JPH10219420A - Warm member and hot member, their production, and warm die and hot die using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the service life of warm and hot members, such as dies, and to prevent the occurrence of peeling of a mixture layer and the occurrence of the origin or propagation passage of cracks by forming a mixture layer composed essentially of iron sulfide and iron oxide and containing nitrogen on the surface of a member and controlling the weight concentration ratio between sulfur and oxygen in the mixture layer to a slightly high value in a specific range. SOLUTION: A mixture layer, composed essentially of iron sulfide and iron oxide and containing nitrogen, is formed on the surface of a member prepared by using a steel as a base material, and the weight concentration ratio between sulfur and oxygen, S/O, in the mixture layer is limited to a value satisfying 0.5<S/O<10. Further, a nitrided layer can be formed on the member-body side of the mixture layer. When the concentration ratio (S/O) is <=0.5, the coefficient of friction of sliding parts, such as machine parts, and that between a point of operation of the press of a die and a work cannot be reduced sufficiently. Conversely, when (S/O) is >=10, the adhesion between the main body of the member or die, prepared by using a steel as a base material, or the mixture layer and the nitrided layer formed on the main-body side of the member or die becomes insufficient, and peeling and falling off become liable to occur, and as a result, the resultant member and die cannot withstand long- time service.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a warm member made of steel used in a warm or hot state, a method for producing the member, and a warm mold using the same. .

[0002]

2. Description of the Related Art Conventionally, for example, a hot tool steel represented by SKD61 and SKT4 stipulated by JIS is mainly used in a hot forging die (hereinafter referred to as a die) using steel as a base material. SKD7, SKD8, high-speed steel, and improved steels having higher high-temperature strength than these are used for applications requiring durability. In recent years, in response to demands for higher precision and higher processing efficiency of products to be processed,
While maintaining the mold toughness, wear resistance and
For the purpose of imparting seizure resistance, surface treatment has generally been applied. As a surface treatment method performed on such a mold, a single nitriding treatment by an ion method, a salt bath method, a gas method, or the like is mainly used.

For example, Japanese Patent Application Laid-Open No. 7-138733 discloses that
In order to reduce heat crack resistance and plastic flow of the mold, the temperature is raised to 950 ° C after ion nitriding and high-frequency heating is used to reduce the fragile, high-concentration nitrogen compounds called the white layer on the outermost surface. A method has been proposed in which the nitrogen diffusion layer is deepened to 3.0 mm. Also, Japanese Patent Application Laid-Open No. 57-54
No. 551 proposes a hot working mold that performs ion nitriding at a low temperature (350 to 450 ° C.) for the purpose of preventing seizure while maintaining the toughness of the mold core. Has a mold life of 2 times compared with the conventional nitriding material.
This is an improvement of the mold life of about 30%, which is not necessarily a dramatic improvement of the mold life.

[0004] In recent years, near-net shaping has resulted in a complicated product shape and a large flow of material during processing.
The friction with the working surface of the mold becomes excessive, the surface of the mold is softened more by the frictional heat, and the transformation point of the mold itself (700 to
(900 ° C.).
As a result, the properties that the mold itself should have are lost, the high-temperature properties are significantly reduced, and the mold wear phenomenon is accelerated to shorten the life. In addition, in molds that have been subjected to a single nitridation treatment, such as ion nitridation, which is currently performed as the mainstream of surface treatment, part of the formed nitride is decomposed due to overheating, and the effect is not sufficient. There was a problem that it could not be demonstrated.

[0005] As a method other than the single nitriding treatment, Japanese Patent Application Laid-Open No. 4-228557 discloses a method for improving lubricating oil holding properties of pistons and cylinders used in hydraulic pumps and motors of construction machinery. Gas sulphonitriding methods and devices have been proposed for cold sliding members used in. Japanese Patent Application Laid-Open No. 60-39155 proposes that a first layer mainly composed of ferric sulfide (FeS ₂ ) is formed on the surface of an iron-based product by introducing a decomposition gas of ammonium sulfide and an ammonia gas. The layer has a structure in which iron nitride of Fe ₄ N is formed.

