JPH04259385A - Formation of signal pattern utilizing change in magnetic characteristic - Google Patents

Abstract

PURPOSE:To form signal patterns (magnetic scale) by utilizing a stainless steel which is widened in compsn. range than heretofore and changing the metal structure with remelting solidification without undergoing a strong working stage by irradiation with a laser beam, thereby changing magnetic characteristics as well. CONSTITUTION:A stainless steel layer 2 having the coexistence structure of the austenite and ferrite within the range enclosed by points A (15.2% Cr equiv., 8.0% Ni equiv.), B (21.2% Cr equiv., 3.2% Ni equiv.), C (40.0% Cr equiv., 13.0% Ni equiv.), D (37.0% Cr equiv., 30.0% Ni equiv.), as shown in scheeffler phase diagram of attached Fig. is disposed on the surface of parts and high-density energy, such as YAG laser 3, is impressed in a prescribed signal pattern shape to the surface of this stainless steel 2 to locally remelt and solidify the steel layer by rapid cooling, by which the structure obtd. at a high cooling rate is formed. This stainless steel has the magnetic characteristics different from the magnetic characteristics of the structure of the stainless steel part which is not remelted and solidified by rapid cooling.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming signal patterns (magnetic scales, etc.) with different magnetic characteristics on a metal surface, which is used in non-contact sensors for detecting position and speed.

0002

2. Description of the Related Art A signal pattern (magnetic scale) can be formed by changing the magnetic properties of a metal material by remelting and solidifying the metal surface by irradiating it with a laser beam. As an example, when an unstable austenitic steel member of 18% Cr-7% Ni is cold-drawn and straightened to form a deformation-induced martensitic structure, and the surface is melted and solidified by laser irradiation, that part becomes austenite (a non-magnetic material). ) to become A non-magnetic/ferromagnetic pattern is formed by forming a pattern in which re-melted parts and non-melted parts are alternately repeated. When such a surface is scanned with a magnetic detector, a pulse signal corresponding to the pattern is obtained, and if this signal is counted,
The displacement and speed of members can be detected (for example, Sumitomo Metals, Vol. 42-3 (1990), pp.
21-26).

[0003] In addition, a crystalline overlay weld layer is formed on a metal substrate with an alloy that becomes amorphous by rapid solidification, and this is rapidly melted and solidified by laser (high-density energy) irradiation to form an amorphous layer. Forms a layered pattern. Displacement and velocity can be similarly detected by scanning an alternating pattern of crystalline and amorphous portions with a magnetic detector. The applicant has also filed an invention related to this technology in Japanese Patent Application No. 1-324163, 2-
It was proposed in No. 93926, No. 2-93930, etc.

0004

[Problem to be solved by the invention] In the former case of the conventional example, it is necessary to prepare austenitic steel with a specific composition in order to make it martensitic, and strong working processes such as cold drawing and straightening are necessary. It is also necessary to control the degree of processing, and furthermore, the shape of the applicable member is limited. Furthermore, in the latter case, it is necessary to specially prepare an alloy to be made amorphous, and an extremely high cooling rate is required for making the alloy amorphous.

The purpose of the present invention is to use stainless steel with a wider composition range than before, and to change the metal structure and magnetic properties by remelting and solidifying by laser beam irradiation, without going through a strong working process. The object of the present invention is to provide a method for forming a signal pattern (magnetic scale).

[0006]

[Means for Solving the Problems] The above-mentioned object is achieved by forming a point A (
15.2% Cr equivalent, 8.0% Ni equivalent), B (21.
2% Cr equivalent, 3.2% Ni equivalent), C (40.0% C
r equivalent, 13.0% Ni equivalent), D (37.0% Cr equivalent, 30.0% Ni equivalent). The stainless steel whose surface is machined to a predetermined dimension, and where high-density energy such as a laser is applied to the surface of the stainless steel in a predetermined signal pattern shape to locally remelt and rapidly solidify the stainless steel without applying the high-density energy. This is achieved by a method of forming a signal pattern that utilizes a change in magnetic properties, which is characterized by making the magnetic properties different from the structure of the part and, if necessary, applying a finishing surface treatment.

