JPH0475307B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an improvement of a magnetic scale steel rod used in the mechatronics field. (Prior art and its problems) In recent years, with the development of mechatronics, magnetic scales have come to be used as position detection mechanisms as shown in FIG. 6A. The characteristics required for this material for magnetic scales are that the combination of ferromagnetism and non-magnetism as shown in FIG. 6A can be easily realized industrially.
In FIG. 6A, 1 is a base material part, 2 is a solution-treated (non-magnetic) part, and 3 is a position detection sensor. As a specific method, for example, JP-A-58-
As shown in Japanese Patent No. 7517, a metal compound is chemically plated on the surface of a metal material and then heated with a particle beam such as a laser to form magnetically altered parts at predetermined intervals. Also, JP-A-57-
Publication No. 16309 discloses a method of irradiating the surface of a metal material with a high-energy beam to locally heat-treat the surface and magnetically change the material to form a scale. However, these require expensive detection equipment because the difference in magnetic properties between the scale part and the base part is small.
Another disadvantage was that detection reliability was low. Therefore, as a countermeasure to this problem, examples have been shown of applying very expensive magnetic materials such as alloys with 25% by weight Fe and 75% by weight Ni, but this is only expensive and does not offer much strength or wear resistance. Not only are there many restrictions on usage, but the magnetic properties are also far from perfect. On the other hand, it is known that certain types of austenitic stainless steels are non-magnetic in the solution state, but undergo a strain-induced transformation during cold working and become ferromagnetic. There is a possibility that a scale can be realized. The purpose of the present invention is to improve the composition of a steel rod for magnetic scales in order to improve its performance as a material for magnetic scales based on this phenomenon, thereby achieving a steel rod for magnetic scales that is inexpensive, has high strength, and has excellent magnetic scale performance. Our goal is to provide the following. (Means for solving the problems) The present invention contains Cr, Ni, or further contains Mo.
In a metastable austenitic steel containing M _D =
413−462×(C+N)−9.2Si−8.1Mn−13.7Cr−
The M _D value expressed by the formula 9.5Ni−18.5Mo is 15℃ or higher, and the saturation magnetic flux density is composed of a component that satisfies the conditions of 2Ni + 100
By cold drawing the wire to 5KG or more and 12KG or less, and heating the local area to form a solution, the saturated magnetic flux density of the area is reduced.
The gist of this is that it is non-magnetic and weighs less than 0.1KG. As a steel for magnetic scales, while it can be made completely non-magnetic by solution treatment, excellent properties cannot be obtained unless ferromagnetism is developed as much as possible by cold working. As a result of detailed research into material components to achieve this, the inventors found that non-magnetization and ferromagnetization are contradictory, and in order to achieve this, it is necessary to properly select trace elements. I found that I had to control it. Specifically, the characteristics necessary for a magnetic scale material are as follows. The base material must be ferromagnetic and have a saturation magnetic flux density of 5KG or more. The solution-treated part is a non-magnetic material, and the saturation magnetic flux density
Must be less than 0.1KG. In the present invention, in order to obtain these characteristics, each specification is limited as described above. The reasons for this limitation will be described in detail below. As mentioned above, the magnetic scale utilizes the difference in magnetic properties between the ferromagnetic part and the non-magnetic part for position detection.
Therefore, in order to obtain the above-mentioned required characteristics, it is necessary to maintain the ferromagnetism and nonmagnetism at a certain level. Figure 1 shows the relationship between the saturation magnetic flux density of the base material and the reciprocating error of the magnetic sensor. Here, the reciprocating (output) error of a magnetic sensor is the amount of change (peak output difference, △V) in the "peak voltage in the output waveform" when the sensor or magnetic scale material is reciprocated as shown in Figure 6 (b). It is then divided by 1/2 of the peak voltage width (peak output value, V) and expressed as a percentage. That is, the round trip (output) error is expressed as [ΔV/(V/2)]×100%. Since this numerical value has a very large effect on positional accuracy, it is an important characteristic for magnetic scales. Therefore, a reciprocating error of 4.0% or less is a practical allowable range, but it can be seen from Fig. 1 that a saturation magnetic flux density of 5 KG or more is required to maintain this. Of course, as mentioned above, the characteristics of the magnetic scale are influenced not only by the ferromagnetism of the base material but also by the degree of nonmagnetism of the solution-treated part, and the larger the difference between the two, the better the characteristics (the smaller the error). Figure 1 shows that the saturation magnetic flux density of the solution-treated part is 50 to 70G.
