JPH0772302B2 - Manufacturing method of steel bar for magnetic scale - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement in a method for manufacturing a steel rod for a magnetic scale used in the field of mechatronics.

(Prior art and its problems) With the development of mechatronics in recent years, a magnetic scale as shown in Fig. 10 has come to be used as a position detection mechanism, but conventionally a 18Cr-7Ni steel bar was used. It had been. In FIG. 10, 1 is a base metal part, 2 is a solution-ized (non-magnetic) part, 3
Indicates a position detection sensor.

However, the above 18Cr-7Ni system may have insufficient non-magnetism in the solution state, and this tendency becomes remarkable especially when Ni is adjusted to a low level in order to enhance the process-induced magnetism. .

In addition, since the High-Ni type is disadvantageous in terms of cost,
The use of Mn-Cr system in which
-HighCr-based ones have drawbacks such as δ-ferrite being generated during solution treatment and non-magnetism cannot be maintained, and ε-martensite is generated, resulting in lack of processing-induced ferromagnetization properties. It was hindered.

That is, the magnetic grading material must meet the two requirements of ensuring non-magnetism in the solution state and ferromagnetization by cold drawing, and structurally δ ferrite and ε martens Holds the occurrence of the site and α'by cold working
It must promote the production of martensite.

On the other hand, it has been found by experiments conducted by the present inventors that these characteristics are changed by changing the composition ratio of Mn, Cr, C and N.

That is, the present invention provides a method of manufacturing a steel rod for magnetic grading of Mn-Cr system which can satisfy the above-mentioned requirements, reduce cost and improve magnetic grading characteristics.

(Means for Solving Problems) As a characteristic that a typical magnetic scale portion as shown in FIG. 10 should have, a base material portion is a ferromagnetic material and a saturation magnetic flux density of at least 5000 G or more is required. To have.

The solution-treated part must be non-magnetic and have a magnetic permeability of 1.02 or less.

The base material plays a role as a structural member and has ductility and impact resistance (RA ≧ 30%) in order to withstand repeated impact during use.

Low alloy steel cost so that it can be used as a structural member.

is necessary.

The present inventors tried various experimental studies in order to realize a steel rod satisfying these requirements by adjusting constituent elements and selecting processing conditions.

Generally, it is difficult to request the contradictory properties of ferromagnetism and non-magnetism of a steel rod having one kind of component system. However, it is difficult to have ferromagnetism in the solution state as seen in unstable austenitic steels represented by 18-8 stainless steel, and it is difficult to have ferromagnetism after cold working. It is possible to realize the above-described requirements by making the material ferromagnetic by cold working and then locally re-solutionizing it by a method such as laser irradiation to demagnetize only that portion.

Therefore, Cr-Ni-based unstable austenitic steel is considered to have the potential to have such properties.
Although the practical application of the Cr-7Ni component system has already been examined, the cost of this component system is higher than that of commonly used low alloy steel.

The non-magnetism in the solution state is unstable and the position detection accuracy is low.

Etc. remained the problem.

Therefore, the inventors of the present invention focused on unstable austenite by Mn-Cr system, adjusted the component elements, selected the processing conditions to obtain a steel rod for magnetic graduation that overcomes these problems, and established the present invention. .

First of all, the problem of high cost was greatly improved by using Mn instead of Ni, and it was expected that it could be almost solved.Therefore, the remaining problem is a component system having the function to be equipped as a magnetic scale material. We conducted various experiments and researches to find out the processing conditions.

Unstable austenitic steels obtained with high Mn and high Cr systems generally tend to form δ ferrite in the solution state and are difficult to demagnetize.

Even if the production of δ ferrite can be suppressed due to the non-magnetization, ε martensite remains. Although ε-martensite is non-magnetic and has no problem as a property in a solution state, it inhibits ferromagnetization by cold working.

Therefore, it was considered difficult to use as a magnetic scale material.

Therefore, the present inventors arranged the four conditions that the magnetic scale material should have as follows, and examined the components and processing conditions including the range that was conventionally overlooked.

