WO2016085203A1 - High-hardness martensitic stainless steel with excellent antibacterial property and preparation method therefor - Google Patents

Abstract

A high-hardness martensitic stainless steel with excellent antibacterial property and a preparation method therefor are disclosed. The disclosed high-hardness martensitic stainless steel with excellent antibacterial property comprises: 0.45-0.65 wt% of C; 0.02-0.06 wt% of N; 0.1-0.6 wt% of Si; 0.3-1.0 wt% of Mn; 0.1-0.4 wt% of Ni; 13-14.5 wt% of Cr; 0.4-0.6 wt% of Mo; 0.8-1.2 wt% of W; 1.5-2.0 wt% of Cu; and the balance of Fe and inevitable impurities. According to the present invention, there is an advantage enabling the preparation of the martensitic stainless steel for knives, the martensitic stainless steel having high hardness, high corrosion resistance and excellent antibacterial property, by uniformly distributing fine chromium carbide and e-Cu precipitates in the microstructure of a batch annealed material of a high-carbon martensitic stainless steel containing Cu. In addition, according to the present invention, there is an advantage of causing no rust formation on a material after an antibacterial evaluation.

Description

High hardness martensitic stainless steel with excellent antimicrobial properties and preparation method thereof

The present invention relates to a high hardness martensitic stainless steel excellent in antibacterial properties and a method for producing the same.

With the recent improvement in living standards, the user's interest in hygiene and safety is increasing, and as a result, the hygienicity that can suppress the reproduction of bacteria such as Escherichia coli and Staphylococcus aureus is enhanced, as well as the most important feature of stainless steel. The development of functional antibacterial stainless steel is required.

As a method for imparting antibacterial function to stainless steel, a method of expressing antibacterial property by adding metal elements such as Ag and Cu to stainless steel is known as the most common method.

Ag is known to exhibit superior antimicrobial properties compared to Cu, but the material is very expensive and not only causes deterioration of corrosion resistance, but also uniformly disperses / distributes in the base due to the characteristics of the element having a small capacity and relatively high specific gravity. The disadvantage is that it is difficult.

Since Cu is inexpensive compared to Ag and exhibits excellent properties as an antimicrobial component, it is reported that when a certain amount of Cu is added to stainless steel, it exhibits excellent antibacterial properties.

The antimicrobial mechanism of Cu-added stainless steel is summarized as follows.

In the case of stainless steel to which a certain amount of Cu is added, the Cu element present in the surface layer is ionized by a small amount of water on the steel surface to activate Cu 2+ ions. Activated Cu2 + ions can slow down the activity of SH group enzymes required for normal reaction of bacteria such as Escherichia coli and Staphylococcus aureus, thereby killing the bacteria and enhancing hygiene.

On the other hand, in the case of STS steel, since a high-density passivation film is formed on the surface, the amount of Cu 2+ ions that can be eluted in the form of ions through contact with moisture through the dissolved Cu atoms is inevitably limited.

In addition, the antimicrobial properties are inferior, and the duration of the antimicrobial activity is inevitably shortened.

In order to solve this problem, recently, a method of finely depositing a Cu-rich precipitated phase (e-Cu) by special heat treatment for a predetermined time in an appropriate temperature range has been proposed.

In this case, Cu 2+ ion elution is activated from the e-Cu precipitated phase protruding to some surface layer portions by special heat treatment, thereby improving stable antibacterial property for a long time.

Shaking flask method and film adhesion method are the most widely used methods for evaluating antimicrobial properties.

Shake flask method is mainly used for waterproof / water repellent material, severe surface relief material and good absorbent material. Film adhesion method is mainly used for materials that are smooth and the product itself is not absorbent.

In the case of metal materials, the antimicrobial properties are mainly evaluated using the film adhesion method, and the JIS Z 2801 standard is generally applied. When the antimicrobial evaluation is conducted according to JIS Z 2801, bacteria are cultured for 24 hours using an inoculum containing 0.5 to 0.85% NaCl. Phenomenon occurs.

When rusting occurs, the reliability of the antimicrobial evaluation results of the material is deteriorated.

Therefore, it can be said that it is essential to secure corrosion resistance so that no anti-rusting phenomenon can be observed after bacterial culture.

The present invention proposes a high hardness martensitic stainless steel and a method of manufacturing the same having excellent antimicrobial properties that do not occur in the material after antimicrobial evaluation while chromium carbide is uniformly distributed in the microstructure.

Other objects of the present invention may be derived by those skilled in the art through the following examples.

