JP4844874B2 - Manufacturing method of press-molded products - Google Patents

Description

The present invention is particularly for press forming punch and die like, according to the press die, those concerning the manufacturing process of the press-molded product.

  Conventionally, SKD11 and the like having high hardness and excellent wear resistance have been applied to press dies with sliding in use and the like by containing matrix hardness and Cr-based special carbide. However, in recent years, SKD11 and the like have been subjected to surface treatments such as nitriding, PVD, CVD, salt bath treatment, etc. due to the molding of difficult-to-work materials in dies and the severer sliding environment in press dies.

The above is a technique for improving the wear resistance by increasing the hardness. On the other hand, in recent years, technical development has been made focusing on the self-lubricating property of oxides. For example, there are reports on the study of the bonding state of Cu, Mo, O at various temperatures when Cu-Mo is ion beam deposited on an alumina substrate, and the results of friction tests at various test temperatures. Yes (Non-Patent Document 1). According to this, since a complex oxide of CuO + MoO ₃ is generated at 300 ° C. or higher and increases as the temperature becomes higher, the friction coefficient at 600 ° C. decreases, and excellent sliding characteristics can be obtained. It has been reported.
Surface and Coatings Technology 89, 1997, p. 245-251

  As a method for imparting sliding characteristics, the above-described measures using hard substances such as SKD11 have a problem of adversely affecting the machinability when the material itself is processed into a mold shape. In addition, when the surface treatment is performed, there is a problem that the adhesion between the base material and the coating film is poor, and the base material and the coating film are peeled off.

  On the other hand, in a material provided with a Cu—Mo composite coating that provides excellent sliding characteristics, the base material needs to have high hardness from the viewpoint of wear resistance. Similarly, there is a problem that the adhesion between the base material and the coating film is poor, and the film is peeled off, and further, there are problems of labor and cost for coating.

An object of the present invention is to provide a method for producing a press-formed product by using a press die having excellent self-lubricating properties, which solves the above-described problems.

  As a result of studying the above problems, the present inventor has found that the press mold under the above-mentioned use environment is excellent in lubrication characteristics and wear resistance and has a long service life without coating. It has been found that a press die having excellent lubrication characteristics and wear resistance is optimal. Therefore, by targeting a press die in a state where a complex oxide of Cu and Mo having excellent self-lubricating properties is self-generated on the outermost surface of the base material of martensitic steel by internal oxidation. The present invention has been developed.

That is, the present invention is mass%, C: 0.7 to less than 1.6%, Si: 0.5 to 3.0%, Mn: less than 0.1 to 3.0%, P: 0.05 % (Including 0%), S: 0.01 to 0.12%, Cr: 7.0 to 13.0%, 1 type of Mo or 2 types of Mo and W (Mo + W / 2): 0 0.5 to 1.7%, V: less than 0.7% (including 0%), Ni: 0.3 to 1.5%, Cu: 0.1 to 1.0%, Al: 0.1 to 0.1% In a manufacturing method of a press-molded product, in which a work material is press-molded by a press mold made of martensitic steel containing 0.7% and the balance Fe and unavoidable impurities, the mold being pressed and production workpiece is at the time of sliding, the maximum processing speed of the die and the workpiece is press-formed product, which comprises press molding under conditions of greater than 0.37 m / s It is the law. The maximum processing speed referred to in the present invention is the processing speed when the speed of sliding between the mold and the workpiece during press molding is maximum.

And the press die which has the outstanding self-lubricating property used by the manufacturing method of the press-formed product of the present invention may contain 0.3% or less Nb in mass%.

According to the present invention, by providing a method for producing a press-formed product with a press mold having excellent self-lubricating properties without coating, the cost of the mold can be reduced and the life can be extended. In particular, this technology is indispensable in the field of press dies in a sliding environment.

As described above, an important feature of the present invention is the problem of adhesion between the base material and the coating film, and further, excellent lubrication characteristics and wear resistance can be achieved without troublesome and costly coating. The present invention has achieved a method for producing a press-formed product by using a press die . Specifically, it is a press die aimed at a state in which a complex oxide of Cu and Mo (hereinafter also referred to as Cu-Mo complex oxide) is self-generated on the outermost surface during press molding .

First, the excellent lubrication mechanism characteristics of the Cu—Mo composite oxide will be described.
The Cu—Mo composite oxide is produced as a CuO + MoO ₃ composite oxide in an environment of 300 ° C. or higher in the presence of Cu and Mo. And many are produced | generated as it becomes high temperature. This composite oxide has a layered structure like a solid lubricant such as molybdenum disulfide and graphite, has a weak self-lubricating property that gives a small coefficient of friction, and has a weak bonding force between specific crystal planes or molecules.

