JP2002155346A - High strength stainless steel for subzero treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide high strength stainless steel for subzero treatment in which the modification of shape is easily performance, the increase of strength can easily be attained after working, and also, good surface properties can be obtained even if polishing is performed thereto. SOLUTION: The components in the steel are controlled so as to contain, by weight, 0.09 to 0.17% C, <=1.0% Si, <=1.5% Mn, 4.0 to 7.0% Ni, 14.0 to 17.0% Cr, <=0.10% N and 0.001 to 0.010% B, and the balance Fe with inevitable impurities. Also, the contents of C, Si, Mn, Ni, Cr and N are controlled so that AHV value and SHV value defined by AHV value = 985-135C-14Si-30Mn-43 Ni-29Cr-265N, and SHV value = 1882-255C-43Si-101Mn-70Ni-55Cr-921 N reach the ranges of <=250 in AHV value, and <=350 in HV value. Further, K value = 99-15Si-3Mn-4Cr-94(C+N)-980B is desirably made higher than zero.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a high-strength stainless steel for cryogenic treatment, which is soft in an annealed state and exhibits high strength by cryogenic treatment.

[0002]

2. Description of the Related Art In recent years, applications of stainless steel have been extensively expanded to various fields by utilizing its excellent characteristics.
In order to further expand such applications, it is necessary to develop stainless steel having a plurality of excellent properties. For example, in addition to corrosion resistance, stainless steel polished products require high strength, strict product shapes, and excellent surface properties after polishing. Therefore, development of a high-strength stainless steel having excellent shape correcting properties and surface cleanliness is desired. In addition, stainless steel electronic device parts are required to have high strength and workability for suitably performing punching and the like.

[0003] Conventionally, stainless steel having high strength has SUS4, which is designed to increase the strength by quenching from a high temperature.
Martensitic stainless steel such as 20J2 and SU
Production of work hardening stainless steels such as S301 and SUS304, age hardening stainless steels such as SUS630 and SUS631, and cryogenically processed stainless steels that increase strength by low-temperature quench hardening and subsequent age hardening. Have been.

[0004] Martensitic stainless steel such as SUS420J2 has a high C content and thus has a high hardness after quenching, but has a large quenching distortion, so that the shape of a large plate tends to collapse. In the annealed state, the ferrite phase and C
Since it has a structure composed of r carbide, it is soft as a whole, but the Cr carbide itself is hard, so that a punching jig is greatly worn in applications requiring punchability. Therefore, it has not been generally used in applications requiring precise punching properties.

[0005] Work-hardening stainless steels such as SUS301 and SUS304 increase the strength by producing work-induced martensite by cold rolling.
High strength before being processed into a product and poor ductility. Therefore, the degree of processing in the final product is limited, and the punching jig and the like are damaged quickly in precision punched parts. Also,
The shape greatly depends on the capacity of the cold rolling mill, the rolling method, and the like, and it is difficult to obtain a shape having excellent flatness. Furthermore, even if the shape is corrected after cold rolling, the shape is not sufficiently corrected because of high strength.

[0006] Age hardening stainless steels such as SUS630 and SUS631 have relatively soft hardness before aging treatment, so that their shapes can be modified more sufficiently than SUS301, and the strength can be further improved by aging treatment. Can rise. However, since this stainless steel contains Nb, Al, and the like, carbonitrides and oxides are recognized even before aging treatment, and the stainless steel has not yet been used in general in applications requiring precise punching properties. In addition, since this aging treatment is generally performed in a temperature range of 400 to 900 ° C., not only the formation of precipitates but also the formation of carbonitrides and the like occur simultaneously. These precipitates and carbonitrides reduce the surface cleanliness, and thus cause surface defects in stainless steel mirror-polished products and applications where the surface properties are strictly required. Therefore, it is difficult to apply age-hardened stainless steel to a mirror-polished stainless steel product.

[0007] Cryogenically treated stainless steel is disclosed in
As disclosed in JP-A-293143 and JP-A-4-214842, since the martensite phase is formed by quenching at a low temperature to increase the strength,
It is relatively soft before quenching and has good shape-correcting properties. Further, since the quenching temperature is low, for example, -50 ° C. or less, the hardening treatment can be performed without causing the formation of carbonitride or the like during the quenching.

[0008] These prior arts have the following problems. The cryogenically treated stainless steel disclosed in Japanese Patent Application Laid-Open No. 63-293143 contains a large amount of any of Mn, Cu and Mo.
It is easy to form an S, Cu rich phase, Fe ₂ Mo, and the like.
Also in cryogenic processing stainless steel disclosed in JP-A 4-214842 and JP purpose of improvement of hardenability, Si, since the large amount of added Mn and B, SiO _2, MnS And Cr ₂ B and the like are easily formed. These inclusions and the second phase become surface defects in applications having severe surface properties, such as mirror-polished stainless steel products, and lower the product yield. In applications where severe processing is performed, surface defects occur and the punching jig is worn. Therefore, it is difficult to apply the cryogenically processed stainless steel disclosed in the prior art to a mirror-polished product and a precision stamped product.