According to a preferred embodiment of the present invention, in weight%, C: 0.45-0.65%, N: 0.02-0.06%, Si: 0.1-0.6%, Mn: 0.3-1.0%, Ni: 0.1-0.4%, Cr : Hardness martensite system having excellent antimicrobial properties, containing 13-14.5%, Mo: 0.4-0.6%, W: 0.8-1.2% and Cu: 1.5-2.0%, and the rest contains Fe and unavoidable impurities Stainless steel is provided.

The annealing heat treatment may be performed such that the elongation of the martensitic stainless steel is 18% or more.

The annealing heat treatment may be performed such that at least 90/100 μm 2 chromium carbide is distributed in the martensitic stainless steel structure.

The martensitic stainless steel satisfies the following PREN, and surface alteration does not occur when antimicrobial evaluation is performed using an inoculum containing NaCl, and may exhibit a bacterial reduction rate of 99% or more.

PREN Cr + 3.0 (Mo + 1/2 W) + 16N ≥ 17

The annealing heat treatment is a first cracking process for uniformly distributing Cu precipitates in the structure of the martensitic stainless steel, a second cracking process for uniformly distributing chromium carbide in the structure of the martensitic stainless steel, and the chromium carbide And a third cracking process for spheroidizing the fine particles of.

The first cracking process may be performed at 500 to 600 ° C, the second cracking process may be performed at 800 to 900 ° C, and the third cracking process may be performed at 600 to 750 ° C.

The first cracking process may last for 5 to 15 hours, the second cracking process may last for 15 to 25 hours, and the third cracking process may last for 5 to 15 hours.

The annealing heat treatment is, after the first cracking process up to the second cracking process to increase the temperature at a rate of 40 ~ 200 ℃ / h, after the second cracking process to the third cracking process A cooling process for cooling at a rate of 10 ° C./h or more, and an air cooling process after the third cracking process may be further included.

In addition, according to a preferred embodiment of the present invention, a high hardness martensitic stainless steel manufacturing method having excellent antimicrobial properties, comprising: hot-rolling the cast steel to produce a hot-rolled steel sheet; Performing annealing of the hot rolled steel sheet by annealing heat treatment; And a cold rolled steel sheet manufacturing step of cold rolling the annealed steel sheet in which the soft nitridation is completed, wherein the anneal heat treatment includes a first cracking process for uniformly distributing Cu precipitates in the tissue of the hot rolled steel sheet, within the tissue of the hot rolled steel sheet. Provided is a high hardness martensitic stainless steel manufacturing method having excellent antimicrobial properties including a second cracking process for uniformly distributing chromium carbide and a third cracking process for spheroidizing the fine particles of chromium carbide.

According to the present invention, fine chromium carbide and e-Cu precipitated phases are uniformly distributed in the microstructure of the upper annealing material of Cu-added high carbon martensitic stainless steel, and martensitic stainless steel for coating having excellent hardness, high corrosion resistance and antibacterial properties. There is an advantage to manufacturing steel.

In addition, according to the present invention, there is an advantage that does not occur rust phenomenon in the material after the antimicrobial evaluation.

1 is a view showing an annealing heat treatment process according to an embodiment of the present invention.

2 is a view showing a microstructure photograph of Cu precipitates in the tissue according to the Cu content in the first cracking process according to an embodiment of the present invention.

3 is a view showing a picture of observing the surface of the material after the antimicrobial evaluation, according to an embodiment of the present invention.

According to a preferred embodiment of the present invention, in weight%, C: 0.45-0.65%, N: 0.02-0.06%, Si: 0.1-0.6%, Mn: 0.3-1.0%, Ni: 0.1-0.4%, Cr : Hardness martensite system having excellent antimicrobial properties, containing 13-14.5%, Mo: 0.4-0.6%, W: 0.8-1.2% and Cu: 1.5-2.0%, and the rest contains Fe and unavoidable impurities Stainless steel is provided.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the drawings, similar reference numerals are used for similar elements.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In general, ceramic materials such as esophagus, scissors, razor, and scalpel, which are widely used for medical devices, require high hardness to maintain cutting and abrasion resistance, and require excellent corrosion resistance because they are easily contacted with moisture or stored in a humid atmosphere.

Therefore, martensitic stainless steel to which high carbon is added is mainly used as a raw material for ceramics.

In the case of high carbon martensitic steels for ceramics, steels containing 0.45 to 0.70% carbon by weight, up to 1.0% manganese, up to 1.0% silicon, and 12.0 to 15.0% chromium are widely used for the material.

In the case of such high-carbon martensitic stainless steel for ceramics, the raw material is manufactured by including an annealing process.

