TWI785942B - Matian loose iron series stainless steel material and manufacturing method thereof - Google Patents

Abstract

A Matian loose iron series stainless steel material, which has the following composition: on a mass basis, including C: 0.30~0.60%, Si: 0.05~1.00%, Mn: 0.05~1.50%, P: less than 0.040%, S: 0.030% Below, Cr: 13.0~18.0%, Ni: 0.01~0.30%, Mo: 0.01~1.00%, Al: below 0.030%, N: 0.010~0.350%, Ca: 0.0001~0.0030%, O: 0.001~0.010%, 2.5C+N is more than 1.10%, and the rest is composed of Fe and impurities. The average grain size of the Matian iron-based stainless steel-based carbides is 0.50 μm or less. Also, carbides with a size of 10 μm or more are 0.20 pieces/cm ² or less.

Description

Matian loose iron series stainless steel material and manufacturing method thereof

The present invention relates to a Matian loose iron series stainless steel material and a manufacturing method thereof.

Stainless steel materials used in various knives such as razors, scissors, and kitchen knives require high hardness, so Asada-san iron-based stainless steel materials with a C content are used (for example, Patent Document 1). However, if the content of C is high, carbides will be formed with alloy elements such as Cr, and they will be easily precipitated as coarse eutectic carbides during the manufacturing process. This eutectic carbide is also difficult to be completely dissolved by the annealing step and the like, and causes excessive softening due to a decrease in the solid solution amount of C during quenching. In addition, this eutectic carbide system becomes a corrosion starting point, and therefore not only reduces corrosion resistance, but also causes defects and irregular patterns to occur during processing.

Therefore, Patent Document 2 proposes an asada-san iron-based stainless steel material for knives, which is characterized by containing C: 0.40-0.50%, Si: 0.05-0.60%, Mn: 0.5-1.5%, and P: 0.035% by mass. % below, S: below 0.010%, Cr: 11.0~15.5%, Ni: 0.01~0.30%, Cu: 0.01~0.30%, Mo: 0.01~0.30%, V: 0.01~0.10%, Al: below 0.02%, Sn: 0.002~0.10%, N: 0.010~0.035%, Ca: 0.0001~0.0010%, O: 0.001~0.01%, the rest is composed of Fe and unavoidable impurities, and satisfies Cu+Ni+Mo=0.05~0.30 %, moreover, inclusions with a size of 10 μm or more are 0.2 pieces/cm ² or less.

In addition, Patent Document 3 proposes a method for producing a grain-refined Matian loose iron-based stainless steel material, which is characterized in that it includes: producing a material having Cr: 13.0 to 14.0% by weight, Mo: 1.15 to 1.35% by weight, and C: 0.35 to 0.55% by weight. % by weight, Si: 0.20~0.50% by weight, Mn: 0.20~0.50% by weight, P: 0.025% by weight or less, S: 0.020% by weight or less, remainder: base material composed of Fe and unavoidable impurity elements The step of applying at least one of the high-density transfer introduction method and the ultra-rapid solidification method to the base material, and then performing annealing treatment to obtain a fine-grained iron-steel step, applying cold rolling, After annealing and optional plastic processing into a specific shape, it is a step of quenching to obtain a fine-grained Asada-san iron series stainless steel material. [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2000-273587 [Patent Document 2] Japanese Patent Laid-Open No. 2018-9231 [Patent Document 3] Japanese Patent Laid-Open No. 2003-313612

[Problems to be Solved by the Invention]

However, in the Matian iron-based stainless steel material described in Patent Document 2, since the average grain size of inclusions (especially carbides) is not controlled, workability is insufficient, and irregular patterns may occur. In addition, the Matian loose iron-based stainless steel material described in Patent Document 3 is not suitable for mass production due to the introduction of special steps such as the high-density transfer method or the ultra-rapid solidification method. In addition, the Matian loose iron-based stainless steel material has a large Mo content and is also expensive. In this way, the above-mentioned problem occurs in the conventional Matian loose iron-based stainless steel material in which the C content is reduced.

The present invention was made in order to solve the above-mentioned problems, and an object thereof is to provide an Asada loose iron-based stainless steel material that has good workability, high hardness and corrosion resistance after quenching or quenching and tempering, and can suppress the occurrence of irregular patterns, and a manufacturing method thereof . [means to solve the problem]

The inventors of the present invention have devoted themselves to the study of Matian loose iron series stainless steel, and found that among the inclusions, especially the carbide system is closely related to corrosion resistance, processability and irregular patterns. , Also control the number of carbides with a size of 10 μm or more and the average particle size of carbides, which can completely solve the above problems, and finally complete the present invention.

