JPH044070B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Industrial Application] The present invention relates to a method for manufacturing mechanical parts in which high manganese steel is applied to parts that require excellent rolling fatigue properties, such as rolling bearings and rollers. . [Prior Art] Conventionally, methods for improving the rolling contact fatigue properties of mechanical parts such as gears, rollers, and rolling bearings have focused on improving the rolling contact fatigue properties of mechanical parts such as gears, rollers, and rolling bearings. is C, Mn, Ni, Cr, Mo
methods such as increasing the amount of alloy or special heat treatment,
Surface hardening treatments such as induction hardening, carburizing, nitriding, and thermal spraying have been used. The method of [problem to be solved by the invention] is extremely expensive;
Also, depending on the shape and size of the parts, some parts may require special heat treatment. This method is not only expensive, but also impossible for large parts. Furthermore, in the case of carburizing, grain boundary oxidation, and thermal spraying,
This includes problems such as peeling from the base material. [Means and effects for solving the problems] The present invention is directed to the production of mechanical parts with excellent rolling contact fatigue properties that are equivalent to or better than conventional mechanical parts with high rolling contact fatigue properties. This method provides a high manganese steel-based meat whose chemical composition is in weight percent [] C: 0.7 to 1.5%, Si: 0.5% or less, Mn: 10 to 15%, the balance being Fe and unavoidable impurities. Mound or [] C: 0.7 to 1.5%, Si: 0.5% or less, Mn: 10 to 15%, Ni: 6% or less, Cr: 3% or less, Cu: 1.5% or less,
Mo: 3% or less, V: 3% or less, and Ti: 2%
A build-up of high manganese steel containing one or more of the following, the balance being Fe and unavoidable impurities, is applied to at least the raceway, the formed build-up layer is heated to 500-700℃, and then After tempering and pearlitizing heat treatment, it is then reheated and heat treated at 750 to 950°C to disperse hard spherical carbides, preferably solution treated at 1000 to 1200°C, and then rapidly cooled to form austenite. Get single phase, then 500-700
℃, fired here to perform pearlitization heat treatment, and then reheated to 750 ~
It is heat treated at 950℃ to disperse hard spherical carbides. In the present invention, the term "rolling surface" refers to a surface that is subject to rolling fatigue, and includes, for example, the bearing surface of a rolling bearing, the circumferential surface of a roller, and the like. Hereinafter, the structure and operation of the present invention will be explained in detail. Conventionally, high manganese steel overlay has been used only for repairing high manganese cast steel products. This is because in the case of use conditions where rolling fatigue occurs, that is, in use conditions where stress is applied but no impact force is applied, the overlay surface of high manganese steel will only have a Hv of about 450 to 500. It was thought that the built-up layer did not have excellent rolling contact fatigue properties. However, as a result of the inventors' research on rolling contact fatigue properties of various overlays, it was found that high manganese steel-based overlays have excellent rolling contact fatigue properties. Based on the results of the above-mentioned research, the mechanical parts manufactured by the present invention have one or multiple high manganese steel build-up layers built up on a base material in order to deal with the problem of rolling contact fatigue. In the present invention, the high manganese steel used for overlaying has high rolling fatigue properties consisting of C: 0.7 to 1.5%, Si: 0.5% or less, Mn: 10 to 15%, the balance being Fe and unavoidable impurities. or C: 0.7 to 1.5 in weight%
%, Si: 0.5% or less, Mn: 10 to 15%, and to this,
Ni: 6% or less, Cr: 3% or less, Cu: 1.5% or less,
Mo: 3% or less, V: 3% or less, and Ti: 2%
