KR102282041B1 - Ferritic stainless steels with high strength and toughness and method of manufacturing the same - Google Patents

Abstract

The method of manufacturing a high-strength and high-toughness stainless steel material according to an embodiment of the present invention includes (a) carbon (C): 0.65 to 1.0% by weight, chromium (Cr): more than 0 and 19% by weight or less, silicon (Si): 0.25 ~ 0.4% by weight, manganese (Mn): 0.35 to 0.50% by weight, molybdenum (Mo): 1.5 to 2.5% by weight, nitrogen (N): more than 0 and not more than 0.12% by weight and the remainder consisting of iron (Fe) and other unavoidable impurities homogenizing the ingot; (b) forming a plate by rolling the ingot subjected to the homogenization heat treatment; and (c) performing an accumulation rolling bonding process on the plate materials.

Description

A stainless steel material with high strength and toughness and a manufacturing method therefor {Ferritic stainless steels with high strength and toughness and method of manufacturing the same}

The present invention relates to a material and a method for manufacturing the same, and more particularly, to a high-strength and high-toughness stainless steel material applicable to a kitchen knife and a method for manufacturing the same.

In general, materials used for manufacturing kitchen knives are mainly high-carbon steel-based and stainless steel-based materials. Kitchen knives made of high-carbon steel materials are easy to grind and have excellent hardness, so they have good edge retention performance. However, they have a problem of quickly discoloring due to poor corrosion resistance. On the other hand, a kitchen knife made of a stainless steel-based material has good corrosion resistance, but has a problem in that the hardness is relatively low and the edge retention performance is bad.

On the other hand, the accumulation rolling joining process is a process applicable only to ductile materials such as aluminum alloy, copper alloy, or ultra-low carbon steel having a carbon content of 0.005 wt% or less. There is no known technique for applying the accumulative rolling bonding process to high-strength stainless materials such as kitchen knives.

As a related prior art, there is Republic of Korea Patent Publication No. 10-2001-0047607 (published on June 15, 2001, title of the invention: hot rolling method of austenitic stainless steel).

The problem to be solved by the present invention is a high-performance stainless steel material capable of applying a cumulative rolling bonding process having a corrosion resistance of 0.5 mm/yr at a sulfuric acid concentration while having a high hardness of about 700 Hv based on the Vickers hardness, and a method for manufacturing the same will provide

A method of manufacturing a high-strength and high-toughness stainless steel material according to an embodiment of the present invention for achieving the above object is (a) carbon (C): 0.65 to 1.0% by weight, chromium (Cr): more than 0 and 19% by weight or less, Silicon (Si): 0.25 to 0.4% by weight, manganese (Mn): 0.35 to 0.50% by weight, molybdenum (Mo): 1.5 to 2.5% by weight, nitrogen (N): more than 0 and not more than 0.12% by weight and the remainder iron (Fe) and homogenizing an ingot made of other unavoidable impurities; (b) forming a plate by rolling the ingot subjected to the homogenization heat treatment; and (c) performing an accumulation rolling bonding process on the plate materials; includes

In the method of manufacturing the high-strength and high-toughness stainless steel material, the step (c) includes: (c-1) implementing a first multi-layer structure material by overlapping and rolling the plate materials up and down; and (c-2) cutting the first multi-layer structure material and then overlapping and rolling the cut first multi-layer structure material up and down to implement a second multi-layer structure material; may include.

In the method of manufacturing the high-strength and high-toughness stainless steel material, the step (c) includes (c-3) cutting the n-th multi-layer structure material and then overlapping the cut n-th multi-layer structure material up and down and rolling By doing so, the step of implementing the (n+1)-th multi-layered material may be further included, but the (c-3) step may be repeatedly performed while sequentially increasing n as a positive integer of 2 or more.

In the method of manufacturing the high-strength and high-toughness stainless material, the ingot is titanium (Ti): more than 0 0.015% by weight or less, niobium (Nb): more than 0 0.12% by weight or less, and zirconium (Zr): more than 0 0.02% by weight It may be made by further containing at least one or more selected from the following.

In the method of manufacturing the high-strength and high-toughness stainless material, the ingot is carbon (C): 0.75 to 0.85 wt%, chromium (Cr): 14 to 16 wt%, silicon (Si): 0.25 to 0.4 wt%, manganese ( Mn): 0.35 to 0.50% by weight, molybdenum (Mo): 1.8 to 2.2% by weight, nitrogen (N): 0.05 to 0.09% by weight, titanium (Ti): 0.005 to 0.015% by weight, and the remaining iron (Fe) and other inevitable It may consist of impurities.

In the method of manufacturing the high-strength and high-toughness stainless material, the chromium (Cr) may satisfy a composition range of 8 to 19% by weight in the ingot.