Further, Katagiri et al. (The Japan Institute of Metals, Vol. 51, No. 10, (1987), pp. 930-934) use a colorless ammonium sulfide solution and a hydrogen sulfide concentration of 150 pp.
m, an ammonia concentration of 75%, a treatment temperature of 580 ° C., and a treatment time of 1 to 6 hours, whereby a porous ferrous sulfide (FeS) layer is formed on the outermost surface by subjecting the steel material to nitrosulphurizing treatment. It is reported that a surface layer in which iron oxide (Fe ₃ O ₄ ) coexists was obtained. Other, 7-42
No. 566 discloses an iron oxide in which triiron tetroxide (Fe ₃ O ₄ ) is formed in a base material for the purpose of preventing corrosion under an underground burial, such as bolts and nuts made of mild steel and cast iron, or for the purpose of preventing rust and improving the appearance of the ground. A formation method and the like have been proposed.

[0007]

Generally, the wear of a metal mold during plastic working of a high-temperature workpiece proceeds in the following course. The mold surface receives a thermal shock due to the following contact with the workpiece. That is, the surface of the high-temperature workpiece is pressed strongly onto the mold working surface, flows along the die-sculptured surface, and undergoes plastic working while generating frictional heat and generating heat due to plastic deformation. During this operation, the surface of the mold rapidly rises in temperature and expands. When the work is completed, the workpiece is quickly released from the mold. The mold surface starts to cool at the same time as the workpiece is released, and contracts.

[0008] As a result of the repetitive plastic working of the workpiece as described above, not only the mold surface is subjected to thermal fatigue due to expansion and contraction, but also the mold surface softened by heat is affected by the processing stress and the like. The resistance to the stress generated due to expansion and contraction is reduced, and heat crack and plastic flow are likely to occur on the surface layer of the mold, and wear such as wear proceeds. At this time, especially when the surface of the mold and the workpiece are in direct contact, the seizure phenomenon is likely to occur. When seizure occurs, heat transfer from the workpiece to the surface of the mold is facilitated, and wear of the mold proceeds more rapidly.

For this reason, in a normal operation, a lubricant or a release agent is applied to the mold surface every cycle, and these are interposed in a film form between the mold surface and the workpiece.
There is an advantage that the work surface of the mold does not come into direct contact with the workpiece. On the other hand, since the above-mentioned cooling agent is applied to the heated surface of the mold, the cooling rate is increased, and the mold shrinkage per unit time is disadvantageously increased. As described above, a normal hot forging die is a single-nitrided die, and a mechanical part having a sliding portion conventionally used on a relatively low temperature side near room temperature. Has been subjected to a nitrosulphurizing treatment. Japanese Patent Application Laid-Open No. 4-228557 discloses that FeS ₂ having a high lubricating oil content is subjected to secondary heat treatment at 200 to 350 ° C., and ferrous sulfide (FeS ₂ ) is formed on the outermost surface of a steel member. It is formed to enhance the lubrication effect. However, for example, when a workpiece that has been subjected to such processing is molded under high pressure from a workpiece heated to a high temperature targeted by the present invention,
Since the binding force of ferric sulfide is weak, peeling or falling off easily occurs, and it cannot be used as a warm-heat mold.

Further, since each layer proposed in Japanese Patent Application Laid-Open No. 60-39155 is porous, when applied to a metal mold, a material to be processed at a high temperature, for example, 600 ° C. or higher is formed under a high pressure. Then, it is likely to be a starting point of a heat crack or a propagation path, which is not suitable for use. Further, the method proposed by Katagiri et al. Uses a colorless ammonium sulfide solution as a feedstock, so that the weight concentration ratio (S / O) of sulfur and oxygen in the surface layer obtained is less than 0.5, and The coefficient of friction between the surface and the work material cannot be reduced sufficiently, and as described above, it tends to be a starting point or a propagation path for heat cracks caused by the porous layer. It is not always suitable for the use of the mold. The layers formed on the surface of the steel base material by the conventional sulphiditriding method have a porous structure when the work material heated to a high temperature is plastically worked like a mold to which the present invention is applied. This was likely to be a starting point of a heat crack or a passage for propagation caused by the material layer, and could not function sufficiently.