A high manganese steel having high rolling fatigue properties containing one or more of the following, with the balance being Fe and unavoidable impurities. The reason why this group composition is limited as described above will be explained below. (a) C, Mn The C and Mn components influence the stability of the austenite matrix structure and the work hardening properties, and are 0.7
The combination of ~1.5% C and 10~15% Mn has the most stable austenite and high work hardening properties. Therefore, C is 0.7~1.5%, Mn is 10~
It was set at 15%. (b) Si Si is effective in deoxidizing the weld metal and preventing inclusion of intervening impurities in the welded part, but if it is 0.5 or more,
The upper limit was set at 0.5% because the effect would reach saturation. (c) Ni Ni stabilizes austenite, so
In the case of parts that require welding, it is added to suppress carbide precipitation, but the effect is saturated even if it is added in an amount of 6% or more, so the upper limit was set at 6%. (d) Cr, Mo Cr and Mo are added to parts that require a high yield point in order to increase yield point and hardness, but Cr and Mo should not be added in an amount of 3% or more. If the
%. (e) Cu Adding Cu to Cr-added high manganese steel is effective in increasing toughness, so it is added especially for parts that require toughness, but the effect is saturated even when added at 1.5% or more. , set the upper limit to 1.5
%. (f) V, Ti These ingredients have the effect of improving strength, so they are added to parts that require high strength, but adding 3% or more of V and 2% or more of Ti improves toughness. decreases, so the upper limit of V is 3
% and Ti were set at 2%. Furthermore, as a result of research, high manganese steel build-up layer
It was found that film-like carbides were precipitated at grain boundaries in the metal structure of AS overlay. This film-like carbide is harmful to rolling fatigue properties,
For mechanical parts that do not cause problems in terms of base material, thermal stress, or cost, 1000 to 1200℃
After solution treatment, it is desirable to rapidly cool the grain boundary carbide to eliminate it. Furthermore, for mechanical parts that are used under particularly severe conditions, the aim is to disperse hard spherical carbide in the overlay layer to the extent that no problems arise in terms of base material material, thermal stress, or cost. Heat treatment is applied to improve the metal structure. In addition, dispersing hard spherical carbide is
Effective in improving rolling fatigue properties. Specific examples of the heat treatment for dispersing the spherical carbide include the following two examples. As shown in Figure 1, heat to 500-700℃,
Here, it is tempered and pearlitized heat treated.
Subsequently, after reheating, heat treatment is performed at 750-950°C. During the reheating, the cementite in the pearlite becomes spheroidal, and hard spherical carbides are dispersed in the γ single phase. 1000 ~ prior to pearlitization heat treatment
A method of solution treatment at 1200℃. The reason for this is as follows. If a large amount of film-like carbides are precipitated at grain boundaries in AS overlay, or if segregation is significant, carbides and segregation will affect the state of pearlite precipitation, and the dispersion state of spheroidal carbides will change. Therefore, it is desirable to perform solution treatment at 1000 to 1200°C before pearlitization heat treatment to eliminate film-like carbides and reduce segregation. The heat treatment process in this case is shown in FIG. [Examples] Comparative Example 1 Machine parts were manufactured according to the method of the present invention and subjected to a rolling fatigue test. First, AS overlay is applied to the circumferential surface of a round bar (SC46) with a diameter of 20 mm, and then machined to the shape, dimensions, and finishing accuracy shown in Figure 3 to manufacture the wheel-shaped member (test piece) 1. did. This build-up is a two-layer build-up, the lower layer (first layer) is 2.5 mm thick, and the upper layer (second layer) is 2.5 mm thick, and the material of the welding rod used for welding them is the first layer. As shown in No. 1 in the table. In this example, there was a risk of cold cracking, so SUS 309 and 0.49%C-0.16%Si-13.9% were used.
