JPH039169B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a press working method, and particularly to a press working method for a quasi-austenitic stainless steel sheet in which a martensitic structure is induced during press working.

(2) Background of the technology Various metal-based and waste metal-based materials are used as materials for press working. Among them,
As structural materials, materials such as stainless steel and aluminum have excellent properties such as good appearance and corrosion resistance even without surface treatment, and are therefore often used as press working materials. but,
Aluminum generally has a problem of low strength, so its range of applications is limited. In this point,
Stainless steel has high strength and various other excellent properties, so it has a very wide range of applications as a press working material.

Here, the term "semi-austenitic stainless steel sheet" refers to an austenitic stainless steel sheet among various austenitic stainless steel sheets that has a property of inducing a martensitic structure during press working, for example, drawing work. This type of quasi-austenitic stainless steel includes, for example, SUS301 specified in JIS standard G4303.
This corresponds to austenitic stainless steels from SUS316L to SUS316L. Here, the amount of martensite induced as a result of processing as described above will be referred to as the amount of processing-induced martensite.

This quasi-austenitic stainless steel sheet is characterized by its chemical composition (particularly Ni (nickel) and C (carbon)).
It has processing characteristics such that the amount of deformation-induced martensite is slightly influenced by the amount of processing (the amount of plastic deformation due to press working), the processing temperature (the temperature of the blank and press die during press working), etc. Furthermore, the amount of deformation-induced martensite greatly affects the performance of the processed product, such as mechanical properties such as strength (hardness) and elongation (toughness). In addition, the method of checking the amount of martensite in the product is to check the amount of martensite using a non-destructive ferrite scope.

FIGS. 1 to 6 are diagrams schematically showing the characteristics in press working of a quasi-austenitic stainless steel plate. In these figures, the amount of deformation-induced martensite is simply indicated as the amount of martensite. FIG. 1 shows that the amount of martensite increases as the amount of processing increases. Note that FIGS. 2 to 6 are characteristic diagrams when the amount of processing is constant. Figure 2 shows that strength (hardness) increases as the amount of martensite increases, and Figure 3 shows that, conversely, as the amount of martensite increases, elongation (toughness) decreases. It is shown that. FIG. 4 shows that the amount of martensite decreases as the processing temperature increases. Figure 5 shows that as the Ni content increases, the amount of martensite decreases, and Figure 6, contrary to the case in Figure 5, shows that the higher the C content, the more the martensite amount increases. . As shown in these figures, quasi-austenitic stainless steel can vary depending on various conditions, even when made from the same material.
It has the characteristic that the amount of deformation-induced martensite differs. For example, in the case of SUS304 specified in JIS G4303, the C content is specified to be 0.08% or less, and the Ni content is specified to be in the range of 8.00 to 10.50%. Therefore, even if such JIS standard stainless steel sheets are purchased, the content of C and Ni will vary within the specified range, and as a result, the amount of induced martensite after pressing will take various values. Become. As a result, a difference occurs in the performance of the processed product, that is, the mechanical properties, etc., and the corrosion resistance may deteriorate. Therefore, quasi-austenitic stainless steel sheets are cheaper than austenitic ones, but in press working, as mentioned above, the performance of the product, especially the mechanical properties, tends to vary, and the desired performance cannot be achieved. There is a problem in that it is difficult to obtain accurate properties (mechanical properties, corrosion resistance, etc.), and the pressing method has become a problem.

(3) Prior Art and Problems In the conventional press working method for quasi-austenitic stainless steel sheets, the chemical composition conditions and working temperature conditions of the stainless steel sheets were not taken into consideration. For this reason, as mentioned above, even if JIS standard stainless steel sheets are purchased, the content of Ni and C varies from purchase lot to purchase, and the temperature of the blank and mold is different because the ambient temperature differs in summer and winter. There is a problem in that the performance of the product varies from material purchase lot to material purchase lot or from season to season due to differences in quality. Furthermore, since press working is a processing method that usually mass-produces the same product, it goes without saying that a large number of products are processed in succession. Therefore, as the press work progresses, the temperature of the press mold (punch, die, etc.) itself increases due to frictional heat during the work. The heat of this press mold is transferred to the blank, raising the temperature of the blank itself. As a result, for example, the processing temperature conditions will be different between the first product and the 30th product, and the amount of martensite will be different, as shown in FIG. 4 above. Therefore, a difference in the amount of martensite means a difference in product performance, that is, strength (hardness) and elongation (toughness), as shown in FIGS. 2 and 3 above.

