Martensitic stainless cold-rolled annealed material and method for manufacturing same

Abstract

Provided according to the present invention is a martensitic stainless cold-rolled annealed material comprising, in wt%, 0.55% to 0.75% of C, 0.01% to 0.05% of N, 0.10% to 0.80% of Si, 0.20% to 0.80% of Mn, 12.5% to 15.5% of Cr, 0.01% to 0.50% of Ni, 0.01% to 0.20% of V, and 0.001% to 0.020% of Ti, with the balance being Fe and inevitable impurities, wherein the material satisfies formula (1) below, and comprises pores per unit area in a range of 1×104 ea / mm2 to 50×104 ea / mm2. Formula (1): 80 ≤ 3[Cr]+17[Si]+100[C]−200[V]−400[Ti] ≤ 110 (wherein [Cr], [Si], [C], [V], and [Ti] refer to the content of each element)

Description

Martensitic stainless steel cold-rolled annealed material and method for manufacturing the same

[0001] The present invention relates to a martensitic stainless steel cold-rolled annealed material and a method for manufacturing the same.

[0002] As living standards improve, the application of cold-rolled annealed martensitic stainless steel with high hardness, high strength, and high corrosion resistance is increasing in applications such as surgical scalpels and household razor blades. These applications require high hardness, high strength, and corrosion resistance, and to secure high hardness and high strength characteristics, a tempered martensite structure created by strengthening heat treatment and tempering is utilized.

[0003] Conventionally, methods have mainly been proposed to remove primary carbides generated in martensitic steel by heat-treating the material in an equilibrium temperature range where primary carbides do not occur. In other words, while conventional technology aims to improve quality in terms of mechanical properties by controlling coarse carbides, it has the problem of inferior polishability.

[0004] The objective of the present invention, which aims to solve the aforementioned problem, is to provide a martensitic stainless steel cold-rolled annealed material with improved polishability by appropriately controlling the number of pores per unit area through the alloy composition and manufacturing method, and a method for manufacturing the same.

[0005] The problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by a person skilled in the art from the description below.

[0006] A martensitic stainless steel cold-rolled annealed material according to one example of the present invention comprises, in weight%, C: 0.55% to 0.75%, N: 0.01% to 0.05%, Si: 0.10% to 0.80%, Mn: 0.20% to 0.80%, Cr: 12.5% ​​to 15.5%, Ni: 0.01% to 0.50%, V: 0.01% to 0.20%, and Ti: 0.001% to 0.020%, with the remainder being Fe and unavoidable impurities, satisfying the following formula (1), and having a void per unit area of ​​1*10 4 ea / mm 2 Up to 50*10 4 ea / mm 2 Include in the range.

[0007] Equation (1): 80 ≤ 3[Cr]+17[Si]+100[C]-200[V]-400[Ti] ≤ 110

[0008] (Here, [Cr], [Si], [C], [V], and [Ti] represent the content of each element)

[0009] In addition, the martensitic stainless steel cold-rolled annealed material according to one example of the present invention may further include Mo: 0.01% to 0.90% by weight.

[0010] In addition, the martensitic stainless steel cold-rolled annealed material according to one example of the present invention may have an average thickness of 0.05 mm to 4.0 mm.

[0011] In addition, the martensitic stainless steel cold-rolled annealed material according to one example of the present invention may not crack when ground with a grinding stone of #240 grit.

[0012] In addition, for a martensitic stainless steel cold-rolled annealed material according to one example of the present invention, the polishing time may be less than 60 seconds.

[0013] A method for manufacturing a martensitic stainless steel cold-rolled annealed material according to an example of the present invention comprises the steps of: preparing a cast billet satisfying the following formula (1), wherein, in weight percent, C: 0.55% to 0.75%, N: 0.01% to 0.05%, Si: 0.1% to 0.8%, Mn: 0.20% to 0.80%, Cr: 12.5% ​​to 15.5%, Ni: 0.01% to 0.50%, V: 0.01% to 0.20%, and Ti: 0.001% to 0.020%, and the remainder being Fe and unavoidable impurities; and reheating the cast billet at 1200°C to 1300°C for 1 to 5 hours. The method comprises the steps of: manufacturing a hot-rolled steel sheet by hot-rolling the reheated cast billet at 1000°C to 1200°C with a reduction rate of 90% to 98%; coiling the hot-rolled steel sheet at a temperature of 700°C or higher; hot-rolling annealing by maintaining at 800°C to 900°C for 3 to 10 hours, followed by maintaining at 700°C to 790°C for 5 to 15 hours; and cold-rolling annealing at 700°C to 900°C for 40 to 100 seconds.

