JP5645151B1 - Stainless steel intermediate material for blades - Google Patents

Abstract

Provided is an intermediate material for stainless steel for blades having an excellent carbide distribution that can be increased in hardness by a short heat treatment during quenching. It is an intermediate material of stainless steel for blades after hot rolling which is substantially FCC phase and before annealing, and the composition is mass%, C: 0.46-0.72%, Si: 0.15-0.55 %, Mn: 0.45 to 1.00%, Cr: 12.5 to 13.9%, Mo + W / 2: 0 to 2.0%, the balance consisting of Fe and impurities, the depth from the surface of the rolled surface An intermediate material of stainless steel for blades with a KAM value of 0.5?

Description

  The present invention relates to an intermediate material of stainless steel for blades used in, for example, razors, cutters, knives, knives, and the like.

Conventionally, martensitic stainless steel has been widely used as a material for blades such as razors, cutters, knives, knives and the like. In particular, it is known that a strip of high carbon martensitic stainless steel containing about 13% Cr and about 0.65% C by mass is optimal as a material for a razor. High carbon martensitic stainless steel (hereinafter referred to as “stainless steel for blades”) used for such applications is usually used after quenching and tempering, and is required to have high hardness during use. It has been.
Stainless steel for blades is usually manufactured through the following manufacturing process.
First, a raw material is melted and cast to produce a raw material. Next, the material is hot-rolled to produce an intermediate material. In some cases, the material is subjected to a lump process by hot forging or hot rolling.
Next, the intermediate material is first annealed to produce an annealed material. Further, cold rolling and subsequent strain relief annealing are repeated as many times as necessary on the annealed material to produce a cold rolled steel strip having the desired thickness. Then, the cold rolled steel strip is quenched and tempered to complete the stainless steel for blades.

Furthermore, the stainless steel for blades becomes a final product through processing steps such as cutting and cutting. In addition, generally the transaction in the stainless steel for blades is often made in the form of either an annealed material or a cold rolled steel strip.
The above-described stainless steel for blades has been proposed as a technique that can achieve high hardness in a short time by heat treatment during quenching. For example, as a typical example, Japanese Patent Laid-Open No. 5-39547 (Patent Document 1) discloses that heat treatment can be performed in a short time during quenching by controlling the carbide density of a stainless steel razor steel. Yes.

JP-A-5-39547

Proceedings of the Japan Society of Mechanical Engineers (A), 2005, 71, 712, p. 1722

As described above, various proposals have conventionally been made as techniques focusing on the features of the cold-rolled steel strip for shortening the quenching time and increasing the hardness of the stainless steel for blades.
However, there are few studies focusing on the characteristics of the intermediate material before annealing after hot rolling, the characteristics of the intermediate material, the characteristics of the annealed stainless steel for post-annealing stainless steel circulated as a semi-finished product, and cold rolling Regarding the relationship with the carbide distribution in the steel strip, it was difficult to say that it was fully elucidated.
For this reason, due to the lack of knowledge about how the intermediate material should be, there has been a problem that the excellent quenching characteristics inherent in the stainless steel for blades cannot be sufficiently brought out.
An object of the present invention is to provide an intermediate material of stainless steel for blades having excellent carbide distribution that can be increased in hardness by a short heat treatment during quenching.

The present inventors have studied by paying attention to the distribution of carbides that affect the hardenability and hardness of stainless steel for blades and the relationship between the intermediate materials of stainless steel for blades affecting the distribution of carbides.
First, it was found out that the amount of strain before annealing among the features of the intermediate material of the stainless steel for blades affects the distribution of carbides after the annealing of the intermediate material.
And by leaving the strain in the final pass of the hot rolling of the intermediate material of the stainless steel for blades that is substantially the FCC phase, the KAM value by the SEM-EBSD method becomes 0.5 ° or more, or The present inventors have found that the distribution of carbides after annealing can be improved when the half width of the (200) plane of the FCC phase in X-ray diffraction is 0.3 ° or more.
That is, the present invention is an intermediate material for stainless steel for blades after hot rolling and before annealing , having an FCC phase of 80% by volume or more as measured by an X-ray diffractometer , and the composition is C: 0.46 in mass%. ˜0.72%, Si: 0.15 to 0.55%, Mn: 0.45 to 1.00%, Cr: 12.5 to 13.9%, Mo + W / 2: 0 to 2.0%, The balance is made of Fe and impurities, and is an intermediate material of stainless steel for blades having a KAM value of 0.5 ° or more by the SEM-EBSD method at a position where the depth from the surface of the rolled surface is 1/4 of the plate thickness. is there.
Further, the present invention provides a stainless steel for blades in which the half width of the (200) plane of the FCC phase is 0.3 ° or more in X-ray diffraction at a position where the depth from the surface of the rolled surface is 1/4 of the plate thickness. It is an intermediate material of steel.