During the annealing, the material reacts with carbon and chromium in the ferrite matrix to disperse and precipitate fine particles in the form of chromium carbide, and it is easy to apply stainless steel manufacturing processes such as rolling and pickling as the dissolved carbon content in the substrate is lowered. Do.

In addition, the fine chromium carbide uniformly distributed in the ferrite matrix allows the rapid re-application of chromium and carbon to the high temperature austenite phase in the reinforcement heat treatment process performed by the ceramics manufacturer. And important factors for improving corrosion resistance.

Accordingly, in order to secure high carbon martensitic steel for coatings having excellent hardness and corrosion resistance, it is essential to distribute the fine chromium carbide uniformly in the microstructure.

On the other hand, as described above, in the case of the metal material may be a rust phenomenon when the antimicrobial evaluation, the high-carbon martensite steel for ceramics may also cause a problem that the reliability of the antimicrobial evaluation results deteriorate.

Patents related to antimicrobial martensitic stainless steels include Japanese Patent Application Laid-Open No. 9-195016, Japanese Patent Laid-Open Publication No. 9-195016 regarding martensitic stainless steel having excellent antimicrobial property by uniformly distributing an e-Cu precipitated phase. 9-256116, etc., but there was no information about the factors that are expected to have a significant effect on the antimicrobial and bacterial reduction rate, such as the rust of the material when the antimicrobial evaluation.

Therefore, in order to develop high hardness martensitic stainless steel having excellent antimicrobial properties, it is essential to secure chromium carbide uniformly in the microstructure and to prevent corrosion resistance of the material after antimicrobial evaluation.

The present invention relates to a high-strength martensitic stainless steel having excellent antimicrobial properties and a method for manufacturing the same, in weight%, C: 0.45 to 0.65%, N: 0.02 to 0.06%, Si: 0.1 to 0.6%, and Mn: 0.3 Alloy containing 1.0%, Ni: 0.1-0.4%, Cr: 13-14.5%, Mo: 0.4-0.6%, W: 0.8-1.2% and Cu: 1.5-2.0%, the remainder being Fe and inevitable impurities It is characterized by producing martensitic stainless steel having a component and exhibiting a bacterial reduction rate of 99.9% or more by JIS Z 2801 antimicrobial evaluation method.

Content of the alloying element which comprises the high carbon martensitic stainless steel for ceramics of this invention is demonstrated.

If the content of C is low, the hardness of the martensitic stainless steel is reduced after hardness, so that cutting and abrasion resistance cannot be secured. Therefore, 0.45% or more of C is added. On the other hand, if the content is excessively high, the corrosion resistance of the material itself is lowered due to excessive formation of chromium carbide, and the upper limit is limited to 0.65% because there is a fear of formation of coarse carbide in the annealing structure due to carbon segregation.

N is an element added to improve the corrosion resistance and hardness at the same time, even if added instead of C does not cause local fine segregation has the advantage of not forming coarse precipitate in the product. To achieve this effect add at least 0.02%. However, if excessively added, pore due to nitrogen may occur during casting, so the upper limit is limited to 0.06%.

Since Si is an essential element for deoxidation, 0.1% or more is added. However, the addition of a high content of Si lowers the pickling property and increases the brittleness of the material, so the upper limit thereof is limited to 0.6%.

Since Mn is an essential element for deoxidation, 0.3% or more is added. However, when excessively added, the upper limit is limited to 1.0% because it inhibits the surface quality of the steel and suppresses the securing of high hardness properties through residual austenite formation of the final heat treatment material.

Ni is an element that is inevitably carried from scrap metal in the steelmaking process, and 0.1% or more is added. However, when a high content of Ni is formed, it is difficult to obtain high hardness properties by forming residual austenite of the final heat treatment material. Therefore, the upper limit is 0.4%.

Since Cr is a basic element ensuring corrosion resistance, 13% or more is added. However, excessive addition increases the manufacturing cost, and increases the fine segregation of chromium components in the tissue, causing localization of chromium carbide, thereby lowering the corrosion resistance and hardness of the reinforcement heat treatment, so the upper limit is limited to 14.5%. .

Mo has an excellent effect on improving the corrosion resistance, so 0.4% or more is added. However, excessive addition results in an increase in the manufacturing cost and limits the upper limit to 0.6%.

W has an effect of improving the corrosion resistance and increasing the heat treatment hardness, so 0.8% or more is added. However, excessive addition inhibits the increase in manufacturing cost and processability, so the upper limit is limited to 1.2%.