[0014] Equation (1): 80 ≤ 3[Cr]+17[Si]+100[C]-200[V]-400[Ti] ≤ 110

[0015] (Here, [Cr], [Si], [C], [V], and [Ti] represent the content of each element)

[0016] In addition, a method for manufacturing a martensitic stainless steel cold-rolled annealed material according to one example of the present invention may further include the steps of hot-rolled pickling and cold-rolling after the hot-rolled annealing.

[0017] In addition, in the method for manufacturing a martensitic stainless steel cold-rolled annealed material according to one example of the present invention, the total reduction rate of the cold rolling in all passes may be 40% to 80%.

[0018] In addition, in the method for manufacturing a martensitic stainless steel cold-rolled annealed material according to one example of the present invention, the sum of the reduction rates of the first pass and the second pass among the total passes of the cold rolling may be 10% to 30%.

[0019] In addition, a method for manufacturing a martensitic stainless steel cold-rolled annealed material according to one example of the present invention may further include a step of strengthening heat treatment at 1000°C to 1100°C for 100 seconds to 600 seconds after the cold-rolled annealing step.

[0020] A martensitic stainless steel cold-rolled annealed material according to one example of the present invention has 1*10 pores per unit area 4 Up to 50*10 4 ea / mm 2 By controlling the range, grinding time can be reduced and cracks during grinding can be prevented.

[0021] Figure 1 is a scanning electron microscope (SEM) image showing the number of pores generated inside the carbide and between the carbide and the matrix of Invention Example 4 according to one example of the present invention.

[0022] Preferred embodiments of the present invention are described below. However, embodiments of the present invention may be modified in various other forms, and the technical concept of the present invention is not limited to the embodiments described below. Furthermore, the embodiments of the present invention are provided to more completely explain the present invention to those with average knowledge in the relevant technical field.

[0023] The terms used in this application are used merely to describe specific examples. For this reason, singular expressions include plural expressions unless the context clearly requires them to be singular. Additionally, it should be noted that terms such as “comprising” or “comprising” used in this application are used to clearly indicate the presence of features, steps, functions, components, or combinations thereof described in the specification, and are not used to preliminarily exclude the existence of other features, steps, functions, components, or combinations thereof.

[0024] Meanwhile, unless otherwise defined, all terms used in this specification shall be understood to have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Accordingly, unless explicitly defined in this specification, specific terms should not be interpreted in an overly ideal or formal sense. For instance, singular expressions in this specification include plural expressions unless the context clearly indicates an exception.

[0025] Additionally, terms such as "about," "substantially," etc., in this specification are used to mean at or near the stated value when inherent manufacturing and material tolerances are presented in the said sense, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosed content in which precise or absolute values ​​are mentioned to aid in understanding the invention.

[0026] First, a martensitic stainless steel cold-rolled annealed material according to one example of the present invention will be described.

[0027] A martensitic stainless steel cold-rolled annealed material according to one example of the present invention comprises, in weight%, C: 0.55% to 0.75%, N: 0.01% to 0.05%, Si: 0.10% to 0.80%, Mn: 0.20% to 0.80%, Cr: 12.5% ​​to 15.5%, Ni: 0.01% to 0.50%, V: 0.01% to 0.20%, and Ti: 0.001% to 0.020%, with the remainder being Fe and unavoidable impurities, satisfying the following formula (1), and having a void per unit area of ​​1*10 4 ea / mm 2 Up to 50*10 4 ea / mm 2 Include in the range.