  Since the stainless steel for blades manufactured using the intermediate material of stainless steel for blades of the present invention can be hardened by a short heat treatment during quenching, it is particularly suitable for applications such as thin razors.

It is a schematic diagram which shows a test piece collection position and an evaluation surface. It is a drawing substitute photograph which shows an example of the metal structure of the annealing material of the intermediate material of the stainless steel for blades of this invention. It is a drawing substitute photograph which shows an example of the metal structure of the annealing material of the intermediate material of the stainless steel for blades of a comparative example. It is a drawing substitute photograph which shows an example of the metal structure of the annealing material of the intermediate material of the stainless steel for blades of this invention.

As described above, an important feature of the present invention is that the distribution of carbides after annealing of the intermediate material is improved by controlling the amount of residual strain in the intermediate material before annealing.
First, the most characteristic KAM (Kernel-Average-Misorientation) value will be described.
<KAM value by SEM-EBSD method is 0.50 ° or more>
In the present invention, residual strain plays an important role. The KAM value defined in the present invention is, for example, as described in Non-Patent Document 1, as a method for measuring residual strain, SEM (Scanning-Electron-Microscope) -EBSD (Electron-Backscatter-Diffraction) method (electron beam backscatter diffraction method (scanning). The KAM value by electron microscope-crystal orientation analysis)) is described. According to the inventor's study, the KAM value by the SEM-EBSD method of the intermediate material of the stainless steel for blades having the above-described composition is the carbide distribution of the annealed material of the stainless steel for blades obtained using the intermediate material. It was confirmed to correlate with.
Specifically, it can be said that there is little residual strain when the KAM value of the stainless steel intermediate material for blades is less than 0.50 ° by the SEM-EBSD method. When annealing is subsequently performed, coarse carbides are likely to precipitate at the grain boundaries as compared with a material having a large amount of residual strain. As a result, for example, the toughness decreases after quenching and tempering when used for a blade. Therefore, it is necessary to make the average value of KAM values by the SEM-EBSD method 0.50 ° or more. The larger the KAM value, the more the residual strain is preferable. However, if the KAM value exceeds 2.00 °, the variation due to the position of the residual strain tends to increase, so the preferable upper limit of the KAM value is 2.00 ° or less.

Next, the half width will be described.
<Half width of (200) plane of FCC phase in X-ray diffraction is 0.3 ° or more>
In the present invention, residual strain plays an important role, and it is known that there is a correlation between the half width and the residual strain. According to the inventor's study, the half-value width in the X-ray diffraction of the intermediate material of the stainless steel for blades having the above-described composition is the carbide distribution of the annealing material of the stainless steel for blades obtained using the intermediate material, and It was confirmed that there was a correlation.
Specifically, it can be said that the residual strain is small when the half width of the (200) plane of the FCC phase in the X-ray diffraction of the stainless steel intermediate material for blades is less than 0.3 °. When annealing is subsequently performed, coarse carbides are likely to precipitate at the grain boundaries as compared with a material having a large amount of residual strain. As a result, for example, the toughness decreases after quenching and tempering when used for a blade. Therefore, the half width of the (200) plane of the FCC phase in X-ray diffraction needs to be 0.3 ° or more. The larger the half width, the more the residual strain is preferable. However, if it exceeds 1.0 °, the variation due to the position of the residual strain tends to increase, so the upper limit of the preferred half width is 1.0 ° or less.