[0011]

SUMMARY OF THE INVENTION The inventor of the present invention, for example, when using as a mold made of steel as a base material, how to directly use the mold such as heat of a workpiece heated to a high temperature or heat generated by plastic deformation. It was examined whether it can be shut off without being transmitted to the surface and the life of the mold can be greatly improved. As a result, it is possible to modify the surface of the mold itself to form a dense surface treatment film that is less likely to seize between the mold surface and the workpiece, and has both a lubricating effect and a heat insulating effect. It has been found that if possible, the generation of frictional heat is suppressed, the surface of the mold is softened by heat transfer, and the life of the mold can be improved. As a result of repeated experiments on various films formed on the surface layer of the member by the inventor, a mixture layer containing nitrogen mainly composed of iron sulfide and iron oxide was formed, and the weight of sulfur and oxygen in the mixture layer was particularly high. Concentration ratio (S / O)
Was found to be very effective when the value was limited to a higher specific range.

That is, a first aspect of the present invention is to provide a member made of steel as a base material having a mixture layer containing nitrogen mainly composed of iron sulfide and iron oxide on a surface layer portion thereof, wherein sulfur and oxygen in the mixture layer are contained. Wherein the weight concentration ratio (S / O) has a region satisfying the expression 0.5 <S / O <10. Further, the second invention has a mixture layer containing nitrogen mainly composed of iron sulfide and iron oxide on a surface layer portion of a member made of steel as a base material, and a weight concentration ratio of sulfur and oxygen (S) in the mixture layer. /
O) has a region satisfying the expression 0.5 <S / O <10, and at least a nitride layer is formed on the member body side of the mixture layer, and the nitride layer includes a white layer and a nitrogen diffusion layer. It is a member for warmth characterized by the above-mentioned.

According to a third aspect of the present invention, a member containing steel as a base material has a mixture layer containing nitrogen mainly composed of iron sulfide and iron oxide at a surface layer portion, and a weight concentration ratio of sulfur and oxygen in the mixture layer ( S /
O) has a region satisfying the expression of 0.5 <S / O <10, and at least a nitride layer is formed on the member body side of the mixture layer, and the nitride layer is a nitrogen diffusion layer. It is a member for warm and hot. The concentration of S in the mixture layer is preferably 5 to 30 by weight%. The mixture layer is preferably a dense layer having a thickness of 0.1 to 20 μm, and the nitride layer has a maximum hardness of 900 μm.
HV or more is good.

[0014] A fourth invention for producing the above-mentioned warm / hot member is as follows.
A colorless ammonium sulfide solution and a yellow ammonium sulfide solution are supplied into the gas generating container at a ratio of 6: 1 to 1: 1. A mixture of a gas on the liquid surface to be generated and a carrier gas composed of nitrogen gas or argon gas is used. Hydrogen sulfide gas concentration of 100 to 600 ppm, ammonia gas concentration of 0.1
Adjusted to ~ 1.0%, a warming member made of steel as a base material was arranged and introduced into a reactor heated to 460 to 600 ° C, and nitrogen gas and ammonia gas supplied from separate containers were used. The ammonia concentration in the reactor is 10 to 70
%, And the gas sulphonitriding treatment may be performed.