This is an example of almost completely non-magnetic material. In this manner, when the solution-treated part is completely non-magnetic, the sensor output remains constant as the saturation magnetic flux density of the base metal part changes, but the reciprocating error decreases as it increases. That is, in order to suppress the reciprocating error of the magnetic sensor to 4% or less, which is the practical allowable range, the saturation magnetic flux density of the base material must be 5 KG or more, and the present invention is limited to this value. On the other hand, FIG. 2 shows the influence of the saturation magnetic flux density of the solution-treated section on the reciprocating error. As is clear from the figure, when the saturation magnetic flux density of the solution-treated portion increases and nonmagnetism cannot be maintained, the sensor output decreases, and as a result, the reciprocating error increases. In order to reduce the reciprocating error to 4.0% or less, which is the practical allowable range, it is necessary to make the saturation magnetic flux density of the solution treatment part 100G (0.1KG) or less, and the present invention is limited to this value. Next, in the present invention, the steel type components that can realize such magnetic properties are limited. The present inventors believe that Cr-Ni metastable austenite can be used as an evaluation index for stability against processing.
Using the M _D value, we organized the magnetic properties obtained by solution treatment and wire drawing. The result is the third
It is shown in FIG. M _D value is 413−462×(C+N)−9.2Si−8.1Mn−
It is expressed by the formula 13.7Cr−9.5Ni−18.5Mo, and Figure 3 shows how the saturation magnetic flux density after wire drawing changes depending on the M _D value, and Figure 4 shows how the saturation magnetic flux density changes depending on the M D value after wire drawing. Each figure shows how the saturation magnetic flux density increases. It can be seen from Figure 3 that if the M _D value is 15℃ or less, the required 5KG cannot be secured even if the degree of processing is increased (the same can be seen from Figure 4). Furthermore, from Fig. 4, it can be seen that when the M _D value is 12°C, the increase in saturation magnetic flux density due to wire drawing reaches a ceiling at about 4.5KG, and the required 5KG cannot be secured.
For these reasons, in the present invention, the _MD value is limited to 15°C or higher. Furthermore, as shown in Fig. 4, when the saturation magnetic flux density increases due to cold wire drawing and exceeds 12 kg, processing cracks occur. This is because the amount of deformation-induced martensite generated exceeds the allowable limit and causes cracks.For this reason, the upper limit of the saturation magnetic flux density is limited to 12KG in the present invention. Figure 5 shows the saturation magnetic flux density in the solution state for Ni,
It shows how it changes depending on Cr, C, and N. The increase in saturation magnetic flux density in the solution state is mainly due to the generation of δ ferrite. When Ni, C, and N decrease, they promote the generation of δ ferrite, while when Cr decreases, the generation of δ ferrite decreases. 2Ni+100×(C+N)-Cr was used as an index to organize the change in saturation magnetic flux density due to the generation of δ ferrite in this solution state. The result is shown in FIG. As is clear from the figure, the required non-magnetic level is achieved.
To ensure 100G (0.1KG) or less, 2Ni + 100×
The value of (C+N)-Cr is required to be 2.0 or more. For these reasons, in the present invention, 2Ni+100×(C
+N)-Cr value was limited to 2.0 or more. (Example) The effects of the present invention will be explained by examples. In this example, No. 1, 5, 8, 11, 14 listed in the table below,
Steels Nos. 16, 19, and 21 to 27 were melted in a 150Kg vacuum melting furnace and hot forged into 32φ bars, which were externally machined to 25φ and used for testing.

【table】

[Table] In Examples Nos. 1 to 4, the M _D value was 12.3, which was below the range of the present invention. For this reason, the saturation magnetic flux density in the solution state maintains a sufficiently low value of 20G or less, but after wire drawing, even if the degree of processing is increased to 57%.
It only reaches 4420G, and there is no tendency for it to increase even if it is processed further. Therefore, after drawing the wire to each degree of processing and processing the solution scale with a laser, the accuracy was measured using the detection device shown in Figure 6, and as a result, the accuracy was less than 5 kg in both cases, so the reciprocating error was 5.4% ~
14.5%, which exceeds the practical allowable range of 4.0%. In Example Nos. 5 to 15, the M _D values were all 18.0 to 64.5, which were within the range of the present invention. However, Example No. 5,
In No. 8, the increase in saturation magnetic flux density due to cold wire drawing is only 3050G and 4500G, respectively, which is within the scope of the present invention.