Cu is the most important alloy element in the stainless steel of the present invention, and e-Cu is formed by ordinary annealing, thereby securing antibacterial properties. In addition, the higher the content, the greater the amount of e-Cu precipitates, and the higher the elution amount of Cu2 +, which improves the antibacterial properties. do.

Martensitic stainless steel according to an embodiment of the present invention having the composition as described above is produced by hot-rolling and hot-rolled steel sheet after manufacturing the cast by continuous casting or ingot casting.

After that, the hot rolled steel sheet manufactured is subjected to soft nitriding operation through annealing heat treatment in order to secure good workability before proceeding such as precision rolling to a thickness usable for coating.

As shown in Figure 1, the annealing heat treatment according to an embodiment of the present invention is a first cracking process to uniformly distribute the spherical Cu precipitates preferentially in the structure of martensitic stainless steel, and the chromium in the structure of the hot rolled steel sheet A second cracking step of uniformly distributing the carbide, and a third cracking step of spheroidizing the fine particles of the chromium carbide.

And, the temperature rising process for increasing the temperature of the hot-rolled steel sheet from the first cracking process to the second cracking process, and the cooling process of lowering the temperature of the hot-rolled steel sheet from the second cracking process to the third cracking process And, after the third cracking process is further performed an air cooling process for cooling the hot-rolled steel sheet.

First, the first cracking process according to an embodiment of the present invention is a process of uniformly distributing Cu precipitates in the structure of the hot rolled steel sheet, and uniformly heating the hot rolled steel sheet for 5 to 15 hours in a constant temperature of 500 to 600 ° C. It is a process.

In this process, the fine Cu precipitate is uniformly distributed in the tissue as shown in FIG. These Cu precipitates generally act as precipitation starting points of chromium carbides, which are well known to precipitate first at grain boundaries, thereby inducing uniform deposition of chromium carbides in the second cracking process.

In the first cracking process, if the cracking temperature is lower than 500 ° C, no Cu precipitates are formed. If the cracking temperature is higher than 600 ° C, chromium carbides are precipitated at the same time as the Cu precipitates. Uniform distribution of carbides cannot be ensured.

In addition, when the cracking time is less than 5 hours in the first cracking process, Cu deposition does not occur and thus it is impossible to secure a uniform distribution of chromium carbides. If the cracking time exceeds 15 hours, the size of the Cu precipitates increases while the number decreases. As a result, the Cu precipitates are distributed, and as a result, it becomes difficult to secure a uniform distribution of chromium carbides.

Therefore, the first cracking process is preferably cracked for 5 to 15 hours in a constant temperature atmosphere of 500 ~ 600 ℃.

Next, the temperature raising process according to an embodiment of the present invention is a process of increasing the temperature of the hot-rolled steel sheet at a rate of 40 ~ 200 ℃ / h from the first cracking process to the second cracking process.

When the temperature increase rate is 40 ° C / h or less during the temperature increase process, the time passing through the temperature range where the chromium carbide is coarse, for example, 700 ~ 750 ° C increases, the size of the chromium carbide is coarse and the chromium distributed in the microstructure The density of carbides can be reduced.

On the other hand, if the temperature increase rate is 200 ° C./h or more, the transit time in the temperature section where the chromium carbide is coarsened is reduced to secure fine chromium carbides, but the carbide diffusion time is reduced, resulting in unbalanced distribution of chromium carbides. There are disadvantages that result.

Therefore, the temperature increase rate in the temperature increase process is more than 40 ℃ / h, it is preferable to adjust the range to less than 200 ℃ / h.

Subsequently, the second cracking process according to an embodiment of the present invention is a process of uniformly distributing chromium carbide in the structure of the hot-rolled steel sheet after the temperature raising process, and the hot-rolled steel sheet in a constant temperature atmosphere of 800 to 900 ° C. It is the process of heating uniformly for 25 hours. In this process, chromium carbide is uniformly distributed in the tissue.

When the cracking temperature is 800 ° C. or less, agglomerates may be formed due to chromium carbide locally precipitated at the grain boundary during the cracking process, and when it is 900 ° C. or more, coarse chromium carbides are formed near the grain boundaries. And coarse chromium carbide causes local material imbalance of the material, making it difficult to secure ductility and causing material quality degradation during final heat treatment.

In addition, if the cracking time in the second cracking process is 15 hours or less, it is advantageous to form fine chromium carbides, but the chromium carbides are not uniformly distributed, but may be clustered and distributed. As a result of coalescence and coarsening of localized chromium carbides, process efficiency decreases due to an increase in heat treatment time and manufacturing costs increase.

Therefore, the second cracking process is preferably cracked for 15 to 25 hours in a constant temperature atmosphere of 800 ~ 900 ℃.