As described above, in applications where high strength, workability capable of suitably performing punching and the like, strict product shape, and excellent surface properties after polishing are required, the current stainless steel is used. At present, steel grades satisfying all characteristics have not been obtained.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to make it easy to correct the shape and to have excellent workability such as punching.
An object of the present invention is to provide a high-strength stainless steel for cryogenic treatment, which can easily achieve high strength after processing and can obtain good surface properties even after polishing.

[0011]

The present invention according to claim 1 is characterized in that, by weight%, C: 0.09 to 0.17%, Si: 1.
0% or less, Mn: 1.5% or less, Ni: 4.0 to 7.0
%, Cr: 14.0 to 17.0%, N: 0.10% or less, B: 0.001 to 0.010%, the balance being F
e and unavoidable impurities, and AHV value = 985-135C-14Si-30Mn-43Ni-29Cr-265
N SHV value = 1 882−255C−43Si−101Mn−70Ni−55Cr−
AHV value and SHV value defined by 921N are AHV value ≦ 25
0, C, Si, M so that SHV value ≧ 350
It is a high-strength stainless steel for cryogenic treatment characterized by containing n, Ni, Cr and N.

According to the present invention, the content of each element is set so as to sufficiently satisfy the component range of the metastable austenitic stainless steel, and AHV which is an index indicating the hardness after annealing as described later. Since the range of the SHV value, which is an index indicating the hardness after the chill treatment, is set based on experiments, it is relatively soft in the annealed state, and can exhibit high strength by the chill treatment. by this,
It is possible to easily perform shape correction and processing in a relatively soft state after annealing, and by cryogenic processing after processing,
Higher strength can be achieved. In addition, Mo, Cu, which are elements that easily form different phases such as inclusions and carbonitrides,
Since Ti, Nb, Zr, W, V and Al are contained in the inevitable impurities and are not intentionally added, formation of foreign phases such as inclusions and carbonitrides can be prevented. Thereby, good surface properties can be obtained even if polishing is performed after the deep cooling process.

The present invention according to claim 2 is characterized in that:
C: 0.09 to 0.17%, Si: 1.0% or less, M
n: 1.5% or less, Ni: 4.0 to 7.0%, Cr: 1
4.0 to 17.0%, N: 0.10% or less, B: 0.0
0.01 to 0.010%, the balance being Fe and unavoidable impurities, and AHV value = 985-135C-14Si-30Mn-43Ni-29Cr-265
N SHV value = 1882-255C-43Si-101Mn-70Ni-55Cr-9
21N K value = 99-15Si-3Mn-4Cr-94 (C + N) -9 80B AHV value, SHV value and K value defined by AHV value ≦ 250, SHV value ≧ 350 and K value ≧ 0 Thus, it is a high-strength stainless steel for cryogenic treatment characterized by containing C, Si, Mn, Ni, Cr, N, and B.

According to the present invention, the content of each element is set so as to sufficiently satisfy the component range of the metastable austenitic stainless steel, and AHV which is an index indicating the hardness after annealing as described later. The values, the SHV value, which is an index indicating hardness after deep cooling, and the range of the K value, which is an index indicating workability after annealing, are set based on experiments, so that they are relatively soft and favorable in the annealed state. It exhibits workability, for example, bendability and punching workability, and can exhibit high strength after deep cooling. This makes it possible to suitably perform bending, punching, and the like in a relatively soft state after annealing, and achieve high strength by deep cooling after processing. In addition, among the elements which are likely to form different phases such as inclusions and carbonitrides in the stainless steel, the elements contained as the basic components of stainless steel are regulated by the K value, and other elements which are likely to form different phases are intended. Since it is not chemically added, it is possible to prevent generation of surface defects during processing and wear of the punching jig.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a simplified view showing a production process of an abrasive product made of high-strength stainless steel for cryogenic treatment according to an embodiment of the present invention. In the first step, smelting is performed. In this step, after melting is performed in a vacuum melting furnace, casting of a steel ingot is performed. The steel composition is adjusted to satisfy the steel composition of the metastable austenitic stainless steel according to claim 1. In the second step, after forging the cast steel ingot, hot rolling is performed. In the third step, cold rolling is performed after solution treatment of the hot-rolled steel sheet. In the fourth step, annealing is performed to form an annealed structure in which a small amount of a martensite phase is formed in the austenite single phase or the austenite phase. Cold rolling and annealing are repeatedly performed until the thickness of the cold-rolled steel sheet reaches the target thickness. In the fifth step, the shape is corrected and the annealed cold-rolled steel sheet is corrected to be flat.
In the sixth step, processing is performed, and the cold-rolled steel sheet whose shape has been corrected is processed so as to have a target product shape. In the seventh step, a deep cooling process is performed at a temperature of −50 ° C. or less. By this treatment, a martensite phase is formed from the austenite phase in the annealed state. In the eighth step, polishing is performed, and the production of the polished product ends.