Figure 7 is a diagram showing how the amount of martensite changes with respect to the manufacturing order (manufacturing number) of products continuously processed by the conventional press working method, and at the same time
FIG. 3 is a diagram showing how the amount of martensite changes due to differences in Ni content. As is clear from the figure, as the mold temperature rises, the amount of martensite decreases rapidly from the first product to about the 30th product, and then continues until about the 60th product. It gradually decreases, and then becomes a substantially constant value as the mold temperature stabilizes. In addition, in Figure 7, when the Ni content is 8.5% and 9.0% for the same SUS304, the amount of martensite is approximately 5 to 5% as shown in the figure.
A difference of 10% occurs. In this way, when pressing semi-austenitic stainless steel, the processing temperature and the chemical content of the material are related to each other.
Subtly affects the amount of martensite. As mentioned above, in conventional processing methods, certain types of stainless steel sheets, such as SUS304
However, the amount of chemical components (mainly Ni and C)
There is a range, and the amount of deformation-induced martensite varies depending on the temperature change of the press mold accompanying machining, so there is a large dispersion in product performance, and the disadvantage is that the target performance cannot always be maintained constant. .

(4) Purpose of the Invention In view of the drawbacks of the above-mentioned conventional methods, the present invention provides a method for processing a certain limited type of stainless steel sheet due to deformation, e.g.
Even if it is SUS304, its chemical component content (mainly Ni
There is a range for and C), but by controlling the amount of deformation-induced martensite to a desired constant value, it is possible to accurately achieve the target performance of the product and always bring this performance to the product at a constant level. The object of the present invention is to provide a method for pressing a quasi-austenitic stainless steel sheet, which allows for press working of a semi-austenitic stainless steel plate.

(5) Structure of the Invention According to the present invention, in press working of a semi-austenitic stainless steel sheet, the amount of chemical components of the stainless steel sheet is detected in advance, and the processing characteristics are adjusted according to the amount of chemical components. From the material information, select and set the processing temperature corresponding to the desired performance of the product to be processed and the amount of processing so that the amount of deformation-induced martensite induced in the press process becomes the desired value, and then press the stainless steel plate and press mold. Provided is a method for processing a quasi-austenitic stainless steel sheet, characterized in that the amount of deformation-induced martensite is set to a desired value by heating or cooling the stainless steel sheet to the set temperature in advance and pressing the stainless steel sheet at the set temperature. This is achieved by doing.

(6) Embodiments of the invention Hereinafter, embodiments of the invention will be described in detail based on the drawings. FIGS. 8 to 10 are diagrams for explaining embodiments of the present invention.

FIG. 8 is a diagram showing changes in the amount of martensite in products that are successively processed based on the processing method of the present invention with respect to the manufacturing order (manufacturing number). It corresponds to this. As is clear from FIG. 8, according to the processing method of the present invention, the amount of martensite is maintained at a substantially constant value from the first product to the 150th product. There is. Comparing this Fig. 8 with the above-mentioned Fig. 7 (conventional example), it is found that the product produced by the processing method of the present invention has an extremely stable amount of martensite at a predetermined constant value than the product produced by the conventional processing method. It can be seen that it is maintained as follows.

