JPH0743903B2 - Metal hub for magnetic disk - Google Patents

Description

TECHNICAL FIELD The present invention relates to a metal bubb for a disk, and more particularly to a metal hub for a high hardness magnetic disk having improved press workability.

(Prior Art) As shown in FIG. 1, a magnetic disk metal hub 1 is a disk-shaped one mounted at the center of a floppy disk.
This is the part that the floppy disk rotates around when it is activated. While press-molding into the shape shown, centering hole 2 in the center and chucking hole 3 beside it
Is formed. The centering hole 2 has a shape that is bent inward, and is subjected to considerably severe processing together with the peripheral edge portion 4.

Conventionally, ferritic stainless steel such as SUS430 has been used for a metal hub for disks. This is because non-magnetic austenitic stainless steel cannot be used because the metal hub for floppy disks needs to be attached and detached by a magnet.

In recent years, magnetic recording devices and equipment have been remarkably developed, and, for example, floppy disks have become remarkably widespread, and the production volume of metal hubs used therein has also expanded significantly.

By the way, the magnetic disk metal hub is closely contacted and driven by the disk driver, and the positioning pin slides on the metal hub, so if abrasion powder adheres to the magnetic sheet, it may cause a malfunction, so severe wear resistance is required. It On the other hand, the magnetic disk metal hub has a small shape and is manufactured by press molding.
Further, since it is necessary to reduce the amplitude of the floppy disk due to rotation and strict shape accuracy is required when processing the metal hub, a material excellent in secondary workability, that is, press formability is required.

Since a large amount is produced as described above, press formability suitable for it is required. In addition, today, as more advanced functions are required, the wear resistance further deteriorated as a metal hub for magnetic disks.
And excellent magnetic properties, that is, high magnetic permeability and low coercive force are required.

Conventionally, hard rolling is performed using SUS430 to improve wear resistance, and then press working on a metal hub or press working on a metal hub to improve wear resistance,
It was produced by either Cr or Ni plating.

However, if the method of performing hard rolling raises the hardness and improves the wear resistance too much, the secondary workability will be greatly reduced this time, and it will be sufficient as a metal hub that requires strict shape accuracy. Molding becomes impossible. Therefore, conventionally, a material with a hardness of about Hv230 by hard rolling and an elongation of about 3% is used.

Such a conventional technique has a problem that the wear resistance is not sufficient or press cracks are generated in the secondary processing.

On the other hand, those plated with Cr or Ni have sufficient wear resistance, but they cause a significant cost increase. It is desired that the metal hub for a disk, which is used in a large amount as in today's day, is slightly cheaper.

(Problems to be Solved by the Invention) As described above, as a metal disk magnetic hub,
It has been considered that the wear resistance and the secondary workability have a relationship between the front and back, and both cannot be satisfied at the same time.

Therefore, in order to practically satisfy both characteristics,
The required performance is being secured by plating Cr or Ni on a soft material that is not hard rolled.

However, such a conventional method has many processing steps such as a plating processing, and the cost is inevitable.

Thus, an object of the present invention is to provide a pressed metal hub for a magnetic disk, which can satisfy both wear resistance and secondary workability at the same time.

Another object of the present invention is to provide an inexpensive metal hub for a magnetic disk capable of satisfying both wear resistance and secondary workability at the same time by improving the material surface without performing Cr plating or Ni plating. It is to be.

(Means for Solving Problems) In order to achieve such an object, the present inventors examined whether or not the wear resistance and the secondary workability could be improved in terms of the alloy composition. First, the metal hub for magnetic disks is required to have the following characteristics.

Good moldability.

It has excellent wear resistance.

Must have magnetic properties equivalent to or better than SUS430.

Therefore, in order to satisfy such characteristics, by increasing the Si amount in the conventional ferritic stainless steel to increase its hardness, while reducing the toughness by increasing the Si amount, by optimizing the Ni amount, Furthermore, they have found that an optimum material for a magnetic disk metal hub can be obtained by adjusting the composition range so as to prevent cold-crack cracking of the slab, and completed the present invention.

