JPH0312047A - Steel plate for information recording and recording method using the same - Google Patents

Abstract

PURPOSE:To improve corrosion resistance and heat resistance of a recording medium by using a steel plate comprising a specified ferrite stainless steel or martensite stainless steel as a mother layer and a nickel surface layer, and irradiating this plate with high density energy beam for recording. CONSTITUTION:The multilayered steel plate for information recording consists of a mother layer 1 comprising ferromagnetic ferrite stainless steel or martensite stainless steel containing Cr by 9 - 20wt.%, and a Ni surface layer 2 (nonmagnetic). By irradiating this plate with high-density energy beam such as laser beam or electron beam according to the information pattern, the surface layer 2 and the mother layer 1 are partly molten to make an alloy. This alloy state then solidifies to form the molten area 3 having nonmagnetic austenite structure. Thereby, the recording medium has excellent corrosion resistance and heat resistance.

Description

Detailed Description of the Invention (Industrial Application Field) This invention relates to an information recording medium having a matrix made of a metal material having excellent mechanical strength, corrosion resistance, heat resistance, etc., and particularly an information recording medium having a matrix made of stainless steel. The present invention relates to a recording steel plate and an information recording method using the same.

(Prior Art) In recent years, magnetic recording products such as cash cards and magnetic tickets have come into widespread use. These magnetic recording products print striped or
Alternatively, a magnetic material is formed in the form of a film, and the materials used as the magnetic material are T Fears, (Co
) 7 Pet's, Ra0, 6 Fear3, etc., these materials are laminated onto a substrate, and in many cases, a protective coat is further applied thereon. The binarized bit information is recorded and read.

On the other hand, magnetic scales used for positioning in various industrial fields, such as the mechatronics field, are also a type of information medium that utilizes magnetism. In such application fields, magnetic recording media based on highly durable metal materials have been proposed, taking into consideration the environment in which they are used.

For example, in Japanese Patent Publication No. 62-32407, a type of alloy (specifically, Fe25χ-N+7
A method of writing magnetic domains by locally heat-treating a 5χ alloy has been proposed.

In magnetic card products such as the above-mentioned cash card,
Challenges include preventing crimes such as forgery and falsification, as well as troubles caused by damage and loss of information, and technical issues such as durability, moisture resistance, and stability against external magnetic fields are becoming apparent.

On the other hand, magnetic scales used in the industrial field have mechanical strength,
It must be highly reliable with excellent wear resistance and corrosion resistance.One of the inventors of the present invention used a base material of deformation-induced martensitic structure as a magnetic scale particularly suitable for industrial use. He proposed a magnetic scale that was made non-magnetic by changing the metal structure by melting a part of it (Japanese Patent Application Laid-Open No. 62
-83620).

The magnetic scale of the invention is easy to manufacture, inexpensive, and provides a high signal-to-noise ratio. However, with plate materials, it is difficult to obtain sufficient processing-induced martensite, the width of the melted area by the laser beam is on the order of millimeters, and the information density is too low, and in the case of plate materials, thermal deformation is significant, so it is difficult to obtain sufficient processing-induced martensite. It is difficult to provide a card-like function as an information card.

(Problem to be Solved by the Invention) The object of the present invention is to overcome the drawbacks of conventional magnetic recording media for everyday general use or industrial use, to have excellent heat resistance and durability, and to be resistant to information loss due to external magnetic fields. The purpose of the present invention is to provide a new information recording medium and an information recording method using the same.

(Means for Solving the Problems) The magnetic scale described in JP-A-62-83620 mentioned above uses austenitic stainless steel in which deformation-induced martensite is precipitated as a base material. However, in the case of sheet materials, it is difficult to control the martensitic rate due to deformation compared to the case of manufacturing bars, and it is difficult to obtain stable magnetic properties. hot rolling, cold rolling,
The fact that it involves complicated processes such as coil winding, and that the austenitic stainless steel itself is 5 as shown in Figure 3 below.
This is because, as is clear from Chaeffler's diagram, it is difficult to obtain deformation-induced martensite with good reproducibility because the structure is in an unstable region.

