GB2163778A - Magnetic medium used with magnetic scale - Google Patents

Magnetic medium used with magnetic scale Download PDF

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Publication number
GB2163778A
GB2163778A GB08518273A GB8518273A GB2163778A GB 2163778 A GB2163778 A GB 2163778A GB 08518273 A GB08518273 A GB 08518273A GB 8518273 A GB8518273 A GB 8518273A GB 2163778 A GB2163778 A GB 2163778A
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United Kingdom
Prior art keywords
magnetic
alloy
magnetic scale
scale
weight
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GB08518273A
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GB2163778B (en
GB8518273D0 (en
Inventor
Kenji Indo
Hiroshi Yamakawa
Kenzaburou Iijima
Yoshinori Hayashi
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Sokkisha Co Ltd
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Sokkisha Co Ltd
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Publication of GB8518273D0 publication Critical patent/GB8518273D0/en
Publication of GB2163778A publication Critical patent/GB2163778A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/30—Ferrous alloys, e.g. steel alloys containing chromium with cobalt

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Power Engineering (AREA)
  • Hard Magnetic Materials (AREA)
  • Soft Magnetic Materials (AREA)

Abstract

The magnetic medium is prepared from a Cr-Co-Fe base alloy consisting of 15 to 40% by weight of Cr, 5 to 35% by weight of Co, 0.1 to 5% by weight of any one or more of Ti, V, Zr, Nb, Mo, W, Mn, Ni, Si, Cu, Zn, Ge and Ta except Mo alone and Fe as the remainder. The alloy avoids the segregation of any component, thereby contributing to the improvement of the instrumentation precision of the magnetic scale, and suppressing the occurrence of instrumentation errors from thermal expansion or abrasion.