[0028] Equation (1): 80 ≤ 3[Cr]+17[Si]+100[C]-200[V]-400[Ti] ≤ 110

[0029] (Here, [Cr], [Si], [C], [V], and [Ti] represent the content of each element)

[0030] The reasons for limiting the compositional range of each alloying element are explained below. Unless otherwise noted, the unit is weight percent.

[0031] The content of C may be 0.55% to 0.75% by weight.

[0032] C is an essential element for improving the hardness of steel and must be added in an appropriate amount to ensure hardness after quenching and tempering heat treatments; therefore, C can be added in an amount of 0.55% or more. However, if the content is excessive, the toughness of the steel sheet may decrease, so considering this, the upper limit of the C content may be limited to 0.75%. Preferably, the C content may be 0.58% to 0.72%, and more preferably, the C content may be 0.56% to 0.70%.

[0033] The content of N may be 0.01% to 0.05% by weight.

[0034] N, like C, is an element effective in improving the hardness of steel, so considering this, N may be added in an amount of 0.01% or more. However, if the N content is excessive, chromium nitride, a low-temperature precipitate, is formed and the γ phase remains, which may result in insufficient strength after strengthening heat treatment, and if the N content is excessive, fatigue resistance may be compromised, so considering this, the upper limit of the N content may be limited to 0.05%. Preferably, the N content may be 0.02% to 0.04%.

[0035] The Si content may be 0.10% to 0.80% by weight.

[0036] Si is added for the deoxidation of steel. In addition, Si is an element effective for securing strength through solid solution strengthening. Considering this, Si may be added in an amount of 0.10% or more. However, if the Si content is excessive, it may form scale on the surface of the steel during hot rolling, thereby impairing surface quality; therefore, considering this, the upper limit of the Si content may be restricted to 0.80%. Preferably, the Si content may be 0.11% to 0.70%, and more preferably 0.12% to 0.49%.

[0037] The Mn content may be 0.20% to 0.80% by weight.

[0038] Mn is a highly effective element for improving hardenability and producing solid solution strengthening effects by forming substitutional solid solutions within the matrix structure. Additionally, if the Mn content is low, it may not sufficiently combine with S (sulfur) introduced as impurities in the steel, which can cause continuous casting cracks; therefore, considering this, Mn may be added at a level of 0.20% or more. However, if the Mn content is excessive, the toughness of the steel may be degraded; therefore, considering this, the upper limit of the Mn content may be restricted to 0.80%. Preferably, the Mn content may be 0.32% to 0.70%, and more preferably 0.33% to 0.43%.

[0039] The Cr content may be 12.5% ​​to 15.5% by weight.

[0040] Cr is an effective element for improving corrosion resistance and for improving hardness and wear resistance by forming chromium carbides. Considering this, Cr can be added in an amount of 12.5% ​​or more. However, if the Cr content is excessive, hardenability may increase more than necessary, and manufacturing costs may rise. Considering this, the upper limit of the Cr content may be restricted to 15.5%. Preferably, the Cr content may be 13.0% to 15.0%.

[0041] The Ni content may be 0.01% to 0.50% by weight.

[0042] Ni is an essential element added to martensitic stainless cold-rolled annealed materials to transform the metal structure into an austenite structure in the hot working region. Additionally, Ni is an element that improves corrosion resistance and hardenability when added in trace amounts. Considering this, Ni may be added in an amount of 0.01% or more. However, if the Ni content is excessive, workability may deteriorate, and after strengthening heat treatment, an excessive amount of austenite may remain, making it difficult to secure the hardness of the product and increasing manufacturing costs. Considering this, the upper limit of the Ni content may be restricted to 0.50%. Preferably, the Ni content may be 0.11% to 0.40%, and more preferably, 0.11% to 0.25%.

[0043] The content of V may be 0.01% to 0.20% by weight.

[0044] V is an element effective in suppressing the coarsening of chromium carbides by forming carbides. Additionally, V is an element effective in preventing grain coarsening and improving wear resistance during heat treatment, so it may be included in an amount of 0.01% or more. However, if the V content is excessive, carbides may be formed more than necessary, which may lower the toughness of the steel and increase manufacturing costs; therefore, considering this, the upper limit of the V content may be restricted to 0.20%. Preferably, the V content may be 0.05 to 0.15 weight%, and more preferably 0.05% to 0.12%.