Within the above composition range, point E (17.8%
Cr equivalent, 7.5% Ni equivalent), F (21.0% Cr equivalent, 5.0% Ni equivalent), G (38.0% Cr equivalent, 1
6.8% Ni equivalent), H (36.0% Cr equivalent, 27.
It is preferable to use stainless steel within the range (0% Ni equivalent) because the detection signal intensity described later is large. It is advantageous in detecting magnetic properties that the component (ie, the substrate) is made of a non-magnetic metal such as austenitic stainless steel.

[0008] By forming a stainless steel layer on the surface of a component by overlay welding at a cooling rate of 103° C./second or less, the metal structure shown in the Schaeffler phase diagram can be obtained. Alternatively, a material having a metal structure shown in the Schaeffler phase diagram is joined to the surface of the component by a method such as welding. The cooling rate during remelting and rapid solidification is 2 x 103 ~ 107
℃/sec, and as described later, the 0% ferrite amount line (a) and 1 in the Schaeffler phase diagram.
The distance between the 00% ferrite amount lines (b) becomes narrower, and the ratio of austenite and ferrite amounts is different from that of the overlay welded metal (stainless steel) layer, and the metal structure (fine rod-shaped eutectic solidification) A tissue or massive coagulation (partitionless coagulation) tissue can be obtained (Nakao, Nishimoto:
“Laser Glazing of Stainless Steel”, Production and Technology, V
ol. 42, No. 3 Summer issue, Production Technology Promotion Association (1990), 39-44).

[0009] The high-density energy is preferably a YAG laser beam, but may also be an electron beam, an arc discharge, or the like.

0010

[Operation] In the present invention, as shown in the Schaeffler phase diagram,
When formed under rapid cooling conditions with a cooling rate of 103 °C/second or less, stainless steel is used in the region where austenite and ferrite coexist, and this stainless steel is melted in a short time by pulsed laser light irradiation, and then rapidly solidified. (Cooling rate:
2 × 103 to 107 °C/sec), the molten solidified portion has a ratio of austenite to ferrite and a metal structure similar to that of the base metal (stainless steel portion not irradiated with laser).
The magnetic properties also change.

In the Schaeffler phase diagram showing the metallographic structure of welding (welding, overlaying, etc.) of steel including stainless steel, as shown in FIG. The vertical axis is the nickel (Ni) equivalent (the sum of the austenite stabilizing element Ni and other elements that have the same effect as Ni). Basically, the metal structure in the region where the Ni equivalent is large and the Cr equivalent is small becomes austenite, and in the region where the Ni equivalent is small and the Cr equivalent is large it becomes ferrite, and the Ni equivalent and Cr equivalent exist in an appropriate ratio. Ferrite, austenite, and martensite coexist in this region.

[0012] The region where the ferrite-austenite coexistence structure is formed is determined by the following formula, where the Ni equivalent is a variable Yn and the Cr equivalent is a variable Xc: 1.101Xc-8.139≧Yn≧0.32
5Xc-3.953 (Xc≧0, Yn≧0) ...
1 formula, line (a) is the boundary line of 0% ferrite (100% austenite), line (b) is 100%
This is the boundary line of the amount of ferrite (0% austenite).

Note that Yn≦−0.801Xc+25.52(Xc
≧0, Yn≧0)...A region expressed by the formula 2 (line (c
), martensite is mixed in). The Schaeffler phase diagram is a structure diagram when the weld metal is solidified at a cooling rate of about 103 °C/second or less, and as the cooling rate becomes faster, the ferrite-austenite coexistence structure shown in equation 1 becomes narrower. (a) and (b) are the following three formulas: Yn=0.87Xc-8.67 (Xc≧0, Y
n≧0)... Approaches line (d) of equation 3. This is disclosed on page 41, FIG. 4 of the above-mentioned reference. Further, the phase diagram of the metal structure (fine rod-shaped eutectic solidification structure or massive solidification structure) obtained by increasing the cooling rate is disclosed on the same page 41, FIG. 3.