Description

SPECIFICATION Magnetic medium used with magnetic scale This invention relates to an instrumentation system involving a magnetic scale, and more particularlyto the improvement of a magnetic medium used with said magnetic scale.
As is well known, an instrumentation system for measuring a length or angle by means of a magnetic scale is characterized buy a high precision of measurement and applied in various industrial fields. Recently, the magnetic scale type instrumentation system has aiso been widely accepted inthefield of automatic control. An instrumentation system provided with the above-mentioned type of magnetic scale comprises a magnetic scale in which a plurality of AC magnetized patterns are arranged art a prescribed pitch and a movable, magnetic head made so that it can face any required one of said plural AC magnetized patterns.
With the above-mentioned instrumentation system, eitherthe magnetic scale or magnetic head is fixed, and the other is coupled to a movable body. Asignal issued from the magnetic head when said movable body is carried is electrically processed thereby to measure the distance covered by said movable body.
The magnetic medium used with the aforementioned magnetic scale is required to have a magnetic property of a higher coercive force (Hc) than 300 oersteds, to be saved from the effect of an external magnetic field, and further a higher residual magnetic flux density (Br) than 1,000 gausses, in order to issue a more powerful signal. To date, a magnetic medium which satisfies the above-mentioned magnetic requirements and has an excellent workability has been prepared from an alloy based on copper (Cu), nickel (Ni) and iron (Fe).This alloy material has been manufactured with a composition of, for example, 65 to 75% by weight of Cu, 17to 30% by weight of Ni and 5% or more by weight of Fe.
When subjected to aging at a temperature around 600"C, the above-mentioned alloy is increased in the coercive force and facilitates cold working afterthe aging treatment. Therefore, said alloy offers the advantage of being easily fabricated into a plate or round rod to be used as a magnetic scale. Nevertheless, it has been found that said alloy is still accompaneed with a number of drawbacks.
In the first place, a Cu-Ni-Fe alloy has a structure rich in copper nickel and iron nickel with nickel as a common component. Consequently the copper portion of said Cu-Ni structure is subject to segregation.
As a result, said Cu-Ni-Fe alloy as a whole fails to have a uniform magnetic property.Thisfact has been experimentally discovered by the present inventors.
Therefore, the elimination of the above-mentioned segregation bears great importance for the magnetic medium ofthe above-mentioned type.
In the second place, the Cu-Ni-Fe alloy has a thermal expansion coefficient of 13.5 x 10-6to 14.0 x 10-6/ C.
On the other hand, a supportfor holding a magnetic scale preparedfromtheaforementioned Cu-Ni-Fe alloy isgenerallyformed of iron. The iron has a smallerthermal expansion coefficient (10.0 x 10-6to 11.0 x 1 O-6/ C) than said alloy. When, therefore, the magnetic scale composed of the aforementioned alloy is held by said iron support at both ends, the magnetic scale is subject to sagging, depending on temperature changes, or undergoes a tension, thereby leading to instrumentation errors.
The present inventors' experiments prove that when a magnetic scale 1 meter in length and 2 mmxp in diameter has been prepared from Cu-Ni-Fe alloy having a thermal expansion coefficient of 13.5 x 10-5/0C, a length difference of 35 microns appears between said magnetic scale and an iron support having a thermal expansion coefficient of 10.0 x 10-6/ C when a temperature change of 1 00C appears.
In the third place, the Cu-Ni-Fe alloy has a small Young's modulus, such as 13,000 to 14,000 kg/mm2.
When, therefore, the above-mentioned magnetic scale 2 mm in diameter and 1 meterin length is prepared from the aforesaid Cu-Ni-Fe alloy and is held by the iron support at both ends, a sagging occurring atthe central portion of the magnetic scale becomes too noticeable to be overlooked. In otherwords, the magnetic scale is prominently inclined in the direction in which the magnetic head travels. This drawback, too, brings about instrumentation errors.
This invention has been accomplished in view ofthe above-mentioned circumstances, and is intended to provide a magnetic medium for a magnetic scale as is unlikely to bring about the aforesaid segregation, contributes to the improvement ofthe instrumentation precision ofthe magnetic scale, minimizes instrumentation errors arising from the thermal expansion of the components and possesses high wear resistance.
To attaintheabove-mentioned object,thisinven- tion provides a magnetic medium four a magnetic scale, said magnetic medium being prepared from a Cr-Co-Fe base alloy composed of 15 to 40% by weight of Cr, Sto 35% byweight of Co, 0.1 to 5% byweightof any one or more ofTi,V,Zr, Nb, Mo,W, Mn, Ni, Si, Cu, Zn, GeandTa except Mo alone, and Feasthe remainder.Said magnetic medium has a coercive force Hc of 300 to 1,000 oersteds, a residual magnetic flux density Br of 7,000 to 15,000 gausses, hardness Hv 350 to 600, thermal expansion coefficient of 9.5 to 11.5 x 10-6/ C, Young's modulus of 20,000 to 23,000 Kg/mm2 and segregation pitch shorterthan 10 microns.