[0045] The Ti content may be 0.001% to 0.020% by weight.

[0046] Typically, since Ti is an element added to general-purpose ferritic steels such as 409L and 439 steels, even if there is no Ti component in the raw materials during the manufacture of the present invention at a steelmaking plant that produces such general-purpose steels, it may be introduced from the ladle and mold and present in small amounts. However, since Ti can combine with C to form TiC precipitates that can impair martensite strength, Ti is controlled to be 0.020% or less.

[0047] Meanwhile, the above Mo may be added in combination during steel manufacturing, and the content of Mo may be 0.01% to 0.90% by weight.

[0048] Since Mo is an element effective in improving corrosion resistance and hardenability, it may be optionally included in the present invention. Additionally, since Mo plays a role in inhibiting the refinement and growth of carbides together with V, Mo may be added at a level of 0.01% or more in consideration of this. However, if the Mo content is excessive, the manufacturing cost may increase. Considering this, the upper limit of the Mo content may be restricted to 0.90%.

[0049] The remaining component of the present invention is iron (Fe). However, since unintended impurities from raw materials or the surrounding environment may inevitably be incorporated during the ordinary manufacturing process, they cannot be excluded. As these impurities are known to any person skilled in the ordinary manufacturing process, all details thereof are not specifically mentioned in this specification.

[0050] A martensitic stainless steel cold-rolled annealed material according to one example of the present invention can satisfy the following formula (1), and has 1*10 pores per unit area 4 ea / mm 2 Up to 50*10 4 ea / mm 2 It can be included in the range.

[0051] Equation (1): 80 ≤ 3[Cr]+17[Si]+100[C]-200[V]-400[Ti] ≤ 110

[0052] (Here, [Cr], [Si], [C], [V], and [Ti] represent the content of each element)

[0053] Voids refer to empty spaces that occur within the carbide or between the carbide and the matrix. Voids existing within the carbide or between the carbide and the matrix can facilitate polishing and potentially reduce polishing time. However, if an excessive number of voids are formed, they can act as a crack source, causing cracks during polishing.

[0054] Meanwhile, Cr and C facilitate the formation of carbides, and the addition of Si can promote the formation of voids by hardening the matrix. In the case of V and Ti, they hinder the formation of carbides composed of Cr and C, thereby suppressing the formation of voids within the carbides or between the carbides and the matrix. Equation (1) above is a relational equation derived by controlling the relationship between these components and the number of voids inside the martensitic cold-rolled annealed material, that is, the number of voids per unit area. Specifically, when Equation (1) is less than 80, the number of voids per unit area is 1*10 4 If the number is less than 1, the polishing time after strengthening heat treatment increases and polishability significantly decreases, and if Equation (1) exceeds 110, the number of voids is 50*10 4 ea / mm 2 Cracks occur when polishing after heat strengthening treatment exceeding [value]. Here, a crack refers to the destruction of the material due to impact, and the presence or absence of a crack is determined by visual inspection. Accordingly, the range of the above equation (1) is controlled to 80 to 110, preferably 85 to 105, and more preferably 90 to 100, and the number of voids per unit area is 1*10 4 ea / mm 2 Up to 50*10 4 ea / mm 2 It can be, preferably 2*10 4 ea / mm 2 Up to 48*10 4 ea / mm 2 It may be. FIG. 1 is a scanning electron microscope (SEM) image showing the number of pores generated inside the carbide and between the carbide and the matrix of Invention Example 4 according to one example of the present invention. Referring to FIG. 1, the width is 24 μm and the height is 18 μm, so 432 μm 2 Since there are 18 voids per unit area, the number of voids per unit area is 4*10 4 ea / mm 2 It can be calculated as.

[0055] In addition, the average thickness of the martensitic stainless steel cold-rolled annealed material according to one example of the present invention may be 0.05 mm to 4.0 mm. The thickness of the cold-rolled annealed material was measured as the length in the vertical direction from the outermost part of one surface of the annealed material toward the opposite surface of said surface, and the average value of the thicknesses of any 10 points was defined as the average thickness of the cold-rolled annealed material.

