JP7029308B2 - Stainless clad steel sheet, its manufacturing method, and cutlery - Google Patents

Description

The present invention relates to a stainless clad steel sheet, a method for manufacturing the same, and a cutting tool.

High-hardness materials (for example, high carbon steel, high carbon stainless steel, martensitic stainless steel) have been used for cutting tools such as kitchen knives and knives to improve sharpness, but they are brittle due to their poor toughness. There is a drawback. Therefore, in recent years, clad steel sheets in which such a high-hardness material is combined with a laminated material having excellent toughness have been used for blades.

For example, Patent Document 1 proposes to use a clad steel sheet in which a base material made of high carbon steel or high carbon stainless steel is combined with a laminated material made of low carbon stainless steel for a cutting tool. Further, Patent Document 2 proposes to use a clad steel sheet in which a steel carbon steel made of high carbon steel and a laminated material made of low carbon steel are combined for a cutting tool.

Japanese Unexamined Patent Publication No. 11-76642 Japanese Unexamined Patent Publication No. 10-6037

However, although the toughness of the clad steel sheets of Patent Documents 1 and 2 is improved by the laminated material, there is a problem that the corrosion resistance tends to be lowered.
The present invention has been made to solve the above problems, and an object of the present invention is to provide a stainless clad steel sheet having a high hardness base material and excellent corrosion resistance and toughness, and a method for manufacturing the same. do.
Another object of the present invention is to provide a blade having excellent corrosion resistance and toughness while having good sharpness.

As a result of investigating the cause of the deterioration of the corrosion resistance of the clad steel sheet, the present inventors mainly caused the galvanic corrosion, and the natural potential difference between the base material and the laminated material constituting the clad steel sheet was large. It was found that corrosion is more likely to proceed. Then, they find that the above problems can be solved by selecting and combining a base material having a high hardness and a laminated material having good toughness so that the natural potential difference is 200 mV / SCE or less, and complete the present invention. It came to.

That is, in the present invention, the natural potential difference between the base material made of martensitic stainless steel containing 0.4 to 1.3% by mass of C and having a hardness HRC of 55 or more and the base material is 200 mV / SCE or less. , A stainless clad steel plate having a laminated material made of a double-phase stainless steel containing a ferrite phase and a martensitic phase.

Further, the present invention is a method for manufacturing the stainless clad steel sheet.
A laminating step of laminating the laminated material on the base material, and
It is a method of manufacturing a stainless clad steel sheet including a hot rolling step of hot-pressing while keeping a vacuum state between the base material and the laminated material.
Further, the present invention is a blade having the stainless clad steel plate.

According to the present invention, it is possible to provide a stainless clad steel sheet having a high hardness base material and excellent corrosion resistance and toughness, and a method for producing the same.
Further, according to the present invention, it is possible to provide a blade having good sharpness and excellent corrosion resistance and toughness.

It is sectional drawing of the stainless clad steel plate. It is a perspective view for demonstrating the laminating process in the manufacturing method of a stainless clad steel sheet. 6 is a graph showing the evaluation results of sharpness after a composite cycle corrosion test (CCT) in the blades of Examples 1 and 4, Comparative Examples 7 and 12 to 15.

Hereinafter, the stainless clad steel plate of the present invention, a method for producing the same, and a preferred embodiment of the cutting tool will be described, but the present invention should not be construed as being limited to these, and as long as it does not deviate from the gist of the present invention. , Various changes, improvements, etc. can be made based on the knowledge of those skilled in the art. The plurality of components disclosed in each embodiment can form various inventions by appropriate combinations. For example, some components may be deleted from all the components shown in the embodiment, or components of different embodiments may be combined as appropriate.

