JP2616504B2 - Method of forming signal pattern using change in magnetic characteristics - Google Patents

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 a signal pattern having different magnetic properties (such as a magnetic scale) on a metal surface, which is used for a non-contact type sensor for detecting a position or a speed.

[0002]

2. Description of the Related Art A signal pattern (magnetic scale) can be formed by utilizing the change of magnetic properties of a metal material by remelting and solidifying by irradiating a laser beam to a metal surface. As an example, an 18% Cr-7% Ni unstable austenitic steel member is cold-drawn and straightened into a work-induced martensite structure, and when the surface is melt-solidified by laser irradiation, the portion becomes austenitic (nonmagnetic material). ). A nonmagnetic / ferromagnetic pattern is formed by forming a pattern in which a remelted portion and a non-melted portion are alternately repeated. When such a surface is scanned by a magnetic detector, a pulse signal corresponding to the pattern is obtained, and if this signal is counted,
The displacement and speed of the member can be detected (for example, see Sumitomo Metal, Vol. 42-3 (1990), pp. 21-26).

[0003] In addition, an alloy that becomes amorphous by rapid solidification is formed on a metal substrate to form a crystalline overlay welding layer, which is rapidly melted and solidified by laser (high-density energy) irradiation to form an amorphous layer. A layer pattern is formed. If an alternating pattern of a crystalline portion and an amorphous portion is scanned by a magnetic detector, displacement and velocity can be similarly detected. Applicants have also filed an invention relating to this technology with Japanese Patent Application No. Hei.
No. 93926 and 2-93930.

[0004]

In the former case of the prior art, an austenitic steel having a specific composition must be prepared for martensitization, and a cold drawing and a strong working step of straightening are required. In addition, it is necessary to control the degree of processing, and the shape of the applied member is further limited. Also,
In the latter case, it is necessary to specially prepare an alloy to be amorphized, and an extremely high cooling rate is required for amorphization (amorphization).

An object of the present invention is to change the metal structure by remelting and solidifying by laser light irradiation without changing the metal structure, using a stainless steel having a wider composition range than before, and also changing the magnetic characteristics. Thus, a method of forming a signal pattern (magnetic scale) is provided.

[0006]

SUMMARY OF THE INVENTION The above object is achieved by forming a point A on the surface of a component as shown in the Schaeffler phase diagram of the accompanying drawings.
(15.2% Cr equivalent, 8.0% Ni equivalent), B (21.2%
Cr equivalent, 3.2% Ni equivalent), C (40.0% Cr equivalent,
13.0% Ni equivalent), D (37.0% Cr equivalent, 30.0%
A stainless steel layer having a coexisting structure of austenite and ferrite within a range surrounded by Ni equivalent) is arranged, the surface of the component is machined to a predetermined size, and a high-density energy such as a laser is applied to the surface of the stainless steel by a predetermined signal. Applying to the pattern shape to locally re-melt and quench solidify to make the magnetic properties different from the structure of the stainless steel part to which the high-density energy is not applied, and to perform finishing surface processing as necessary This is achieved by a method of forming a signal pattern using a change in magnetic characteristics characterized by the following.

Within the above composition range, point E (17.8% C
r equivalent, 7.5% Ni equivalent), F (21.0% Cr equivalent, 5.
0% Ni equivalent), G (38.0% Cr equivalent, 16.8% Ni equivalent)
) And H (36.0% Cr equivalent, 27.0% Ni equivalent) are preferred because they are large in the detection signal intensity described later. The fact that the component (ie, the substrate) is made of a non-magnetic metal, such as austenitic stainless steel, is advantageous for detecting magnetic properties.