As described above, the component of the high-strength stainless steel for cryogenic treatment in the present embodiment reduces the amount of the martensite phase formed in the annealed state, in other words, the relatively soft component mainly composed of the austenite phase. The state is adjusted so that the strength of the steel is increased by increasing the amount of the martensite phase produced by the deep cooling treatment.

The adjustment of the amount of the martensite phase is performed by adjusting the stability of the austenite phase. That is, if the austenite phase becomes too stable, even if the cryogenic treatment is performed, almost no martensite phase will be generated, so that high strength cannot be achieved. Conversely, if the austenite phase becomes too unstable, a large amount of martensite phase will be formed in the annealed state, making processing difficult. On the other hand, if the stability of the austenite phase is proper, the amount of martensite generated in the annealed state is reduced to maintain a relatively soft state, and the amount of martensite phase generated is increased by deep cooling treatment. Thus, high strength can be achieved.

The component of the high-strength stainless steel for cryogenic treatment in the present embodiment is C: 0.09 to 0.17 by weight%.
%, Si: 1.0% or less, Mn: 1.5% or less, Ni:
4.0 to 7.0%, Cr: 14.0 to 17.0%, N:
0.10% or less, B: 0.001 to 0.010%, with the balance being Fe and unavoidable impurities, further defined by the following formulas (1) and (2) from the viewpoint described below. AHV value and SHV value are AHV value ≦ 250,
It is set so that SHV value ≧ 350. (1),
(2) Each element in the formula is represented by weight%. AHV value = 985-135C-14Si-3 0Mn-43Ni-29Cr-265N ... (1) SHV value = 1882-255 C-43Si-101Mn-70Ni-55Cr-921N ... (2)

Generally, as an index of the stability of a metastable austenitic stainless steel, an Ms point which is a martensite transformation start point at the time of quenching and an Md30 which is an index of generation of work-induced martensite are used. . These indices are for estimating the stability of the austenite phase and the amount of martensite formed, and are applied, for example, when the magnetic permeability after annealing and the difficulty of working are considered. On the other hand, when the shape correction property is a problem as in the present invention, the strength level at which the shape correction can be performed more easily than the generation amount of the martensite phase after annealing, that is, the hardness after annealing is important. Become. In addition, as an index in a product, in addition to the surface properties after polishing, a strength level that can prevent deformation due to collision of objects and the like, that is, hardness after deep cooling is important.

The present inventors conducted experiments with various components based on the above idea, and analyzed the data. As a result, the AHV value and the hardness level after deep cooling were used as indices indicating the hardness level after annealing. The SHV value was found as an index to represent. As shown in equations (1) and (2), the AHV value and SH
The coefficient of each element of the V value is a negative value, and the hardness after annealing and after the deep cooling decreases as the added amount of each element increases. Further, the coefficient of each element indicates that as the value increases, the influence on the hardness increases even with the same amount of addition. Therefore, it can be seen that the influence of C and N is particularly large.

The components of the high-strength stainless steel for cryogenic treatment in the present embodiment are set so that surface defects do not occur during polishing. The present inventors have conducted various studies on the relationship between the surface properties and the steel composition after polishing, and as a result, in order to prevent surface defects during polishing, elements that easily form inclusions and carbonitrides have been reduced as much as possible. It has been found that suppression is effective. For example, elements such as Ti, Nb, and Mo easily form hard carbides and the like during cooling after annealing even if they are added in trace amounts. The formed hard phase such as carbide is hard to be polished as compared with the base material at the time of polishing, so it becomes convex, and then falls off to generate scratches on the polished surface. Further, carbide mainly composed of Cr is also a hard foreign phase, and causes the same surface defects.

Further, as a result of confirming the state of carbide formation after annealing of the stainless steel with respect to the C content, in the case of C-containing steel of more than 0.17% by weight, the diffusion of C necessary for forming carbide is sufficiently generated. It has been found that carbides are formed after cooling, but in C-containing steels of 0.17% by weight or less, the diffusion of C required for forming carbides does not occur, and thus no carbides are formed.