  For the press die of the present invention, it is considered that the Cu—Mo composite oxide film by the internal oxidation of the base material itself is self-formed on the outermost surface, so that it has excellent lubrication characteristics. The overall improvement in sliding characteristics is achieved by being excellent in abrasion. Therefore, the base material constituting the present invention is such that the internal oxidation of Cu and Mo proceeds to self-form the Cu—Mo composite oxide that is the basis of the present invention, and each is 3.0 mass% or less. A high-hardness martensitic steel containing Mo and Cu is preferable.

  And as for the press metal mold | die of this invention, it is preferable that the maximum processing speed with the to-be-processed material in press processing exceeds 0.37 m / s as the use conditions. If it is 0.37 m / s or less, heat generation due to sliding is small, and it is presumed that the self-formation of the Cu—Mo composite oxide film is insufficient. Therefore, it is preferable that the maximum processing speed is more than 0.37 m / s. Preferably, the maximum processing speed exceeds 0.56 m / s.

Then, the base material constituting the present invention, in mass%, C: less than 0.7~1.6%, Si: 0.5~3.0%, Mn: less than 0.1 to 3.0% , P: less than 0.05% (including 0%), S: 0.01 to 0.12%, Cr: 7.0 to 13.0%, one kind of Mo or two kinds of Mo and W ( Mo + W / 2): 0.5 to 1.7%, V: less than 0.7% (including 0%), Ni: 0.3 to 1.5%, Cu: 0.1 to 1.0%, al: 0.1 to 0.7% only containing a steel consisting of balance of Fe and unavoidable impurities, a martensitic steel is expected that the internal oxidation of the proceeds smoothly. You may contain 0.3% or less of Nb.

Hereinafter, for the press die of the present invention, the component composition of the upper Kihaha material will be described. In addition, the description of% which shows content of each element is the mass%.
C is an important element that partly dissolves in the base to give strength, and partly forms carbides to increase wear resistance and seizure resistance. Here, since the ratio of C in steel to solute C and carbide is mainly determined by the interaction with Cr, it is desirable to define C simultaneously by recognizing the interaction with Cr. Therefore, in order to make a practical base material that satisfies both machinability and heat treatment deformation stability in a well-balanced manner, the component range of C is 0.7 to less than 1.6% in view of the following Cr content. Good. Preferably, it is 0.9 to 1.3%.

  Si is an important element for the base material of the present invention. Si is usually added in an amount of about 0.3% as a deoxidizer. However, in the present invention, it is feared that the quenching hardness is lowered as a result of favoring a component design that suppresses expansion during quenching. In order to suppress the softening phenomenon up to around 490 ° C., it is desirable to set it to 0.5% or more higher than usual. In addition, since excessive inclusion causes formation of delta ferrite, the upper limit is preferably 3.0%. More preferably, it is 0.9 to 2.0%.

  Mn, like Si, is used as a deoxidizer, and in this case, it contains at least 0.1%. However, since an excessive content impairs machinability, it is desirable to set the upper limit to 3.0%. More preferably, it is 0.1 to 1.0%.

  S is an element useful for improving machinability. However, if contained in excess, the toughness is reduced, so at most 0.12% or less is desirable, and if added, 0.01 to 0.12% is good. Preferably, it is 0.03 to 0.09%.

  Cr is an element indispensable for improving the hardenability of the base material and forming carbide. Here, as in the case of C, since the ratio of Cr in the steel to solute Cr and carbide is determined by the interaction with C, the content can also be defined simultaneously by recognizing the interaction with C. desirable. Therefore, in order to provide a practical sliding member that satisfies both the machinability and the heat treatment deformation stability in a well-balanced manner, the component range of Cr is 7.0 to 13.0% in view of the above C content. Good. Preferably, it is 8.0 to 11.0%.

Mo is an essential element that is expected to exhibit the self-lubricating mechanism characteristics of the present invention by including 3.0% or less. However, in adjusting the mechanical characteristics as a base material, Mo and W are the same. The effect is imparted, and the degree thereof can be defined by (Mo + W / 2) from the relationship of atomic weight. Mo and W are elements that are responsible for secondary hardening of tool steel, and are often added to high-speed tool steel that requires high hardness especially in application to small products such as tools and drills. Also in the present invention, Mo and W can be added as greatly contributing to a matrix state exhibiting secondary curing, but if less than 0.5%, a sufficient effect cannot be obtained, while these elements are not obtained. Since it promotes change in size, excessive addition is not good for large products such as cold molds. Therefore, in the press die of the present invention, the base material is preferably 0.5 to 1.7% of one kind of Mo or two kinds of Mo and W (Mo + W / 2). More preferably, it is 0.75 to 1.5%.