High-strength and high-toughness stainless steel material according to an embodiment of the present invention for achieving the above object is carbon (C): 0.65 to 1.0% by weight, chromium (Cr): more than 0 and 19% by weight or less, silicon (Si): 0.25 ~ 0.4% by weight, manganese (Mn): 0.35 to 0.50% by weight, molybdenum (Mo): 1.5 to 2.5% by weight, nitrogen (N): more than 0 and not more than 0.12% by weight and the remaining iron (Fe) and other unavoidable impurities. It is realized by performing an accumulation rolling bonding process.

The high-strength and high-toughness stainless material is titanium (Ti): more than 0 0.015% by weight or less, niobium (Nb): more than 0 and 0.12% by weight or less, and zirconium (Zr): at least one selected from more than 0 and 0.02% by weight or less It may be made by further containing.

The high strength and high toughness stainless steel material is carbon (C): 0.75 to 0.85 wt%, chromium (Cr): 14 to 16 wt%, silicon (Si): 0.25 to 0.4 wt%, manganese (Mn): 0.35 to 0.50 wt% %, molybdenum (Mo): 1.8 to 2.2 wt%, nitrogen (N): 0.05 to 0.09 wt%, titanium (Ti): 0.005 to 0.015 wt%, and the remaining iron (Fe) and other unavoidable impurities.

In the high-strength and high-toughness stainless steel material, the chromium (Cr) may satisfy a composition range of 8 to 19% by weight.

According to an embodiment of the present invention, it is possible to implement a high-strength and high-toughness stainless steel material for accumulative rolling bonding with improved corrosion resistance and a manufacturing method thereof. Of course, the scope of the present invention is not limited by these effects.

1A and 1B are a portion of a state diagram calculated to develop a high-strength and high-toughness stainless steel material according to an embodiment of the present invention.
2a and 2b are tissue photographs evaluated to develop a high-strength and high-toughness stainless steel material according to an embodiment of the present invention.
3A and 3B are a portion of a state diagram calculated to develop a high-strength and high-toughness stainless steel material according to an embodiment of the present invention.
4A and 4B are a portion of a state diagram calculated to develop a high-strength and high-toughness stainless steel material according to an embodiment of the present invention.
6 is a view schematically illustrating an accumulation rolling bonding process in a method of manufacturing a high-strength and high-toughness stainless material according to an embodiment of the present invention.
6a to 7d are graphs showing the tensile test results for the specimen according to the experimental example of the present invention for each temperature.
8A to 8B are graphs showing the results of the evaluation of the corrosion resistance at room temperature for the specimen according to the experimental example of the present invention.
9A to 9C are graphs showing hardness evaluation results for specimens according to Experimental Examples of the present invention.
10 is a photograph of a kitchen knife implemented by a manufacturing method according to an experimental example of the present invention.

Hereinafter, a high-strength and high-toughness stainless steel material and a manufacturing method thereof according to an embodiment of the present invention will be described in detail. The terms described below are appropriately selected in consideration of their functions in the present invention, and definitions of these terms should be made based on the content throughout this specification.

In general, materials used for manufacturing kitchen knives are mainly high-carbon steel-based and stainless steel-based materials.

Kitchen knives made of high-carbon steel materials are easy to grind and have excellent hardness, so they have good edge retention performance. However, they have a problem of quickly discoloring due to poor corrosion resistance. Such a high-carbon steel-based material is, for example, carbon (C): 0.98 to 1.1 wt%, chromium (Cr): 1.3 to 1.6 wt%, silicon (Si): 0.15 to 0.35 wt%, manganese (Mn): 0.25 ~ 0.45% by weight, P (phosphorus): more than 0 0.025% by weight, sulfur (S): may have a composition range consisting of more than 0 and 0.025% by weight or less and the remainder iron (Fe).

On the other hand, a kitchen knife made of a stainless steel-based material has good corrosion resistance, but has a problem in that the hardness is relatively low and the edge retention performance is bad. Such a stainless steel-based material, for example, carbon (C): 0.25 to 0.35% by weight, chromium (Cr): 14 to 16% by weight, molybdenum (Mo): 0.85 to 1.10% by weight, manganese (Mn): greater than 0 1.0 wt % or less, nitrogen (N): 0.3 to 0.5 wt %, nickel (Ni): 0 to 0.5 wt % or less, and the remaining iron (Fe) may have a composition range.

An object of the present invention is to provide a high-performance stainless steel material having a high hardness of about 700 Hv based on the Vickers hardness and corrosion resistance of 0.5 mm/yr at a sulfuric acid concentration and a method for manufacturing the same.