First, ensuring non-magnetism in the solution state, then ensuring a saturation flux density of 5000 G or more by working, and ensuring the ductility of the steel rod after working.

As a result, in the composition ratio of Mn, Cr, C and N, Mn was set from 14.0 to
19.0 wt%, Cr 3.0 to 10.0 wt%, C + N 0.3 to 0.5
% By weight, and Rd after solutionizing a steel rod composed of such components
It was clarified that the above-mentioned three conditions were satisfied by drawing the wire to a workability of 20 to 25%, and the present invention was established.

That is, the manufacturing method of the steel rod for magnetic graduation according to the present invention is M
n; 14.0 to 19.0 wt%, Cr; 3.0 to 10.0 wt%, C + N; 0.3
~ 0.4% by weight, the balance of which is Fe and unavoidable impurities, after solution heat treatment, 20-25% cold drawing is carried out to have a saturated magnetic flux density of 5KG or more. The gist is to ensure that the portion to be magnetized is locally non-magnetized by locally heating it to form a solution.

Next, the reasons for limiting the components and processing conditions will be specifically described.

1) Mn is an austenite-stabilizing element and as shown in Fig. 14
If it is less than 10% by weight, it becomes difficult to secure non-magnetic property (permeability μ ≦ 1.02) in the solution state (1050 ° C.), so it is set to 14.0% by weight or more.

On the other hand, if it exceeds 19% by weight, wire drawing workability is deteriorated, austenite is stabilized, and ferrite work induction is reduced. As a result, it becomes difficult to make it ferromagnetic as shown in FIG. 2 (processing impossible for Rd ≧ 20%, saturation magnetic flux density of 4 KG or more is not possible), so the content was made 19 wt% or less.

The results shown in FIGS. 1 and 2 are for the case where Cr is 5.0% by weight and C + N is 0.3% by weight.

2) Regarding Cr, which is effective in stabilizing austenite by the combined addition of Mn and Mn within the range of the present invention (14.0 to 19.0 wt%),
When Cr exceeds 10% by weight, δ ferrite is generated, and it becomes difficult to secure nonmagnetic property (permeability μ ≦ 1.02) in the solution state (1050 ° C) as shown in Fig. 3. Since it is difficult to secure non-magnetism, it was set to 3.0 to 10% by weight.

The results shown in FIG. 3 show that Mn is 15.0% by weight and C + N is 0.
3% by weight.

3) C + N Since it is an austenite stabilizing element and less than 0.3% by weight, it is difficult to secure non-magnetism in the solution state (1050 ° C.) as shown in FIG.

On the other hand, if it exceeds 0.5% by weight, the wire drawing workability is deteriorated and the austenite is stabilized and the work induction of ferrite is reduced. As a result, as shown in FIG. 5, it becomes difficult to make the material ferromagnetic by processing (processing with Rd ≧ 20% is impossible, saturation magnetic flux density is 4 KG or more is not possible), so 0.5% by weight or less.

The results shown in FIGS. 4 and 5 are for Mn of 15.0% by weight and Cr of 5.0% by weight.

4) Cold Workability The present invention relates to a method of manufacturing a steel rod obtained by subjecting a steel rod having the above component distribution to solution treatment and then cold drawing.

This cold working has the required ferromagnetism, and by making the local solution, it is possible to make only that part non-magnetic.

Thus, this cold drawing is required to control the ferromagnetism and mechanical properties (especially ductility) of the steel bar to the required range. FIG. 6 shows the results of the investigation conducted by the inventors of the present invention to investigate how the saturation magnetic flux density and the drawing change by cold-drawing a steel rod having the above-described composition.

As is clear from the figure, when it is less than 20%, the saturation magnetic flux density of 4KG or more cannot be obtained, and when it exceeds 25%, the ductility (drawing) is extremely lowered. For these reasons, the present invention limits the workability to the range of 20 to 25%.

The results shown in FIG. 6 are obtained when Mn is 15.0% by weight, Cr is 5.0% by weight, and C + N is 0.3% by weight.