In order to include a white layer and a nitrogen diffusion layer in at least the nitride layer formed on the member body side, the fourth layer
The heating temperature of the reaction furnace of the present invention is set to a high value of 500 to 600 ° C., and the ammonia concentration in the reaction furnace is set to a high value of 20 to 600 ° C.
It is good to make it 70%. Further, in order to include only the nitrogen diffusion layer in the nitride layer formed at least on the member body side,
The heating temperature of the reactor of the fourth invention is lowered to 460 to 550 ° C.
And the ammonia concentration in the reactor
It is good to be ~ 40%. Further, the warming member constituted by the first to third inventions is preferable as a warming mold.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One of the features of the member for warming and warming of the present invention is that a member containing steel as a base material has a mixture layer containing nitrogen mainly containing iron sulfide and iron oxide on a surface layer portion thereof. The sulfur / oxygen weight concentration ratio (S / O) in the mixture layer is 0.5 <S / O <
It is limited to 10. When the sulfur / oxygen concentration ratio (S / O) in the mixture layer is 0.5 or less, the friction coefficient between a workpiece and a sliding part such as a machine part or a mold working surface can be sufficiently reduced. On the contrary, in the case of 10 or more, the adhesion between the steel base material and the mold body or the nitride layer formed on the mold body or the member of the mixture layer or the mold body becomes insufficient.
Since it is easy to peel off or fall off and cannot endure long-term use, it is set to less than 10.

Another feature is that at least a nitride layer is formed on the member or the mold body side on which the mixture layer is formed, and the nitride layer is formed of a white layer and a nitrogen diffusion layer. It consists of In the case of a mold in which a member having a portion that slides with a counterpart material at a relatively high temperature or a workpiece is plastically processed under high pressure, the nitrided layer compensates for insufficient strength of the surface of the member or the mold body. In addition, when the mixture layer is partially worn out after long-term use, it has the effect of preventing the seizure resistance from being reduced in a short time. In addition, the above-mentioned nitrided layer, for example, the shape of the die sculpture surface of the mold is relatively less uneven,
Or in the case of plastic working easy workpiece it is called a white layer called ε-Fe ₂ ~ ₃ N and nitrogen diffusion layer γ'-
It is preferable to form a white layer made of Fe ₄ N and a nitrogen diffusion layer.

In the case where the surface of the engraved surface has large undulations and a mold with sharp projections and valleys, or the material to be processed is difficult to process even if the undulations are small, the above hard white layer is used. Is likely to be a starting point of crack generation, so it is preferable to form a nitride layer having only a nitrogen diffusion layer without a white layer. For the same reason, the concentration of S in the mixture layer that satisfies the constitutional requirements of the first to third inventions of the present invention is preferably 5 to 30 by weight%, and the thickness of the mixture layer is as described above. In order to exhibit the effect, the thickness is required to be 0.1 μm. Conversely, if the thickness exceeds 20 μm, it is easy to peel off, so that a dense layer of 0.1 to 20 μm is desirable. More preferably, the hardness of the nitrided layer is adjusted to 900 HV in order to supplement the strength of the member or the mold body.
It is better to do above.

The hot members to which the present invention is applied include, for example, rolls for forming aluminum wheels, sliding members such as rails and guides, pins used in the hot state such as extrusion pins, core pins, core pins, and the like. In addition to the extrusion dies, gears, molds for valve molding, hot molds for forging or press molding, and the like, members used in an atmosphere in which a workpiece or a counterpart material is exposed to a temperature of 400 ° C. or more, It is suitable as a member used at a temperature of 600 ° C. or higher, particularly 800 ° C. or higher.

In order to manufacture the hot-working member of the present invention which satisfies the above constitutional requirements, in particular, a hot-working mold, there is, for example, a method of using an ammonium sulfide solution as a source of sulfuration and oxidation. This method is advantageous for forming a weight concentration ratio (S / O) of sulfur and oxygen in the dense mixture layer containing nitrogen mainly composed of iron sulfide and iron oxide, which is more than 0.5, on the surface layer of the member. is there.

That is, a colorless ammonium sulfide solution having a low hydrogen sulfide concentration and a high water content (JI
SK8943) and a yellow ammonium sulfide solution having a high hydrogen sulfide concentration and a low water content (JIS K8942) to form a mixed solution, and the generated gas on the liquid surface is mixed with nitrogen gas or argon gas as a carrier gas. The hydrogen sulfide gas concentration is adjusted to 100 to 600 ppm and the ammonia gas concentration is adjusted to 0.1 to 1.0%, and the members to be treated are arranged and introduced into a reaction furnace heated to 460 to 600 ° C. It is only necessary to adjust the concentration of ammonia in the reaction furnace to 10 to 70% with nitrogen gas and ammonia gas supplied from another container such as a cylinder or the like, and perform the sulphinitriding treatment for a predetermined time.