Thus, the present invention is based on such findings,
The gist is, in wt%, C: 0.12% or less, Si: more than 1.0%, 3.5% or less, Mn: 0.10 to 2.0%, Cr: 11 to 23%, Ni: 0.2 to 3.0%, N: 0.12% or less, optionally Cu: 1.0% or less and / or Mo: 3.0% or less, and also optionally Nb: 1.0% or less, and Ti,
Al and Zr each contain one or more of 0.5% or less, and A = (Ni + 0.5Mn + 35C + 40N) -0.31 (Cr + 1.5Si + 0.5Nb + 12Ti + 6Al + 1.5Mo + 12Zr) A value determined by the relational expression is -2.7 to It is a metal hub for a magnetic disk obtained by pressing a ferritic stainless steel plate having a composition of Fe and inevitable impurities in the range of 0.

As described above, the effect on the wear resistance improvement by adding a particularly large amount of Si is not yet fully understood, but it is considered that the addition of Si forms a surface oxide film rich in lubricity. To be As in the past, hard rolling may harden the wear surface, use compressive residual stress, reduce the roughness of the wear surface, etc. It is speculated that by increasing the amount, the new surface of the hard rolling is covered with the Si-rich lubricious surface oxide film as described above.

Thus, according to the present invention, it is possible to obtain a metal hub for a disk that is press-formed from ferritic stainless steel having excellent wear resistance, and in the present invention, if desired, Ca: 0.01% Hereinafter, a material further containing at least one or more of B: 0.01% or less, Mg: 0.04% or less, and rare earth element: 0.04% or less may be used.

(Operation) Next, the reason why the steel composition is limited as described above in the present invention will be described in detail.

C, N: C, N all strengthen the substrate as an interstitial solid solution element,
To improve wear resistance, (C + N) is at least 0.
02% is preferable. However, if the amount of (C + N) becomes large, the secondary workability deteriorates accordingly, so the upper limits of C and N were made 0.12% respectively. Preferably,
(C + N) ≦ 0.14%.

Si: Si is the most important element for constituting the present invention, and is an element essential for improving wear resistance and secondary workability and for measuring magnetic performance, and the amount thereof exceeds 1%. It is effective to be added. However, even if added over 3.5%,
Since the toughness is significantly deteriorated and the manufacturability is impaired, the content is limited to 3.5% or less in the present invention. It is preferably 2.0 to 2.5%.

Mn: Mn is effective as a deoxidizing and desulfurizing agent during normal steelmaking, and 0.1%
On the other hand, when the wear resistance is improved by substitutional solid solution strengthening as in the present invention, secondary workability can also be improved by the combined addition of Si. However, if added in a large amount, it hinders hot workability, so 2.
Limit to 0% or less.

Cr: Cr is 11% in order to ensure corrosion resistance as stainless steel.
The above is added. Preferably, 16% or more is added. Although the corrosion resistance is improved as the amount of addition is increased, however, the cost of adding an excessively large amount is increased and a ferritic stainless steel satisfying the limitation of the A value cannot be obtained. Therefore, the upper limit is set to 22%.

Ni: Ni is effective for improving the toughness of Si-added steel, and is necessary for improving the secondary workability of hard rolled materials by adding it in combination with Si.

This effect is seen at the addition of 0.2% or more, and the degree of improvement increases as the addition amount increases, but 3.0%
Even if added in excess, the effect will be saturated, and addition of an excessively large amount will result in high cost, so the upper limit is made 3.0%. Preferably, it is more than 0.6% and 2.0% or less.

Cu: Cu is a desired additive element, and it is effective to improve the secondary workability of the hard material by the composite addition of Si like Ni and Mn. However, even if added in an amount exceeding 1.0%, the effect cannot be sufficiently exhibited, and rather the hot workability is adversely affected, so the upper limit was made 1.0% or less.

Mo: Mo is a desired additive element, and is an element having an effect of improving corrosion resistance equal to or more than Cr. It also has the effect of improving the secondary workability and wear resistance of the hard material.
However, the addition of Mo increases the cost, and the addition of a large amount embrittles the base material, so it is limited to 3.0% or less.

Nb, Ti, Al, Zr: These elements have the effect of improving the secondary workability of ferritic stainless steel. However, even if Nb is added in excess of 1.0% and Ti, Al, and Zr are each added in excess of 0.5%, their performance will be saturated, and inclusions such as nitrides will be scattered. Secondary workability is rather deteriorated. Therefore, the upper limits for these elements are Nb
Is 1.0%, and Ti, Al, and Zr are each 0.5%.