[0056] When the thickness of the cold-rolled annealed material is less than 0.05 mm, there is a problem with the rolling load being very large, and when it exceeds 4.0 mm, there is a problem with the cold-rolled annealed material being difficult to pass through the equipment.

[0057] In addition, the martensitic stainless steel cold-rolled annealed material according to one example of the present invention may not crack when polished with a grinding wheel of #240 roughness, and the polishing time may be less than 60 seconds. The polishing conditions were such that a piece was cut to a size of 100mm x 100mm, lapping polishing was performed using a grinding wheel of #240 roughness, and the time taken to polish to a thickness of 0.5mm was measured. A lower number in the roughness index indicates a rougher polished surface, while a higher number indicates a finer polished surface. #240 roughness corresponds to the roughness of standard polishing materials that are frequently used and is generally used in the initial stages of polishing; it is used to control the flatness or thickness of the material surface rather than the gloss of the material surface. However, it is not limited to this, and if it can be expressed in a manner corresponding to the above measurement method, it may be understood by modifying it with various measurement methods.

[0058] Hereinafter, a method for manufacturing a martensitic stainless steel cold-rolled annealed material according to an example of the present invention having the alloy composition described above will be explained.

[0059] A method for manufacturing a martensitic stainless steel cold-rolled annealed material according to an example of the present invention comprises the steps of: preparing a cast billet satisfying the following formula (1), wherein, in weight percent, C: 0.55% to 0.75%, N: 0.01% to 0.05%, Si: 0.1% to 0.8%, Mn: 0.20% to 0.80%, Cr: 12.5% ​​to 15.5%, Ni: 0.01% to 0.50%, V: 0.01% to 0.20%, and Ti: 0.001% to 0.020%, and the remainder being Fe and unavoidable impurities; and reheating the cast billet at 1200°C to 1300°C for 1 to 5 hours. The method comprises the steps of: manufacturing a hot-rolled steel sheet by hot-rolling the reheated cast billet at 1000°C to 1200°C with a reduction rate of 90% to 98%; coiling the hot-rolled steel sheet at a temperature of 700°C or higher; hot-rolling annealing by maintaining at 800°C to 900°C for 3 to 10 hours, followed by maintaining at 700°C to 790°C for 5 to 15 hours; and cold-rolling annealing at 700°C to 900°C for 40 to 100 seconds.

[0060] Equation (1): 80 ≤ 3[Cr]+17[Si]+100[C]-200[V]-400[Ti] ≤ 110

[0061] (Here, [Cr], [Si], [C], [V], and [Ti] represent the content of each element)

[0062] According to a method for manufacturing a martensitic stainless steel cold-rolled annealed material according to an example of the present invention, in order to secure a thickness of 0.05 mm to 4.0 mm for the martensitic stainless steel cold-rolled annealed material, a cast billet with a thickness of 250 mm to 320 mm can be hot-rolled with a reduction rate of 90 to 98%.

[0063] The method for manufacturing a martensitic stainless steel cold-rolled annealed material of the present invention may include a coiling step after hot rolling; and a hot-rolled annealing step. The coiling step may be performed at a temperature of 700°C or higher. The hot-rolled annealing step may be a step of charging into a hot-rolled annealing furnace at a temperature of 600°C or higher, maintaining at 800°C to 900°C for 3 to 10 hours, and then maintaining at 700°C to 790°C for 5 to 15 hours to perform hot-rolled annealing.

[0064] In addition, a method for manufacturing a martensitic stainless steel cold-rolled annealed material according to an example of the present invention may further include the steps of hot-rolled pickling and cold-rolling after the hot-rolled annealing. The hot-rolled pickling may be carried out under general conditions used in the relevant technical field. In addition, in the method for manufacturing a martensitic stainless steel cold-rolled annealed material according to an example of the present invention, the total reduction rate of the entire pass of the cold-rolling may be 40% to 80%.

[0065] In addition, in the method for manufacturing a martensitic stainless steel cold-rolled annealed material according to one example of the present invention, the sum of the reduction rates of the first pass and the second pass among the total passes of the cold rolling may be 10% to 30%.