The metal structure shown in the Schaeffler phase diagram can be obtained by forming the stainless steel layer on the surface of the component by overlay welding at a cooling rate of 10 ³ ° C./sec or less.
Alternatively, a material having the metal structure shown in the Schaeffler phase diagram is joined to the component surface by a technique such as welding.
Cooling rate during remelting quenching and solidification is 2 × 10 ³ to 10 ⁷ ° C
/ Sec, and the 0% ferrite amount lines (a) and 100% in the Schaeffler phase diagram as described later.
% Ferrite content line (b) becomes narrower, and the metal structure (fine rod-like eutectic solidification structure) with a different ratio of austenite content and ferrite content and different from that of the metal (stainless steel) layer of overlay welding Or a massive solidification (partitionless solidification) structure can be obtained (Nakao, Nishimoto: Laser glazing of stainless steels), Production and Technology, Vol.
42, No.3 Summer Issue, Production Technology Promotion Association (1990), 39-
44).

The high-density energy is preferably YAG laser light, and may be electron beam, arc discharge or the like.

[0010]

In the present invention, as shown in the Schaeffler phase diagram,
When formed under quenching conditions of a cooling rate of 10 ³ ° C / sec or less, a stainless steel in a region where austenite and ferrite coexist is used, and this stainless steel is melted in a short time by pulsed laser beam irradiation and immediately quenched. Solidification (cooling rate: 2
× 10 ³ to 10 ⁷ ° C / sec), the ratio of austenite to ferrite and the metal structure of the melt-solidified portion change with respect to the base material (stainless steel portion not irradiated with laser), and the magnetic properties also change. Change.

In a Schaeffler phase diagram showing the metallographic structure of welding (welding, overlaying, etc.) of steel including stainless steel, as shown in FIG. 1, the horizontal axis is chromium (Cr) equivalent (ferrite stabilizing element Cr, The ordinate is the nickel (Ni) equivalent (the sum of the austenite stabilizing element Ni and other elements having the same effect as Ni) on the vertical axis. 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, ferrite, and the Ni equivalent and the Cr equivalent are present in an appropriate ratio. In the region, ferrite, austenite, and martensite coexist.

In the region where the ferrite-austenite coexistence structure is formed, the Ni equivalent is defined as a variable Yn and the Cr equivalent is defined as a variable Xc, and the following equation is obtained: 1.101 Xc−8.139 ≧ Yn ≧ 0.325Xc−3.953 (Xc .Gtoreq.0, Yn.gtoreq.0) (1) where line (a) is a boundary line of 0% ferrite (100% austenite) amount, and line (b) is 100%
It is a boundary line of the amount of ferrite (0% austenite).

[0013] It should be noted that Yn ≦ −0.801Xc + 25.52 (Xc ≧ 0, Yn ≧ 0)... In the region (below the line (c)) represented by the expression 2, martensite is mixed. Schaeffler phase diagram deposited metal is 10 ³ ° C.
FIG. 4 is a microstructure diagram when solidified at a cooling rate of about 1 / sec or less. When the cooling rate is higher, the lines (a) and (b) are as follows so that the ferrite-austenite co-existing structure represented by Formula 1 becomes narrower. Equation (3): Yn = 0.87Xc-8.67 (Xc ≧ 0, Yn ≧ 0)... Equation 3 approaches the line (d). This is disclosed in the above-cited reference, page 41, FIG. A phase diagram of a metal structure (fine rod-shaped eutectic solidification structure or massive solidification structure) obtained by increasing the cooling rate is disclosed in FIG.

Therefore, in the region represented by the formula (1), the amount of ferrite and the amount of austenite can be changed by increasing (changing) the cooling rate. 1.101Xc-8.139 ≧ Yn ≧ 0.87Xc-8.67 (Xc ≧ 0, Yn ≧ 0) of the region (Xc ≧ 0, Yn ≧ 0) ... A region represented by Formula 4 (between the lines (a) and (d)) ), The amount of ferrite decreases (that is, the austenite region expands), while 0.87Xc-8.67 ≧ Yn ≧ 0.325Xc−3.953 (Xc ≧ 0, Yn ≧ 0) In the region represented by the formula (5) (the region between the 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 coexistence region of ferrite and austenite represented by the equation (1) in the Schaeffler phase diagram, the austenite of the metal structure is basically increased by increasing the cooling rate. The ratio between the amount of ferrite and the amount of ferrite changes and the metallurgical structure itself changes, as does the magnetic properties. When the change in magnetic characteristics (difference in signal intensity from the detector (resonant coil)) was examined in relation to the stainless steel composition, the closed region (points A, B, C, and D) in FIG. Within the range of region (a), a change in magnetic characteristics can be evaluated. further,
Within the range of the closed region (region surrounded by points E, F, G, and H) in FIG. 1, a more distinct change in magnetic characteristics can be obtained. On the other hand, if the Ni equivalent and the Cr equivalent are too large, it becomes difficult to process, and the cost of raw materials increases.