B, Ca, Mg, rare earth elements: B and Ca increase strength and ductility at high temperatures even when added in a trace amount, and are effective in improving hot workability. It is also effective in improving wear resistance. However, if it exceeds 0.01%, embrittlement is caused, so the addition amounts of B and Ca are both limited to 0.01% or less.

For the same reason, Mg and rare earth elements are also limited to 0.04% or less.

Regarding A value: When the A value is smaller than -2.7, the precipitation of γ phase is reduced at high temperature, and cold block cracking of the slab occurs. On the other hand, when the A value is larger than zero (0), the γ phase becomes too much. ,
Ear cracking occurs during hot rolling, which significantly impairs productivity. Therefore, in the present invention, since it is a high Si material, this A value is limited to an appropriate range of -2.7 to 0.

The invention will now be described in more detail in connection with examples.

Example A 10 kg flat steel ingot having each steel composition shown in Table 1 was melted in a small experimental high frequency furnace. The obtained steel ingot has a heating temperature of 1200 ° C.
After hot rolling from 50mm thickness to 4mm thickness at
By annealing at 00 ° C and cold rolling, a cold rolled annealed material having a thickness of 0.6 mm was manufactured.

From the cold rolled annealed material thus obtained, the Vickers hardness
Hard rolling was performed so as to be Hv230, and the mechanical properties, abrasion resistance, and secondary workability were evaluated.

The wear resistance was evaluated by sliding a steel ball of a constant load on the surface of the test material without lubrication by the Bowden test and the number of sliding times until the frictional force sharply increased.

The secondary workability was evaluated by elongation in a tensile test and an Erichsen test according to JIS Z2247.

In addition, the evaluation of hot workability is performed by splitting the edge crack of the rolled material and the cast slab when hot rolling from 50 mm to 4 mm thickness at a heating temperature of 1200 ° C and evaluating whether there is internal cracking at that time. did. The toughness of the hot rolled material was evaluated by performing an impact test (2 mm V notch) after annealing the hot rolled 4 mm thick plate material at a predetermined temperature.

The results are also summarized in Table 1.

Regarding the magnetic properties required for a metal hub for a magnetic disk, the steel according to the present invention having the chemical composition shown in Table 2 and SUS430 for comparison were subjected to cold rolling annealing and hard rolling. JIS C 25 for both
It measured according to the measuring method shown by 31.

The results are shown in Table 3. It is clear that the steel according to the present invention has better magnetic properties than the conventional SUS430.

Further, a representative example of a steel-scale mass-produced material for steel according to the present invention shown in Table 2 and a conventional SUS430 were hard rolled to a predetermined hardness, and a metal hub for a magnetic disk was manufactured by press working. In order to improve the wear resistance of the metal hub, the steel according to the present invention has a higher hardness than that of SUS430. The plate thickness was 0.30 mm. Table 4 shows the typical mechanical properties of both steel types that were put to practical use.

It is clear from a comparison between the two that the steel according to the present invention has excellent Erichsen value, which is an index of press workability, and elongation particularly in the direction perpendicular to the rolling direction, even if the hardness is higher than that of the conventional steel. It is that you are. Even in the actual press work, when the inner radius of the shoulder portion of the metal pub is made small in order to make the dimensional accuracy after processing strict, the conventional steel SUS430 often causes cracking. In this case, even though the hardness was high, cracks did not occur even if the same press die was used, and the dimensional accuracy was good.

(Effects of the Invention) As described in detail above, according to the present invention, a metal hub for a disk, which is particularly excellent in wear resistance and has a long service life and high reliability, can be obtained and, together with its inexpensive characteristics, affects the field. There are big profits.