<The position where the depth from the surface of the rolling surface is 1/4 of the plate thickness>
In the present invention, the measurement of the KAM value by the above-mentioned SEM-EBSD method or the measurement of the half-value width of the (200) plane of the FCC phase in X-ray diffraction has a thickness of 1 from the surface of the rolled surface. Measure the position of / 4.
In the present invention, the “rolling surface” means a surface in contact with the rolling roll during rolling of the intermediate material of the stainless steel for blades, as shown in FIG. The reason for using the rolling surface side for evaluation is that the amount of strain introduced by rolling is not uniform in the thickness direction, so that the evaluation can be performed under the same conditions by fixing the evaluation surface and thickness. .
In the present invention, the position where the depth from the surface is ¼ of the plate thickness is selected because a large grain size is introduced at the time of hot rolling in the vicinity of the surface, so that the crystal grain size generated by recrystallization is small. Therefore, it is not suitable for the measurement of the KAM value and the half width. On the other hand, at the intermediate position of the plate thickness, the amount of reduction during the final pass is small, and the difference in strain due to the presence or absence of the final pass is 1 / This is because the difference between the KAM value and the half-value width is less likely to occur because it is smaller than the position 4.
Further, for the measurement of the half width of the (200) plane of the FCC phase in X-ray diffraction, a position where the depth from the surface is 1/4 of the plate thickness is selected for the same reason as described above. This is because, near the surface, a large strain is introduced during hot rolling, so that the crystal grain size generated by recrystallization is small, so it is not suitable for the measurement of the half width. This is because the amount of reduction at the final pass is small at the position, and the difference in the amount of distortion due to the presence or absence of the final pass is small compared to the position of ¼ of the plate thickness, so that it is difficult to produce a difference in half width.
In the measurement of the half width, the (200) plane of the FCC phase was selected because in the alloy system having the composition defined in the present invention, the above-mentioned orientation has a peak that takes the maximum intensity in X-ray diffraction. Because. Since the peak intensity is low except for the (200) plane, the effect on the half-value width due to the difference in strain is small compared to the (200) plane. Therefore, it is sufficient to measure the half width of the (200) plane.

Next, the alloy composition that gives the basic characteristics defined in the present invention will be described. In addition, content of each element is the mass%.
<C: 0.46 to 0.72%>
The reason why C is set to 0.46 to 0.72% is to achieve sufficient hardness as a blade and to suppress crystallization of eutectic carbide during casting and solidification to a minimum. If C is less than 0.46%, sufficient hardness as a blade cannot be obtained. On the other hand, if it exceeds 0.72%, the crystallization amount of the eutectic carbide increases due to the balance with the Cr amount, which causes chipping at the time of cutting. The lower limit of the preferable amount of C is 0.50%, more preferably 0.65%. Moreover, the upper limit of the preferable amount of C is 0.70%.
<Si: 0.15-0.55%>
Si is added as a deoxidizer during refining. In order to obtain a sufficient deoxidation effect, 0.15% or more of Si remains. On the other hand, if it exceeds 0.55%, the amount of inclusions increases and causes chipping during cutting. Therefore, Si is 0.15 to 0.55%. Si also has the effect of increasing the temper softening resistance. When 0.20% or more of Si is added, the hardness can be further increased. Therefore, the lower limit of the preferable Si amount is 0.20%. Moreover, the upper limit of the preferable Si amount is 0.35%.
<Mn: 0.45 to 1.00%>
Mn is also added as a deoxidizer during refining in the same manner as Si. If an attempt is made to obtain a sufficient deoxidation effect, 0.45% or more of Mn will remain. On the other hand, when it exceeds 1.00%, hot workability will fall. Therefore, Mn is set to 0.45 to 1.00%. The minimum of the preferable amount of Mn is 0.65%. Moreover, the upper limit of the preferable amount of Mn is 0.85%.

<Cr: 12.5 to 13.9%>
The reason why Cr is set to 12.5 to 13.9% is to achieve sufficient corrosion resistance and to suppress crystallization of eutectic carbide during casting and solidification to a minimum. If Cr is less than 12.5%, sufficient corrosion resistance as stainless steel cannot be obtained, and if it exceeds 13.9%, the amount of eutectic carbides crystallizes and causes chipping during cutting. The lower limit of the preferable Cr amount is 13.0%. Moreover, the upper limit of the preferable Cr amount is 13.6%.
<Mo + W / 2: 0 to 2.0%>
Mo and W may be added without addition (0%). However, since they are elements that improve the corrosion resistance, 2.0% can be added as the upper limit if necessary. However, if Mo + W / 2 exceeds 2.0%, the solid solution strengthening becomes strong, the deformation resistance becomes high, and the hot workability is deteriorated, so the content of Mo + W / 2 is made 0-2.0%.
The elements other than those described above are Fe and impurities.
Typical impurity elements include P, S, Ni, V, Cu, Al, Ti, N, and O. These elements are inevitably mixed, but may be restricted to the following ranges. preferable.
P ≦ 0.03%, S ≦ 0.005%, Ni ≦ 0.15%, V ≦ 0.2%, Cu ≦ 0.1%, Al ≦ 0.01%, Ti ≦ 0.01%, N ≦ 0.05% and O ≦ 0.05%.