FIG. 1 is a cross-sectional view of the stainless clad steel plate of the present embodiment.
The stainless clad steel sheet 1 of the present embodiment has a base material 2 and a laminated material 3. The laminated material 3 may be provided on one surface of the base material 2 as shown in FIG. 1 (a), or may be provided on both sides of the base material 2 as shown in FIG. 1 (b). ..
The base material 2 is made of high-hardness martensitic stainless steel, and when the stainless clad steel plate 1 is used for a cutting tool, it plays a role as a cutting edge.
The hardness HRC (Rockwell hardness) of the martensitic stainless steel is 55 or more, preferably 57 or more, and more preferably 59 or more. On the other hand, the upper limit of the hardness HRC of the martensitic stainless steel is not particularly limited, but is generally 63, preferably 62.

Martensitic stainless steel contains 0.4-1.3 mass% C. Within such a range, characteristics such as workability, wear resistance, and fatigue life can be ensured while increasing the hardness of martensitic stainless steel.
The composition of the martensitic stainless steel is not particularly limited except for the content of C. In a preferred embodiment, the martensite-based stainless steel has C: 0.4 to 1.3% by mass, Si: 1.0% by mass or less, Mn: 0.5 to 1.0% by mass, P: 0.04. Mass% or less, S: 0.015% by mass or less, Ni: 0.6% by mass or less, Cr: 12.0 to 19.0% by mass, Mo: 0.01 to 1.5% by mass, Cu: 0. It contains 5% by mass or less and N: 0.1% by mass or less, and has a composition in which the balance is composed of Fe and unavoidable impurities.
Here, in the present specification, the “unavoidable impurity” means a component such as O that is difficult to remove. This component is inevitably mixed in at the stage of melting the raw material.

In a more preferred embodiment, the martensitic stainless steel has the following composition.
The content of C is preferably 0.41 to 0.8% by mass, more preferably 0.41 to 0.55% by mass.
The Si content is preferably 0.01 to 0.8% by mass, more preferably 0.1 to 0.7% by mass.
The Mn content is preferably 0.52 to 0.8% by mass, more preferably 0.54 to 0.6% by mass.
The content of P is preferably 0.001 to 0.035% by mass, more preferably 0.01 to 0.03% by mass.

The content of S is preferably 0.001 to 0.010% by mass, more preferably 0.002 to 0.008% by mass.
The Ni content is preferably 0.01 to 0.4% by mass, more preferably 0.01 to 0.3% by mass.
The Cr content is preferably 12.1 to 15.5% by mass, more preferably 12.3 to 13.5% by mass.
The Mo content is preferably 0.01 to 1.0% by mass, more preferably 0.01 to 0.1% by mass.
The Cu content is preferably 0.01 to 0.3% by mass, more preferably 0.02 to 0.1% by mass.
The content of N is preferably 0.01 to 0.08% by mass, more preferably 0.01 to 0.05% by mass.

The thickness of the base material 2 may be appropriately adjusted according to the use of the stainless clad steel sheet 1, and is not particularly limited. When the stainless clad steel plate 1 is used for a blade, the lower limit of the thickness of the base material 2 is preferably 0.3 mm, more preferably 0.4 mm, and more preferably 0.5 mm from the viewpoint of ensuring rigidity. On the other hand, the upper limit of the thickness of the base material 2 is preferably 2.0 mm, more preferably 1.5 mm, still more preferably 1.0 mm from the viewpoint of ensuring workability.

The laminated material 3 is made of a double-phase stainless steel having good toughness, and plays a role of increasing the toughness of the stainless clad steel sheet 1.
Further, the laminated material 3 has a natural potential difference of 200 mV / SCE or less with respect to the base material 2.
Generally, in a combination of different types of metal materials, the presence of an electrolyte solution (water, salt water, etc.) causes a battery action. Then, the base natural potential metal material serves as the anode, the noble natural potential metal material serves as the cathode, and the base natural potential metal material selectively corrodes. Corrosion due to such a phenomenon is called galvanic corrosion (electrocorrosion), and it has been found that even with conventional clad materials, corrosion resistance is reduced due to this galvanic corrosion.