  Ni is a preferable element for inclusion in the present invention, which combines with Al, which will be described later, to form and precipitate a Ni—Al-based intermetallic compound, thereby achieving secondary curing and suppression of deformation at the same time. Moreover, when it contains the below-mentioned Cu, it is also a useful element which suppresses red heat | fever brittleness. However, if it is less than 0.3%, a sufficient effect cannot be obtained. On the other hand, an excessive content exceeding 1.5% raises the solid solubility limit of C in Fe and inhibits workability in the annealed state. 0.3 to 1.5% is preferable. More preferably, it is 0.4 to 1.5%, and still more preferably 0.5 to 1.3%.

Cu is an essential element that is expected to exhibit the self-lubricating mechanism characteristics of the present invention by containing 3.0% or less as in Mo, but depending on the content of the appropriate amount, Cu metal phase is about 480 ° C. or more. Since this becomes a precipitation nucleus of the intermetallic compound, it is possible to precipitate the Ni-Al intermetallic compound, which originally precipitates at a higher temperature, just near the secondary hardening temperature of the tool steel. To do. Therefore, it is a preferable element to contain in order to maximize the effect of canceling the size change due to precipitation of the Ni—Al intermetallic compound and the secondary hardening. However, when Cu is added in a large amount, red heat embrittlement occurs. Therefore, in the present invention, it is preferable to specify 0.1 to 1.0%. More preferably, it is 0.2 to 0.8%.

As described above, Al combines with Ni to form a Ni—Al-based intermetallic compound such as Ni ₃ Al or NiAl, and is responsible for secondary hardening by precipitation. Further, since the matrix shrinks due to this precipitation reaction, the element is a preferable element for inclusion in the present invention, which cancels out the expansion reaction at the time of secondary hardening in the tool steel and consequently suppresses deformation. However, if it is less than 0.1%, a sufficient effect cannot be obtained. On the other hand, excessive Al exceeding 0.7% causes remarkable delta ferrite formation. Is preferred. More preferably, it is 0.1-0.5%, More preferably, it is 0.15-0.45%.

  Nb is a preferable element contained in the base material for the press die of the present invention because it has a function of making the distribution of carbides in the structure uniform and reducing heat treatment deformation. In particular, a content of 0.03% or more is preferable. However, if the amount of the MX compound formed by the content is too large, the machinability is impaired.

The following elements may be included in the base material of the present invention as long as they are within the following ranges.
Since P is an element that inhibits toughness, it is limited to less than 0.05%, preferably 0.02% or less. V can be added to improve hardenability, but is an element that hinders machinability, so even if it is contained, it is limited to less than 0.7%, preferably 0.5% or less. To do.

  The base material of the present invention preferably has a component composition satisfying the above and can be made of steel with the balance being substantially Fe. For example, other than the above-mentioned element types, if Fe and other elements are steels with a total of 20% or less, 10% or less, 5% or less, and the balance is steel composed of Fe and inevitable impurities, excellent self-lubrication A press die having excellent mechanical properties, which is expected to have mechanical properties, and further achieves size change suppression properties and secondary curing at the same time.

In the present Example 1, the die temperature at the time of actually using for press molding is assumed, and self-generation of Cu—Mo composite oxide by internal oxidation is evaluated.
First, a steel ingot obtained by ingot-making after vacuum melting is hot-worked, and a sample of martensitic steel (the size is the balance) of the chemical components (mass%) shown in Table 1 and the balance Fe and inevitable impurities. 15 × 15 × 3 mm). These samples were quenched (1030 ° C. × 1 h) and tempered (500 ° C. × 1 h twice), then mirror-polished, and then heat treated at 500 ° C. assuming the actual mold temperature in use. (Oxidizing atmosphere) was applied to obtain an evaluation sample. And the surface state (configuration of the self-generated film) of the obtained sample was measured and evaluated by an X-ray photoelectron spectrometer (ESCA).

  In ESCA measurement, surface sputtering is performed by integrating 0 (outermost surface), 3, 6, 9, 12, 15, 30, 45, 60, 75, 90, 105, 120 minutes, corresponding to the respective sputtering times. The component states at the outermost surface and the position in the depth direction were evaluated. Sample No. As for 1, the bonding state of Cu after 0 minutes and 3 minutes after sputtering is shown in FIG. 1, and the bonding state of Mo after 0 minutes and 120 minutes after sputtering is shown in FIG.