Here, the concentration of H ₂ S in the on-liquid gas (head gas) of the colorless ammonium sulfide solution is 30 ppm at 25 ° C., and the H ₂ S concentration in the on-liquid gas of the yellow ammonium sulfide solution is 1250 ppm. Therefore, in order to satisfy the constituent requirements to be formed on the surface layer of the member, the ratio of the colorless ammonium sulfide solution to the yellow ammonium sulfide solution is set in the range of 6: 1 to 1: 1 and H _{2 in the} gas above the liquid surface is adjusted.
The S concentration is in the range of 100 ppm to 600 ppm.

In the above nitrosulphurizing process, at least the nitriding layer formed on the member body side contains a white layer and nitrogen diffusion, by increasing the heating temperature of the reaction furnace and increasing the nitrogen diffusion efficiency. It is desirable to increase the concentration of ammonia in the reactor as a source of nitriding. For this purpose, the heating temperature of the reaction furnace is preferably 500 to 600 ° C., and the ammonia concentration in the reaction furnace is preferably 20 to 70%. Further, in order for the nitrided layer formed at least on the member main body side to contain only the nitrogen diffusion layer, the heating temperature of the reaction furnace is lowered to suppress the diffusion of nitrogen, and the ammonia in the reaction furnace serving as a nitriding supply source is reduced. It is desirable to lower the concentration. For this purpose, the heating temperature of the reactor is preferably 460 to 550 ° C., and the ammonia concentration in the reactor is preferably 10 to 40%.

In addition to the ammonium sulfide solution, ammonium sulfite-hydrate,
An ammonium sulfite solution or the like can also be used. The surface layer of the member or mold used during warm or hot,
It is dense, not porous in terms of form, and has a low friction coefficient and a high heat insulating effect due to its composition.Especially in the case of a hot mold, there is a large amount of iron sulfide that contributes to the improvement of seizure resistance It is important that On the other hand, the mold base material used for the hot mold of the present invention is SK specified in JIS standard.
Hot tool steels having high temperature strength and toughness typified by D61 and SKT4 are suitable, and can be applied to SKD7, SKD8, high-speed steels or higher-grade steels having higher high-temperature strengths than these, if necessary. can do.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments. (Example 1) Steel having the composition shown in Table 1 was prepared, and both steel 1 and steel 2 were tempered to 48HRC by quenching and tempering. Thereafter, a round bar test piece having a shape of 5 mm in diameter and 20 mm in length was prepared, and its end face was finished with a grindstone. Hot baking tests were performed on these test pieces that had been subjected to various surface treatments shown in Table 2. In the hot baking test, one end of the test piece was attached to a chuck of a drilling machine, rotated at 1540 rpm, and the other end of the test piece was pressed against a block made of SNCM439 heated to 600 ° C. and frictionally slid for 30 seconds. The load was 0.31 to 1.70 KN, and the value obtained by dividing the pressing load at which seizure occurred by the cross-sectional area was evaluated as the seizure limit surface pressure (MPa) to evaluate the seizure resistance.

[0026]

[Table 1]

[0027]

[Table 2]

Table 3 shows the surface structure after various surface treatments and the test results. The seizure limit surface pressure of the member of the present invention is 69.9 to 8
It is in the range of 6.6 MPa and is 2. compared with ion nitriding.
2 to 2.7 times, 1.2 to 1. 1 times as compared to gas sulphonitriding using salt bath sulphinitriding A and a colorless ammonium sulphide solution.
4 times, 1.8 to 2.3 times compared to the salt bath sulphonitriding B. Thus, it can be seen that the members of the present invention have significantly improved seizure limit surface pressure as compared with the comparative members. In addition,
Was microstructure observed by cutting a test piece end after reaching the seizure limit surface pressure, they both are present a re-hardened structure, that has been heated to a temperature above the AC ₁ transformation point of steel It was recognized that a large amount of frictional heat was generated. This indicates that the member of the present invention can significantly reduce frictional heat generation.