5) Saturation magnetic flux density In the position detection mechanism as shown in FIG. 10, the degree of non-magnetism of solution-treated part 2 (low magnetic permeability) and the degree of ferromagnetism of base material 1 (high saturation magnetic flux density) Influences the detection accuracy.

That is, when the non-magnetic property of the solution heat treated portion 2 is completely ensured, the detection accuracy is proportional to the saturation magnetic flux density of the base material portion 1. The result of the investigation of the situation is shown in FIG.

As is clear from the figure, the round trip error showing the detection accuracy at 5 kg or more is stabilized at a high constant level. Therefore, the present invention requires a saturation magnetic flux density of 5 KG or more.

In addition, the result of FIG. 7 (a) shows that Mn is 15.0 wt% and Cr is 6.0.
%, And C + N is 0.3% by weight. The round-trip error β on the vertical axis of FIG. 9 (a) is as shown in FIG. It is represented by. Further, in FIG. 4B, the solid line indicates the forward direction, the broken line indicates the backward direction, and E on the vertical axis indicates the starting force applied to the detection sensor 3.

(Examples) Part 1) The effects of the present invention will be described with reference to Examples. Steel Nos. 1 to 24 having the components shown in the following table were melted in a 150 kg vacuum melting furnace, hot-rolled into a 32φ bar material, externally cut to 25φ, and subjected to a test.

In Examples No. 1 to 6, the effect of Mn and the reason for limitation were demonstrated.

That is, the 25φ test steel was subjected to solution treatment at 1050 ° C., the magnetic permeability was measured, and the drawing after drawing and the saturation magnetic flux density were measured.

As a result, in Comparative Examples Nos. 1, 5 and 6, No. 1 having a low Mn compounding ratio has a high magnetic permeability during solution treatment, and a high No.
In Nos. 5 and 6, the saturation magnetic flux density after wire drawing was low.

On the other hand, in the invention examples Nos. 2, 3 and 4, values satisfying both the magnetic permeability and the saturation magnetic flux density were obtained.

Next, in Examples Nos. 7 to 12, the effect of Cr and the reason for limitation were verified.

That is, after the solution treatment of the 25φ test steel at 1050 ° C,
The magnetic permeability was measured.

As a result, in Comparative Examples Nos. 7, 11 and 12, No. 7 having a low Cr content and Nos. 11 and 12 having a high Cr content had high co-permeabilities and non-magnetism was not secured.

In contrast, the invention examples Nos. 8, 9 and 10 are completely demagnetized.

Next, in Examples Nos. 13 to 20, the effect of C + N and the reason for limitation were demonstrated.

That is, in Examples Nos. 13 to 17, the test steel of 25φ was 1
After solution treatment at 050 ° C, the magnetic permeability was measured. Further, in Examples Nos. 18 to 20, after solution treatment, wire drawing was performed, and the diaphragm and the saturation magnetic flux density were measured.

As a result, in Comparative Examples Nos. 13, 14, 15, 18, 19, and 20, Nos. 13, 14, and 15 having a low C + N compounding ratio, respectively, have a high magnetic permeability in a solution state and a high C + N ratio. .18, 19, and 20 had low saturation magnetic flux density after drawing.

On the other hand, in the invention examples Nos. 16 and 17, the magnetic permeability in the solution state is low, and the diaphragm after drawing and the saturation magnetic flux density also show high values.

Finally, in Examples Nos. 21 to 24, the reasons for limiting the wire drawing workability and the saturation magnetic flux density were demonstrated.

That is, the sample steel of 25φ was subjected to solution treatment at 1050 ° C., drawn, and drawn and the saturation magnetic flux density was measured. Furthermore, magnetic graduation processing by laser irradiation was performed, and the detection accuracy by a magnetic sensor was also measured.

As a result, in No. 21 which is a comparative example, the detection accuracy of the magnetic scale portion is 14.1%, which is lower than 5.0% and 4.0% of Nos. 22 and 23 which are invention examples. Further, in Comparative Example No. 24, the workability was as high as 30% and the drawing was reduced to 13%.