In the stainless clad steel sheet 1 of the present embodiment, by using the laminated material 3 having a natural potential difference as described above, galvanic corrosion is less likely to occur between the stainless clad steel sheet 1 and the base material 2, so that the corrosion resistance of the stainless clad steel sheet 1 can be improved. can.
The natural potential difference is preferably 150 mV / SCE or less, more preferably 130 mV / SCE or less, still more preferably 110 mV / SCE or less, from the viewpoint of stably suppressing galvanic corrosion. On the other hand, the smaller the natural potential difference, the less likely it is that galvanic corrosion will occur, so the lower limit thereof is not particularly limited.

The double-phase stainless steel used for the laminated material 3 contains a ferrite phase and a martensite phase. In a preferred embodiment, the duplex stainless steel is a duplex stainless steel composed of a ferrite phase and a martensite phase.
The volume ratio of the ferrite phase to the martensite phase is not particularly limited, but is preferably 30:70 to 20:80. With such a volume ratio, toughness can be ensured.

The composition of the double-phase stainless steel is not particularly limited as long as it has the above-mentioned characteristics. In a preferred embodiment, the double-phase stainless steel has C: 0.01 to 0.2% by mass, Si: 2.0% by mass or less, Mn: 2.0% by mass or less, and P: 0.04% by mass or less. , S: 0.01% by mass or less, Ni: 0.5 to 4.0% by mass, Cr: 10.0 to 20.0% by mass, Cu: 2.0% by mass or less, Mo: 2.0% by mass It contains the following and N: 0.1% by mass or less, and has a composition in which the balance is composed of Fe and unavoidable impurities. Further, the double-phase stainless steel having this composition has B: 0.015% by mass or less, Ti: 0.5% by mass or less, Nb: 0.5% by mass or less, Al: 0.2% by mass or less, REM. : 0.2% by mass or less, Y: 0.2% by mass or less, Ca: 0.1% by mass or less, Mg: 0.1% by mass or less can further contain one or more.

In a more preferred embodiment, the double-phase stainless steel has the following composition.
The content of C is preferably 0.01 to 0.1% by mass, more preferably 0.02 to 0.08% by mass.
The Si content is preferably 0.01 to 1.0% by mass, more preferably 0.1 to 0.8% by mass.
The Mn content is preferably 0.01 to 1.0% by mass, more preferably 0.1 to 0.9% by mass.
The content of P is preferably 0.001 to 0.035% by mass, more preferably 0.01 to 0.033% by mass.

The content of S is preferably 0.001 to 0.008% by mass, more preferably 0.001 to 0.006% by mass.
The Ni content is preferably 0.8 to 3.0% by mass, more preferably 1.0 to 2.5% by mass.
The Cr content is preferably 12.0 to 19.0% by mass, more preferably 14.0 to 18.0% by mass.
The Cu content is preferably 0.01 to 1.0% by mass, more preferably 0.02 to 0.1% by mass.
The Mo content is preferably 0.01 to 1.0% by mass, more preferably 0.01 to 0.1% by mass.
The content of N is preferably 0.001 to 0.015% by mass, more preferably 0.003 to 0.01% by mass.

Similar to the base material 2, the thickness of the laminated material 3 may be appropriately adjusted according to the use of the stainless clad steel plate 1, and is not particularly limited. When the stainless clad steel plate 1 is used for a blade, the lower limit of the thickness of the laminated material 3 is preferably 0.3 mm, more preferably 0.4 mm, and more preferably 0.5 mm from the viewpoint of ensuring toughness. On the other hand, the upper limit of the thickness of the laminated material 3 is preferably 2.0 mm, more preferably 1.5 mm, still more preferably 1.0 mm from the viewpoint of ensuring the adhesion to the base material 2.