Sample No. In the case of 1, the state of Cu cannot be determined because the Auger peak is unclear at a depth of 3 minutes after sputtering as shown in FIG. 1, but CuO is formed on the outermost surface of 0 minutes of sputtering. I understand that. In addition, as shown in FIG. 2, Mo forms MoO ₃ on the outermost surface of 0 minutes of sputtering, and is in the Mo state at a depth position after 120 minutes of sputtering.

On the other hand, sample No. In the case of 2, neither CuO nor MoO ₃ was detected.

From the results described above, sample No. 1 only shows that a CuO—MoO ₃ composite oxide film is formed on the outermost surface.

  In the present Example 2, the member Nos. Shown in Table 2 based on the test results of Example 1 were used. 3 and 4 are applied to a press die, and the seizure property when press molding is performed is evaluated.

  In this evaluation, the member No. A seizure evaluation test was carried out under the molding conditions shown in FIG. In the apparatus of FIG. 3 in which the punch moves up and down by the link mechanism, the punch reaches the maximum machining speed under the condition that the punch and the workpiece are in contact with each other at the moment when the tip of the punch comes into contact with the workpiece (workpiece).

  On the other hand, in order to suppress “wrinkles” generated in the workpiece during press forming, it is effective to increase the “wrinkle holding force” for fixing the end portion of the workpiece. However, if this force increases. Conversely, seizure is more likely to occur. Therefore, in this test, the “maximum wrinkle pressing force” capable of press forming without seizure was measured in punch forming at a constant maximum processing speed. In other words, seizure occurs when the force that presses the end of the workpiece exceeds the maximum wrinkle holding force, so the greater the maximum wrinkle holding force, the better the seizure resistance, and no wrinkle occurs. Various shapes can be formed at high speed.

  FIG. 4 shows the test results. In the apparatus of FIG. 3, the processing speed is controlled by the molding speed [number of molding shots per unit (spm)], and the molding speed at that time is also shown.

From FIG. 4, member No. which is the press die of the present invention is shown. 3, the maximum blank holding force can be molded without seizure, enough to raise the processing rate was up from 1.2 kgf / cm ² to 1.4 kgf / cm ^2. Member No. No. 3 was not subjected to heat treatment to self-generate a Cu—Mo composite oxide film before using the mold, and the oxide film was not generated at the start of molding, but gradually due to heat generated during molding. It is expected that the Cu—Mo composite oxide film is self-generated. Therefore, the maximum wrinkle holding force when the processing speed is slow is a little small, but when the processing speed is increased, the self-generation of the Cu-Mo composite oxide film due to heat generation is promoted and the seizure resistance is improved. Seems to grow.

On the other hand, member No. In 4, the maximum blank holding force can be molded without sticking the higher the machining speed was lowered from 1.0 kgf / cm ² to 0.4 kgf / cm ^2. About this, since Cu is not added to the steel of the base material, the Cu—Mo composite oxide film is not formed even by heat generation during forming. Accordingly, as the molding speed is increased and the use environment becomes severe, the seizure resistance deteriorates and the maximum wrinkle holding force decreases.

It is a figure which shows the surface electronic bonding state when the steel of this invention composition is heat-oxidized, and is a figure explaining an example of the effect of this invention. It is a figure which shows the surface electronic bonding state when the steel of this invention composition is heat-oxidized, and is a figure explaining an example of the effect of this invention. It is a schematic diagram of the seizure evaluation test apparatus used in the examples of the present invention. It is a figure which shows the result of the seizure evaluation test of the press metal mold | die of this invention example and a comparative example.

Claims (2)

In mass%, C: 0.7 to less than 1.6%, Si: 0.5 to 3.0%, Mn: less than 0.1 to 3.0%, P: less than 0.05% (0% S): 0.01 to 0.12%, Cr: 7.0 to 13.0%, 1 type of Mo or 2 types of Mo and W (Mo + W / 2): 0.5 to 1.7 %, V: Less than 0.7% (including 0%), Ni: 0.3 to 1.5%, Cu: 0.1 to 1.0%, Al: 0.1 to 0.7% included In a manufacturing method of a press-formed product, press-molding a workpiece by a press die made of martensitic steel composed of the remaining Fe and inevitable impurities ,
Press-molded product characterized in that press-molding is performed under a condition in which the maximum working speed between the mold and the workpiece exceeds 0.37 m / s when the mold and the workpiece during press molding slide. Manufacturing method . The method for producing a press-formed product according to claim 1, wherein the press die is steel containing 0.3% or less Nb in mass%.