Therefore, in forming the ferromagnetic part and the non-magnetic part that record information patterns, the present inventors found that the metal structure suitable for the ferromagnetic part is more stable than austenitic stainless steel in which deformation-induced martensite is partially precipitated. The idea was to use ferritic or martensitic stainless steel, which has ferromagnetism. However, these ferromagnetic stainless steels do not become non-magnetic even if they are locally melted; in order to become non-magnetic, the chemical composition must be such that the area becomes an austenitic structure. . The present invention, which has been made from this point of view, first focuses on the following multilayer steel plate for information recording.

"Multi-layer steel plate for information recording comprising a mother layer of ferritic stainless steel or martensitic stainless steel of ferromagnetic type containing 9 to 20% by weight of rCr and a surface layer of nickel covering at least one side of the base layer" and also the present invention uses the above-mentioned steel plate, ``irradiates the surface with a high-density energy beam according to the information pattern, melts and alloys part of the surface layer and the base layer, solidifies it to form a non-magnetic austenite structure, and then ``An information recording method characterized by recording an information pattern consisting of a ferromagnetic part and a non-magnetic part.''

FIG. 1 is a diagram illustrating the principle of the multilayer steel plate of the present invention and an information recording method using the same.

FIG. 1(a) is an enlarged cross-sectional view of a multilayer steel plate, where 1 is a ferromagnetic base layer made of ferritic or martensitic stainless steel. 2 is a nickel layer (hereinafter referred to as Ni layer) formed thereon. This Ni layer can be formed by any method such as plating, vapor deposition, rolling cladding method, etc.

Figure 1(b) is a diagram in which a part of the surface of the multilayer steel plate is melted to form an alloy (having the composition of austenitic stainless steel) in which base layer 1 and Ni layer 2 are melted together. be. This part is marked as fused part 3, and only this part becomes non-magnetic. That is, by forming the melted portion 3 with a predetermined size and distribution, necessary information is recorded on the temporary surface.

FIG. 1(c) shows a state in which recorded information is read by scanning the magnetic disk 4.

In addition, if it is necessary to record on both sides of the plate, the Ni layer 2 may be formed on both sides of the base layer 1 and processed as described above.

The Ni layer after the recording process is no longer needed.

It is not necessary to remove this layer, but especially when this steel plate is used in harsh environments, the Ni layer may peel off, damaging the appearance, or increasing surface roughness, reducing reading accuracy. Therefore, it is desirable to remove the Ni layer after recording information.

As shown in Figure 1, the method of the present invention involves forming a Ni layer in advance on the surface of the base layer of ferromagnetic ferritic or martensitic stainless steel, and locally melting only the necessary parts. It is a characteristic of

Therefore, for the melting operation, it is necessary to select a method that can melt minute parts with high precision.

High energy density beams such as laser beams, electron beams etc. are suitable for this purpose. In particular, it is practical to use a laser beam that does not require a vacuum device.

When the base layer and Ni layer are melted and alloyed by irradiation with a high energy density beam, it is necessary to ensure that the melted part has the composition of austenitic stainless steel.To do this, the composition of the base layer, In addition to the thickness of the Ni layer, it is necessary to appropriately select the shape and depth of the melt penetration, that is, the beam irradiation conditions. It is also important to ensure surface flatness so that reading by a magnetic head or the like can be performed smoothly. These points will be described in detail below.

(Function) First, the reason why the content of chromium (C') in the base layer was set to 9 to 20% (in this specification, % means total weight %) is explained.
In alloying with the i-layer, the Cr content of the steel, which becomes austenite msa with the smallest weight and exhibits nonmagnetic properties, is 14 to 1.
However, if the Ni layer is thickened to a certain extent, a nonmagnetic fused part can be obtained even by alloying with an inexpensive martensitic stainless steel with a Cr content of about 6 to 14%.