As described above, in the examples shown in the following table, it is understood that the invention examples have obtained satisfactory characteristics as the steel rod for magnetic graduation.

No. 2) Using No. 2 steel shown in the table of Example No. 1), 1050 ° C.
After solution treatment, wire drawing of Rd = 24% was performed, the obtained steel rod was surface-ground, and the surface layer portion was solution-treated by laser irradiation. Then, the magnetizing force of the solution-annealed part of the steel bar and the base metal part 10 ⁴ Oe
Magnetic flux density was measured.

The results are shown in Fig. 8 (a) and (b). As is clear from the figure, the steel rod manufactured by the method of the present invention is locally solution-treated by a method such as laser irradiation so that the portion (solution-treated portion 2) can be demagnetized and used as a magnetic scale. I understand.

Part 3) Fig. 9 shows the difference in the work-induced magnetism depending on the compounding ratios of Mn, Cr, and C + N. In Fig. 9, ○-○ is 15.0% by weight of Mn and 5.
0% by weight, C + N is 0.3% by weight, Are the same as above, respectively, 10.0% by weight, 1.0% by weight and 0.2% by weight, and ●-● are also 21.0% by weight, 15.0% by weight and 0.
5% by weight is shown.

As is clear from the figure, ○-○ and wire drawing rate of 20-25%
It can be seen that only those within the range of 5 have a saturation magnetic flux density of 5 KG or more and satisfy the present invention.

(Effect of the invention) As described above, the present invention is Mn; 14.0 to 19.0 wt%, C
r; 3.0 to 10.0% by weight, C + N; 0.3 to 0.4% by weight, with the balance being Fe
After the solution treatment of the material consisting of unavoidable impurities, it is cold drawn to 20 to 25% to have a saturation magnetic flux density of 5KG or more, and then the portion of the material to be non-magnetized is heated. Since it is a method of manufacturing a steel rod for magnetic graduation formed by solution heat treatment, it has two characteristics: properties required for a steel rod for magnetic graduation, namely, ensuring non-magnetism in a solution state and making it ferromagnetic by cold drawing.
The two characteristics are sufficiently satisfied, and it is also advantageous in terms of cost.
Therefore, according to the present invention, it is possible to sufficiently meet the demands in the field of mechatronics, which has made remarkable progress in recent years, especially in robots and the like.

[Brief description of drawings]

Fig. 1 is a diagram showing the effect of Mn on the magnetic permeability in the solution state, Fig. 2 is a diagram showing the effect of Mn on the change of the saturation magnetic flux density by wire drawing, and Fig. 3 is the solution state. Fig. 4 shows the effect of Cr on the magnetic permeability of Fig. 4, Fig. 4 shows the effect of C + N on the magnetic permeability in the solution state, and Fig. 5 shows the effect of C + N on the change of the saturation magnetic flux density by wire drawing. FIG. 6 is a diagram showing changes in magnetic characteristics and aperture due to wire drawing, FIGS. 7 (a) and (b) is a diagram showing changes in round trip error due to saturation magnetic flux density, and FIG. 8 (a) ( (B) is a diagram showing an example of a magnetic scale using the steel rod of the present invention, and FIG. 9 is Mn, Cr, C + N.
FIG. 10 is a view showing a difference in processing-induced magnetism according to FIG. 10, and FIG. 10 is a view showing an example of a position detecting mechanism by a magnetic scale.

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Claims (1)

[Claims] 1. A steel bar containing Mn; 14.0 to 19.0 wt%, Cr; 3.0 to 10.0 wt%, C + N; 0.3 to 0.4 wt% and the balance being Fe and inevitable impurities, and then cold-treated at 20 ~ 25% wire drawing to have a saturation magnetic flux density of 5KG or more, and then the portion of the steel rod to be non-magnetized is locally heated to form a solution, which is a method for manufacturing a steel rod for magnetic graduation. .