The change in magnetic properties in the metal structure of stainless steel can be detected by comparing the unchanged portion with the changed portion,
For this purpose, a magnetic / electrical property detector such as a sensing coil, a Hall element, and an MR element can be used.
Therefore, the surface of the base material (layer) in which the stainless steel having the composition according to the present invention has a ferrite-austenite coexisting structure in the Schaeffler phase diagram is re-melted by laser light irradiation according to the signal pattern shape and solidified at high speed by cooling. By forming a portion having changed magnetic characteristics, a signal pattern (magnetic scale or the like) can be formed.

Before and after this remelting quenching and solidification treatment,
Machining, including grinding and polishing, the surface of the stainless steel layer not only increases the accuracy of the signal pattern, but also allows the detector probe to contact the surface of the stainless steel layer if it contacts the surface of the stainless steel layer. This has the effect of smoothing the sliding of the probe, reducing the gap between the probe and the probe, and preventing the probe from being damaged.

If the signal pattern (remelting / quenching / solidification region / portion) is formed so as to be periodically repeated in a specific direction, a signal (magnetic scale signal) in which different magnetic characteristic values are alternately repeated is obtained. When the width is reduced or increased continuously in a specific direction, a signal whose magnetic characteristic value gradually decreases or increases can be obtained. With these signals, the position and speed of the member can be specified and calculated.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings with reference to embodiments and comparative examples of the present invention. The ring rotor shown in FIG. 2 was manufactured as follows. First, an austenitic steel SUS304 (non-magnetic metal) cylindrical ring 1 was prepared and had an outer diameter of 37.7 mm, an inner diameter of 30.0 mm, and a width of 8.0 mm. A groove having a width of 4.0 mm and a depth of 0.5 mm was formed at the center of the outer periphery of the ring 1 by machining. Table 1 shows the alloy powder of stainless steel having the composition shown in Table 1. 1 to 23 (samples) were prepared.

[0020]

[Table 1]

The alloy powder Nos. 1 to 23
In the Schaeffler state diagram is as shown in FIG.
The alloy powder prepared in the groove of the ring 1 is continuously supplied, and the alloy powder is irradiated with a CO ₂ laser of
The powder was continuously melted by the rotation of, and the molten material removed from the laser was immediately solidified to form the build-up layer 2.

CO ₂ laser beam: A laser beam focused to a size of 2 mm in diameter by a focusing lens was scanned by a beam oscillator so as to have a width of 5 mm. CO ₂ laser output: 2.5 Kw Laser scanning speed: 200 mm / min By this build-up welding, a stainless build-up layer 2 having a structure corresponding to the Schaeffler phase diagram is formed on the entire circumference of the ring 1, and the outer diameter is reduced to 37 by grinding. The thickness of the belt-shaped laser cladding layer 2 was 4 mm wide and 0.3 mm deep.

As shown in FIG. 2, a pulse YAG laser beam 3 is condensed on the laser cladding layer 2 into a minute spot by a condenser lens 4 and has a width at a scale (scale) interval W (2.25 mm). A re-melting and quenching treatment (spot treatment) was performed so as to form a spot treatment part 5 of d (1.125 mm). The laser spot processing conditions were as follows. YAG laser beam: Focused to a size of 0.2 mm in diameter with a focusing lens.