The stainless clad steel sheet 1 of the present embodiment having the above-mentioned characteristics can be manufactured according to a method known in the art. Specifically, the mating material 3 may be laminated on the base material 2, then hot-rolled, annealed, pickled, and then cold-rolled. Further, if necessary, quenching and tempering may be performed after cold rolling.
In a preferred embodiment, the method for manufacturing the stainless clad steel sheet 1 is a laminating step of laminating the laminated material 3 on the base material 2 and a hot rolling step of hot-pressing while maintaining a vacuum state between the base material 2 and the laminated material 3. And include. In particular, by heat-pressing the space between the base material 2 and the laminated material 3 while maintaining the vacuum state, the adhesion between the base material 2 and the laminated material 3 can be improved.
The method of holding the space between the base material 2 and the laminated material 3 in a vacuum state is not particularly limited, and for example, the laminated body of the base material 2 and the laminated material 3 may be arranged in a vacuum environment.

Here, FIG. 2 shows a perspective view for explaining the laminating process of the preferred embodiment.
In the laminating step, the pipe 10 is sandwiched between the base material 2 and the laminated material 3, the outer edge portion 4 of the laminated material 3 is welded to the base material 2, and then the base material 2 and the laminated material 3 are connected to each other via the pipe 10. It involves evacuating between and sealing the pipe 10. Here, the tip of the pipe 10 sandwiched between the base material 2 and the laminated material 3 may be arranged at the outer edge portion 4, but the tip of the pipe 10 is not blocked when the laminated material 3 is welded. It should be noted that. The method for sealing the pipe 10 is not particularly limited, but for example, the pipe 10 may be crushed. By using the above method, it is not necessary to perform hot rolling in a vacuum environment, so that existing manufacturing equipment can be used.

The stainless clad steel sheet 1 of the present embodiment has a high hardness as a base material and is excellent in corrosion resistance and toughness, so that it can be used in various applications in which hardness, corrosion resistance and toughness are required. Among them, the stainless clad steel sheet 1 of the present embodiment is particularly suitable for use as a cutting tool.

In a preferred embodiment, the blade has the stainless clad steel sheet 1 described above. When the stainless clad steel sheet 1 is used as a cutting tool, the cutting edge may be formed by rough polishing and finish polishing the portion to be the cutting edge. This blade has excellent corrosion resistance and toughness, and the base material has a high hardness, so that the sharpness is also good.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
First, 11 types of stainless steel sheets (SUS1 to 11) and 2 types of steel sheets (steel 1 and 2) having the composition and metallographic structure shown in Table 1 were produced. Specifically, a 190 mm thick slab having the composition shown in Table 1 is heated at 1230 ° C. for 2 hours, rolled to a thickness of 55 mm, and then the oxide scale on the surface is ground and removed to form a 45 mm thick stainless steel sheet and a stainless steel plate. Obtained a steel plate.

(Example 1)
Using the stainless steel plates shown in Table 2 as the base material 2 and the laminated material 3, a cutting tool having the laminated material 3 on both sides of the base material 2 was produced. Specifically, first, a pipe 10 is provided between the base material 2 and the laminated material 3. Next, the outer edge portion 4 of the laminated material 3 was welded to the base material 2 so as not to block the pipe 10. Next, the space between the base material 2 and the laminated material 3 was evacuated through the pipe 10 to create a vacuum state, and the tip of the pipe 10 was crushed and sealed in that state to obtain a laminated body. Next, the laminate was heated at 1230 ° C. for 2 hours, rolled to a thickness of 4 mm, and then annealed at 800 ° C. for 4 hours. Then, the oxidation scale on the surface was removed by pickling, and cold rolling was performed to a thickness of 2 mm. At this time, the thickness of the base material 2 was 0.8 mm, and the thickness of the laminated material 3 was 0.6 mm. Next, the obtained cold rolled plate was punched into a blade shape, quenched at 1060 ° C, and tempered at 170 ° C for 4 hours. Then, the portion to be the cutting edge was rough-polished and finish-polished to form the cutting edge, and a cutting tool was obtained.

