quenching and tempering and surface treatment such as carburizing and nitriding.

  Embodiments will be described below with reference to the drawings.

  In this embodiment, an embodiment in which the steel member 100 is a plate material will be described. The block diagram of the steel member 100 in a present Example is as FIG. In this embodiment, stainless steel (JIS standard: SUS304, manufactured by Nisshin Steel Co., Ltd., 0.05 wt.%) Having a length of 50 mm, a width of 50 mm, and a thickness of 10 mm was used as the material 101 to be processed for the steel member 100.

  The first layer 102 and the second layer 103 are made of stainless steel powder (DAP304L, manufactured by Daido Special Steel), with additive-free stainless steel powder A and 2.0 wt.% Graphite powder (manufactured by Sigma-Aldrich) on the surface. The two powders of the supported stainless steel powder B were mixed at a specified weight ratio to obtain respective raw material powders. In this embodiment, the raw material powder of the first layer 102 has a carbon concentration of 0.4 wt.% (Stainless steel powder A: stainless steel powder B = 8: 2 (weight ratio)), and the raw material powder of the second layer 103 has a carbon concentration of 0. .8 wt.% (Stainless powder A: stainless powder B = 6: 4 (weight ratio)) and mixed uniformly with a V-type mixer to obtain a raw material powder for each layer. Note that FIG. 1 is a schematic diagram for easily distinguishing each layer, and the actual film thickness is as shown in Table 1 shown later. Theoretically, the carbon concentration at the time of powder adjustment matches the carbon concentration of the layer after film formation, but carbon is damaged during the material adjustment and film formation process, so the carbon concentration of the layer is higher than the concentration of the raw material powder. Slightly lower value.

  The method of forming the first layer and the second layer in this example is as shown in FIG. The first layer and the second layer are formed using a cold spray method, using nitrogen gas as a carrier gas, a pressure of 4 MPa, a material temperature of 400 ° C., and a nozzle distance of 20 mm. Formed. When the material to be treated is heated, the powder easily adheres, and the adhesion between the layers is further improved. Thereafter, the raw material powder was changed to form a second layer by the cold spray method under the same conditions. And in order to make the graphite powder carry | supported by the stainless steel powder B dissolve in each layer, it heat-processed for 800 degreeC and 30 minutes, and it was set as the steel member 100 by rapidly cooling at 100 degreeC or more per second.

Comparative Example 1

  In the configuration of Example 1, the carbon concentration of the first layer is 0.8 wt. % Was formed by the cold spray method, and the second layer was not formed. Other formation conditions are the same as those in the first embodiment.

  In the example 1, a surface treatment layer having a thickness of about 1 mm and a Vickers hardness (Hv) of 920 on the surface of the steel member 100 and having excellent adhesion without delamination even after the Falex test was obtained. However, in the case of Comparative Example 1, minute peeling was observed between the material to be processed 101 and the first layer 102, and a problem occurred in adhesion.

  In this embodiment, an embodiment in which the steel member 100 is a shaft member will be described. The schematic diagram of the steel member 100 in the present embodiment is as shown in FIG. For the steel member 100 of this example, a workpiece 101 made of chromium molybdenum steel (JIS standard: SCM415, manufactured by Daido Steel Co., Ltd., 0.15 wt.%) Having a diameter of 30 mm and a length of 300 mm was used. A first layer 102, a second layer 103, and a third layer 104 were formed on the tip of the material to be processed.

  FIG. 5 shows a schematic cross-sectional view of A-A ′ attached to FIG. 4. The cross-sectional view shows up to C-C '. The first layer 102, the second layer 103, and the third layer 104 are formed at the tip of the workpiece 101, and all three layers are 100 mm from the tip, and all the three layers are 100 mm to 110 mm. Only the first layer 101 was formed in the first layer 101 and the second layer 102 in the range of 110 mm to 120 mm. FIG. 4 is a schematic diagram for making it easy to distinguish each layer, and the actual film thickness is as shown in Table 2 shown later.

  Each of these layers is composed of chromium molybdenum steel powder A made of chromium molybdenum steel powder (SCM415, Epson Atmix) of the same standard as the material to be treated 101, and only the carbon concentration of chromium molybdenum steel powder A is 2.0 wt. Each raw material powder was obtained by mixing two kinds of powders of chrome molybdenum steel powder B increased to% by a specified weight ratio. In this embodiment, the raw material powder of the first layer 102 has a carbon concentration of 0.4 wt.% (Chromium molybdenum steel powder A: chromium molybdenum steel powder B = 86: 14 (weight ratio)), and the raw material powder of the second layer 103. With a carbon concentration of 0.6 wt.% (Chromium molybdenum steel powder A: chromium molybdenum steel powder B = 76: 24 (weight ratio)), and the raw material powder of the third layer 103 with a carbon concentration of 0.8 wt.% (Chromium molybdenum steel) Powder A: Chromium molybdenum steel powder B = 65: 35 (weight ratio)) and mixed uniformly with a V-type mixer to obtain raw material powder of each layer.