A Mn welding rod was used. In each of the component ratios shown in Table 1, the balance is Fe and unavoidable impurities. The wheel-like member 1 manufactured in this way was set in a testing machine and its rolling fatigue characteristics were measured. A Nishihara metal wear tester was used as the tester, and the fatigue durability limit of the test piece 1 shown in FIG. 3 was examined at a slip of 9% and a roller rotation speed of 800 rpm. A set of two of the above specimens were used as the test specimens. The results are shown in Table 2. In Table 2, As overlay indicates that no treatment such as heat treatment was performed after overlay. Comparative Example 2 In Comparative Example 1, the manufactured mechanical parts were subjected to solution treatment as follows, and then rolling contact fatigue properties were measured in the same manner. 1100℃×2Hr Cooling/Water cooling (WQ) at heating rate of 100℃/min or less The results are shown in Table 2. Comparative Examples 3 and 4 Machine parts were manufactured in the same manner as in Comparative Examples 1 and 2, except that the composition of the upper layer was changed to that shown in Table 1 No. 2, and their rolling contact fatigue properties were measured. The results are shown in Table 2. Comparative Examples 5 and 6 Machine parts were manufactured in the same manner as in Comparative Examples 1 and 2, except that the composition of the upper layer was changed to that shown in Table 1 No. 3, and their rolling contact fatigue properties were measured. The results are shown in Table 2. Comparative Examples 7 and 8 Machine parts were manufactured in the same manner as in Comparative Examples 1 and 2, except that the compositions of the upper and lower layers were changed to those shown in Table 1 No. 4, and their rolling contact fatigue properties were measured. The results are shown in Table 2. Comparative Examples 9 and 10 Machine parts were manufactured in the same manner as in Comparative Examples 1 and 2, except that the compositions of the upper and lower layers were changed to those shown in Table 1 No. 5, and their rolling contact fatigue properties were measured. The results are shown in Table 2. Comparative Examples 11 and 12 Machine parts were manufactured in the same manner as in Comparative Examples 1 and 2, except that the compositions of the upper and lower layers were changed to those shown in Table 1 No. 6, and their rolling contact fatigue properties were measured. The results are shown in Table 2. Comparative Examples 13 and 14 Machine parts were manufactured in the same manner as in Comparative Examples 1 and 2, except that the composition of the upper layer was changed to that shown in Table 1 No. 7, and their rolling contact fatigue properties were measured. The results are shown in Table 2. Comparative Examples 15 and 16 Machine parts were manufactured in the same manner as in Comparative Examples 1 and 2, except that the composition of the upper layer was changed to that shown in Table 1 No. 8, and their rolling contact fatigue properties were measured. The results are shown in Table 2. Comparative Examples 17 and 18 Machine parts were manufactured in the same manner as in Comparative Examples 1 and 2, except that the composition of the upper layer was changed to that shown in Table 1 No. 9, and their rolling contact fatigue properties were measured. The results are shown in Table 2. Comparative Examples 19 and 20 Machine parts were manufactured in the same manner as in Comparative Examples 1 and 2, except that the composition of the upper layer was changed to that shown in Table 1, No. 10, and their rolling contact fatigue properties were measured. The results are shown in Table 2. Comparative Examples 21 and 22 Machine parts were manufactured in the same manner as in Comparative Examples 1 and 2, except that the composition of the upper layer was changed to that shown in Table 1, No. 11, and their rolling contact fatigue properties were measured. The results are shown in Table 2. Comparative Examples 23 and 24 Machine parts were produced in the same manner as in Comparative Examples 1 and 2, except that the composition of the upper layer was changed to that shown in Table 1, No. 12, and their rolling contact fatigue properties were measured. The results are shown in Table 2. Example 1 The mechanical parts manufactured in Comparative Example 5 (the material was No. 3 in Table 1 as described above) were heat treated as shown in FIG. 1, and their rolling contact fatigue properties were measured. The results are shown in Table 3. Note that the specific heat treatment conditions are as follows. Pearlitization heat treatment 600℃×25Hr Temperature increase rate 5℃/min Cooling: Air cooling Dispersion heat treatment 850℃×2Hr Temperature increase rate 5℃/min Cooling: Air cooling Example 2 In Example 1, the second step was performed prior to pearlitization treatment. Solution treatment was performed as shown in the figure, and the rolling contact fatigue properties were measured. 1100℃×2Hr Temperature rising rate 5℃/min or less Cooling: Water cooling The results are shown in Table 3. Example 3 The machine parts manufactured in Comparative Example 11 (the material was No. 6 in Table 1 as described above) were heat treated as shown in FIG. 1, and their rolling contact fatigue properties were measured. The results are shown in Table 3. Note that the specific heat treatment conditions are as follows. Pearlitization heat treatment 600℃×25Hr Temperature increase rate 5℃/min or less Cooling: Water-cooled Dispersion heat treatment 850×2Hr Temperature increase rate 5℃/min or less Cooling: Water cooling Example 4 In Example 1, the first step before pearlitization treatment Solution treatment was performed as shown in Figure 2, and its rolling contact fatigue properties were measured. 1100℃×2Hr Heating rate: 5℃/min Cooling: Water cooling The results are shown in Table 3. Comparative Examples 25 to 27 Machine parts manufactured by casting and finishing to have the shapes, dimensions, and surface accuracy shown in FIG. 3 were measured for their rolling contact fatigue characteristics. The results are shown in Table 3. The materials of Comparative Examples 25 to 27 are as follows. Comparative example 25: SCMnCrM2 〃 26: SCSiMn2 〃 27: SF55A In addition, the correspondence between this comparative example and the JIS standard is
Shown in the table.