[0066] The above cold rolling annealing can be performed at 700°C to 900°C for 40 to 100 seconds. If the temperature is below 700°C or the time is less than 40 seconds during cold rolling annealing, the recrystallization growth rate is slow, resulting in excessively high hardness and low mechanical properties, and the number of voids generated inside the carbide and between the carbide and the matrix is ​​50*10 4 ea / mm 2 Exceeding this may cause cracks to occur during grinding. Additionally, if the temperature exceeds 900℃ or the cold rolling annealing time exceeds 100 seconds, non-uniform grains are formed due to an increase in grain size, making it difficult to secure strength, and the number of voids becomes 1*10 4 ea / mm2 There is a problem where the grinding time increases because it becomes less than that.

[0067] In addition, a method for manufacturing a martensitic stainless steel cold-rolled annealed material according to one example of the present invention may further include a step of strengthening heat treatment at 1000°C to 1100°C for 100 seconds to 600 seconds after the cold-rolled annealing step.

[0068] The present invention will be explained in more detail below through the following examples. However, the following examples are merely illustrative of the present invention, and the scope of the present invention is not limited thereto.

[0069] {Example}

[0070] A 200 mm thick slab having the alloy composition according to Table 1 below was reduced by 0 to 6% using an inline roller to prepare a cast billet. The cast billet was reheated at 1250°C for about 3 hours, and then hot-rolled at 1050°C to a final thickness of 5 mm. The manufactured hot-rolled steel sheet was then coiled at 700°C. The coiled coil was loaded into a hot-rolling annealing furnace at 600°C for hot-rolling annealing, held at 850°C for 10 hours, and then held at 750°C for 10 hours to perform hot-rolling annealing. Subsequently, it was pickled and cold-rolled from 5 mm to 2.5 mm with a total reduction rate of 50%, with the sum of the reduction rates of the first and second passes set to 15%. Subsequently, cold-rolled annealing heat treatment was performed at 780°C for 60 seconds, and the cross-section of the cold-rolled annealed material was observed using a scanning electron microscope (SEM) to measure the number of pores per unit area, both inside the carbide and between the carbide and the matrix. The results are shown in Table 2.

[0071] In addition, a strengthening heat treatment was performed on the cold-rolled annealed material by holding at 1050°C for 300 seconds followed by rapid cooling. The strengthened heat-treated stainless steel cold-rolled annealed material was cut into 100mm x 100mm pieces and lapping was performed using a #240 grit grinding wheel, and the time required to grind to a thickness of 0.5mm was measured. A crack refers to the failure of the material due to impact; if a crack occurred during grinding, the evaluation of the grinding time was stopped, and the occurrence of the crack is indicated in Table 2 below. It was marked with O if a crack occurred and with X if no crack occurred.

[0072] Classification CSI Mn Cr Ni Ti N Mo V Comparative Example 10.7 90.5 20.5 514.4 0.2 20.0 10.0 2-0.01 Comparative Example 20.7 10.7 70.3 215.3 0.2 80.0 10.0 3-0.02 Comparative Example 30.6 50.7 20.3 415.3 0.3 60.0 10.0 2-0.01 Comparative Example 40.6 20.7 90.4 714.7 0.2 90.0 10.0 4-0.01 Inventive Example 10.7 0.4 90.3 213.3 0.1 40.0 10.0 3-0.05 Inventive Example 20.6 70.2 30.3 715.10.1 90.0 10.0 4-0.09 Inventive Example 30.690.430.4313.30.250.010.020.070.1 Invention Example 40.730.110.41130.120.010.03-0.12 Invention Example 50.560.170.3613.60.230.010.02-0.07 Comparative Example 40.570.220.4113.50.180.020.04-0.08 Comparative Example 50.590.370.5812.60.190.010.02-0.13 Comparative Example 60.40.140.3913.50.210.010.04-0.04 Comparative Example 70.30.280.4413.10.330.010.03-0