Furthermore, the present invention is to provide a high-strength and high-toughness stainless steel material capable of accumulation rolling bonding. The accumulative roll bonding process was developed as a method of grain refinement, and it is a process that can increase strength and toughness at the same time and can manufacture a multi-layered metal with an elegant pattern. However, the accumulation rolling joining process is a process applicable only to ductile materials such as aluminum alloy, copper alloy, or ultra-low carbon steel having a carbon content of 0.005 wt% or less. There is no known technique for applying the accumulative rolling bonding process to high-strength stainless materials such as kitchen knives.

In contrast to the cladding process known so far for manufacturing a kitchen knife, the applied material is high-carbon steel and the rolling process is a process in which a plurality of sheets are implemented at once in one pass, the accumulation rolling bonding process disclosed in the present invention It is different in that the applied material is stainless steel, and the rolling process is a multi-pass process.

High-strength and high-toughness stainless steel material

High strength and high toughness stainless steel material according to an embodiment of the present invention is carbon (C): 0.65 to 1.0% by weight, chromium (Cr): more than 0 and 19% by weight or less, silicon (Si): 0.25 to 0.4% by weight, manganese (Mn): 0.35 to 0.50% by weight, molybdenum (Mo): 1.5 to 2.5% by weight, nitrogen (N): more than 0 and 0.12% by weight or less, and the remaining iron (Fe) and other unavoidable impurities.

Hereinafter, the role and content of each component included in the high-strength and high-toughness stainless steel material according to an embodiment of the present invention will be described.

carbon (C)

Carbon (C) is an element added to secure strength. In addition, carbon reacts with Nb, Ti, etc. to promote the formation of fine carbides, thereby effectively contributing to strength improvement through precipitation strengthening. The carbon (C) may be added in a content ratio of 0.65 to 1.0% by weight based on the total weight of the high-strength and high-toughness stainless steel material according to an embodiment of the present invention. When the content of carbon is less than 0.65% by weight of the total weight, it may be difficult to secure sufficient strength. Conversely, when the content of carbon exceeds 1.0% by weight of the total weight, there may be a problem in that coarse carbide is generated and hardness and strength are lowered. 1A and 1B are a portion of a state diagram calculated to develop a high-strength and high-toughness stainless steel material according to an embodiment of the present invention. The phase diagram disclosed in FIG. 1A is part of the phase diagram for the Fe-0.8C-0.44Mn-0.33Si-Cr material, and the phase diagram disclosed in FIG. 1B is part of the phase diagram for the Fe-15Cr-0.44Mn-0.33Si-C material. . 1A and 1B, specifically, when the carbon content exceeds 1.0% by weight of the total weight, coarse carbides in the liquid phase (eg, M ₂₃ C ₆ , M ₇ C ₃ ; where M is Chromium (Cr) and/or manganese (Mn)) may be crystallized to lower hardness and strength. On the other hand, when the content of carbon is 0.65% by weight or more of the total weight, both carbide M ₂₃ C ₆ and carbide M ₇ C ₃ are precipitated in the solid phase, which may be effective in increasing hardness and strength.

2a and 2b are tissue photographs evaluated to develop a high-strength and high-toughness stainless steel material according to an embodiment of the present invention. Specifically, Figure 2a is a photograph of the structure of the stainless material after general rolling (left: 0.8 wt% carbon content, right: 1.2 wt% carbon content), and Figure 2b is a stainless steel material after accumulation rolling bonding (left: 0.8 wt%). It is a photograph of the structure of carbon content of weight %, right: 1.2 weight % carbon content). Referring to FIGS. 2A and 2B , it can be seen that the stainless material containing 1.2% by weight of carbon is a factor that interferes with the accumulation rolling bonding due to the formation _{of coarse carbide M 7} C _{3 .} Therefore, an alloy design was performed based on a stainless material containing 0.8% by weight of carbon. On the other hand, _{by lowering the M 7} C ₃ carbide formation temperature, it is possible to prevent the formation of _{coarse M 7} C _{3 carbide.}

Chromium (Cr)

Chromium (Cr) is a ferrite stabilizing element, and when added to C-Mn steel, it delays the diffusion of carbon due to a solute interference effect, thereby affecting particle size refinement. The chromium may be added in a content ratio of greater than 0 to 19% by weight or less based on the total weight of the high-strength and high-toughness stainless material according to an embodiment of the present invention. Strictly, the chromium (Cr) may be 8 to 19% by weight in the material. When the content of chromium exceeds 19% by weight of the total weight of the material and is added in a large amount, the manufacturing cost of steel can be increased, coarse carbides are formed at grain boundaries, and thus the ductility of the steel can be reduced, and the properties of the steel from the viewpoint of toughness and hardenability are reduced. can give 1A and 1B, specifically, when the content of chromium exceeds 19% by weight of the total weight of the material, coarse carbides in the liquid phase (for example, M ₂₃ C ₆ , M ₇ C ₃ ; where M Silver chromium (Cr) and/or manganese (Mn)) may be crystallized to lower hardness and strength. On the other hand, when the content of chromium is 8% by weight or more of the total weight of the material, both carbide M ₂₃ C ₆ and carbide M ₇ C ₃ are precipitated in the solid phase, which may be effective in increasing hardness and strength.