That is, the present invention is a Matian loose iron series stainless steel material, which has the following composition: on a mass basis, including C: 0.30~0.60%, Si: 0.05~1.00%, Mn: 0.05~1.50%, P: 0.040% Below, S: below 0.030%, Cr: 13.0~18.0%, Ni: 0.01~0.30%, Mo: 0.01~1.00%, Al: below 0.030%, N: 0.010~0.350%, Ca: 0.0001~0.0030%, O : 0.001~0.010%, 2.5C+N is 1.10% or more, the rest is composed of Fe and impurities, the average particle size of carbides is 0.50 μm or less, and the aforementioned carbides with a size of 10 μm or more are 0.20 pieces/cm ² or less.

[發明的效果] In addition, the present invention is a method for producing a Matian loose iron-based stainless steel material, which includes a hot rolling step in which the flat steel billet is heat-treated for 1 to 5 hours at a temperature above T represented by the following formula (1), and then hot-rolled, The flat billet has the following composition: based on the quality, it contains C: 0.30~0.60%, Si: 0.05~1.00%, Mn: 0.05~1.50%, P: 0.040% or less, S: 0.030% or less, Cr: 13.0 ~18.0%, Ni: 0.01~0.30%, Mo: 0.01~1.00%, Al: below 0.030%, N: 0.010~0.350%, Ca: 0.0001~0.0030%, O: 0.001~0.010%, 2.5C+N is More than 1.10%, the rest is composed of Fe and impurities.

[Effect of the invention]

According to the present invention, there can be provided a Matian loose iron-based stainless steel material and a manufacturing method thereof, which have good workability, high hardness and corrosion resistance after quenching or quenching and tempering, and can suppress the occurrence of irregular patterns.

[Mode of Carrying Out the Invention]

Embodiments of the present invention will be specifically described below. The present invention is not limited to the following embodiments, and within the scope of not departing from the gist of the present invention, according to the common knowledge of those skilled in the art, those who appropriately modify, improve, etc. the following embodiments should also be understood as belonging to the scope of the present invention . In addition, "%" indication about a component in this specification means "mass %" unless otherwise specified.

The Matian loose iron-based stainless steel material according to the embodiment of the present invention has the following composition: C: 0.30~0.60%, Si: 0.05~1.00%, Mn: 0.05~1.50%, P: 0.040% or less, S: 0.030% or less , Cr: 13.0~18.0%, Ni: 0.01~0.30%, Mo: 0.01~1.00%, Al: below 0.030%, N: 0.010~0.350%, Ca: 0.0001~0.0030%, O: 0.001~0.010%, 2.5 C+N is more than 1.10%, and the rest is composed of Fe and impurities.

Here, in this specification, the term "steel material" refers to materials of various shapes such as steel plates. Also, the so-called "steel plate" includes the concept of steel strip. Furthermore, the so-called "impurities" refer to components that are mixed in due to raw materials such as ores and scraps, and various main factors in the manufacturing process when stainless steel materials are produced industrially, and those that are permitted within the scope of not causing adverse effects on the present invention . Examples of impurities include Zn, Pb, Se, Sb, H, Ga, Ta, Mg, Zr, and the like. When these elements are contained as impurities, Zn≦100ppm, Pb≦100ppm, Se≦100ppm, Sb≦500ppm, H≦100ppm, Ga≦500ppm, Ta≦500ppm, Mg≦120ppm, Zr≦120ppm.

In addition, the Matian iron-based stainless steel material according to the embodiment of the present invention may further contain V: 0.50% or less, Nb: 0.30% or less, Ti: 0.3% or less, Cu: 4.0% or less, Sn: 0.100% or less, B: 0.0050% % or less, Co: less than 0.30% or more. Hereinafter, each component is demonstrated in detail.