[0029]

[Table 3]

In Table 3, sample No. 6 and sample N
o. 8 (all correspond to comparative members), 12 and sample no. Observation of cross-sectional structure and EPM of the surface of the test piece subjected to the same treatment as No. 20 (each of which corresponds to the present invention member)
A (microscopic X-ray analyzer) was used to perform line analysis, and the results are shown in FIGS. 1, 2, 3 and 4, respectively. FIG. 1 shows the results of salt bath oxynitridation A, which is out of the scope of the member of the present invention, in which the maximum concentration of S in the uppermost mixture layer of the surface treatment layer is 2.2 wt%, and the amount of sulfur and oxygen in the mixture layer is Concentration ratio (S /
O) was 0.29 and the thickness of the mixture layer was 22 μm. FIG. 2 also shows the case of the salt bath oxynitridation B which is not the object of the present invention, in which the maximum concentration of S in the mixture is 1.1 wt% and the concentration ratio of sulfur to oxygen (S / O) in the mixture layer. 0.03,
The thickness of the mixture layer was 5 μm.

On the other hand, as shown in FIG. 3, the maximum concentration of S in the mixture layer of the surface treatment layer corresponding to the member of the present invention is 21 wt%, and the concentration ratio of sulfur to oxygen (S / O) is 1. 24
In FIG. 4, the maximum concentration of S is 20 wt%, and the concentration ratio of sulfur to oxygen (S / O) is 1.
At 18, the mixture layer thickness was 3.5 μm. As described above, the sample No. of the member of the present invention. 12 (FIG. 3) and sample N
o. 20 (FIG. 4) has a high S concentration, and it can be seen that the S / O in the mixture layer is higher than that of the conventional member.

Next, the structures of the above-mentioned mixture layer and the nitride layer on the member body side will be described with an optical microscope structure. Sample No. of the member of the present invention. 12 and sample no. 20 to FIGS. 3 and 4
Shown in FIG. 3 shows that the mixture layer having a thickness of 3 μm described above had a nitride layer on the member body side, and the nitride layer was formed of a nitrogen diffusion layer alone, and the thickness was 0.08 mm. FIG. 4 is formed from the aforementioned mixture layer having a thickness of 3.5 μm, the thickness of which is 5 μm for the white layer and 0.1 μm for the nitrogen diffusion layer, respectively.
4 mm. The constituent materials of the mixture layer and the nitride layer will be described in detail in Example 3 by X-ray analysis.

Example 2 Sample Nos. Shown in Table 3 5 to Sample No. Sample No. 10 (corresponding to a comparative member) 11
From Sample No. 12 and sample no. Sample N from 19
o. 20 (corresponding to the member of the present invention).
The hardness was measured by adding 00 g, and the results of measuring the maximum hardness of each were shown in Table 4. Sample No. of the member of the present invention. 1
1 and sample no. The highest hardness of 12 showed the softest hardness as compared with the other samples, but the highest hardness was 900 HV.
That was all. In addition, the sample No. of the member of the present invention. 19 and sample no. The maximum hardness of 20 was 1033 HV and 1042 HV, respectively, and the maximum hardness was 900 HV or more.

[0034]

[Table 4]

Example 3 Sample Nos. Shown in Table 3 6 and sample no. Sample No. 8 (corresponding to a comparative member) 12
And sample no. FIG. 5 shows the results of X-ray analysis using the X-ray diffractometer from the outermost surface of the surface of the test piece subjected to the same treatment as No. 20 (corresponding to the member of the present invention). X
The line diffraction conditions were as follows: applied voltage 40K using a Co target.
V and the applied current of 200 mA, the diffraction angle (2θ) is 30.
From 120 ° to 120 °. Sample No. of FIG. 6 and sample no. The results of the qualitative analysis of No. 8 showed that the iron oxide was Fe ₃ O ₄ and the iron nitride was Fe ₃ N and Fe ₄ N, and no iron sulfide was detected. Sample No. of FIG. The qualitative analysis results of No. 12 showed that iron sulfide was FeS, iron oxide was Fe ₃ O _4, and iron nitride was Fe ₄ N. Sample No. of FIG. The qualitative analysis results of No. 20 showed that iron sulfide was FeS, iron oxide was Fe ₃ O _4, and iron nitride was Fe ₃ N and Fe ₄ N.