Next, the cooling process according to an embodiment of the present invention is a process of cooling the hot rolled steel sheet at 600 to 750 ° C. from the second crack process to the third crack process, cooling the hot rolled steel sheet at a rate exceeding 10 ° C./h. It is desirable to. If the cooling rate is 10 ° C./h or less, the time through the temperature range in which the size of the chromium carbide microstructure is coarsened is increased, which causes the chromium carbide microstructure in the microstructure to coarsen, resulting in enhanced heat treatment. It becomes difficult to secure corrosion resistance and high hardness.

According to an embodiment of the present invention, the third cracking process is a process of forming a fine particle of chromium carbide in the hot rolled steel sheet at low temperature by proceeding after the cooling process, and heating the hot rolled coil at a constant temperature for 5 to 15 hours at 600 to 750 ° C. It is the process of maintaining and heating uniformly.

The minimum temperature condition for spheroidizing chromium carbide is 600 ° C., and if it exceeds 750 ° C., the spheroidized chromium carbide grows excessively, reducing the number of chromium carbides and reducing ductility.

In addition, if the constant temperature holding time of the third cracking process is 5 hours or less, the progress of spheroidization of chromium carbide is insufficient, and if it is 15 hours or more, the spheroidized carbides grow excessively to form coarse microstructures.

Therefore, the third cracking process is preferably cracked for 5 to 15 hours in a constant temperature of 600 ~ 750 ℃.

After the third cracking process, the hot-rolled steel sheet is air-cooled in air to complete the annealing heat treatment process.

After the soft nitriding through the annealing heat treatment is completed, a cold rolled steel sheet manufacturing step of cold rolling an annealing steel sheet is performed, and a step of reinforcing heat treatment is performed using the cold rolled steel sheet processed to a desired thickness and shape.

Reinforcement heat treatment is carried out in three stages. The first stage is an austenizing → quenching heat treatment step of reusing carbides uniformly distributed by annealing.

In this heat treatment step, the heat treatment is performed for 10 seconds to 5 minutes at 1000 ℃ to 1150 ℃. Here, if the heat treatment temperature is less than 1000 ℃ can not obtain the hardness required for the blade steel, and if the heat treatment temperature exceeds 1150 ℃, the problem of hardness decrease due to excessive formation of residual austenite due to the increase of inventory capacity Can be.

In addition, when the heat treatment time is less than 10 seconds, the hardness required for the blade steel also can not be obtained, and even when the heat treatment time exceeds 5 minutes, grain (growth) may grow and residual austenite may be generated.

After completion of the quenching heat treatment, some residual austenite is subjected to a subzero heat treatment for 10 seconds to 5 minutes at a temperature of about −70 ° C. to phase transform the martensite. Then, to secure the ductility of the manufactured martensitic steel, a tempering treatment of about 400 to 600 ° C. is performed for 30 minutes to 2 hours, followed by air cooling to complete the strengthening heat treatment process.

Hereinafter, the present invention will be described through embodiments of the present invention. However, the following examples are preferred embodiments of the present invention, and the scope of the present invention is not limited by the following examples.

First, a hot rolled steel sheet according to Examples and Comparative Examples containing the composition shown in Table 1 below and the remainder containing iron (Fe) and unavoidable impurities (wt%) was prepared. For reference, the corrosion resistance between steel grades was quantified by attaching the PREN (Equation 1), which is one of the indicators to evaluate the corrosion resistance of stainless steel.

Equation 1) PREN = Cr + 3.0 (Mo + 1/2 W) + 16N

Steel grade	C	Si	Mn	Cr	Ni	Mo	W	Cu	N	PREN
Comparative Example 1	0.683	0.408	0.693	13.21	0.308	0	0	0	0.03	13.69
Comparative Example 2	0.687	0.402	0.730	13.24	0.296	0	0	0.51	0.04	13.88
Comparative Example 3	0.651	0.4	0.688	13.3	0.299	0	0	1.02	0.06	14.26
Comparative Example 4	0.700	0.380	0.638	12.76	0.310	0	0	1.46	0.03	13.24
Comparative Example 5	0.692	0.424	0.722	13.55	0.302	0	0	1.98	0.05	14.35
Comparative Example 6	0.695	0.391	0.701	13.16	0.3	0	0	2.52	0.04	13.8
Comparative Example 7	0.49	0.305	0.517	13.98	0.307	0.51	1.05	0	0.031	17.69
Comparative Example 8	0.56	0.313	0.472	13.81	0.295	0.49	1.01	0	0.029	17.36
Comparative Example 9	0.62	0.298	0.505	14.01	0.308	0.51	1.03	0	0.03	17.67
Comparative Example 10	0.66	0.312	0.528	13.92	0.310	0.48	1.02	1.50	0.028	17.44
Example 1	0.45	0.297	0.489	13.91	0.287	0.48	0.99	1.52	0.029	17.40
Example 2	0.5	0.299	0.506	14.14	0.302	0.49	0.95	1.5	0.03	17.61
Example 3	0.56	0.298	0.509	14	0.301	0.5	One	1.52	0.03	17.58
Example 4	0.6	0.291	0.503	13.95	0.305	0.49	0.98	1.5	0.03	17.47