Silicon (Si)

Silicon (Si) is added as a deoxidizer to remove oxygen in steel in the steelmaking process. In addition, silicon may also have a solid solution strengthening effect. The silicon may be added in a content ratio of 0.25 to 0.4% by weight based on the total weight of the high-strength and high-toughness stainless steel material according to an embodiment of the present invention. When the content of silicon is less than 0.25% by weight of the total weight, the effect of adding silicon cannot be properly exhibited. Conversely, when the content of silicon exceeds 0.4% by weight of the total weight, when a large amount is added, a problem may be given to the surface quality by generating a red scale during reheating and hot rolling.

Manganese (Mn)

Manganese (Mn) is an element that not only contributes to securing strength as a solid solution strengthening element but also improves the hardenability of steel. Manganese may be added in a content ratio of 0.35 to 0.50 wt% based on the total weight of the high-strength and high-toughness stainless material according to an embodiment of the present invention. When the manganese content is less than 0.35% by weight, the effect of solid solution strengthening cannot be sufficiently exhibited. In addition, when the content of manganese exceeds 0.50 wt%, it may combine with sulfur (S), an impurity, to generate MnS inclusions or cause central segregation in the ingot, and thus the ductility of high-strength and high-toughness stainless materials This may decrease and corrosion resistance may decrease.

Molybdenum (Mo)

Molybdenum (Mo) can contribute to securing hardenability of steel and is a very effective element for securing high-temperature strength. The molybdenum may be added in a content ratio of 1.5 to 2.5% by weight based on the total weight of the high-strength and high-toughness stainless material according to an embodiment of the present invention. If the content of molybdenum is less than 1.5% by weight of the total weight, the above-described effects cannot be realized, and when the content of molybdenum exceeds 2.5% by weight of the total weight and a large amount is added, the manufacturing cost of the steel is increased and the ductility of the steel is improved by promoting the generation of intergranular carbides. There are problems that can reduce

Nitrogen (N)

Nitrogen (N) forms nitride-based precipitates, contributes to grain refinement, and may contribute to securing high-temperature strength. The nitrogen may be added in a content ratio of greater than 0 and 0.12% by weight or less of the total weight of the high-strength and high-toughness stainless steel material according to an embodiment of the present invention. When the nitrogen content exceeds 0.12% by weight, the impact value may be reduced.

High-strength and high-toughness stainless steel material according to an embodiment of the present invention satisfies the above composition conditions and at the same time titanium (Ti): more than 0 and 0.015% by weight or less, niobium (Nb): more than 0 and 0.12% by weight or less, and zirconium ( Zr): It may be made by further containing at least one selected from more than 0 and 0.02% by weight or less.

Titanium (Ti)

Titanium (Ti) is an element having a crystal grain size refinement effect by forming high-temperature Ti (C, N). In the high-strength and high-toughness stainless material according to an embodiment of the present invention, titanium (Ti) may be added in a content ratio of greater than 0 to 0.015% by weight or less based on the total weight.

3A and 3B are a portion of a state diagram calculated to develop a high-strength and high-toughness stainless steel material according to an embodiment of the present invention. The phase diagram disclosed in FIG. 3a is a part of the phase diagram for the Fe-1.2C-15Cr-2Mo-0.3Si-0.4Mn-0.01Ti-0.05N material, and the phase diagram disclosed in FIG. 3b is Fe-1.2C-15Cr-2Mo-0.3 Part of the phase diagram for Si-0.4Mn-0.02Ti-0.05N material. 3A and 3B, specifically, when the content of titanium (Ti) exceeds 0.015% by weight of the total weight of the material, coarse TiN precipitates are crystallized in the liquid phase, which may cause a problem in that hardness and strength are lowered. .

Niobium (Nb)

Niobium (Nb) is an element that improves strength by precipitating in the form of NbC or Nb (C,N). In the high-strength and high-toughness stainless material according to an embodiment of the present invention, niobium (Nb) may be added in a content ratio of greater than 0 to 0.12% by weight or less based on the total weight.