From the above, when considering the result of EPMA of the mixture layer shown in Example 1 comprehensively, Sample No. 6 and sample no. Although the mixture layer of No. 8 contained 2.5 wt% and 1.1 wt% of small amounts of S, respectively, it was confirmed that it was substantially formed of Fe ₃ O ₄ and Fe ₃ N. The nitride layer on the member body side of the mixture layer is composed of Fe ₃ N (white layer) and F
e ₄ N (nitrogen diffusion layer) was confirmed. Next, the sample No. 12 and sample no. It was confirmed that the mixture layer of No. 20 substantially contained Fe ₃ N with FeS and Fe ₃ O ₄ as the main components. The nitride layer on the member body side of the mixture layer was the sample No. Sample No. 12 is formed of Fe ₄ N (nitrogen diffusion layer) alone. 20 is Fe ₃ N (white layer) and Fe ₄
It was confirmed to be formed from N (nitrogen diffusion layer).

Example 4 Sample Nos. Shown in Table 3 6 and sample no. Sample No. 8 (corresponding to a comparative member) 12
And sample no. The surface resistance of the test piece treated in the same manner as that of Sample No. 20 (corresponding to the member of the present invention) was measured from the surface by a continuous load-type surface property measuring instrument in order to evaluate the adhesion at the interface between the mixture layer and the nitride layer. Table 5 shows the results. The measurement conditions of the continuous weighting type surface property measuring machine were as follows: a diamond scratching needle of 30μ was used, and the moving speed was 0.2 mm / sec.
c, 500 g of full scale vertical load was used.

[0038]

[Table 5]

Sample No. of the member of the present invention 12 and sample N
o. It was confirmed that the scratch resistance of No. 20 was higher than that of the comparative member. From this, it can be said that the adhesiveness of the mixture layer of the present invention is better than that of the comparative member. Further, Sample No. was determined from the form of the surface layer.
6 and sample no. Sample No. 8 of the member of the present invention, while the mixture layer of Sample No. 8 was in a porous form. 12 and sample no.
The mixture layer of No. 20 is in a dense form. For example, in response to thermal stress applied to a mold in a high-temperature forging operation, a porous and poorly adhered comparative member is a starting point or a propagation point of a heat crack due to the porosity. However, since the member of the present invention has improved adhesion and a dense form, it can be expected to improve the life when used as a mold for warming.

Example 5 Sample No. 3 in Table 3 2,4
Hot forging dies used for ring pressure molding having the surface layer structures of 6, 8, 10, 12, 18, and 20 were prepared. The dimensions of the mold are 148mm in diameter and 66m in height
m. Steel No. 2 was rough-worked to a mold approximate size, tempered to 48 HRC by quenching and tempering, and after finishing to the above-mentioned size, each was subjected to surface treatment so as to obtain a predetermined surface layer structure. Forging was performed using a 1600-ton forging press and SCM42 heated to 1200 ° C by high frequency.
The 0H work was forged every 14 seconds after the upset processing. Table 6 shows the life of the mold.

[0041]

[Table 6]

Each of the molds reached the end of its life due to damage due to wear. It can be seen that the mold of the present invention has a mold life approximately twice as long as that of the comparative mold as compared with the comparative mold which is a conventional mold, and is excellent in wear resistance.

[0043]

As described above, in the warm member and the warm mold having the surface layer structure of the present invention, the iron sulfide mainly has the effect of suppressing the heat load due to frictional heat and the heat insulating effect. It is possible to improve the life of the mold, and the effect of mainly preventing the oxide layer from being thickened by Fe ₂ O ₃ or FeO generated during use in the mold,
Since the form of the mixture layer is dense and the adhesion between the mixture layer and the nitride layer is improved, there is an advantage that the mixture layer does not easily become a starting point of cracks or a propagation path of a crack during use, and is used for a long time. It is highly effective.