The high carbon martensitic stainless steel slab for coatings having the composition shown in Table 1 was prepared, and hot rolled steel sheet (thickness 3 mm) was manufactured through hot rolling, and at the same time, the edge quality of the hot rolled material was confirmed.

Subsequently, after the heat treatment was performed using the manufactured hot-rolled steel sheet using the following annealing conditions, microstructure observation and elongation evaluation were performed.

[Annealing Heat Treatment Condition]

-First cracking process: 10 hours at 500 ℃

-Temperature rise process: temperature increase rate 100 ℃ / hr

2nd crack process: 20 hours at 850 degreeC

-Cooling process: temperature drop rate 10 ℃ / hr

3rd crack process: 7 hours at 650 degreeC

Then, the cold rolled steel sheet (thickness 1.5mm) was manufactured through cold rolling, and the edge quality of the cold rolled material was confirmed.

In addition, the heat-treatment was performed under the following conditions, and the antimicrobial evaluation was performed using one strain (E. coli) according to JIS Z 2801.

[Reinforced heat treatment condition]

Austenitizing: 5 minutes at 1100 ℃

-Quenching: Oil quenching at room temperature

Deep freezing: 5 minutes at -70 ℃

Tempering / Sintering: 30 minutes at 500 ℃

In addition, surface observation was performed to confirm the presence / absence of the rusting phenomenon about the evaluated material. The results are shown in Table 2.

Steel grade	Hot rolled edge quality	Upper Annealing Material			Cold Rolled Edge Quality	Reinforced heat treatment material
		Elongation (%)	Precipitate uniformity			Surface finish	Bacterial Reduction (%)
			Cr carbide	Cu precipitation phase
Comparative Example 1	Good	21.1	Inferior	Inferior	Good	U	99.9
Comparative Example 2	Good	20.8	Inferior	Inferior	Good	U	99.9
Comparative Example 3	Good	19.3	Inferior	Inferior	Good	U	99.9
Comparative Example 4	Good	19.2	Good	Good	Good	U	99.9
Comparative Example 5	Good	19.2	Good	Good	Good	U	99.9
Comparative Example 6	Inferior	17.5	Good	Good	Inferior	U	99.9
Comparative Example 7	Good	21.4	Good	Good	Good	radish	92.5
Comparative Example 8	Good	21.1	Good	Good	Good	radish	94.1
Comparative Example 9	Good	20.4	Good	Good	Good	radish	94.4
Comparative Example 10	Good	17.3	Good	Good	Inferior	radish	99.9
Example 1	Good	21.6	Good	Good	Good	radish	99.9
Example 2	Good	20.1	Good	Good	Good	radish	99.9
Example 3	Good	19.8	Good	Good	Good	radish	99.9
Example 4	Good	19.4	Good	Good	Good	radish	99.9

On the other hand, when the Cu content is 2.5% or more (Comparative Example 6), it is confirmed that a large amount of cracks are generated at the edge of the material after hot rolling, which is attributed to the hot workability inferiority due to the addition of a large amount of Cu. . In addition, the elongation was estimated to be less than 18% after the annealing.

Based on the above results, it can be seen that the Cu content should be limited to 2% or less in order to secure good hot workability.

On the other hand, in the case of adding Mo, W, etc. to improve the corrosion resistance (Comparative Examples 7 to 10, Examples 1 to 4), while showing good hot rolling property regardless of the amount of 0.45 to 0.70% of C added, After the cold rolling progress, when the C content exceeds 0.65%, it is confirmed that a large amount of cracks are generated at the edge portion of the cold rolled steel sheet, and the elongation after the annealing is observed to be lower than 18%. This is believed to be attributable not only to the formation of coarse carbides due to the large amount of C, but also to the formation of precipitates of additive elements such as W and Cu.

Based on the above results, it can be seen that the content of C should be limited to 0.65% or less in order to secure good cold workability.

In addition, the chromium carbide and Cu precipitated phases were observed through observation of the microstructure of the annealing material.