<C: 0.30~0.60%> C is an element necessary for obtaining a specified hardness (Vickers hardness) after quenching or quenching and tempering. In order to stably obtain a hardness of 500HV or more, the C content must be set to 0.30% or more. If C is added too much, the sharpening during quenching will be accelerated and the corrosion resistance will be impaired. At the same time, the toughness after quenching or tempering will also decrease due to the lack of solid solution of carbonitrides. Therefore, the content of C must be set to 0.60% or less. Considering the decrease in hardness or toughness caused by changes in heating conditions during quenching or quenching and tempering, the lower limit of the C content is preferably 0.32%, and the upper limit is preferably 0.58%.

<Si: 0.05~1.00%> Si is an element necessary for deoxidation during melting and refining, and is also an element useful for suppressing the formation of an oxide film during quenching. Also, when the Si content is low, deoxidation tends to be insufficient, and carbides increase, and rust may occur starting from them, resulting in lowered corrosion resistance. Therefore, the content of Si must be made 0.05% or more. On the other hand, the Si-based system narrows the temperature range of the single-phase ferrite and impairs the quenching stability, so the content of Si must be set to 1.00% or less. From the viewpoint of stably obtaining the above-mentioned effects due to Si, the lower limit of the Si content is preferably 0.07%, and the upper limit is preferably 0.98%.

<Mn: 0.05~1.50%> The Mn series is an element added as a deoxidizer, and at the same time helps to expand the single-phase domain of Vostian iron to improve hardenability. If Mn is not added sufficiently, the two-phase region will expand and the α phase will increase. As a result, Cr carbonitrides also increase, and a Cr-deficient layer is formed around them, which tends to be the starting point of rust and lowers the corrosion resistance. Therefore, it is necessary to make the content of Mn 0.05% or more. From the viewpoint of stably obtaining the above-mentioned effect due to Mn, the lower limit of the Mn content is preferably 0.07%. On the other hand, Mn-based metals exceeding the requirements lower the corrosion resistance, promote the formation of an oxide film during quenching, and increase the subsequent grinding load. Therefore, it is necessary to set the content of Mn to 1.50% or less. In consideration of the decrease in corrosion resistance due to grains such as MnS, it is preferably 1.45% or less.

＜P: 0.040% or less＞ P is an element contained as an impurity in a main raw material such as molten iron or ferrochrome as a raw material. It is an element harmful to the toughness and corrosion resistance of hot-rolled annealed sheet or quenched material. Therefore, the content of P must be set to 0.040% or less, preferably 0.038% or less. On the other hand, the lower limit of the P content is not particularly limited, but excessive reduction will cause problems such as the need to use high-purity raw materials, resulting in increased costs, so the lower limit of the P content is preferably 0.010%.

<S: 0.030% or less> The S series forms sulfide-based inclusions and deteriorates the general corrosion resistance (general corrosion or pitting corrosion) of steel materials. In addition, the S series lowers the hot workability and increases the edge cracking sensitivity of the hot-rolled sheet. Therefore, the S content must be set at 0.030% or less, preferably 0.025% or less. Also, the lower limit of the S content is not particularly limited, but the lower the S content, the better the corrosion resistance, but on the other hand, the desulfurization load increases and the manufacturing cost increases. Therefore, the lower limit of the S content is preferably 0.001%.

<Cr: 13.0~18.0%> Cr is an element used to maintain the corrosion resistance required for the main application of Matian iron-based stainless steel materials. Therefore, the content of Cr must be set to 13.0% or more. On the other hand, from the standpoint of suppressing the generation of residual washer after quenching, the Cr content must be set to 18.0% or less. From the viewpoint of stably obtaining the above-mentioned effects due to Cr, the lower limit of the Cr content is preferably 13.1%, and the upper limit is preferably 17.8%.

<Ni: 0.01~0.30%> Like Mn, the Ni system is an element for stabilizing ferrite, and also has the effect of improving the toughness after quenching or quenching and tempering. On the other hand, if Ni is contained in a large amount, the press formability of the hot-rolled annealed sheet will be reduced due to solid solution strengthening, and at the same time, the production cost will increase because it is an expensive element. Therefore, the content of Ni must be made 0.30% or less. On the other hand, Ni is an element effective in suppressing the progression of pitting corrosion. From the viewpoint of stably obtaining the above-mentioned effect due to Ni, the lower limit of the Ni content is preferably 0.02%, and the upper limit is preferably 0.27%.