On the other hand, Mn and Cu form soft hetero phases such as a MnS and Cu rich phase. Unlike the above-mentioned hard carbides and inclusions, these are polished more than the base material during polishing, and conversely, concave pits are easily formed. Further, when the electric field polishing is performed, the potential is lower than that of the base material, so that preferential melting promotes the formation of pits.

As described above, when the hard and soft hetero phases are formed, surface defects are easily generated by polishing. Therefore, in the present embodiment, Mo, Cu, Ti, Nb, Z
The contents of r, W, V, Al, and the like are limited to the amounts of inevitable impurities, and intentional addition of these elements is not performed.

The reason for limiting the numerical values of the present embodiment will be described below. The upper limit of the AHV value is limited to 250
If the AHV value exceeds the upper limit, the shape cannot be sufficiently corrected in the shape correction in the fifth step. That is, if the AHV value exceeds the upper limit, the cold-rolled annealed sheet is hard and the cold-rolled annealed sheet cannot be flattened. The reason why the lower limit of the SHV value is limited to 350 is that when the SHV value is lower than the lower limit value, the strength of the molded product after the deep cooling treatment is low, and it is difficult to prevent the deformation of the molded product due to external force. This is because the durability becomes insufficient.

C is an important element for increasing the strength of the martensite phase generated by the cryogenic treatment. C content is limited to the range of 0.09 to 0.17%,
If the C% is less than the lower limit, sufficient strength cannot be obtained by the deep cooling treatment. If the C% exceeds the upper limit, carbides are formed during the cooling of the annealing in the fourth step as described above, This is because surface defects are likely to occur during polishing in the eighth step.

[0027] Si is an element that increases the hardness of the martensite phase. The reason why the Si content is limited to 1.0% or less is that if the Si content exceeds the upper limit, the strength after annealing in the fourth step becomes high, and the shape correction in the fifth step becomes difficult, and This is because the formation of inclusions is promoted and surface defects are likely to occur during the polishing in the eighth step. Si
Is preferably contained in an amount of 0.05% or more as an element for increasing the hardness of the martensite phase and a deoxidizing agent.

Mn is an austenite-forming element and is necessary for obtaining an austenite phase in an annealed state. Mn
The content is limited to 1.5% or less because, when Mn% exceeds the upper limit, the amount of inclusions such as MnS increases, and pit-like surface defects tend to occur during polishing. . Mn is preferably contained as an austenite-forming element and a deoxidizing agent in an amount of 0.05% or more.

Ni is an austenite forming element and is necessary for obtaining an austenite phase in an annealed state. Further, it is an important element for adjusting the hardness after annealing and chilling treatment, that is, the AHV value and the SHV value. N
The i content is limited to the range of 4.0 to 7.0%,
If the Ni% is less than the lower limit, the austenite phase may become too unstable, and the Ni
%, The austenite phase may be too stable.

Cr is an element necessary for maintaining the corrosion resistance of stainless steel. Cr content of 14.0 to 1
The reason why the content is limited to the range of 7.0% is that the content of Cr is less than the lower limit.
This is because the corrosion resistance of stainless steel cannot be ensured, and Cr% exceeding the upper limit impairs the structural stability and lowers the toughness of the martensite phase.

N, like C, is an element that increases the strength of the martensite phase. The N content is limited to 0.10% or less because if N% exceeds the upper limit, the amount of nitride formed increases, and surface defects are likely to occur during polishing. N is 0.005 for strengthening the martensitic phase.
% Is preferably contained.

B is an element effective for improving hot workability and hardenability. B content is 0.001 to 0.010
The reason why the content is limited to the range of B% is that there is a possibility that hot working cracks may occur if B% is less than the lower limit. This is because surface defects are likely to occur.

As described above, in this embodiment, C, Si,
Since Mn, Ni, Cr, N, and B are set so as to satisfy the component range of the metastable austenitic stainless steel, and the ranges of the AHV value and the SHV value are set based on experiments, martensite is used in the annealed state. The formation of the phase is stopped in a small amount to maintain a relatively soft state, and the deep cooling allows the martensite phase to be generated in a large amount to exhibit high strength. Therefore, shape correction and processing can be easily performed in a relatively soft state after annealing. In addition, since the strength can be increased by the deep cooling treatment after the processing, the durability of the product can be improved. In addition, Mo, Cu, Ti, Nb, Zr, W, and V, which are elements that easily form a different phase such as inclusions and carbonitrides,
And the content of Al is stopped by the inevitable mixing amount,
Since it is not added intentionally, it is possible to prevent the formation of foreign phases such as inclusions and carbonitrides. Therefore, good surface properties can be obtained without causing surface defects even when polishing is performed after the deep cooling process.

As described above, the high-strength stainless steel for cryogenic treatment of the present embodiment can be easily modified in shape and processed, and can have high strength easily after processing. Even so, good surface properties can be obtained, so that the use of stainless steel can be expanded. Examples of applications are as follows.