First, in Comparative Examples 1 to 6, it was confirmed that the uniformity of the chromium carbide increased as the Cu content increased from 0 to 2.5% at a constant C content, especially when the Cu content was added at 1.5% or more. Carbide density of more than / 100㎛ 2 can be secured, so it is possible to secure high hardness and excellent corrosion resistance after reinforcing heat treatment.

On the other hand, when the added Cu content is increased by more than 1.5%, it was confirmed that the Cu precipitated phase distributed in the annealing structure is uniformly distributed as shown in Figure 2 (b).

In more detail, when the Cu content is added to less than 1.5% as shown in Figure 2 (a) can form a non-uniform Cu precipitated phase may cause an antimicrobial inferiority. On the other hand, in the case of FIG. 2 (b) added more than 1.5%, the Cu precipitated phase is uniformly distributed in the matrix, and thus, excellent antimicrobial expression may be possible.

Based on the above results, in order to secure excellent corrosion resistance and antimicrobial properties of high hardness, the amount of Cu added should be added at least 1.5%. However, considering the processability of the material, the amount of added Cu should be limited to 1.5 to 2.0% or less. .

After the completion of the reinforcement heat treatment using the hot-rolled steel sheet was carried out to evaluate the antimicrobial and confirmed the surface rust phenomenon of the material.

First, the antimicrobial evaluation according to the Cu addition amount and the surface rusting phenomenon of the evaluation material were observed for the material to which Mo and W of Comparative Examples 1 to 6 were not added. As a result, it was confirmed that it exhibits a high antibacterial property of 99.9% regardless of the amount of Cu added.

However, as a result of observing the surface layer part of the evaluation material, it was confirmed that the surface rust phenomenon according to the corrosion resistance inferior as shown in Fig. 3 (a). Thus, it is unclear whether the cause of antimicrobial expression is due to the influence of Cu contained in the material itself or the effect of Fe ions eluted from rust generation such as rust.

Therefore, in order to secure a reliable quantitative evaluation result, it is required to improve the corrosion resistance of the material that does not cause surface layer deterioration, such as suppressing the corrosion of the material during the antimicrobial evaluation.

On the other hand, in the case of the steel sheet to which a certain amount of Mo, W is added to improve the corrosion resistance (Comparative Examples 7 to 10 and Examples 1 to 4), as shown in FIG. It was confirmed that this was not formed. In other words, it was confirmed that the corrosion resistance was not observed in the evaluation of the antimicrobial properties of the steel sheet melted by setting Cr, Mo, W, N, etc. so that the PREN value expressed in Equation 1) was 17 or more. .

As a result of antimicrobial evaluation on the material having improved corrosion resistance, steel sheets without Cu (Comparative Examples 7-9) exhibited a thermally-reduced bacterial reduction rate of less than 95%, whereas steel sheets containing 1.5% or more of Cu content ( Comparative Example 10 and Examples 1 to 4) It was confirmed that excellent antibacterial properties of 99.9% were expressed.

Based on the above results, in order to secure excellent antimicrobial properties, it is possible to add an element that improves the corrosion resistance of materials such as Mo and W to set the PREN value to 17 or more and add more than 1.5% Cu to ensure excellent antibacterial properties. In addition, it can be seen that after the antimicrobial evaluation, the anti-rusting phenomenon can be suppressed to obtain a reliable antimicrobial evaluation result.

 From the above results, in terms of weight% according to the present invention, C: 0.45 to 0.65%, N: 0.02 to 0.06%, Si: 0.1 to 0.6%, Mn: 0.3 to 1.0%, Ni: 0.1 to 0.4%, Cr: 13 to Applicability of the conditions set forth in the present invention for martensitic stainless steels containing 14.5%, Mo: 0.4-0.6%, W: 0.8-1.2% and Cu: 1.5-2.0%, the remainder containing Fe and unavoidable impurities When the dull and reinforced heat treatments are applied, it can be seen that the corrosion resistance does not occur when evaluating the antimicrobial activity of JIS Z 2801, and that it is possible to manufacture high hardness martensitic stainless steels having excellent antimicrobial resistance of 99.9% or more.

In the present invention as described above has been described by the specific embodiments, such as specific components and limited embodiments and drawings, but this is provided to help a more general understanding of the present invention, the present invention is not limited to the above embodiments. For those skilled in the art, various modifications and variations are possible from these descriptions. Therefore, the spirit of the present invention should not be limited to the described embodiments, and all the things that are equivalent to or equivalent to the claims as well as the following claims will belong to the scope of the present invention. .