<Mo: 0.01~1.00%> Mo is an element effective in improving the corrosion resistance of the mosaic iron structure containing δ ferrite. From the viewpoint of obtaining this effect, it is necessary to make the content of Mo 0.01% or more. On the other hand, Mo is a stabilizing element of the ferrite phase, and excessive addition narrows the temperature range of the single-phase ferrite phase and impairs the quenching properties. Therefore, the content of Mo needs to be 1.00% or less. From the viewpoint of stably obtaining the above-mentioned effect by Mo, the lower limit of the Mo content is preferably 0.02%, and the upper limit is preferably 0.50%, more preferably 0.30%.

＜Al: less than 0.030%＞ In addition to being added as a deoxidizing element, Al is also an element that improves oxidation resistance. However, when Al is contained in a large amount, carbides tend to become larger. Therefore, the content of Al must be 0.030% or less, preferably 0.025% or less, more preferably 0.020% or less. On the other hand, the lower limit of the content of Al is not particularly limited, and Al may not be contained. However, from the viewpoint of obtaining the above-mentioned effect due to Al, the lower limit of Al is preferably 0.001%. Here, Al is T.Al.

<N: 0.010~0.350%> Like C, N is an element necessary for obtaining a predetermined hardness (Vickers hardness) after quenching or quenching and tempering. In particular, in the embodiment of the present invention, in order to reduce the content of C, it is necessary to contain N as its substitute. In addition, when N is in solid solution, it also has the effect of improving corrosion resistance. From the viewpoint of obtaining these effects, the content of N must be 0.010% or more. However, the N-based may form Cr-based nitrides to form a Cr-deficient layer, which lowers the corrosion resistance in those cases. Also, if N is added excessively, the control system at the steelmaking stage becomes difficult, and bubble-based defects tend to be formed. If bubble-based defects are formed, they are likely to become the starting point of rust, and not only the corrosion resistance is lowered, but also the yield rate may be lowered. Therefore, the content of N must be set to 0.350% or less. From the viewpoint of stably obtaining the above-mentioned effects due to N, the lower limit of the N content is preferably 0.020%, more preferably 0.025%, and most preferably 0.036%, and the upper limit is preferably 0.300%, more preferably The best is 0.290%.

<Ca: 0.0001~0.0030%> Ca is added for composition adjustment in the steelmaking stage, and it acts as a powerful deoxidizing material, and has the effect of promoting deoxidation. However, since Ca is a powerful deoxidizing element, most of it floats up in the molten steel as inclusions, and hardly remains in the steel. However, if a large amount of Ca is added, CaO is contained in steelmaking inclusions, which is highly likely to be a starting point of rust, and the corrosion resistance is lowered. Therefore, the content of Ca must be 0.0030% or less, preferably 0.0010% or less. On the other hand, since it is impossible to remove even fine inclusions, it is difficult in the manufacturing process to make the content of Ca less than 0.0001%. Therefore, the content of Ca is made 0.0001% or more.

<O: 0.001~0.010%> In order to reduce inclusions, O is an important element together with Al and Ca. When a large amount of O is added, the number of large inclusions (especially carbides) remaining in the steel increases, which adversely affects the corrosion resistance. Therefore, the O content must be set to 0.010% or less. In addition, O should be reduced as much as possible, but excessive reduction will increase the cost, so the content of O is set at 0.001% or more. From the viewpoint of the balance between cost and corrosion resistance, the lower limit of the O content is preferably 0.002%, and the upper limit is 0.009%.

＜2. 5C+N is more than 1.10%＞ C and N are elements necessary to obtain a predetermined hardness (Vickers hardness) after quenching or quenching and tempering as described above. In the embodiment of the invention, the content of N is reduced instead of C, and C contributes 2.5 times of N to the hardness. Therefore, from the viewpoint of the obtained specified hardness, 2.5C+N must be 1.10% or more, preferably 1.25% or more. Also, the upper limit of 2.5C+N is not particularly limited, but is preferably 1.80%, more preferably 1.70%, and most preferably 1.60%.

<V: 0.50% or less> The V series forms fine carbonitrides and contributes to the formation of elements that improve corrosion resistance, and can be added as needed. However, if V is added excessively, there is a possibility that the precipitates will be coarsened, and as a result, the toughness after quenching will decrease. Therefore, the content of V is 0.50% or less, preferably 0.30% or less, more preferably 0.20% or less. Also, the lower limit of the V content is not particularly limited, but V is mixed into the alloy raw material as an unavoidable impurity, and it is difficult to remove it in the refining step. Also, from the viewpoint of obtaining the above effects, the lower limit of the V content is preferably 0.01%, more preferably 0.02%, and most preferably 0.03%.