On the other hand, if the amount of Ni is finally contained in the melted zone in an amount of 8 to 10%, an austenitic structure will be formed. Therefore, since the original Cr11 of the base layer is diluted by alloying, the appropriate range of the Cr content of the base layer is 9 to 20%.

Since the structure of the mother layer needs to be ferromagnetic, the mother layer is made of C.
Ferritic stainless steel with an r content of 9 to 20%, or
It is made of martensitic stainless steel.

Next, the desirable conditions for locally melting and alloying by irradiating a high energy density beam are as follows.

The power density of the high energy density beam is l×10S ~
If the power density is smaller than l×105~1.0'w8■1, stable melting of one layer cannot be obtained; 0
If it is larger than 'w/c■2, the Ni layer tends to scatter or evaporate, making alloying difficult, and the surface roughness after solidification reaches 5μm to 10μm in Rax. Normal reading becomes difficult. The beam diameter is preferably 300 μm or less because it is necessary to narrow down the beam diameter as much as possible in order to increase the recording density as an information card and to obtain the above power density in a package.

FIG. 2 is an enlarged view of the vicinity of the fusion zone in FIG. 1(b). In the same figure, the thickness of the Ni layer is t (μm)
Therefore, it is desirable that the variation in t be 2 μm or less, that is, if t is the average thickness, it is 1-1±6, but it is desirable that δ be 1 μm or less.

In addition, it is desirable to suppress the roughness expressed by Rwxax (μ麟) on the surface of the Ni layer to 2μ or less, and the variation in the thickness t (μ) of the N1 layer and the surface roughness Re1ax to 2μ
If it exceeds m, even if the beam output stability is good during melting with a high-density energy beam, the amount of Ni in the molten part will fluctuate in places where there are large variations in thickness or roughness.
This is because the magnetic properties change.

Similarly, the average penetration depth D of the molten zone 3 in FIG.
It is preferable that the following formulas (3) and (4) be satisfied in relation to the formula) and the Cr equivalent (Creq + formula (2) below).

N1eq (χ)=χold+30×χc+o, sxχMn
−■Creq (χ)=χCr+χMo+1.5Xχs
i + o, sxχNb -... ■ (χ indicates weight%) The average) volume and filling depth are as follows! It can be determined. That is, in Figure 2, if DH: maximum penetration depth (μ+s), then the average penetration depth D (μm) is D=AXD
, becomes.

Here, A is a coefficient depending on the cross-sectional shape of the melted part. If the cross-section of the melted part is completely rectangular, A = 1.0. If the cross-section is triangular, A = 1.0.
=0.5. Since the actual cross-sectional shape is in between these, A is usually in the range of 0.6 to 0.9.

The average penetration depth as above, L and Cr equivalent,
The relational expression with the Ni equivalent was determined by controlling the austenitization rate of the molten zone and determining the conditions under which a recording zone with a good S/N ratio could be obtained. FIG. 3 shows this range on a 5chaffler diagram (from Nikkan Kogyo Shimbun's "Stainless Steel Handbook"). Third
The shaded region in the figure is a region where a stable austenite structure can be changed, and it is desirable to satisfy equations (3) and (4) so that the Cr equivalent and old equivalent can be obtained.

(Example) A Ni layer was formed by various methods on one side surface of various base layers (thickness: 1.0+n+) having a composition of ferritic or martensitic stainless steel. The surface was irradiated with a high-energy-density beam to locally melt and form an alloy.

Table 1 shows the composition of the base layer, the means for forming the X4 layer and its thickness, and the beam irradiation conditions.

Table 2 shows the shape of the molten part formed under the conditions in Table 1, its composition, and the 900k
The S/N ratio when a high frequency wave of llz was applied and the magnetic flux due to IUI induction was detected is shown.