(Application Example 1) Since a press plate for manufacturing an electronic component and a laminated board is formed by pressure, it is necessary to have strength enough to withstand deformation by the pressure, and a metal plate is used. . Since the shape of the press plate is directly reflected on the product shape, strict flatness is required. Further, since the surface defect of the press plate is also transferred as it is, the defect rate of the surface is strictly regulated. Since the steel of the present invention can satisfy all of these required properties,
It can be suitably applied as stainless steel for press plates.

(Application Example 2) A support frame used for fixing and transporting a thinly sliced silicon single crystal or the like as a printed board and an original plate of an electronic component, or used for cutting a silicon chip having a circuit formed thereon. Such a dicing saw tape frame or the like is required to have a thickness and flatness equal to or less than a silicon single crystal. Further, strength is required to prevent deformation when used repeatedly. Furthermore, if the missing powder of the inclusions falls off during the polishing step, surface defects such as jumping into the polished product occur, so that the requirements for the surface properties are severe. Since the steel of the present invention can satisfy all of these required characteristics, it can be suitably applied as a stainless steel for a support frame.

(Application Example 3) Since the interior rearview mirror of an automobile may be scattered in the event of an accident and cause damage to the human body, the use of mirror-polished metal, glossy plated products, and the like has begun. For a curved mirror installed at a corner of a road, a transition from glass to a metal plate is being studied in order to prevent damage due to a flying object during a typhoon. These mirror-finished products require the same reflectance as that of glass in order to maintain a sense of visual stability for humans. Therefore, excellent surface properties are required, and a product shape for obtaining a reflected image without distortion is required. Since the steel of the present invention can satisfy all of these required properties,
It can be suitably applied as stainless steel for mirror-finished products.

(Application Example 4) The surface receiving plate of a Thompson blade for shearing paper or the like is required to have flatness in order to improve the shearing accuracy, and is also required to have high strength because of contact with the blade.
Since the steel of the present invention satisfies all of these required properties,
It can be suitably applied as stainless steel for surface receiving plates.

(Application Example 5) A tip saw for cutting a mower or food needs to have not only hardness required for cutting but also small blade run-out when rotating at high speed with a thin plate. Required. Since the steel of the present invention satisfies all of these required characteristics, it can be suitably applied as a stainless steel for a tip saw.

FIG. 2 is a simplified view showing a manufacturing process of a precision electronic device component using high-strength stainless steel for cryogenic treatment according to another embodiment of the present invention. The precision electronic device component of this embodiment is required to have high strength and excellent workability. For the processing of this part, processing methods such as punching, shearing and bending are used. Therefore, excellent workability is a property that can prevent the occurrence of cracks and surface defects during bending, and a property that the finishing accuracy of punching and shearing is good. This is a characteristic that can minimize the wear of the punching jig and the shearing blade after processing.

In the first step, smelting is performed. In this step, after melting is performed in a vacuum melting furnace, a steel ingot is cast. The steel composition is adjusted so as to satisfy the steel composition of the metastable austenitic stainless steel according to the second aspect.
In the second to fifth steps, hot rolling, cold rolling, annealing, and shape correction are performed in the same manner as in the polishing product manufacturing process of FIG. This annealing forms an annealed structure in which a small amount of a martensite phase is formed in the austenite single phase or the austenite phase. In the sixth step, a process such as a bending process and a punching process is performed, and the cold-rolled steel sheet after the shape-corrected annealing is processed so as to have a target product shape.
In the seventh step, the deep cooling process is performed at a temperature of -50C or lower. By this treatment, a martensite phase is formed from the austenite phase in the annealed state and hardened.

The component of the high-strength stainless steel for cryogenic treatment in the present embodiment is C: 0.09 to 0.17 by weight%.
%, Si: 1.0% or less, Mn: 1.5% or less, Ni:
4.0 to 7.0%, Cr: 14.0 to 17.0%, N:
0.10% or less, B: 0.01% or less, with the balance being Fe and unavoidable impurities.
A defined by the formula (2) and the following formula (3)
HV value, SHV value and K value are AHV value ≦ 250, SH
It is set so that V value ≧ 350 and K value ≧ 0.
(3) Each element in the formula is represented by weight%. K value = 99-15Si-3Mn-4Cr-94 (C + N) -980B ... (3)

As described above, the AHV value is an index indicating the hardness level after annealing, and the SHV value is an index indicating the hardness level after deep cooling. Therefore, by limiting the upper limit of the AHV value in this manner, the hardness level after annealing can be softened, and the bending workability can be improved. By limiting the lower limit of the SHV value in this way, it is possible to increase the product strength. The precision electronic device component of the present embodiment further has a property that surface defects do not occur during bending, and a property that the finishing accuracy of punching and shearing is good,
Characteristics that can minimize the wear of the punching jig and the shearing blade after the punching process and the shearing process are required.