Therefore, in the region expressed by equation 1, the amount of ferrite and austenite can be changed by increasing (changing) the cooling rate. Within that area 1.101Xc-8.139≧Yn≧0.87
Xc-8.67 (Xc≧0, Yn≧0)... In the region expressed by formula 4 (the region sandwiched between lines (a) and (d)), the amount of ferrite decreases (that is, the austenite region expands), while 0.87Xc-8.67≧Yn≧0.325X
c-3.953 (Xc≧0, Yn≧0) ... 5
In the region expressed by the formula (the region between lines (d) and (b)), the amount of ferrite increases (that is, the ferrite region expands).

Since ferrite is ferromagnetic and austenite is non-magnetic, in the ferrite-austenite coexistence region expressed by equation 1 in the Schaeffler phase diagram, basically by increasing the cooling rate, the austenite in the metal structure is The ratio between the amount of ferrite and the metal structure itself changes, and the magnetic properties also change. When we examine the change in magnetic properties (difference in signal intensity from the detector (resonant coil)) in relation to the stainless steel composition, we find that the closed region (
Changes in magnetic properties can be evaluated within the range (A) (area surrounded by points A, B, C, and D). Furthermore, within the closed region (area surrounded by points E, F, G, and H) A in FIG. 1, a more distinct change in magnetic properties can be obtained. Furthermore, if the Ni equivalent and Cr equivalent are too large, it becomes difficult to process and further increases the cost of raw materials, so they are limited to the above ranges.

[0016] Changes in magnetic properties in the metal structure of stainless steel can be detected by comparing unchanged parts and changed parts.
For this purpose, a magnetic/electrical property detector such as a sensing coil, a Hall element, or an MR element can be used. Therefore, the surface of the base material (layer) of stainless steel having the composition according to the present invention having a ferrite-austenite coexistence structure according to the Schaeffler phase diagram is remelted by laser beam irradiation according to the signal pattern shape, and is rapidly cooled and solidified. By forming parts with changed magnetic properties, the signal pattern (
magnetic scale, etc.).

[0017] Before and after this remelting and rapid solidification treatment,
Machining the surface of the stainless steel layer, including grinding and polishing, not only increases the accuracy of the signal pattern, but also improves the accuracy of the detector probe when it comes into contact with the surface of the stainless steel layer. This has the effect of smoothing the sliding motion of the probe, reducing the gap between the probe and the probe, and preventing damage to the probe.

[0018] If the signal pattern (remelted, rapidly solidified region/portion) is formed to repeat periodically in a specific direction, a signal (magnetic scale signal) in which different magnetic characteristic values are alternately repeated can be obtained, or If the width is formed so as to continuously decrease or increase in a specific direction, a signal in which the magnetic characteristic value gradually decreases or increases can be obtained. These signals allow the position and speed of the member to be specified and calculated.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail by way of embodiments and comparative examples with reference to the accompanying drawings. The ring rotor shown in FIG. 2 was manufactured as follows. First, a cylindrical ring 1 made of austenitic steel SUS304 (non-magnetic metal) is prepared, and its outer diameter is 37.7 mm.
The inner diameter was 30.0 mm, and the width was 8.0 mm. The ring 1 has a width of 4.0 mm and a depth of 0.0 mm at the center of the outer circumference.
A 5 mm groove was formed by machining. Stainless steel alloy powder No. with the composition shown in Table 1. Samples 1 to 23 (samples) were prepared.

[0020]

[Table 1]

[0021] These alloy powders No. 1-23
When written in the Schaeffler state diagram, it becomes as shown in Figure 4. The prepared alloy powder is continuously supplied into the groove of ring 1, and the alloy powder is irradiated with a CO2 laser under the following conditions.The powder is continuously melted by the rotation of ring 1, and the molten material that comes off from the laser is It immediately solidified to form a built-up layer 2.

CO2 laser beam: A laser beam focused to a diameter of 2 mm by a condenser lens was scanned by a beam oscillator to a width of 5 mm. CO2 laser output: 2.5Kw Laser scanning speed: 200mm/min By this overlay welding, a stainless steel overlay layer 2 with a structure corresponding to the Schaeffler phase diagram is formed around the entire circumference of the ring 1, and by grinding, the outer diameter is reduced to 37mm. 5 mm to form a band-shaped laser build-up layer 2 with a width of 4 mm and a depth of 0.3 mm.