4A and 4B are a portion of a state diagram calculated to develop a high-strength and high-toughness stainless steel material according to an embodiment of the present invention. The phase diagram disclosed in FIG. 4a is a part of the phase diagram for the Fe-1.2C-15Cr-2Mo-0.3Si-0.4Mn-0.05Nb-0.05N material, and the phase diagram disclosed in FIG. 4b is Fe-1.2C-15Cr-2Mo-0.3 Part of the phase diagram for Si-0.4Mn-0.1Nb-0.05N material. 4A and 4B, specifically, when the content of niobium (Nb) exceeds 0.12% by weight of the total weight of the material, coarse precipitates are crystallized in the liquid phase, which may cause a problem in that hardness and strength are lowered.

Zirconium (Zr)

Zirconium (Zr) is an element that increases corrosion resistance. In the high-strength and high-toughness stainless steel material according to an embodiment of the present invention, zirconium (Zr) may be added in a content ratio of greater than 0 to 0.02% by weight or less based on the total weight.

5A and 5B are a portion of a state diagram calculated to develop a high-strength and high-toughness stainless steel material according to an embodiment of the present invention. The phase diagram disclosed in FIG. 5a is a part of the phase diagram for the Fe-1.2C-15Cr-2Mo-0.3Si-0.4Mn-0.01Zr-0.05N material, and the phase diagram disclosed in FIG. 5b is Fe-1.2C-15Cr-2Mo-0.3 Part of the phase diagram for Si-0.4Mn-0.02Zr-0.05N material. 5A and 5B, specifically, when the content of zirconium (Zr) exceeds 0.02% by weight of the total weight of the material, coarse precipitates are crystallized in the liquid phase, which may cause a problem in that hardness and strength are lowered.

Hereinafter, a method for manufacturing a stainless steel material having high strength and high toughness according to an embodiment of the present invention having the above-described alloying element composition will be described.

Manufacturing method of high-strength and high-toughness stainless steel material

A method of manufacturing a high-strength and high-toughness stainless material according to an embodiment of the present invention includes (a) carbon (C): 0.65 to 1.0 wt%, chromium (Cr): greater than 0 and 19 wt% or less, silicon (Si): 0.25 ~ 0.4% by weight, manganese (Mn): 0.35 to 0.50% by weight, molybdenum (Mo): 1.5 to 2.5% by weight, nitrogen (N): more than 0 and not more than 0.12% by weight and the remainder consisting of iron (Fe) and other unavoidable impurities Homogenizing heat treatment of the ingot (S100); (b) rolling the ingot subjected to the homogenization heat treatment to form a plate (S200); and (c) performing an accumulation rolling bonding process on the plate materials (S300); includes

6 is a view schematically illustrating an accumulation rolling bonding process in a method of manufacturing a high-strength and high-toughness stainless material according to an embodiment of the present invention.

Referring to FIG. 6 together, the (c) step (S300), which is an accumulation rolling joint, includes (c-1) implementing a first multi-layer structure material by overlapping and rolling the plate materials up and down (S310); and (c-2) cutting the first multi-layer structure material and then overlapping and rolling the cut first multi-layer structure material up and down to implement a second multi-layer structure material (S320); may include.

Further, in step (c), (c-3) cutting the n-th multi-layer structure material and then rolling the plurality of cut n-th multi-layer structure materials up and down to overlap the (n+1)-th multi-layer structure Implementing the material (S330); further comprising, wherein the (c-3) step (S330) is characterized in that the n is a positive integer of 2 or more and is repeatedly performed while sequentially increasing.

If the above-described accumulation rolling bonding process is specifically described, a) carbon (C): 0.65 to 1.0 wt%, chromium (Cr): more than 0 and 19 wt% or less, silicon (Si): 0.25 to 0.4 wt%, manganese ( Mn): 0.35 to 0.50% by weight, molybdenum (Mo): 1.5 to 2.5% by weight, nitrogen (N): more than 0 and 0.12% by weight or less, and the remaining iron (Fe) and other unavoidable impurities. S100); (b) rolling the ingot subjected to the homogenization heat treatment to form a plate (S200); (c-1) implementing a first multi-layer structure material by overlapping and rolling the plate materials up and down (S310); and (c-2) cutting the first multi-layer structure material and then overlapping and rolling the cut first multi-layer structure material up and down to implement a second multi-layer structure material (S320); may include

Subsequently, in step S330 performed after step S320, when n is 2, after cutting the second multi-layer structure material, the cut second multi-layer structure material is vertically overlapped. and implementing a third multi-layer structure material by rolling it, and when n is 3, cut the third multi-layer structure material and then overlap the cut third multi-layer structure material up and down It may include the step of implementing the fourth multi-layer structure material by rolling.