The present inventors have conducted various studies on the above-mentioned characteristics, and have obtained the following findings. In general, for these processes, the material is soft, and the smaller the work hardening of the material, the easier the process is. However,
If the work hardening is too small, for example, during punching and shearing, the tip of the punch and the shearing blade, which are the punching jig, is less likely to cause shear failure, and as a result, the shear resistance increases and the life of the punch and the blade becomes longer. May be reduced. In addition, when work hardening is small and shear fracture does not easily occur, burr on the processed end surface is likely to increase,
It is not preferable in terms of the finishing accuracy of the product. Hard foreign phases such as inclusions and carbonitrides in the stainless steel wear out the punching jig and the shearing blade during punching and shearing, and hard foreign phases existing near the plate surface deform during deformation. Causes surface defects such as cracks and pinholes. A soft foreign phase such as a Cu-rich phase existing in the vicinity of the plate surface in the stainless steel also causes surface defects due to a difference in deformability during processing. Therefore, in order to satisfy the above characteristics, it is effective to suppress the generation amount of the different phase as low as possible.

The present inventors conducted experiments with various components based on such findings, and investigated and analyzed the workability from the viewpoint of the amount of work hardening and the generation of a different phase. The K value was found. That is, the K value is an index representing the finishing accuracy and the ability to form a different phase in the punching and shearing processes. More precisely, the basic components of the stainless steel, Si, Mn, Cr, C,
It is an index indicating the finishing accuracy and the ability to form a different phase in stamping and shearing by N and B. As shown in the above equation (3), the coefficient of each element of the K value is a negative value,
The K value decreases as the added amount of each element increases.
Therefore, by regulating the lower limit of the K value, it is possible to suppress the size of burrs at the time of punching and shearing and the amount of heterophase generated in the stainless steel.

In the present embodiment, the content of the hetero-phase forming elements other than the basic components of the stainless steel is suppressed as low as possible. For example, Ti, Nb
Elements such as Mo and Mo, even when added in trace amounts, tend to form a different phase such as hard carbide during cooling after annealing, and cause surface defects during bending and wear of the punching jig and shear blade. Further, Cu forms a soft hetero-phase such as a Cu-rich phase, and generates surface defects during bending. Therefore, Mo, Cu, Ti, Nb, Zr, W, V and Al
As in the embodiment shown in FIG. 1, the content of such elements is limited to the amount of inevitable impurities, and intentional addition of these elements is not performed.

Next, the reasons for limiting the numerical values of this embodiment will be described. The reason for limiting the AHV value and the SHV value is shown in FIG.
This is for the same reason as in the embodiment. The lower limit of the K value is limited to zero at a K value lower than the lower limit, that is, when the K value is negative, the burrs of the processing end face during punching and shearing become large, and This is because the finishing accuracy is reduced. Furthermore, if the K value is negative,
This is because the generation amount of the hetero phase in the stainless steel increases, and as shown in Comparative Examples 17 to 20, 22, and 23 described below, the punching jig is worn out after the punching process and the punch life is shortened.

The upper limits of the contents of C, Si, Mn, Cr, N, and B are 0.17%, 1.0%, 1.5%, 17.0%,
The contents are limited to 0.10% and 0.01%, respectively, because if the content exceeds the upper limit, the amount of formation of foreign phases such as inclusions and carbonitrides increases, and surface defects are easily generated during processing, and This is because the wear of the punching jig increases. The lower limit of C, Ni, and Cr is 0.09%;
The reason why the upper limit of Ni is limited to 7.0% is respectively limited to 0% and 14.0% for the same reason as the embodiment shown in FIG. Further, the other components are limited for the same reason as in the embodiment shown in FIG.

As described above, in the present embodiment, the components are set so as to satisfy the component range of the metastable austenitic stainless steel, and the ranges of the AHV value, the SHV value, and the K value are set based on experiments. Therefore, in the annealed state, the formation of the martensite phase is stopped in a small amount to maintain a relatively soft state, and the deep cooling treatment allows the martensite phase to be generated in a large amount to exhibit high strength. Further, the K value regulates the basic components in the stainless steel so that the amount of formation of hard foreign phases such as inclusions and carbonitrides is reduced, and burrs during punching and shearing are reduced. Therefore, the wear of the punching jig and the shearing blade can be minimized, and the finishing accuracy of the punching process and the shearing process can be improved. In addition, since the strength can be increased by the deep cooling treatment after the processing, the durability of the product can be improved. In addition, Mo, C, which are elements other than the basic components that easily form a different phase such as inclusions and carbonitrides,
Since the contents of u, Ti, Nb, Zr, W, V, and Al are stopped to the unavoidable mixing amount and are not intentionally added, it is possible to prevent the formation of a different phase due to these elements. Therefore, the high-strength stainless steel for cryogenic treatment of the present embodiment can be suitably used as a material for precision electronic device parts, precision punched parts, and the like.