  The method for forming the first layer, the second layer, and the third layer in this example is as shown in FIG. Plasma spraying was used to form each layer. The raw material powder was changed in the order of the first layer, the second layer, and the third layer, and the film was formed under the same conditions. In this configuration, since each layer is partially formed, the spray nozzle 106 is scanned over the material 101 while rotating the material 101 preheated to 400 ° C., and the desired part is partially formed as shown in FIG. Each layer was formed.

  In the configuration of Example 2, the carbon concentration of the raw material powder of the third layer is 1.0 wt. % (Chromium molybdenum steel powder A: chromium molybdenum steel powder B = 54: 46 (weight ratio)). The other formation conditions are the same as those in Example 2.

Comparative Example 2

  In the configuration of Example 2, the carbon concentration of the raw material powder of the first layer is 0.8 wt.% (Chromium molybdenum steel powder A: chromium molybdenum steel powder B = 65: 35 (weight ratio)) by plasma spraying. The second layer and the third layer were not formed. The other formation conditions are the same as those in Example 2.

Comparative Example 3

  In the configuration of Example 2, the carbon concentration of the raw material powder of the third layer was 1.1 wt. % (Chromium molybdenum steel powder A: chromium molybdenum steel powder B = 49: 51 (weight ratio)). The other formation conditions are the same as those in Example 2.

  The steel member 100 obtained in Examples 2 and 3 and Comparative Examples 2 and 3 was smoothed by mechanical polishing and buffing so that the surface roughness (Ra) was 1.0 μm or less, and then the third layer. A Falex test according to ASTM-D-3233 was conducted in lubricating oil on 103 film forming portions. The steel member 100 after the Falex test was cut, the thickness of each layer, the average carbon concentration measured with an electron beam microanalyzer (Shimadzu Corporation), the presence or absence of delamination confirmed with an optical microscope, and the surface roughness of the outermost layer ( Table 2 shows the cross-sectional Vickers hardness measured with a Ra), micro Vickers hardness tester (Shimadzu Corporation).

  In Examples 2 and 3, a surface treatment layer having a thickness of about 1 mm and a Vickers hardness (Hv) of 930 or more on the surface of the steel member 100 and having excellent adhesion without delamination even after the Falex test was obtained. . In each surface-treated layer in each sample, no precipitation of reticulated cementite on the grain boundaries was observed, confirming that no overcarburization occurred.

  On the other hand, in the case of Comparative Example 2, minute separation was observed between the material to be processed 101 and the first layer 102, and a problem occurred in adhesion. Moreover, under the conditions of Comparative Example 3, it was confirmed that the surface roughness after the Falex test was larger than the others, and damage due to wear occurred. As a result of structural observation, precipitation of network cementite peculiar to the hypereutectoid steel of the steel material was observed on the grain boundary, and damage in the overcarburized part was confirmed.

  From the above evaluations, it was confirmed that the steel member having the configuration disclosed in the present invention has a surface treatment layer having excellent surface hardness and adhesion to the material to be treated. In this section, an example of a shaft as a machine part is shown. However, it is obvious that the present invention can be applied to various machine parts such as a drive part, a gear, and a bearing.

100 Steel member 101 Material 102 First layer 103 Second layer 104 Third layer 105 Spray nozzle 106 Thermal spray nozzle

Claims (7)

  At least part of the steel material to be treated has a carbon concentration higher than that of the material to be treated and 1.0 wt. % Or less, and the carbon concentration of the outermost surface layer is the highest among the plurality of layers.   The steel member according to claim 1, wherein the plurality of layers are three or more layers.   The steel member according to claim 1, wherein the material to be processed includes a portion where the plurality of layers are laminated and a portion where the plurality of layers are not laminated.   2. The plurality of layers according to claim 1, wherein a first layer and a second layer are sequentially stacked from the material to be processed side, and the first layer is stacked with a portion where the second layer is stacked. A steel member characterized by comprising a portion not provided. Forming a first layer having a carbon concentration higher than that of the material to be treated by spraying a powder containing carbon on at least a part of the material to be treated made of steel; and
Spraying a powder containing carbon on at least a part of the first layer to form a second layer having a carbon concentration higher than that of the first layer, and
The carbon concentration of the plurality of layers including the first layer and the second layer is 1.0 wt. % Or less, The manufacturing method of the steel member characterized by the above-mentioned.   6. The method according to claim 5, further comprising the step of spraying a powder containing carbon on at least a part of the second layer to form a third layer having a carbon concentration higher than that of the second layer. A method for manufacturing a steel member.   6. The method for manufacturing a steel member according to claim 5, wherein the plurality of layers are formed while heating the material to be processed.

Images