The first multi-layer structure material implemented by the above steps may be a two-layer multi-layer structure material, the second multi-layer structure material may be a four-layer multi-layer structure material, and the third multi-layer structure material The material may be an 8-layer multi-layer structure material, and the fourth multi-layer structure material may be a 16-layer multi-layer structure material.

Experimental example

Hereinafter, preferred experimental examples are presented to help the understanding of the present invention. However, the following experimental examples are only for helping understanding of the present invention, and the present invention is not limited by the following experimental examples.

Table 1 shows the alloy element composition (unit: weight ratio %) for the specimen of this experimental example. In the specimen, the multilayer structure material is a plate material having a width of 250mm, a length of 400mm, and a thickness of 3mm through a homogenization heat treatment at 1200°C after manufacturing an ingot having the composition of Table 1 through vacuum induction melting, rough rolling at 1150°C, and hot rolling. After manufacturing them, the accumulated rolling joining process was applied and implemented.

Experimental example
No. Fe C Cr Si Mn Mo N Ti Nb Zr #One Bal. 1.2 15 0.3 0.4 2 0.05 - - - #2 Bal. 0.8 15 0.3 0.4 2 0.05 - - - #3 Bal. 0.8 15 0.3 0.4 2 0.05 - 0.1 - #4 Bal. 0.8 15 0.3 0.4 2 0.05 0.01 - - #5 Bal. 0.8 15 0.3 0.4 2 0.05 0.01 0.1 - #6 Bal. 0.8 15 0.3 0.4 2 0.05 - - 0.01

Tensile test result

7A to 7D are graphs showing tensile test results for specimens according to an experimental example of the present invention for each temperature. Specifically, FIG. 7A is a result of a tensile test at room temperature, FIG. 7B is a result of a tensile test at 300°C, FIG. 7C is a result of a tensile test at 600°C, and FIG. 7D is a result of a tensile test at 900°C This is the result of performing a tensile test.

7a to 7d, the specimen having high strength at room temperature is Experimental Example 1, Experimental Example 3, Experimental Example 4, and Experimental Example 6 of Table 1, and the specimen having high strength at medium temperature is Experimental Example 1 of Table 1, Experimental Example 4, the specimen having high strength at high temperature is Experimental Example 2 and Experimental Example 4 in Table 1.

It is preferable that the high strength and high toughness stainless steel material according to the technical idea of the present invention maintain low strength at a high temperature to enable the accumulation rolling bonding process, and maintain high strength at room temperature and medium temperature, which is the temperature at which a kitchen knife is used. From this point of view, it can be understood that the specimen of Experimental Example 4 in Table 1 is the best.

Room temperature corrosion resistance evaluation result

8A to 8B are graphs showing the results of the evaluation of the corrosion resistance at room temperature for the specimen according to the experimental example of the present invention. Specifically, Figures 8a and Table 2 are the results of performing the corrosion resistance evaluation at room temperature in the brine condition, Figure 8b and Table 3 are the results of performing the corrosion resistance evaluation at room temperature in the sulfuric acid condition. In the table, K1 to K6 correspond to Experimental Examples 1 to 6 of Table 1.

Sample I _corr
(μA/cm ² ) annual corrosion
(mm/yr) SUS304 0.5 0.006 K1 19.6 0.22 K2 4.5 0.05 K3 17.1 0.19 K4 0.63 0.007 K5 7.8 0.09 K6 15.3 0.17

Sample I _corr
(μA/cm ² ) annual corrosion
(mm/yr) SUS304 138 1.6 K1 546 6.3 K2 276 3.2 K3 480 5.6 K4 40.8 0.47 K5 382 4.4 K6 431 5.0

8A and Table 2, it can be seen that the corrosion resistance of the specimen of Experimental Example 4 in Table 1 is the best in the salt water condition, and with reference to FIGS. 8B and 3, the specimen of Experimental Example 4 in Table 1 It can be seen that the corrosion resistance is the best under sulfuric acid conditions. Excellent corrosion resistance at room temperature in sulfuric acid conditions means excellent uniform corrosion properties.

Sample Icorr
(μA cm ^-2 ) K3_8 2950 K4_16 1917 K4_8 1636

Table 4 shows the results of evaluation of the corrosion resistance at room temperature under sulfuric acid conditions of the materials subjected to accumulation rolling bonding as an experimental example of the present invention. In Table 4, K3_8 corresponds to the 8-layer multi-layer structure material implemented by cumulative rolling bonding to the specimen of Experimental Example 3 in Table 1, and K4_16 is implemented by cumulative rolling bonding to the specimen of Experimental Example 4 in Table 1. It corresponds to a 16-layer multi-layer structure material, and K4_8 corresponds to an 8-layer multi-layer structure material realized by cumulative rolling bonding to the specimen of Experimental Example 4 in Table 1. Referring to Table 4, it can be confirmed that the material of Experimental Example 4 in Table 1 has excellent corrosion resistance properties at room temperature even after accumulation rolling bonding.