Next, the present invention will be described specifically with reference to examples. (Examples 1 to 10) Examples 1 to 10 satisfying all the components of the high-strength stainless steel for cryogenic treatment described in claim 1 of the present invention.
10 and Comparative Examples 1 to 13 deviating from the components described in claim 1 of the present invention, cold-rolled annealed materials and deep-cooled materials were manufactured, and various characteristics were evaluated and compared. These steels were smelted in a 12 kg vacuum melting furnace and forged, then hot-rolled into hot-rolled sheets having a thickness of 3 mm, and cold-rolled and annealed repeatedly to produce cold-rolled annealed sheets having a thickness of 1.0 mm. And Table 1 shows the chemical components, AH, of Examples 1 to 10 and Comparative Examples 1 to 13.
The V value and the SHV value are shown. The chemical component value of each element is shown in% by weight.

[0051]

[Table 1]

A hardness test piece and a test piece for measuring the amount of martensite were collected from the obtained cold-rolled annealed sheet, and the hardness and the amount of martensite after annealing and after a deep cooling treatment at -73 ° C. for 1 hour were measured. did. The amount of martensite was measured with a vibrating sample magnetometer. In addition, width: 10 than the cold rolled annealed plate
A test piece having a diameter of 0 mm and a length of 200 mm was prepared.
After setting a predetermined inter-mesh amount with a shape corrector equipped with three mm rolls, the test piece was passed through one pass to measure the amount of L warpage, and the shape correctability was determined. The predetermined intermeshing amount was set so that test pieces of the same dimensions were prepared from a cold-rolled annealed SUS304 plate, and the amount of warpage in the L direction after one pass of SUS304 was 10 mm. The evaluation was as follows.
The above was evaluated as Δ, and less than 5 mm was evaluated as ×.

Further, a test piece of 100 mm square was prepared from the cold-rolled annealed plate, subjected to a deep cooling treatment at -73 ° C. for 1 hour, and then subjected to mirror polishing with a polishing paper of # 400 to # 1000 and a buff polishing cloth. The number of occurrences of defects on the polished surface was 100
It was counted with a microscope at × magnification. In the evaluation, 2 or less were evaluated as ○, 10 or less as Δ, and 11 or more as ×.
Table 2 shows the evaluation results. The amount of martensite is indicated by volume%.

[0054]

[Table 2]

From Table 2, Examples 1 to 10 all have an AHV value of 250 or less, so that the hardness after annealing is sufficiently low.
It can be seen that the shape correctability is excellent. Further, since the SHV values are all 350 or more, it is understood that the hardness after the deep cooling treatment is sufficiently high. Furthermore, it turns out that the surface properties after mirror polishing are all excellent. In contrast, the AHV value is 250
It can be seen that Comparative Examples 3, 7, and 8 in which the hardness exceeds the threshold value were high in hardness after annealing and poor in shape correction. Further, it is understood that Comparative Examples 1, 2, 9, 10, and 13 having an SHV value of less than 350 have low hardness after the deep cooling treatment and have insufficient durability. Also, M
It can be seen that Comparative Examples 3 to 12 in which n, Si, B, Nb, Mo, V, Cu, Ti and the like are added in large amounts have poor surface properties after polishing.

(Examples 11 to 20) Examples 11 to 20 satisfying all the components of the high-strength stainless steel for cryogenic treatment described in claim 2 of the present invention and the components described in claim 2 of the present invention The cold rolled annealed material and the deep cold treated material were manufactured for Comparative Examples 14 to 30, and various characteristics were evaluated and compared. These steels were melted in a 12 kg vacuum melting furnace, forged, and then hot-rolled into hot-rolled sheets having a thickness of 3 mm.
Cold rolling and annealing were repeated to obtain a cold rolled annealed sheet having a thickness of 0.5 mm. Table 3 shows Examples 11 to 20 and Comparative Examples 14 to
30 chemical components, AHV value, SHV value and K value are shown. The chemical component value of each element is represented by% by weight. Among them, Comparative Example 27 is made of SUS304, Comparative Example 28 is made of SUS301, and Comparative Example 29 is made of SUS420J2.
Comparative Example 30 is made of SUS630.