Now, the processing method in this case is to first detect the chemical components of the material (mainly the content of Ni and C) from the mill sheet, and then consider the correlation between the amount of chemical components and the amount of processing of the product to be processed. The amount of martensite corresponding to the target performance of the product is set, and then the processing temperature corresponding to this amount of martensite is set. Select and set a processing temperature that corresponds to the desired performance and processing amount of the product to be processed so that the amount of processing-induced martensite reaches the desired value, and adjust the processing temperature to this set processing temperature by heating the blank and press mold before pressing. After that, pressing is performed. Note that each of the above-mentioned setting values is set based on data on processing characteristics of the material as shown in FIGS. 1 to 6 mentioned above obtained in advance. Also,
Although the manufacturing order is only shown up to the 150th piece in FIG. 8, in reality, the amount of martensite in the product is maintained constant even in subsequent processing. The fact that the amount of martensite is constant in this way means that the product performance (mainly mechanical properties) is constant, as shown in FIGS. 2 and 3 above. In the above embodiment, the press mold and the material (blank) are heated together to control the temperature, but the temperature may be controlled depending on the needs of product performance, etc.

FIG. 9 shows an example of a diaphragm die with a built-in heater. In the figure, reference numeral 10 indicates a base, and a punch 11 is fixed on this base 10. An upper die 12 and a lower die 13 are fitted to the punch 11 with an appropriate gap and are movable in the vertical direction, and are attached to a press stand 14. Upper die 1
The material (blank) sandwiched between 2 and the lower die 13 is drawn into a product 15 by the upper and lower dies 12 and 13 moving downward (arrow A) and fitting with the punch. Become. A pipe heater 1 with a thermostat is installed in the upper die 12 and the lower die 13.
6 is built in, and the temperature of the upper die 12 and the lower die 13 is controlled to a desired value by this heater. Note that the reference numeral 17 indicates a cushion pin. In addition to this, there is also a method of heating the press mold (die) by embedding a pipe and running hot water through it. On the other hand, when cooling, water is added to the embedded pipe.
The temperature of the press mold can be controlled by flowing cooling water, liquid nitrogen, etc., or by using dry ice, etc.

To control the temperature of the material (blank), there is a method of heating a plurality of blanks 21 by stacking them on a panel heater 20, as shown in FIG. 10, for example. In addition to this, there is also a method of immersing the blank in hot water, a method of using a hot plate, etc. On the other hand, in the case of cooling, there are methods using dry ice, liquid nitrogen, a refrigerator, etc. In addition, the method of checking the amount of martensite in the product is to check the amount of martensite using a non-destructive ferrite scope.

(7) Effects of the Invention As explained above in detail, the method for press working a quasi-austenitic stainless steel sheet of the present invention can be applied to certain limited types of stainless steel, e.g.
Even with SUS304, there is a range in the amount of chemical components, but since the amount of deformation-induced martensite can be controlled to a desired constant value from the beginning of pressing, it is possible to accurately achieve the target performance of the product and maintain this performance. There is a great effect that can always be brought to a product consistently.

[Brief explanation of the drawing]

Figures 1 to 6 show the processing characteristics of quasi-austenitic stainless steel sheets, and Figure 7 shows changes in the amount of processing-induced martensite (%) with respect to the manufacturing order (manufacturing number) of products using conventional processing methods. Figure 8 is a diagram showing changes in the amount of deformation-induced martensite (%) with respect to the manufacturing order (manufactured pieces) of products according to the processing method of the present invention, and Figure 9 is a diagram showing an example of a drawing die with a built-in heater. , FIG. 10 is a diagram showing an example of a state in which the material (blank) is heated. 10...Base, 11...Punch, 12...Upper die, 13...Lower die, 14...Press stand, 1
5... Product, 16... Pipe heater with thermostat, 20... Panel heater, 21... Material (blank).

Claims (1)

[Claims] 1. In press working of a quasi-austenitic stainless steel sheet, the amount of chemical components of the stainless steel sheet is detected in advance, and the amount of work-induced martensite induced in the press work process is determined based on the work characteristic material information according to the amount of chemical components. so that the value is
Selecting and setting a processing temperature corresponding to the desired performance and processing amount of the product to be processed, heating or cooling the stainless steel plate and press die to the set temperature in advance, and performing press working of the stainless steel plate at the set temperature. A method for processing a quasi-austenitic stainless steel sheet, characterized in that the amount of deformation-induced martensite is set to a desired value.