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[Table] (B) Quenching Tempering According to Tables 2 and 3, machine parts in which a build-up of high manganese steel is formed and subjected to decentralized heat treatment according to the present invention have no build-up and Comparative Examples 25-27
It can be seen that the rolling contact fatigue properties are significantly superior compared to those of Examples 1 to 25 in which a build-up was formed but no dispersion heat treatment was performed. [Effects] As is clear from the above examples, the present invention provides a mechanical component with extremely excellent rolling fatigue characteristics. The present invention enables mechanical parts with excellent rolling contact fatigue properties as described above to be obtained by simply forming a build-up on the surface of the part and subjecting it to a predetermined simple heat treatment, and can be implemented at low cost and widely used. It can be put to practical use in various fields.

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams showing different examples of heat treatment applied to the steel of the present invention, respectively, and FIG. 3 is a diagram illustrating the shape and dimensions of a test piece subjected to a fatigue test. 1...Test piece.

Claims (1)

[Claims] 1. A high-manganese steel overlay whose chemical components are C: 0.7 to 1.5%, Si: 0.5% or less, Mn: 10 to 15%, and the balance is Fe and unavoidable impurities. It is applied to at least the rolling surface, and the formed build-up layer is heated to 500 to 700℃, tempered here to perform pearlite heat treatment, and then reheated and heat treated at 750 to 950℃ to form a hard spherical carbide. A method for manufacturing mechanical parts with excellent rolling contact fatigue properties, characterized by dispersing 2. The chemical composition is C: 0.7 to 1.5%, Si: 0.5% or less, Mn: 10 to 15%, the balance being Fe and unavoidable impurities. The formed overlay layer is solution-treated at 1000-1200°C, then rapidly cooled to obtain a single austenite phase, then heated to 500-700°C, tempered here, and subjected to pearlitization heat treatment. The method for producing mechanical parts with excellent rolling contact fatigue properties as set forth in claim 1, characterized in that the method comprises performing a heat treatment at 750 to 950°C to disperse hard spherical carbides. . 3 Chemical components are C: 0.7 to 1.5%, Si: 0.5% or less, Mn: 10 to 15%, Ni: 6% or less, Cr: 3% or less, Cu: 1.5% or less, Mo: 3% or less , V: 3% or less, and Ti:
A build-up of high manganese steel containing one or more of 2% or less, the balance being Fe and unavoidable impurities is applied to at least the raceway surface, and the formed build-up layer is heated to 500 to 700℃. A method for producing mechanical parts with excellent rolling contact fatigue properties, characterized by tempering and pearlitization heat treatment, followed by reheating and heat treatment at 750 to 950°C to disperse hard spherical carbides. 4 Chemical components are C: 0.7 to 1.5%, Si: 0.5% or less, Mn: 10 to 15%, Ni: 6% or less, Cr: 3% or less, Cu: 1.5% or less, Mo: 3% or less , V: 3% or less, and Ti:
A build-up of high manganese steel containing one or more of 2% or less, the balance Fe and unavoidable impurities is applied to at least the raceway, and the formed build-up layer is solution-treated at 1000 to 1200℃. After the treatment, it is rapidly cooled to obtain austenite single phase, then heated to 500-700℃, tempered here to perform pearlitization heat treatment, and then reheated and then heat-treated at 750-950℃. 4. The method of manufacturing a mechanical component having excellent rolling contact fatigue properties according to claim 3, wherein hard spherical carbide is dispersed.