[0057]

[Table 3]

A hardness test piece and a test piece for measuring the amount of martensite were collected from the obtained cold-rolled annealed sheet, and the Vickers hardness and the amount of martensite after annealing and after a deep cooling treatment at −73 ° C. for 1 hour were determined. It was measured. The amount of martensite was measured with a vibrating sample magnetometer. In addition, a bending test piece and a punching test piece were sampled from the cold-rolled annealed plate and subjected to a bending test and a punching test. The bending test was performed on the bending test piece at 18
The occurrence of surface defects was investigated by performing close contact bending at 0 °, and evaluated according to the evaluation criteria shown in Table 4. In the punching test, a punch having a diameter of 3 mm was used to perform a punching test 1000 times on the punched test piece under the condition of no clearance, and the punch and the die after the test were inspected for wear and the evaluation criteria shown in Table 5 were used. Relative evaluation was performed. In Comparative Examples 28 and 30, an aging treatment at 480 ° C. for 1 hour was performed instead of the deep cooling treatment.
A quenching treatment was performed. Table 6 shows the evaluation results. The amount of martensite is expressed in volume%.

[0059]

[Table 4]

[0060]

[Table 5]

[0061]

[Table 6]

As can be seen from Table 6, in Examples 11 to 20, the AHV values are all 250 or less and the K values are all positive.
It can be seen that the hardness after annealing is low and the bendability and punching properties are excellent. Further, since the SHV values are all 350 or more, it is understood that the hardness after the deep cooling treatment is sufficiently high. On the other hand, Comparative Examples 16, 20, and 2 in which the AHV value exceeded 250
1 shows that the hardness after annealing is high and the bending property and the punching property are inferior. Comparative Example 14, in which the SHV value was less than 350,
Nos. 15, 22, 23, 26 and 27 have low hardness after the deep cooling treatment, indicating that the durability of the product is insufficient. In addition, it can be seen that Comparative Examples 17 to 20, 22, and 23 in which the K value is a negative value are inferior in bending property and punching property. Mn, Si,
It can be seen that Comparative Examples 16, 21 to 25, in which B, Nb, Mo, V, Cu, Ti and the like were added in large amounts, had poor bending properties and punching properties. Comparative Examples 28 and 3 which are aging materials
0 indicates that the hardness after annealing is high and the bendability and punching properties are inferior. Also, it can be seen that Comparative Example 29, which is a quenched material, is inferior in bending property and punching property.

[0063]

As described above, according to the first aspect of the present invention, it is possible to easily perform shape correction and processing in a relatively soft state after annealing, and to perform high-temperature processing by deep cooling after processing. Strengthening can be achieved. Further, even if polishing is performed after the deep cooling process, it is possible to prevent the occurrence of surface defects.

According to the second aspect of the present invention, it is possible to suitably perform bending and punching in a relatively soft state after annealing, and to achieve high strength by deep cooling after processing. be able to. Further, it is possible to prevent the occurrence of surface defects due to the bending process, and it is possible to minimize the wear of the punching jig after the punching process.

[Brief description of the drawings]

FIG. 1 is a simplified view showing a manufacturing process of an abrasive product using high-strength stainless steel for cryogenic treatment, which is one embodiment of the present invention.

FIG. 2 is a simplified view showing a manufacturing process of a precision electronic device component using high-strength stainless steel for cryogenic treatment, which is another embodiment of the present invention.

Claims (2)

[Claims] C .: 0.09 to 0.17% by weight,
Si: 1.0% or less, Mn: 1.5% or less, Ni: 4.
0 to 7.0%, Cr: 14.0 to 17.0%, N: 0.
10% or less, B: 0.001 to 0.010%
The balance consists of Fe and unavoidable impurities, and AHV value = 985-135C-14Si-30Mn-43Ni-29Cr-265
N SHV value = 1882-255C-43Si-101Mn-70Ni-55Cr-9
AHV value and SHV value defined by 21N are AHV value ≦ 25.
0, C, Si, M so that SHV value ≧ 350
A high-strength stainless steel for cryogenic treatment, characterized by containing n, Ni, Cr, and N. 2. C: 0.09 to 0.17% by weight,
Si: 1.0% or less, Mn: 1.5% or less, Ni: 4.
0 to 7.0%, Cr: 14.0 to 17.0%, N: 0.
10% or less, B: 0.001 to 0.010%
The balance consists of Fe and unavoidable impurities, and AHV value = 985-135C-14Si-30Mn-43Ni-29Cr-265
N SHV value = 1882-255C-43Si-101Mn-70Ni-55Cr-9
21N K value = 99-15Si-3Mn-4Cr-94 (C + N) -980B The AHV value, SHV value and K value defined by AHV value 250, SHV value 350 and K value ≥0 A high-strength stainless steel for cryogenic treatment, characterized by containing C, Si, Mn, Ni, Cr, N and B.