<Nb: 0.30% or less> Nb is an element that forms carbonitrides and suppresses sensitization or reduction in corrosion resistance due to precipitation of chromium carbonitrides, and is added as necessary. However, if Nb is added excessively, the transformation of mosaic iron will be unstable and the hardness will decrease. Therefore, the content of Nb is 0.30% or less, preferably 0.28% or less, more preferably 0.25% or less. Also, the lower limit of the Nb content is not particularly limited, but from the viewpoint of obtaining the above effects, it is preferably 0.01%, more preferably 0.05%.

<Ti: 0.3% or less> Ti is an element that forms carbonitrides and suppresses sensitization or reduction in corrosion resistance due to precipitation of chromium carbonitrides, and is added as necessary. However, if Ti is added excessively, coarse TiN is formed, causing hot-rolling flaws and a decrease in toughness. Therefore, the content of Ti is set to be 0.3% or less, preferably 0.25% or less. Also, the lower limit of the Ti content is not particularly limited, but from the viewpoint of obtaining the above effects, it is preferably 0.01%, more preferably 0.06%, and most preferably 0.10%.

<Cu: 4.0% or less> Cu is an element that is effective in improving the corrosion resistance of the Matian iron structure containing δ ferrite, and is also an element that contributes to the improvement of the hardenability as a stabilizing element of the ferrite, and is added as needed. However, excessive addition of Cu will result in a reduction in hot workability or an increase in raw material costs. Therefore, the content of Cu is 4.0% or less, preferably 3.8% or less, more preferably 3.5% or less. Furthermore, the lower limit of the content of Cu is not particularly limited, but from the viewpoint of obtaining the above effects, it is preferably 1.0%, more preferably 1.3%, and most preferably 1.5%.

<Sn: 0.100% or less> Sn is an element effective in improving the corrosion resistance after quenching or quenching and tempering, and is added as necessary. However, excessive addition of Sn promotes edge cracking during hot rolling. Therefore, the Sn content is set to be 0.100% or less, preferably 0.090% or less. Also, the lower limit of the content of Sn is not particularly limited, but from the viewpoint of obtaining the above effects, it is preferably 0.002%, more preferably 0.050%.

<B: 0.0050% or less> B is an element effective in improving hot workability, which can be added as needed. However, excessive addition of B may lower the hardenability due to complex precipitation of borides and carbides. Therefore, the content of B is set to be 0.0050% or less, preferably 0.0045% or less. Also, the lower limit of the B content is not particularly limited, but is preferably 0.0002% from the viewpoint of obtaining the above effects.

＜Co: 0.30% or less＞ Co is an element that improves heat resistance, and is added as needed. However, since Co is expensive, if the content of Co is too high, the production cost will increase. Therefore, the content of Co is 0.30% or less, preferably 0.10% or less, more preferably 0.05% or less. Also, the lower limit of the Co content is not particularly limited, but is preferably 0.01% from the viewpoint of obtaining the above effects.

The average grain size of the Matian loose iron-based stainless steel material-based carbides according to the embodiment of the present invention is 0.50 μm or less, preferably 0.48 μm or less. By controlling the average particle size of the carbides within such a range, the workability of Matian loose iron series stainless steel is improved, and the chipping of the blade during tool manufacturing (especially during sharpening processing) is suppressed, and the occurrence of irregular patterns is also suppressed. . The lower limit of the average particle size of carbides is not particularly limited, but is preferably 0.01 μm, more preferably 0.05 μm, and most preferably 0.10 μm. Here, the carbides with a predetermined average particle size are intended to be both eutectic carbides formed during casting and precipitated carbides formed during the rolling step. In addition, the average grain size of carbides can be calculated by observing the cross-section of Matian loose-iron stainless steel material with SEM, measuring the circle-equivalent diameter of each carbide in the observation field, and calculating the average value.