Hardness evaluation result

9A to 9C are graphs showing hardness evaluation results for specimens according to an experimental example of the present invention.

First, FIGS. 9A and 5 show the Vickers hardness of the specimens of Experimental Example 2 in Table 1 separately according to immediately after rolling and subsequent heat treatment temperatures (800°C, 850°C, 900°C, 950°C). The abscissa axis represents the position from the center to the surface in the cross section of the specimen.

Heat treatment temperature [℃] 800 850 900 950 average hardness [Hv] 284.29 336.20 526.35 716.33

Referring to Figure 9a and Table 5, for the specimen of Experimental Example 2 in Table 1, the hardness immediately after rolling is at a level of 500 Hv or less, whereas when the subsequent heat treatment after rolling is performed at 950 ° C, a hardness value of 715 Hv is implemented. Thus, it can be confirmed that the target 700Hv hardness value can be exceeded.

Table 6 shows the average value of Vickers hardness before cumulative rolling bonding for the specimens of the experimental examples in Table 1 according to the position of the cross-section of the specimen. Vickers hardness measurement conditions include a load of 500 gf and a dwell time of 10 seconds.

location Experimental Example 1 Experimental Example 2 Experimental Example 3 Experimental Example 4 Experimental Example 5 Experimental Example 6 surface 538.4 484.4 472.3667 568.7 514 571.7333 quarter 506.4 504.9333 483.4 504.5 495.5 510.1667 center 525.0333 465.7 492.2333 501.9333 583.4 497.5333 medium 523.2778 485.0111 482.6667 525.0444 530.9667 526.4778

Referring to Table 6, it can be seen that the specimens of Experimental Examples 1 to 6 of Table 1 had a hardness of 480 to 525 Hv before accumulation rolling bonding.

Subsequently, FIG. 9b is a result of measuring Vickers hardness after implementing a 16-layer multi-layer structure material by performing an accumulation rolling bonding process on the specimen of Experimental Example 4 of Table 1, and FIG. 9c is Experimental Example 4 of Table 1 This is the result of measuring the Vickers hardness after realizing an 8-layer multi-layer structure material by performing an accumulation rolling bonding process on the specimen of In FIGS. 9B and 9C , a separate heat treatment was not performed after the accumulation rolling bonding process. The abscissa axis represents the position from the center to the surface in the cross section of the specimen.

Referring to FIGS. 9B and 9C , it can be confirmed that, with respect to the specimen of Experimental Example 4 in Table 1, hardness of 700 Hv or higher can be realized without subsequent heat treatment only by the accumulation rolling bonding process.

10 is a photograph of a kitchen knife implemented by a manufacturing method according to an experimental example of the present invention.

The kitchen knife disposed at the top in FIG. 10 is made of the raw material after hot rolling the specimen corresponding to Experimental Example 4 of Table 1, and the kitchen knife disposed at the bottom is the specimen corresponding to Experimental Example 4 of Table 1 4 It is made of 16 layers of multi-layer structure material implemented by applying the cumulative rolling bonding process of the pass, and the kitchen knife placed in the middle is implemented by applying the 3 pass cumulative rolling bonding process to the specimen corresponding to Experimental Example 4 in Table 1 It is made of 8 layers of multi-layered material.

Table 7 shows the accumulation rolling bonding process conditions for realizing the 16-ply multi-layer structure material shown in FIG. 10 . Referring to Table 7, it can be seen that the reduction ratio for each pass of the accumulation rolling joining process is about 50%.

# of rolling pass Roll gap(mm) RPM of roll temperature
(℃) first thickness
(mm) final thickness
(mm) reduction rate
(%) Load
(ton) One One 50 1050
(10min.) 6.7 3.35 50 235 2 One 50 1050
(10min.) 6.7 3.4 49 260 3 One 50 1050
(10min.) 6.8 3.6 47 260 4 One 50 1050
(10min.) 7.2 3.56 50.5 260

So far, high-strength and high-toughness stainless steel materials according to the experimental examples of the present invention and a method for manufacturing the same have been studied. Among the various compositions shown in Table 1, when the composition of Experimental Example 4 is used, it can be confirmed that the tensile properties, room temperature corrosion resistance properties, hardness properties, etc. are the most advantageous.