As shown in FIG. 2, a pulsed YAG laser beam 3 is focused on a minute spot on the laser build-up layer 2 by a condensing lens 4, and a scale interval W (2.25 mm) is applied to the laser build-up layer 2.
), and the remelting and quenching treatment (spot treatment) was performed so that the spot treatment portion 5 had a width d (1.125 mm). The laser spot processing conditions were as follows. YAG laser beam: Condensed to a diameter of 0.2 mm using a condensing lens.

Xe lamp discharge voltage for laser: 440V Laser pulse width: 0.5msec Pulse rate: 50pps Melting spot diameter: 0.28mm Distance between centers of melting spots: 0.2 both vertically and horizontally
mm Cooling rate: 105 ~ 107 °C/sec This YA
In cooling solidification after remelting with the G laser, the cooling rate is faster than in the case of the Schaeffler phase diagram, and the structure (ratio of the amount of austenite to ferrite or the metal structure itself) in the resulting treated part is similar to that in the untreated part ( (parts not irradiated with laser).

Then, the outer periphery of the ring was polished to produce a ring rotor. Overlay layer 2 of manufactured ring rotor
The resonant coil of the detector shown in the block diagram shown in Fig. 3 was placed very close to the detector, and the ring rotor was rotated to examine the signal intensity from the detector. A pulse-like waveform corresponding to the interval (pitch) of the spot processing unit 5 is output from the detector.
It is obtained by the intensity difference (waveform peak-to-peak value) corresponding to the difference in magnetic properties between the laser treated part 5 and the untreated part (as is the build-up layer 2), and the results are shown in Table 1 as the signal output. Also listed.

When considering the signal output values in Table 1 and the sample number positions in FIG. , Furthermore, the closed area in Figure 1 (area surrounded by points E, F, G, and H)
A large signal output can be obtained within the range of A. Although the ring shape was used in the above embodiment, a plate (or even a rod) is used as the base, a build-up layer is formed on it, and a part of it is re-melted and rapidly cooled according to the present invention to form a signal pattern. You can also.

[0027]

[Effects of the Invention] As explained above, in the method for forming a signal pattern according to the present invention, stainless steel with a wider composition range than before is used, and the ferrite-austenite coexistence structure in the Schaeffler phase diagram is first formed. After that, a part of it is remelted and rapidly cooled to a faster cooling rate to change its structure, that is, its magnetic properties, and this change is used for signal detection. Therefore, in the present invention, there is no need for strong working to make martensite as in the conventional method, and the conditions are less restrictive, such as preparing a specific alloy composition required for making it amorphous and a fairly fast cooling rate. That's enough. Furthermore, corrosion resistance is improved in a ferrite-austenite coexistence (mixed) structure compared to a martensitic structure.

[Brief explanation of the drawing]

FIG. 1 is a Schaeffler phase diagram of steel including stainless steel.

FIG. 2 is a perspective view showing the overlay layer of the ring rotor undergoing remelting and rapid cooling treatment using a YAG laser.

FIG. 3 is a block diagram of a detector of magnetic properties.

FIG. 4 Sample No. It is a Schaeffler phase diagram of steel including stainless steel with numbers 1 to 23 filled in.

[Explanation of symbols]

1...Ring 2... Overlay layer 3...YAG laser 4...Condensing lens 5...Spot processing section

Claims (3)

[Claims] Claim 1: On the surface of the part, point A (15.2% Cr equivalent, 8.0
%Ni equivalent), B (21.2%Cr equivalent, 3.2%Ni equivalent)
It has a coexistence structure of austenite and ferrite within the range surrounded by C (40.0% Cr equivalent, 13.0% Ni equivalent), D (37.0% Cr equivalent, 30.0% Ni equivalent). A stainless steel layer is arranged, the surface of the component is machined to a predetermined dimension, and high-density energy such as a laser is applied to the surface of the stainless steel in a predetermined signal pattern shape to locally remelt and rapidly solidify. . A method for forming a signal pattern using a change in magnetic properties, characterized in that the structure of the stainless steel portion to which the high-density energy is not applied is made to have different magnetic properties. 2. The forming method according to claim 1, wherein the part is subjected to a finishing surface treatment after being remelted and rapidly solidified using high-density energy. 3. The method of claim 1, wherein the component is made of a non-magnetic metal.