In the Matian loose iron-based stainless steel material according to the embodiment of the present invention, the number of carbides with a size of 10 μm or more is 0.20 pieces/cm ² or less, preferably 0.19 pieces/cm ² or less. Since carbides with a size of 10 μm or more tend to be the origin of rust, by controlling the number of carbides with a size of 10 μm or more within such a range, rusting can be suppressed and corrosion resistance can be improved. Furthermore, since the carbides with a size of 10 μm or more are as small as possible, there is no particular limitation, but generally, it is 0.01 carbides/cm ² or more. Here, the predetermined number of carbides of 10 μm or more are mainly eutectic carbides formed during casting. In addition, the size of the carbide refers to (longer diameter+shorter diameter)/2 of the carbide. In addition, the number of carbides with a size of 10 μm or more can be calculated by observing the cross section of Matian iron-based stainless steel with an optical microscope, finding the number of carbides with a size of 10 μm or more, and dividing the number by the area of the measurement region.

The hardness (Vickers hardness) after quenching or quenching and tempering of the Asada loose iron series stainless steel material according to the embodiment of the present invention is 500 HV or more. In particular, when using Matian iron-based stainless steel as a knife, the hardness is preferably 550 HV or higher. Also, the upper limit of the hardness is not particularly limited, but is preferably 900HV, more preferably 800HV. Here, quenching is carried out at 1000~1100°C. Tempering is carried out at 100~400°C. After quenching, subzero treatment should be carried out at -200~-50°C. In addition, hardness means the value measured at room temperature (25 degreeC) using the Vickers hardness meter.

The Matian loose iron-based stainless steel material in the embodiment of the present invention is not particularly limited, but is preferably a hot-rolled sheet, a hot-rolled annealed sheet, a cold-rolled sheet, or a cold-rolled annealed sheet.

藉由在如此的條件下進行熱處理，由於可使在鑄造時所生成的共晶碳化物完全地溶體化，故可將碳化物的平均粒徑及大小10μm以上的碳化物之數控制在上述範圍。 The Matian iron-based stainless steel material according to the embodiment of the present invention includes heat treatment for 1 to 5 hours on a flat steel billet having the same composition as the above-mentioned Asada loose iron-based stainless steel material at a temperature equal to or higher than T represented by the following formula (1). The hot rolling step of hot rolling. By performing this hot rolling step, a hot rolled sheet can be obtained.

By performing heat treatment under such conditions, since the eutectic carbides generated during casting can be completely dissolved, the average grain size of carbides and the number of carbides with a size of 10 μm or more can be controlled to the above-mentioned scope.

The conditions of the hot rolling are not particularly limited, but it is preferably finished to a plate thickness of 2~8mm by rough rolling and finish rolling. After hot rolling, the hot rolled sheet is coiled at a coiling temperature of 800°C~900°C. The rolled hot-rolled sheet is in the shape of a coil.

式中、各元素符號為各元素的質量%。 尚且，軟質化步驟所得之熱軋退火板係視需要可進行酸洗。 After the hot-rolling step, the coil-shaped hot-rolled sheet is subjected to a softening step of annealing at a temperature from Ac1 point to (Ac1 point-50° C.) for 1 to 5 hours. By performing this softening step, a hot-rolled annealed sheet can be obtained. In addition, by performing annealing under such conditions, since the coarsening of carbides is suppressed, the average grain size of carbides and the number of carbides having a size of 10 μm or more can be stably controlled within the above-mentioned ranges. Annealing is carried out by keeping the coil-shaped hot-rolled sheet in a heated state at a temperature from Ac1 point to (Ac1 point-50°C). Therefore, it should be noted that annealing is not carried out by heating the coil-shaped hot-rolled sheet to the temperature once it is cooled. Also, the annealing can be performed in a batch annealing furnace. Here, the Ac1 point is calculated by the following formula (2).

In the formula, the symbol of each element is the mass % of each element. Furthermore, the hot-rolled annealed sheet obtained in the softening step can be pickled if necessary.

After the softening process, a cold rolling process of performing cold rolling on the hot-rolled annealed sheet after pickling as necessary is performed. By performing a cold rolling step, a cold rolled sheet can be obtained. The conditions of cold rolling are not particularly limited, as long as they are appropriately adjusted according to the required cold rolled sheet.

After the cold rolling step, the cold-rolled sheet is heated in the temperature range from 100°C to Ac1 point ~ (Ac1 point-50°C) at a heating rate of 50°C/s or more, preferably 100°C/s or more the annealing step. In addition, annealing may be started from the state of the cold-rolled sheet in the temperature range of room temperature (25 degreeC) or more and less than 100 degreeC. By performing this annealing step, a cold-rolled annealed sheet can be obtained. Also, by performing the annealing step under such conditions, since the coarsening of carbides is suppressed, the average grain size of carbides and the number of carbides having a size of 10 μm or more can be stably controlled within the above-mentioned ranges.