Next, an intermediate material of stainless steel for blades of the present invention and a representative method for producing an annealed material using the intermediate material will be described.
First, a stainless steel material for blades is manufactured by melting and casting. For melting, methods such as vacuum melting, atmospheric melting, vacuum arc remelting, electroslag remelting and the like can be applied. For casting, a material can be obtained by casting into a mold or continuous casting. You may perform the homogenization heat processing to the raw material obtained as needed. Furthermore, you may add the lump process by hot forging or hot rolling.
Thereafter, the material is hot-rolled. After performing hot rolling at a reduction rate of 80% or more and the temperature of the material after hot rolling at 1000 to 1250 ° C., the final hot rolling results in a material temperature of 900 ° C. or less and a reduction rate of 10%. The intermediate material of the stainless steel for blades is manufactured by performing the above hot rolling.
The reason why the final hot rolling temperature is set to 900 ° C. or less is to introduce residual strain into the material. In a temperature range exceeding 900 ° C., dynamic recovery and recrystallization are likely to occur, so that residual strain is difficult to be introduced. The reason why the rolling reduction is set to 10% or more is that when the rolling reduction is less than that, residual strain is not sufficiently introduced, and carbides concentrate at the grain boundaries during annealing.
Further, when such hot rolling is performed, the pearlite transformation is not sufficiently performed, so that the intermediate material is substantially an FCC phase. The “intermediate material is substantially an FCC phase” in the present invention refers to a material having a volume of 80% by volume or more as measured by an X-ray diffractometer. At this time, the balance is martensite formed during cooling. About the concrete evaluation method, a specific example is shown in the below-mentioned Example.

By performing an annealing process at 800 to 860 ° C. for 1 to 100 hours on the intermediate material of the stainless steel for blades manufactured by the above-described manufacturing method, an annealed material for stainless steel for blades in which carbides are precipitated is manufactured.
Furthermore, in the case of obtaining a cold rolled steel strip of stainless steel for blades having a thickness of less than 0.5 mm using the above-mentioned stainless steel annealing material for blades, it is possible to manufacture by repeating cold rolling and annealing. Become.
When the above-described cold rolled steel strip of stainless steel for blades is subjected to quenching, tempering, and blade cutting to make a blade, subzero treatment is performed after quenching or coating is performed on the surface after tempering as necessary. Sometimes.

The following examples further illustrate the present invention.
Steel ingots (materials) having chemical components shown in Table 1 were prepared by melting.

From the steel ingot, two raw materials for hot rolling having a width of 350 mm and a thickness of 50 mm were produced in composition 1 and in composition 2 in a hot segmentation process.
After the hot rolling material having composition 1 is heated to 1200 ° C. and subjected to hot rolling with a total rolling reduction of 95% (the temperature of the material after this hot rolling is 1050 ° C.), the final hot rolling is performed. An intermediate material A according to an example of the present invention in which the temperature of the material was 850 ° C. and 15% reduction was produced.
Further, as a comparative example, as the intermediate material B in which the final hot rolling process is omitted, the hot rolling material having the composition 1 is heated to 1200 ° C. to perform hot rolling, and the temperature of the material of the hot rolling is Intermediate material B was produced in a process where the total rolling reduction was 95% at 1050 ° C.
Further, after the hot rolling material having the composition 2 is heated to 1200 ° C. and the total rolling reduction is 95% (the temperature of the material after the hot rolling is 1050 ° C.), the final hot rolling is performed. As the rolling, an intermediate material C according to an example of the present invention in which the temperature of the material was reduced to 15% at 850 ° C. was produced.

Test specimens were collected from the vicinity of the center of the width of the stainless steel intermediate materials 1A, B, and C described above. The sampling position of the test piece was the position shown in FIG. 1, and the longitudinal section 2 was used as the evaluation surface for the metal structure observation surface, and the rolling surface 3 was used as the evaluation surface for EBSD and X-ray diffraction.
The metal structure was observed in the longitudinal section of the collected test piece. In addition, the test piece used for EBSD and X-ray diffraction was prepared by mirror-polishing a position at a depth of 1/4 of the plate thickness from the rolled surface, and further performing electrolytic polishing. Table 2 shows the KAM value of each sample by the EBSD method, the half width, and the FCC amount by the X-ray diffraction method.