[Brief description of drawings]

FIG. 1 is a perspective view of a disk metal hub according to the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 60-38774 (JP, A) JP 59-38300 (JP, B2) JP 56-41694 (JP, B2) JP 61- 44121 (JP, B2) JP 61-46547 (JP, B2)

Claims (6)

[Claims] 1. By weight%, C: 0.12% or less, Si: more than 1.0%, 3.5% or less, Mn: 0.10 to 2.0%, Cr: 11 to 23%, Ni: 0.2 to 3.0%, N: 0.12% The following values are included, and A = (Ni + 0.5Mn + 35C + 40N) -0.31 (Cr + 1.5Si), which has an A value within the range of -2.7 to 0, and a balance Fe and inevitable impurities. Metal hub for magnetic disks obtained by pressing a ferritic stainless steel plate. 2. By weight%, C: 0.12% or less, Si: more than 1.0%, 3.5% or less, Mn: 0.10 to 2.0%, Cr: 11 to 23%, Ni: 0.2 to 3.0%, N: 0.12% Below, Cu: 1.0% or less and / or Mo: 3.0% or less is contained, and A value determined by the relational expression A = (Ni + 0.5Mn + 35C + 40N + 0.3Cu) -0.31 (Cr + 1.5Si + 1.5Mo) is -2.7. A metal hub for a magnetic disk, which is obtained by pressing a ferritic stainless steel plate having a composition of balance Fe and unavoidable impurities in the range of 0 to 0. 3. By weight%, C: 0.12% or less, Si: more than 1.0%, 3.5% or less, Mn: 0.10 to 2.0%, Cr: 11 to 23%, Ni: 0.2 to 3.0%, N: 0.12% In addition, Nb: 1.0% or less and Ti, Al and Zr respectively 0.
5% or less of 1 type or 2 types or more, and A = (Ni + 0.5Mn + 35C + 40N) -0.31 (Cr + 1.5Si + 0.5Nb + 12Ti + 6Al + 12Zr) A value determined by the relational expression is within the range of -2.7 to 0 A metal hub for a magnetic disk obtained by pressing a ferritic stainless steel plate having a composition of balance Fe and inevitable impurities. 4. By weight%, C: 0.12% or less, Si: more than 1.0%, 3.5% or less, Mn: 0.10 to 2.0%, Cr: 11 to 23%, Ni: 0.2 to 3.0%, N: 0.12% Below, Cu: 1.0% or less and / or Mo: 3.0% or less, and Nb: 1.0% or less and Ti, Al and Zr respectively 0.
5% or less of 1 type or 2 types or more, and A = (Ni + 0.5Mn + 35C + 40N + 0.3Cu) -0.31 (Cr + 1.5Si + 0.5Nb + 12Ti + 6Al + 1.5Mo + 12Zr) A value is -2.7 to 0 A metal hub for a magnetic disk obtained by pressing a ferritic stainless steel plate having a composition within the range of which the balance is Fe and inevitable impurities. 5. By weight%, C: 0.12% or less, Si: more than 1.0%, 3.5% or less, Mn: 0.10 to 2.0%, Cr: 11 to 23%, Ni: 0.2 to 3.0%, N: 0.12% In addition, one or more of Ca: 0.01% or less, B: 0.01% or less, Mg: 0.04% or less and rare earth element: 0.04% or less, and A = (Ni + 0.5Mn + 35C + 40N + 0.3Cu) -0.31 (Cr + 1.5Si + 0.5Nb + 12Ti + 6Al + 1.5Mo + 12Zr) A value determined by the relational expression was within the range of -2.7 to 0, and was obtained by pressing a ferritic stainless steel sheet having the composition consisting of balance Fe and unavoidable impurities. Metal hub for magnetic disks. 6. By weight%, C: 0.12% or less, Si: more than 1.0%, 3.5% or less, Mn: 0.10 to 2.0%, Cr: 11 to 23%, Ni: 0.2 to 3.0%, N: 0.12% Further, Cu: 1.0% or less and / or Mo: 3.0% or less, Nb: 1.0% or less and one or more of Ti, Al and Zr each 0.5% or less, and Ca: 0.01% or less, B: 0.01 % Or less, Mg: 0.04% or less and rare earth element: 0.04% or less, one or more, and A = (Ni + 0.5Mn + 35C + 40N + 0.3Cu) -0.31 (Cr + 1.5Si + 0.5Nb + 12Ti + 6Al + 1.5Mo + 12Zr) A metal hub for a magnetic disk obtained by pressing a ferritic stainless steel plate having an A value determined by a relational expression within a range of -2.7 to 0 and having a composition of balance Fe and inevitable impurities.