(Examples 2 to 6 and Comparative Examples 1 to 12)
A cutting tool was produced in the same manner as in Example 1 except that the types of stainless steel plates used for the base material 2 and the laminated material 3 were changed as shown in Table 2.

(Comparative Examples 13 and 14)
Using the stainless steel plate or steel plate shown in Table 2 as the base material 2 and the laminated material 3, a cutting tool was produced in the same manner as in Example 1 except that the laminated body was heated at 1100 ° C. for 2 hours.

(Comparative Example 15)
The slab having the composition shown in Table 1 was heated at 1100 ° C. for 2 hours, rolled to a thickness of 4 mm, and then annealed at 800 ° C. for 4 hours. Then, the oxidation scale on the surface was removed by pickling, and cold rolling was performed to a thickness of 2 mm. Next, the obtained cold rolled plate was punched into a blade shape, quenched at 950 ° C, and tempered at 180 ° C for 1 hour. Then, the portion to be the cutting edge was rough-polished and finish-polished to form the cutting edge, and a cutting tool was obtained.

The cutting tools obtained in the above Examples and Comparative Examples were evaluated as follows.
(Hardness HRC of base material 2)
A test piece of the base material 2 was cut out from a blade, and the hardness HRC was measured using a Rockwell hardness tester.

(Toughness of blades)
According to JIS Z2242: 2005, the toughness of the blade at room temperature (24 ° C.) was measured using a Charpy impact tester. In this evaluation, those having a value of 80 J / cm ² or more are indicated by 〇, and those having a value of less than 80 J / cm ² are indicated by ×.

(Natural potential of base material 2 and laminated material 3)
The test pieces of the base material 2 and the laminated material 3 were cut out from the blade, and the natural potential was measured using SCE (saturated sweetened electrode) as a reference electrode.

(Corrosion resistance of blades)
The corrosion resistance of the blade was evaluated according to JIS Z2371: 2015. Specifically, an aqueous solution (50 ° C.) containing 5% by mass of NaCl was sprayed on the blade at a spraying amount of 1.5 mL / 80 cm ² / h for 48 hours, and the corrosion resistance was evaluated. In this evaluation, those having a rust area ratio of 20% or less are indicated by ⊚, those having a rust area ratio of more than 20% and 40% or less are indicated by ◯, those having a rust area ratio of more than 40% and 70% or less are indicated by Δ, and those having a rust area ratio of more than 70% are indicated by ×.

(Shadow sharpness)
The sharpness of the blade was evaluated using the Honda type sharpness tester.
In the sharpness test, a blade was fixed, and a paper equivalent to a newspaper with a width of 7.5 mm (thickness of about 70 μm) was piled up and a load of about 750 g was applied to perform a reciprocating motion of 20 mm. One round trip was regarded as one cycle, and 100 cycles were carried out, and the number of completely cut papers was counted. The sharpness can be evaluated to be good when the number of sheets of cut paper is 50 or more.

The results of each of the above evaluations are shown in Table 2.

As shown in Table 2, the blades of Examples 1 to 6 had good sharpness, but had better toughness and corrosion resistance than the blades of Comparative Examples 1 to 15.

Next, the sharpness of the blades of Examples 1 and 4, Comparative Examples 7 and 12 to 15 after the combined cycle corrosion test (CCT) was evaluated.
In the combined cycle corrosion test, salt spray (spraying an aqueous solution (35 ° C) containing 5% by mass of NaCl for 15 minutes with a spray amount of 1.5 mL / 80 cm ² / h) → drying (temperature 60 ° C, humidity 30%, 60) Minutes) → Wetting (temperature 50 ° C., humidity 95%, 180 minutes) was set as one cycle, and up to 20 cycles were carried out. The sharpness of the blade was evaluated after 1, 5, 10 and 20 cycles.
The sharpness test was performed in the same manner as described above.
The above evaluation results are shown in FIG.