Claims (12)

1. By weight%, C: 0.45-0.65%, N: 0.02-0.06%, Si: 0.1-0.6%, Mn: 0.3-1.0%, Ni: 0.1-0.4%, Cr: 13-14.5%, Mo: 0.4- A high hardness martensitic stainless steel having excellent antimicrobial characteristics, comprising 0.6%, W: 0.8-1.2%, and Cu: 1.5-2.0%, and the rest containing Fe and unavoidable impurities.
2. The method of claim 1,

   A high hardness martensitic stainless steel having excellent antibacterial property, characterized in that the elongation of the martensitic stainless steel is 18% or more.
3. The method of claim 2,

   High hardness martensitic stainless steel having excellent antimicrobial characteristics, characterized in that more than 90 / 100㎛ 2 chromium carbide is distributed in the martensitic stainless steel structure.
4. The method of claim 3,

   The martensitic stainless steel satisfies the following PREN and has no surface change when evaluating antimicrobial activity using an inoculum containing NaCl, and exhibits a high hardness martensite system having an antimicrobial effect of 99% or more. Stainless steel.

   PREN Cr + 3.0 (Mo + 1/2 W) + 16N ≥ 17
5. The method according to any one of claims 2 to 4,

   In the annealing heat treatment for producing the martensitic stainless steel, the first cracking process for uniformly distributing the Cu precipitates in the structure of the martensitic stainless steel, the agent for uniformly distributing the chromium carbide in the structure of the martensitic stainless steel A high hardness martensitic stainless steel having excellent antimicrobial properties, including a cracking process and a third cracking process for spheroidizing the fine particles of the chromium carbide.
6. The method of claim 5,

   The first cracking process is carried out at 500 ~ 600 ℃, the second cracking process is carried out at 800 ~ 900 ℃, the third cracking process is a high hardness martensitic stainless steel having excellent antibacterial activity at 600 ~ 750 ℃ River.
7. The method of claim 6,

   The first crack process lasts for 5 to 15 hours, the second crack process lasts for 15 to 25 hours, and the third crack process lasts for 5 to 15 hours. River.
8. The method of claim 7, wherein

   The annealing heat treatment is, after the first cracking process up to the second cracking process to increase the temperature at a rate of 40 ~ 200 ℃ / h, after the second cracking process to the third cracking process A high hardness martensitic stainless steel having excellent antibacterial activity, further comprising a cooling process of cooling at a rate of 10 ° C./h or more and an air cooling process after the third cracking process.
9. As a method of manufacturing high hardness martensitic stainless steel with excellent antibacterial properties,

   Hot-rolling the cast steel to produce a hot-rolled steel sheet;

   Performing annealing of the hot rolled steel sheet by annealing heat treatment; And

   Cold rolled steel sheet manufacturing step of cold rolling the annealed steel sheet is completed;

   The annealing heat treatment may include a first cracking step of uniformly distributing Cu precipitates in the structure of the hot-rolled steel sheet, a second cracking step of uniformly distributing chromium carbide in the structure of the hot-rolled steel sheet, and fine particles of the chromium carbide. A high hardness martensitic stainless steel manufacturing method having excellent antimicrobial properties, including a spherical third cracking process.
10. The method of claim 9,

    The first cracking process is carried out for 5 to 15 hours at 500 ~ 600 ℃, the second cracking process is carried out for 15 to 25 hours at 800 ~ 900 ℃, the third cracking process is carried out at 600 ~ 750 ℃ 5 High hardness martensitic stainless steel manufacturing method with excellent antibacterial activity for ~ 15 hours.
11. The method of claim 10,

    The annealing heat treatment is, after the first cracking process up to the second cracking process to increase the temperature at a rate of 40 ~ 200 ℃ / h, after the second cracking process to the third cracking process A high hardness martensitic stainless steel manufacturing method having excellent antibacterial activity, further comprising a cooling process of cooling at a rate of 10 ° C./h or more and an air cooling process after the third cracking process.
12. The method of claim 11,

    Performing a strengthening heat treatment to the cold rolled steel sheet; further comprising,

    The reinforcement heat treatment is a step of austenizing treatment at 1000 ℃ to 1150 ℃ for 10 seconds to 5 minutes in order to re-distribute the uniformly distributed chromium carbide, quenching at room temperature, phase transformation of the residual austenite to martensite In order to prepare a high-strength martensitic stainless steel having excellent antimicrobial activity comprising the step of treating with a sub agent for 10 seconds to 5 minutes at a temperature of -70 ℃, tempering for 30 minutes to 2 hours at 400 ~ 600 ℃.

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