[0073] Classification formula (1) Carbide pore count (10 4 ea / mm 2Grinding Time (seconds) | Crack Occurrence During Grinding Comparison Example 112.5.091 | Measurement Failed O Comparison Example 212.079 | Measurement Failed O Comparison Example 311.7.168 | Measurement Failed O Comparison Example 411.3.555 | Measurement Failed O Invention Example 110.4.24432X Invention Example 294.22937X Invention Example 392.21842X Invention Example 485.9447X Invention Example 581.7256X Comparison Example 577.20.776X Comparison Example 673.10.588X Comparison Example 770.90.397X Comparison Example 870.10.2125X

[0074] *Equation (1) 80 ≤ 3[Cr]+17[Si]+100[C]-200[V]-400[Ti] ≤ 110

[0075] Referring to Table 2 above, Invention Examples 1 to 5 according to the present invention satisfy the value of Equation (1), so the number of carbide pores is 1*10 4 ea / mm 2 Up to 50*10 4 ea / mm 2 It satisfied the condition, and accordingly, it was confirmed that the polishing time was drastically shortened to less than 60 seconds, while the occurrence of cracks during polishing was suppressed. In particular, Fig. 1 is a scanning electron microscope (SEM) image showing the number of pores generated inside the carbide and between the carbide and the matrix of Invention Example 4 according to the present invention. The width is 24 μm and the height is 18 μm, with a unit area of ​​432 μm. 2 Since the number of voids is 18, the number of voids per unit area is 4*10 4 ea / mm 2 It can be confirmed that cracks do not occur during grinding, and the grinding time is 47 seconds, indicating excellent grindability.

[0076] On the other hand, in Comparative Examples 1 to 4, when Equation (1) exceeds 110, the number of carbide pores per unit area is 50*10 4 ea / mm 2 It was confirmed that cracks occurred during grinding in excess.

[0077] In addition, Comparative Examples 5 to 8 have a carbon pore count of 1*10 because the value of Formula (1) according to the present invention is less than 80. 4 ea / mm 2 It was confirmed that the polishing time was very long and the polishability was inferior as it was controlled to less than [amount]. In particular, although Comparative Examples 4 and 6 satisfied the range of the alloy composition according to the present invention, they did not satisfy Equation (1), and thus showed inferior polishability depending on the number of pores of the carbide.

[0078] In addition, the number of carbide pores (10) of the final stainless cold-rolled annealed material produced by the temperature and time of cold-rolled annealing in Table 3 below, based on the composition and manufacturing method of Invention Example 1 above. 4 ea / mm 2 The grinding time and whether cracks occurred during grinding are shown in Table 3 below.

[0079] Cold rolling annealing temperature (°C) Cold rolling annealing time (seconds) Number of carbide pores (10 4 ea / mm 2 ) Grinding Time (seconds) Whether cracks occur during grinding Invention Example 1-17 20561450X Invention Example 1-27 50611648X Invention Example 1-37 80601847X Comparative Example 1-16 805562 Measurement failed O Comparative Example 1-26 606265 Measurement failed O Comparative Example 1-36 405872 Measurement failed O Comparative Example 1-49 50550.3115X Comparative Example 1-5 1000550.2109X Comparative Example 1-67 603565 Measurement failed O Comparative Example 1-77 403270 Measurement failed O Comparative Example 1-87 401100.7130X Comparative Example 1-97 601300.6142X

[0080] Invention Examples 1-1 to 1-3 satisfy a cold rolling annealing temperature of 700°C to 900°C and a cold rolling annealing time of 40 seconds to 100 seconds according to the present invention, such that the number of pores per unit area generated inside the carbide and between the carbide and the matrix is ​​1*10 4 ea / mm 2 Up to 50*10 4 ea / mm 2 It was possible to confirm that it existed.

[0081] On the other hand, Comparative Examples 1-1 to 1-3 or Comparative Examples 1-6 and 1-7 have a cold rolling annealing temperature of less than 700℃ or a cold rolling annealing time of less than 40 seconds, and accordingly, the number of carbide pores is 50*10 4 ea / mm 2 It was found that cracks occurred during grinding exceeding [amount].