As shown in FIG. 3, the blades of Examples 1 and 4 were less likely to have lower sharpness than the blades of Comparative Examples 7 and 12 to 15 even when the combined cycle corrosion test was performed.

As can be seen from the above results, according to the present invention, it is possible to provide a stainless clad steel sheet having a high hardness base material and excellent corrosion resistance and toughness, and a method for producing the same. Further, according to the present invention, it is possible to provide a blade having good sharpness and excellent corrosion resistance and toughness.

The stainless clad steel sheet of the present invention can be used for various blades. Specific examples of blades include kitchen knives or knives for general cooking or work; agricultural tools such as sickles and sickles; blades of industrial equipment used for shearing metal plates such as mechanical shears; cloth, paper, films, etc. Blades used in cutting or punching equipment (eg, Thomson blades, etc.); blades of equipment used for crushing, mixing or kneading. In addition to cutting tools, the stainless clad steel sheet of the present invention can be used for various applications (for example, housings, containers, etc.) that require properties such as high strength, corrosion resistance, and toughness.

1 Stainless clad steel plate 2 Base material 3 Laminating material 4 Outer edge 10 Pipe

Claims (10)

The natural potential difference between the base material made of martensitic stainless steel containing 0.4 to 1.3% by mass of C and having a hardness HRC of 55 or more and the base material is 200 mV / SCE or less, and the ferrite phase and martensitic. A stainless clad steel plate having a laminated material made of double-phase stainless steel including a phase. The martensite-based stainless steel has C: 0.4 to 1.3% by mass, Si: 1.0% by mass or less, Mn: 0.5 to 1.0% by mass, P: 0.04% by mass or less, S: 0.015% by mass or less, Ni: 0.6% by mass or less, Cr: 12.0 to 19.0% by mass, Mo: 0.01 to 1.5% by mass, Cu: 0.5% by mass or less And N: The stainless clad steel plate according to claim 1, which contains 0.1% by mass or less and has a composition in which the balance is composed of Fe and unavoidable impurities. The double-phase stainless steel has C: 0.01 to 0.2% by mass, Si: 2.0% by mass or less, Mn: 2.0% by mass or less, P: 0.04% by mass or less, S: 0. 0.01% by mass or less, Ni: 0.5 to 4.0% by mass, Cr: 10.0 to 20.0% by mass, Cu: 2.0% by mass or less, Mo: 2.0% by mass or less and N: The stainless clad steel plate according to claim 1 or 2, which contains 0.1% by mass or less and has a composition in which the balance is composed of Fe and unavoidable impurities. The double-phase stainless steel has B: 0.015% by mass or less, Ti: 0.5% by mass or less, Nb: 0.5% by mass or less, Al: 0.2% by mass or less, REM: 0.2% by mass. The stainless clad steel plate according to claim 3, further comprising one or more of% or less, Y: 0.2% by mass or less, Ca: 0.1% by mass or less, Mg: 0.1% by mass or less. The stainless clad steel sheet according to any one of claims 1 to 4, wherein the volume ratio of the ferrite phase to the martensite phase is 30:70 to 20:80. The stainless clad steel sheet according to any one of claims 1 to 5, wherein the laminated material is provided on both sides of the base material. The stainless clad steel sheet according to any one of claims 1 to 6, which is used for a blade. The method for manufacturing a stainless clad steel sheet according to any one of claims 1 to 7.
A laminating step of laminating the laminated material on the base material, and
A method for manufacturing a stainless clad steel sheet, which comprises a hot rolling step of hot-pressing while maintaining a vacuum state between the base material and the laminated material. In the laminating step, a pipe is sandwiched between the base material and the laminated material, and the outer edge portion of the laminated material is welded to the base material, and then the base material and the laminated material are connected to each other via the pipe. The method for manufacturing a stainless clad steel plate according to claim 8, which comprises vacuuming the space to seal the pipe. A blade having the stainless clad steel plate according to any one of claims 1 to 7.

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