The Asada loose iron-based stainless steel material according to the embodiment of the present invention manufactured as described above, in addition to the steel composition, the number of carbides with a size of 10 μm or more and the average particle size of the carbides are controlled within a specific range, so the workability is improved. Good, at the same time after quenching or quenching and tempering, the hardness and corrosion resistance are high, and the occurrence of irregular patterns can be suppressed. [Example]

Hereinafter, examples are given to describe the content of the present invention in detail, but the present invention is not limited and interpreted by these.

The steel with the steel composition shown in Table 1 was melted and cast into a 200 mm thick flat billet. After the slab is heat-treated at the temperature and time shown in Table 2, it is hot-rolled (rough rolling and finish rolling) to become a hot-rolled sheet with a thickness of 3mm, and is coiled at a coiling temperature of 850°C. shape. Next, this coil-shaped hot-rolled sheet was moved to a batch annealing furnace, and the softening step was performed at the temperature and time shown in Table 2. Next, after the hot-rolled annealed sheet obtained in the softening step by cold rolling, the annealing step is performed by heating the cold-rolled sheet at the temperature increase rate shown in Table 2 in the temperature range from 100°C to the temperature shown in Table 2 . In addition, the annealing system starts from the state where the cold-rolled sheet is at room temperature (25° C.). Then, pickling is performed. The following evaluation was performed about the obtained cold-rolled annealed sheet (Matian iron series stainless steel material).

(hardness) The obtained cold-rolled annealed sheet was heated to 1000 to 1100°C and quenched, the surface was ground with #80, and the JIS surface hardness (quenching hardness) was measured with a Vickers hardness meter. The measurement temperature was set to room temperature (25° C.). Hardness above 500HV is regarded as qualified.

(corrosion resistance) For the obtained cold-rolled annealed sheet, after heating to 1000~1100°C and quenching, the surface is polished with #600, and the salt spray test is carried out according to JIS Z2371: 2015 "Salt spray test method" for 24 hours, and the rust area ratio is measured. . In the evaluation, less than 10% of the rusted area ratio was regarded as pass (◯), and more than 10% was regarded as fail (x).

(average particle size of carbide) Observing the section parallel to the rolling direction and thickness direction of the obtained cold-rolled annealed sheet by SEM, among the observed carbides in the observation field, the carbide particles and particles with a circle equivalent diameter of less than 0.10 μm are removed Part of the carbide particles protruding from the observation field, take all the carbide particles as the measurement object, measure the circle equivalent diameter (μm), divide the sum of the circle equivalent diameters of the carbide particles of the measurement object by the carbonization of the measurement object The value obtained from the total number of carbide particles is regarded as the average particle diameter (μm) of carbides. However, the total number of carbide particles to be measured is considered to be 100 or more by arbitrarily selecting a number of non-overlapping observation fields of view. The circle-equivalent diameter of carbide particles is calculated from the calculated area of carbide particles by processing SEM images with image processing software.

(Number of the aforementioned carbides with a size of 10 μm or more) For the section parallel to the rolling direction and thickness direction of the obtained cold-rolled and annealed sheet, use an optical microscope ×50 times to visually observe 20 areas of 50mm × 50mm each, calculate the average number, and divide by the observed area area is calculated.

(processability) The obtained cold-rolled annealed sheet is stamped into a knife shape, and the steel material is collected, heated at 1000~1100°C and quenched. Next, the surface of the steel material was ground, and one end surface in the longitudinal direction was wet-grinded to obtain a test material (knife). In the sharpening process, those with no chipping were regarded as pass (○), and those with chipping were regarded as unacceptable (×).

(irregular pattern) The test material (knife) was obtained by the same method as the processability. The test material was visually observed for appearance, and those with no irregularities on the blade surface were judged to be acceptable (◯), and those with irregularities on the blade surface were judged to be unacceptable (×). Table 3 shows the respective evaluation results mentioned above.