That is, carbon (C): 0.75 to 0.85 wt%, chromium (Cr): 14 to 16 wt%, silicon (Si): 0.25 to 0.4 wt%, manganese (Mn): 0.35 to 0.50 wt%, molybdenum (Mo) : 1.8 to 2.2% by weight, nitrogen (N): 0.05 to 0.09% by weight, titanium (Ti): 0.005 to 0.015% by weight, and the remaining iron (Fe) and other unavoidable impurities. In this case, it can maintain low strength at high temperature to enable the accumulation rolling bonding process and high strength at room temperature and medium temperature, which is the temperature at which a kitchen knife is used. In salt water and sulfuric acid conditions, the corrosion resistance properties at room temperature are equivalent to or equal to those of SUS304 material. It was confirmed that the hardness of 800 Hv or more can be realized without additional heat treatment after the accumulation rolling bonding process.

Although the above description has been focused on the embodiments of the present invention, various changes or modifications may be made at the level of those skilled in the art. Such changes and modifications can be said to belong to the present invention without departing from the scope of the present invention. Accordingly, the scope of the present invention should be judged by the claims described below.

Claims (10)

(a) carbon (C): 0.65 to 1.0 wt%, chromium (Cr): 8 to 19 wt%, silicon (Si): 0.25 to 0.4 wt%, manganese (Mn): 0.35 to 0.50 wt%, molybdenum (Mo) ): 1.5 to 2.5% by weight, nitrogen (N): more than 0 0.12% by weight or less, titanium (Ti): 0.005 to 0.015% by weight and the remaining iron (Fe) and other unavoidable impurities comprising the steps of homogenization heat treatment of the ingot;
(b) forming a plate by rolling the ingot subjected to the homogenization heat treatment; and
(c) performing an accumulation rolling bonding process on the plate materials; including,
Step (c) is
(c-1) implementing a first multi-layer structure material by overlapping and rolling the plates to directly abut up and down; and
(c-2) implementing a second multi-layer structure material by cutting the first multi-layer structure material and then overlapping and rolling the cut first multi-layer structure material to directly abut up and down; containing,
A method of manufacturing high-strength and high-toughness stainless steel materials. delete The method of claim 1,
Step (c) is
(c-3) implementing the (n+1)-th multi-layer structure material by cutting the n-th multi-layer structure material and then overlapping and rolling the plurality of cut n-th multi-layer structure materials up and down including,
The step (c-3) is characterized in that the n is a positive integer of 2 or more and is repeatedly performed while sequentially increasing,
A method of manufacturing high-strength and high-toughness stainless steel materials. The method of claim 1,
The ingot is characterized in that it further contains at least one selected from niobium (Nb): more than 0 and 0.12% by weight or less, and zirconium (Zr): more than 0, 0.02% by weight or less,
A method of manufacturing high-strength and high-toughness stainless steel materials. The method of claim 1,
The ingot is carbon (C): 0.75 to 0.85 wt%, chromium (Cr): 14 to 16 wt%, silicon (Si): 0.25 to 0.4 wt%, manganese (Mn): 0.35 to 0.50 wt%, molybdenum (Mo) ): 1.8 to 2.2% by weight, nitrogen (N): 0.05 to 0.09% by weight, titanium (Ti): 0.005 to 0.015% by weight and the remaining iron (Fe) and other unavoidable impurities,
A method of manufacturing high-strength and high-toughness stainless steel materials. delete Carbon (C): 0.65 to 1.0 wt%, Chromium (Cr): 8 to 19 wt%, Silicon (Si): 0.25 to 0.4 wt%, Manganese (Mn): 0.35 to 0.50 wt%, Molybdenum (Mo): 1.5 ~ 2.5 wt%, nitrogen (N): more than 0 0.12 wt% or less, titanium (Ti): 0.005 ~ 0.015 wt%, and the remaining iron (Fe) and other unavoidable impurities. ,
The accumulation rolling bonding process comprises the steps of implementing a first multi-layer structure material by overlapping and rolling the plates having the composition to directly abut up and down; and implementing a second multi-layer structure material by cutting the first multi-layer structure material and then overlapping and rolling the cut first multi-layer structure material to directly abut up and down; containing,
High strength and high toughness stainless steel material. 8. The method of claim 7,
The material is characterized in that it further contains at least one selected from niobium (Nb): more than 0 and less than 0.12% by weight, and zirconium (Zr): more than 0 and less than or equal to 0.02% by weight,
High strength and high toughness stainless steel material. 8. The method of claim 7,
The material is carbon (C): 0.75 to 0.85 wt%, chromium (Cr): 14 to 16 wt%, silicon (Si): 0.25 to 0.4 wt%, manganese (Mn): 0.35 to 0.50 wt%, molybdenum (Mo) ): 1.8 to 2.2% by weight, nitrogen (N): 0.05 to 0.09% by weight, titanium (Ti): 0.005 to 0.015% by weight and the remaining iron (Fe) and other unavoidable impurities,
High strength and high toughness stainless steel material.











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