In the metal structure observation described above, the longitudinal section of the test piece was polished to a mirror surface, then corroded with an aqueous ferric chloride solution, and observed using an optical microscope.
The KAM value was divided into hexagonal areas using a ZEISS SEM (model number “ULTRA55”) and a TSL EBSD measurement / analysis system OIM (Orientation-Imaging-Micrograph). In each region, the Kikuchi pattern was obtained from the reflected electrons of the electron beam incident on the sample surface, and the orientation of the region was measured. The measured orientation data was analyzed using the analysis software OIM Analysis of the same system. The measurement area was 100 μm × 100 μm, and the distance between adjacent pixels was 0.2 μm. A boundary having an orientation difference of 5 ° or more between adjacent pixels was regarded as a grain boundary.
The KAM value was calculated as an average value of orientation differences between individual measurement points and adjacent measurement points excluding the crystal grain boundaries, and was calculated as an average value in all regions constituting the entire measurement surface.
For measurement of the FCC phase amount in X-ray diffraction, RINT2500 manufactured by Rigaku Corporation was used, Co was used as the radiation source, and (200) α, (211) α under the conditions of a voltage of 40 kV and a current of 200 mA. , (200) γ, (220) γ, and (311) γ were calculated using the diffraction line intensity ratio obtained from each surface.

Next, annealing was performed at 840 ° C. for 5 hours using intermediate materials A to C of stainless steel for blades. Then, the test piece was extract | collected from the raw material after annealing so that the vertical cross section described as the evaluation surface 2 including the center vicinity of the width | variety of the rolling material shown in FIG. The metal structure photographs of the intermediate materials A, B and C after annealing are shown in FIGS.
In the metal structure observation, the evaluation surface was polished to a mirror surface, then corroded with an aqueous ferric chloride solution, and observed using a scanning electron microscope.

When the stainless steel intermediate material for blades is annealed, when the KAM value is 0.5 ° or more, or when the half width of the (200) plane of the FCC phase in X-ray diffraction is 0.3 ° or more, As can be seen from FIG. 2 and FIG. 4, it can be seen that the carbide after annealing is distributed more in the grains and has a good structure. On the other hand, as can be seen from FIG. 3, when the KAM value is less than 0.5 or when the half-value width of the (200) plane of the FCC phase in X-ray diffraction is less than 0.3 °, the carbides are separated from the grain boundaries. It coarsely precipitates. With this metal structure, carbides are difficult to decompose during quenching, and remain as coarse carbides even after quenching, and there is a concern that toughness may be reduced.
From the above results, it can be seen that the intermediate material of the stainless steel for blades having a KAM value of 0.5 ° or more, or the stainless steel for blades having a half width of the (200) plane of the FCC phase in X-ray diffraction of 0.3 ° or more. It was confirmed that by performing annealing using an intermediate material, a metal structure of stainless steel for blades suitable for blades such as razors can be realized.

  The stainless steel for blades manufactured using the intermediate material of stainless steel for blades of the present invention has a good distribution of carbides and can be expected to be applied to razors and the like.

1 Intermediate material of stainless steel for cutting tools 2 Longitudinal section 3 Rolled surface

Claims (2)

When measured with an X-ray diffractometer, it is an intermediate material of stainless steel for blades after hot rolling and having an FCC phase of 80% by volume or more and before annealing, and the composition is mass% and C: 0.46 to 0.72%, Si: 0.15 to 0.55%, Mn: 0.45 to 1.00%, Cr: 12.5 to 13.9%, Mo + W / 2: 0 to 2.0%, the balance from Fe and impurities An intermediate material of stainless steel for blades, characterized in that the KAM value by the SEM-EBSD method at a position where the depth from the surface of the rolled surface is 1/4 of the plate thickness is 0.50 ° or more. When measured with an X-ray diffractometer, it is an intermediate material of stainless steel for blades after hot rolling and having an FCC phase of 80% by volume or more and before annealing, and the composition is mass% and C: 0.46 to 0.72%, Si: 0.15 to 0.55%, Mn: 0.45 to 1.00%, Cr: 12.5 to 13.9%, Mo + W / 2: 0 to 2.0%, the balance from Fe and impurities The half-width of the (200) plane of the FCC phase in X-ray diffraction at a position where the depth from the surface of the rolled surface is 1/4 of the plate thickness is 0.3 ° or more. Stainless steel intermediate material.

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