[0082] In addition, Comparative Examples 1-4, 1-5 or Comparative Examples 1-8 and 1-9 had a cold rolling annealing temperature exceeding 900℃ or a cold rolling annealing time exceeding 100 seconds, so the number of carbide pores was 1*10 4 ea / mm 2 Since it is less than that, the resulting grinding time exceeds 100 seconds, so it can be confirmed that the grindability is inferior.

[0083] Although embodiments of the invention disclosed above have been illustrated and described, the disclosed invention is not limited to the specific embodiments described above, and various modifications may be made by those skilled in the art to which the disclosed invention belongs without departing from the essence claimed in the claims.

Claims

1. In weight%, C: 0.55% to 0.75%, N: 0.01% to 0.05%, Si: 0.10% to 0.80%, Mn: 0.20% to 0.80%, Cr: 12.5% ​​to 15.5%, Ni: 0.01% to 0.50%, V: 0.01% to 0.20% and Ti: 0.001% to 0.020%, the remainder comprising Fe and unavoidable impurities, and Satisfying the following equation (1), 1 x 10 voids per unit area 4 ea / mm 2 Up to 50*10 4 ea / mm 2 Martensitic stainless steel cold-rolled annealed material included in the range. Equation (1): 80 ≤ 3[Cr]+17[Si]+100[C]-200[V]-400[Ti] ≤ 110 (Here, [Cr], [Si], [C], [V], and [Ti] represent the content of each element) 2. In Claim 1, The above cold-rolled annealed material is a martensitic stainless steel cold-rolled annealed material further comprising Mo: 0.01% to 0.90% by weight.

3. In Claim 1, A martensitic stainless steel cold-rolled annealed material having an average thickness of 0.05 mm to 4.0 mm.

4. In Claim 1, #240 roughness grinding stone, a martensitic stainless steel cold-rolled annealed material that does not crack when ground.

5. In Claim 4, A martensitic stainless steel cold-rolled annealed material with a polishing time of less than 60 seconds.

6. A step of preparing a cast billet satisfying the following formula (1), comprising, in weight%, C: 0.55% to 0.75%, N: 0.01% to 0.05%, Si: 0.1% to 0.8%, Mn: 0.20% to 0.80%, Cr: 12.5% ​​to 15.5%, Ni: 0.01% to 0.50%, V: 0.01% to 0.20% and Ti: 0.001% to 0.020%, with the remainder being Fe and unavoidable impurities; A step of reheating the above cast billet at 1200℃ to 1300℃ for 1 to 5 hours; A step of manufacturing a hot-rolled steel sheet by hot-rolling the above-mentioned reheated cast billet at 1000℃ to 1200℃ with a reduction rate of 90% to 98%; A step of coiling the above hot-rolled steel sheet at a temperature of 700℃ or higher; A step of hot rolling annealing by maintaining at 800°C to 900°C for 3 to 10 hours, followed by maintaining at 700°C to 790°C for 5 to 15 hours; and A method for manufacturing a martensitic stainless steel cold-rolled annealed material, comprising the step of cold-rolling annealing at 700℃ to 900℃ for 40 seconds to 100 seconds. Equation (1) 80 ≤ 3[Cr]+17[Si]+100[C]-200[V]-400[Ti] ≤ 110 (Here, [Cr], [Si], [C], [V], and [Ti] represent the content of each element) 7. In Claim 6, A method for manufacturing a martensitic stainless steel cold-rolled annealed material, further comprising the steps of hot-rolling pickling and cold-rolling after the above hot-rolled annealing.

8. In Claim 7, The above cold rolling is a method for manufacturing a martensitic stainless steel cold-rolled annealed material, wherein the total reduction rate of the entire pass is 40% to 80%.

9. In Claim 8, A method for manufacturing a martensitic stainless steel cold-rolled annealed material, wherein the sum of the reduction ratios of the first and second passes among the total passes of the above cold rolling is 10% to 30%.

10. In Claim 6, A method for manufacturing a martensitic stainless steel cold-rolled annealed material, further comprising a step of strengthening heat treatment at 1000°C to 1100°C for 100 seconds to 600 seconds after the above cold-rolled annealing step.

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