It has not reached 5000G. Therefore, the round trip error is
12.1% and 5.4%, exceeding the practical allowable range of 4.0%. On the other hand, in Example Nos. 13 and 15, the saturation magnetic flux density after cold wire drawing was 13500G and 13100G, respectively, which is within the range of the present invention.
Processing cracks have occurred because the force exceeded 12000G.
Other examples No. 6, 7, 9, 10, 11, 12, 14
In this case, the M _D value, 2Ni+100×(C+N)-Cr, and the saturation magnetic flux density after wire drawing are all within the range of the present invention, and the reciprocating error is also within the practical allowable range of 4.0% or less. In Example Nos. 16 to 20, 2Ni+100(C+N)-Cr
The value of is 1.5 to 1.7, which is outside the range of the present invention, and therefore the saturation magnetic flux density during solution treatment is 310 to 1.7.
It exceeds 400G and 100G. Therefore, the reciprocating error is 10.1% to 12.1%, which far exceeds the practical allowable range of 4.0%. Further, in Example Nos. 18 and 20, the saturation magnetic flux densities after wire drawing were 12,200G and 13,000G, respectively, which exceeded the range of 12,000G according to the present invention, and therefore processing cracks occurred. In Example Nos. 21 to 25, the amount of Ni was adjusted to 2Ni+100×
The value of (C+N)-Cr was changed. That is, in Example Nos. 21 to 23, the value of 2Ni+100×(C+N)−Cr is 3.2 to 3.6, which is within the range of the present invention, and the saturation magnetic flux density during solutionization is 40 to 50G, which is below 100G. . Therefore, the reciprocating error is 2.9% to 3.1%, which is within the practical allowable range of 4%. On the other hand, Example Nos. 24 to 25
In this case, the value of 2Ni+100×(C+N)-Cr is 0.5 to 1.9, which is below the range of the present invention, and the saturation magnetic flux density during solutionization is 130 to 950G, which exceeds 100G. For this reason, the round trip error is 5.2% to 17.1%, exceeding 4%. Examples Nos. 26 and 27 show examples in which Mo was added.
Both 2Ni+100×(C+N)-G and M _D values satisfy the range of the present invention, and the round-trip error is 3.0% to 3.2
% is within the acceptable range. As described above, according to the claims of the present invention, it is possible to obtain a steel bar for magnetic scales having the required excellent characteristics. (Effect of the invention) As explained above, the present invention contains Cr, Ni,
Alternatively, in a metastable austenitic steel that further contains Mo, M _D =413−462×(C+N)−9.2Si−
When the M _D value expressed by the formula 8.1Mn−13.7Cr−9.5Ni−18.5Mo is 15℃ or higher, and 2Ni+100×(C+
N)-Cr≧2.0, the wire is cold drawn so that the saturation magnetic flux density is 5KG or more and 12KG or less, and the local area is heated to form a solution, so that the saturation magnetic flux density is 0.1KG. Since it is non-magnetic as shown below, it is inexpensive, has high strength, and has excellent magnetic scale performance.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the magnetic properties of the base metal and the sensor reciprocating error, Figure 2 is a diagram showing the relationship between the magnetic properties of the solution-treated part and the sensor reciprocating error, and Figure 3 is the relationship between the saturation magnetic flux density and M _D 30 after wire drawing. Figure 4 is a diagram showing the influence of M _D 30 points on the increase in saturation magnetic flux density due to wire drawing. Figure 5 is a diagram showing the change in saturation magnetic flux density in the solution state depending on the component. Figure 6 A is a drawing showing an example of a position detection mechanism using a magnetic scale, and B is a diagram illustrating the reciprocating error thereof.

Claims (1)

[Claims] 1 In metastable austenitic steel containing Cr, Ni, or even Mo, M _D = 413−462
×(C+N)−9.2Si−8.1Mn−13.7Cr−9.5Ni−
The M _D value expressed by the formula 18.5Mo is 15℃ or more, and it is composed of a component that satisfies the following conditions: 2Ni + 100 × (C + N) - Cr≧2.0, and the saturation magnetic flux density is 5KG or more.
A steel bar for magnetic scales, characterized in that the wire is cold-drawn to a wire of 12KG or less, and the local part is heated to form a solution, thereby making the part non-magnetic with a saturation magnetic flux density of 0.1KG or less.