As shown in Table 3, the cold-rolled annealed sheets (Matian iron-based stainless steel materials) of Examples 1-23 have good hardness and corrosion resistance after quenching. In addition, these cold-rolled annealed sheets have a small average particle size of carbides and a small number of carbides with a size of 10 μm or more, so there is no edge chipping during sharpening processing, and the workability is good. Occurrence of irregular patterns on the surface. On the other hand, in Comparative Examples 1 to 14, any of the cold-rolled annealed steel composition, the average particle size of carbides, and the number of the aforementioned carbides with a size of 10 μm or more was outside the specified range, and the hardness or corrosion resistance after quenching Sexual inadequacy. In particular, when the average grain size of carbides is large and the number of carbides with a size of 10 μm or more is large, chipping occurs during sharpening, resulting in insufficient workability and irregular patterns on the tool surface.

Here, in FIG. 1, the graph of the relationship between 2.5C+N and hardness in the said Example and a comparative example is shown. As shown in Figure 1, there is a proportional relationship between 2.5C+N and hardness. It can be seen that by increasing 2.5C+N, the hardness tends to increase. In particular, it turns out that by controlling 2.5C+N to 1.10% or more, the hardness can be made 500HV or more.

As can be seen from the above results, according to the present invention, there can be provided a Matian loose iron-based stainless steel material and a manufacturing method thereof, which have good workability, and at the same time have high hardness and corrosion resistance after quenching or quenching and tempering, and can suppress the occurrence of irregular patterns. .

[ Fig. 1 ] is a graph showing the relationship between 2.5C+N and hardness in Examples and Comparative Examples.

Claims (8)

A Matian loose iron series stainless steel material, which has the following composition: on a mass basis, including C: 0.30~0.60%, Si: 0.05~1.00%, Mn: 0.05~1.50%, P: less than 0.040%, S: 0.030% Below, Cr: 13.0~18.0%, Ni: 0.01~0.30%, Mo: 0.01~1.00%, Al: below 0.030%, N: 0.010~0.350%, Ca: 0.0001~0.0030%, O: 0.001~0.010%, 2.5C+N is 1.10% or more, the remainder is composed of Fe and impurities, the average particle size of carbides is 0.50 μm or less, and the aforementioned carbides with a size of 10 μm or more are 0.20 pieces/cm ² or less. For example, the Matian loose iron-based stainless steel material in claim 1, which is based on quality, further includes V: 0.50% or less, Nb: 0.30% or less, Ti: 0.3% or less, Cu: 4.0% or less, Sn: 0.100% or less, One or more of B: 0.0050% or less, and Co: 0.30% or less. For example, the Matian loose iron series stainless steel material in claim 1 or 2 has a hardness of 500HV or more after quenching or quenching and tempering. Such as the Matian loose iron series stainless steel material of claim 1 or 2, wherein the aforementioned Matian loose iron series stainless steel material is used for knives. A method for manufacturing Matian loose iron-based stainless steel, which includes a hot rolling step in which a flat steel billet (slab) is heat-treated for 1 to 5 hours at a temperature above T represented by the following formula (1), and then hot-rolled. The billet has the following composition: Based on the quality, it includes C: 0.30~0.60%, Si: 0.05~1.00%, Mn: 0.05~1.50%, P: below 0.040%, S: below 0.030%, Cr: 13.0~18.0% %, Ni: 0.01~0.30%, Mo: 0.01~1.00%, Al: less than 0.030%, N: 0.010~0.350%, Ca: 0.0001~0.0030%, O: 0.001~0.010%, 2.5C+N is 1.10% Above, the remaining part is composed of Fe and impurities;

. For example, the manufacturing method of Matian loose iron-based stainless steel material in Claim 5, wherein the aforementioned flat steel blank system further includes V: 0.50% or less, Nb: 0.30% or less, Ti: 0.3% or less, Cu: 4.0% or less , Sn: 0.100% or less, B: 0.0050% or less, and Co: 0.30% or less. The manufacturing method of Matian loose iron series stainless steel according to claim 5 or 6, wherein after the hot-rolled sheet is coiled at a coiling temperature of 800°C to 900°C in the aforementioned hot rolling step, it is further included at Ac1 point~(Ac1 The softening step of annealing at a temperature of -50°C) for 1 to 5 hours. The manufacturing method of Matian loose iron series stainless steel material as claimed in item 7, which further includes: The cold-rolling step of the hot-rolled annealed sheet obtained by cold-rolling the aforementioned softening step, and An annealing step in which the cold-rolled sheet obtained in the aforementioned cold-rolling step is heated in a temperature range from 100°C to Ac1 point to (Ac1 point-50°C) at a heating rate of 50°C/sec or more.

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