[Brief description of the drawings]

FIG. 1 shows a sample No. of a comparative member. 6 is an electron micrograph showing the structure of the mixture layer of No. 6, a line analysis chart by EPMA, and an optical microscope photograph showing the structure of the nitride layer on the member body side of the mixture layer.

FIG. 2 shows a sample No. of a comparative member. 8 is an electron micrograph showing the structure of the mixture layer of No. 8, a line analysis chart by EPMA, and an optical microscope photograph showing the structure of the nitride layer on the member body side of the mixture layer.

FIG. 3 shows a sample No. of a member of the present invention. 12 is an electron micrograph showing the structure of a mixture layer of No. 12, a line analysis chart by EPMA, and an optical microscope photograph showing the structure of a nitride layer on the member body side of the mixture layer.

FIG. 4 shows a sample No. of the member of the present invention. 20 is an electron micrograph showing the structure of the mixture layer of No. 20, a line analysis chart by EPMA, and an optical microscope photograph showing the structure of the nitride layer on the member body side of the mixture layer.

FIG. 5 shows a sample No. of a comparative member. 6 and sample no. 8 and the sample No. of the member of the present invention. 12 and sample no. 20 X
FIG.

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[Procedure amendment]

[Submission date] February 7, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

[0026]

[Table 1]

Claims (10)

[Claims] 1. A steel-based member having a mixture layer containing nitrogen mainly composed of iron sulfide and iron oxide on a surface layer of a member made of steel, wherein a weight concentration ratio of sulfur and oxygen (S / O) in the mixture layer is ) Is 0.5
A member for warming and warming having a region satisfying a formula of <S / O <10. 2. A member containing steel as a base material has a mixture layer containing nitrogen mainly composed of iron sulfide and iron oxide on a surface layer portion thereof, and a weight concentration ratio of sulfur and oxygen (S / O) in the mixture layer. ) Is 0.5
<S / O <10, wherein at least a nitride layer is formed on the member body side of the mixture layer, and the nitride layer is composed of a white layer and a nitrogen diffusion layer. Intermediate member. 3. A member containing steel as a base material has a mixture layer containing nitrogen mainly composed of iron sulfide and iron oxide on a surface layer portion thereof, and a weight concentration ratio of sulfur and oxygen (S / O) in the mixture layer. ) Is 0.5
A member having a region satisfying the expression <S / O <10, and at least a nitride layer formed on the member body side of the mixture layer, wherein the nitride layer comprises a nitrogen diffusion layer. . 4. A member for hot and warm use, wherein the concentration of S in the mixture layer according to claim 1 is 5 to 30 by weight%. 5. A member for warming and warming, wherein the mixture layer according to claim 1 is a dense layer having a thickness of 0.1 to 20 μm. 6. A hot / hot member wherein the nitride layer according to claim 2 or 3 has a maximum hardness of 900 HV or more. 7. A 6: 1 to 1: 1 mixture of a colorless ammonium sulfide solution and a yellow ammonium sulfide solution in a gas generating vessel.
And the concentration of hydrogen sulfide gas in the mixed gas of the generated gas on the liquid surface and the carrier gas composed of nitrogen gas or argon gas is 100 to 600 ppm, and the ammonia gas concentration is 0.1 to 1.0%. And a warming member having steel as a base material is arranged and introduced into a reaction furnace heated to 460 to 600 ° C., and nitrogen gas and ammonia gas supplied from another container are used for the inside of the reaction furnace. A method for producing a member for hot and warm use, comprising adjusting the ammonia concentration to 10 to 70% and subjecting it to gas sulphiditriding. 8. The method according to claim 7, wherein the heating temperature of the reactor is 500 to 600 ° C., and the ammonia concentration in the reactor is 20 to 70%. 9. The method according to claim 7, wherein the heating temperature of the reactor is 460 to 550 ° C., and the ammonia concentration in the reactor is 10 to 40%. 10. A hot mold comprising the warm member according to any one of claims 1 to 6.