Xe lamp discharge voltage for laser: 440 V Laser pulse width: 0.5 msec Pulse rate: 50 pps Melting spot diameter: 0.28 mm Spacing between centers of melting spot: 0.2 mm both vertically and horizontally Cooling rate: 10 ⁵ ~ 10 ⁷ ° C / sec In the cooling and solidification after remelting by the YAG laser, the cooling rate is faster than in the Schaeffler phase diagram, and the resulting treated part has its structure (ratio between the amount of austenite and the amount of ferrite or the metal structure itself). ) Is different from the non-processed portion (the portion 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 resonance coil of the detector in the block diagram shown in FIG. 3 was arranged very close to, and the signal strength from the detector was examined by rotating the ring rotor. From the detector, a pulse-like waveform corresponding to the interval (pitch) of the spot processing unit 5 is output from the YAG.
The intensity difference (peak-to-peak value of the waveform) corresponding to the difference in magnetic properties between the laser processing part 5 and the non-processing part (as it is) is obtained as a signal output in Table 1. I will write it together.

Considering the values of the signal output in Table 1 and the sample number positions in FIG. 4, a certain amount of signal output can be obtained within the closed area (area surrounded by points A, B, C, and D). Further, a large signal output can be obtained within a range of a closed region (a region surrounded by points E, F, G, and H) in FIG. In the above embodiment, the ring shape was used. However, a plate (or a rod) was used as a base, a build-up layer was formed thereon, and a part thereof was re-melted and quenched according to the present invention to form a signal pattern. You can also.

[0027]

As described above, in the signal pattern forming method according to the present invention, the ferrite-austenite coexistence structure in the Schaeffler phase diagram is first formed by using stainless steel having a wider composition range than before. After that, a part of the structure is changed by remelting and quenching processing at a higher cooling rate to change the structure, that is, the magnetic characteristics, and the change is used for signal detection. Therefore, in the present invention, it is not necessary to perform strong working for forming martensite in the conventional method, and the conditions such as preparation of a specific composition alloy required for amorphousization and a considerably high cooling rate are moderate. Only needs to be done. Furthermore, the corrosion resistance is improved in the ferrite-austenite coexistence (mixed) structure as compared with the martensite structure.

[Brief description of the drawings]

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

FIG. 2 is a perspective view showing that a rebuilding quenching process by a YAG laser is performed on a build-up layer of a ring rotor.

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

FIG. FIG. 2 is a Schaeffler phase diagram of steel including stainless steel in which 1 to 23 are entered.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ring 2 ... Overlay layer 3 ... YAG laser 4 ... Condensing lens 5 ... Spot processing part

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Akira Matsunawa, Inventor, 11-1 Mihogaoka, Ibaraki-shi, Osaka Prefecture Inside of Welding Engineering Laboratory, Osaka University (72) Inventor Seiji Katayama 11-1, Mihogaoka, Ibaraki-shi, Osaka Osaka University Welding Within the Engineering Laboratory (56) References JP-A-2-87014 (JP, A) JP-A-1-174913 (JP, A) JP-A-2-158912 (JP, A) JP-A-3-12047 (JP, A A)

Claims (3)

(57) [Claims] 1. A point A (15.2% Cr equivalent, 8.0% Ni) as shown in the Schaeffler phase diagram of the attached drawing.
Equivalent), B (21.2% Cr equivalent, 3.2% Ni equivalent), C
(40.0% Cr equivalent, 13.0% Ni equivalent), D (37.0%
% Cr equivalent, 30.0% Ni equivalent), a stainless steel layer having a coexisting structure of austenite and ferrite within a range surrounded by, and machining the surface of the part to a predetermined size,
Then, a high-density energy such as a laser is applied to the surface of the stainless steel in a predetermined signal pattern shape to locally re-melt, quench and solidify, and the structure of the stainless steel portion to which the high-density energy is not applied is a magnetic property. The method of forming a signal pattern using a change in magnetic characteristics, wherein 2. The forming method according to claim 1, wherein said component is subjected to a finishing surface treatment after a remelting quenching and solidification treatment by high density energy. 3. The method according to claim 1, wherein said component is made of a non-magnetic metal.