N (L l~3 in Table 2) is one layer formed on the ferritic stainless steel base layer by plating, cladding, or adhesion, and all can be read with a high S/N ratio under appropriate processing conditions. Similarly, Stone 4.5 has martensitic stainless steel as its base layer, and can similarly write and read with a good S/N ratio.

In No. 6, the surface of the Ni layer was subjected to shit blasting to give a surface roughness of Rmax 3 μm. In this example, the dilution ratio between the Ni layer and the base layer varies, and
The variation in the gap between the magnetic head and the surface is too large, making measurement difficult.

In case 7, the surface of the base layer before Ni plating is subjected to sheet blasting to give it a roughness of R+may 4μ, then Ni is plated, and then the plated surface is puff polished to give R1eaχ1.
It is finished in μm. In this example, due to excessive variations in the thickness of the N1 layer, the dilution rate varied similarly to N[L6, so the molten part was not sufficiently demagnetized and the S/N ratio deteriorated.

In Na8, the melt penetration is large relative to the plating thickness, the St equivalent does not reach the appropriate range, and the S/N ratio deteriorates.

These obstacles 6 to 8 can be fully used if data is detected and processed appropriately, but in practical terms, the conditions described above as desirable conditions, such as N111 to 5, are sufficient. The manufactured one is better.

(Effects of the Invention) The information recording steel plate of the present invention can be manufactured by a simple method of using a relatively inexpensive material such as ferritic or martensitic stainless steel as a base layer and forming a Ni layer on the surface thereof. Furthermore, information can be recorded easily and accurately using a laser beam or the like. Due to the nature of the material and the principle of information recording, the recording medium obtained by the present invention has excellent corrosion resistance and heat resistance, and there is little possibility of recording being lost due to external influences.For example, it is possible to use conventional plastic as a substrate. If a magnetic card is exposed to temperatures of about 100°C for 10 minutes, the records will be destroyed, but the magnetic card of the present invention can withstand temperatures of about 500°C.

The information recording steel plate and recording method of the present invention can be widely used in magnetic recording bodies used in daily life such as cash cards, magnetic scales used in various industrial fields, and the like.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the basic concept of the magnetic recording steel material of the present invention, in which (a) is a cross-sectional view of a state in which a Ni layer is formed on the base layer;
(b) is a cross-sectional view in which a melted part (non-magnetic part) is locally formed, and (c) is a diagram showing a recording detection method. FIG. 2 is an enlarged sectional view of the fusion zone. Figure 3 shows Ni equivalent and chromium equivalent and metallurgical &l1
It is a figure showing the relationship with w1. Ho 1 figure

Claims (4)

[Claims] (1) A multilayer steel plate for information recording comprising a base layer of ferromagnetic ferritic stainless steel or martensitic stainless steel containing 9 to 20% by weight of Cr, and a nickel surface layer covering at least one side of the base layer. (2) irradiating the steel plate according to claim 1 with a high-density energy beam according to the information pattern to melt and alloy a part of the surface layer and the base layer, and then solidify it to form a non-magnetic austenite structure; An information recording method characterized by recording an information pattern consisting of a ferromagnetic part and a non-magnetic part on a surface. (3) Irradiation with a high energy density beam, with a focused beam diameter of 300 μm or less and a power density of 1.0 x 10^5 to 1.0
The information recording method according to claim 2, which is performed using a beam of x10^7w/cm^2. (4) The variation in the nickel layer thickness (μm) and the surface roughness Rmax are 2 μm or less, and the average penetration is The information recording method according to claim 2 or 3, wherein the high energy density beam is irradiated so that the depth @D@ (μm) satisfies the following equations (3) and (4). Ni equivalent (Nieq, %)=%Ni+30×%C+0.
5×%Mn...(1) Cr equivalent (Creq, %)=%Cr
+%Mo+1.5×%Si+0.5×%Nb…(2)(
% indicates weight %. ) {(@D@−ι)・Mieq+100×ι}/@D@≧
0.61×{(@D@-ι)・Creq)/@D@}-
6.1...(3)