The above-mentioned alloy of this invention consti tuting a magnetic medium for a magnetic scale has excellent magnetic properties such as a coercive force Hc of 300 to 1,000 oersteds and a residual magnetic flux density Br of 7,000 to 15,000 gausses. However, the following facts should be noted with respect to the subject alloy. If the content of Co of the main components (Cr, Co and Fe) falls below 5% by weight, then the residual magnetic flux density Brfalls. If the Co content rises above 35% by weight, then the coercive force decreases too much. If the Cr content exceeds 40% by weight, the residual magnetic flux density Br of said alloy drops, and if the Cr content falls below 15% by weight, the coercive force Hc of said alloy reduces too much.
The application ofthe above-listed additives Ti, V, Zr, Nb, Mo, W, Mn, Ni, Si, Cu, Zn, Ge and Ta is intended to improve the workability ofthe alloy. However, the addition of Mo in the uncombined form deteriorates the workability ofthe resultant alloy, making it necessary to apply Mo in the form combined with any ofthe aforementioned other additives.
The Cr-Co-Fe base alloy ofthis invention prepared as described above has a coercive force He of 300- 1,000 oersteds and a residual magneticflux density Br of 7,000-15,000 gausses, and constitutes an excellent magnetic medium to be used with a magnetic scale.
The subject alloy is readily plastic worked and cut, and in this respect, too, it is desirable as a magnetic medium for a magnetic scale.
The subject alloy is possessed ofthe undermentioned properties to be applied as a magnetic medium fora magnetic scale.
(1) Thermal expansion coefficient If, as previously mentioned, a difference occurs between the thermal expansion coefficient of the material of a magnetic scale and that of its support member holding the magnetic scale at both ends, the temperature change is likelyto give rise to the sagging ofthemagneticscale, orapplyan unnecessary tension to said scale, thereby leading to instrumentation errors.The conventional Cu-Ni-Fe alloy has a thermal expansion coefficient of 13.5 x 1 - 14.0 X 10-6/"C, which widely differs from the thermal expansion coefficient (10.0 x 10-e - 11.0 X 1 o-6/ C) of standard industrial iron used as a support member, thus resulting in noticeable instrumentation errors.
In contrast, the above-mentioned Cr-Co-Fe alloy of this invention has a thermal expansion coefficient ranging between 9.0 x 10-6 and 13.5x 10-6/"C, thus making it possibleto select a Cr-Co-Fealloy having any optional thermal expansion coefficientfalling within said range. In otherwords, it is possible to provide an alloywhosethermal expansion coefficient matches that of the iron material used as the support of the magnetic scale, thus preventing instrumentation errors from arising from the differentthermal expansion coefficients ofthe magnetic scale and its iron support.
In this connection, it will be noted that the thermal expansion coefficient ofthe subject alloy can be varied with the treating conditions of said alloyafterthe fusion, namely, the initial orterminal temperatures, cooling rate or aging effect. For instance, when water cooled for 30 minutes from a temperature of 1,000 C, the subjectalloy shows a thermal expansion coefficient of 1 3.2x 1 061C. When further cooled down to 500"C and latersubjected to thefinal aging, the subject alloy indicates a thermal expansion coefficient of 9.1 x 10-6/ C.When cooled from 635 C to 500oC at a decrement of 13"C per hour, the subject alloy has a thermal expansion coefficient of 10.2 x 1 0-6/ C.
Therefore, it is possibie to manufacture an alloy having the desired thermal expansion coefficient by properly selecting the aforementioned treating conditions.
(2) Segregation When, as previously mentioned, a material constituting the magnetic scale segregates, a change takes place in the magnetic property of said material, leading to the occurrence of instrumentation errors in the segregated portions of said magnetic scale component.The conventional Cu-Ni-Fe alloy is rich in copper nickel and iron nickel.The copper portion of the copper nickel structure often tends to segregate, thereby failing to provide an alloy having a uniform magnetic property.
In contrast, it has been disclosedthattheCr-Co-Fe alloy of this invention can be treated with sufficient care to prevent such segregaton. If, a magnetic scale is produced with a length of, for example, about 1 meter, it is required to let instrumentation errors resulting from the segregation fall within an allowable range, it is necessaryto reduce the segregation extent to less than 10 microns.
(3) Young's modulus When a long magnetic scale is supported at both ends, the central portion ofthe scale is subject to sagging as previously described, resulting in instrumentation errors. The maximum extent o of said sagging may be expressed as = Kl/E where: K = a constant I = the length ofthe magnetic scale E = Young's modulus It is seen from the above equation thatthe max imum extent of sagging can be progressively reduced, asYoung's modulus is increased. On the other hand, Young's modulus has to be extended accordingly, as the length I ofthe magnetic scale is increased.
The above-mentioned Cr-Co-Fe alloy of this invention has Young's modulus of 20,000to 23,000 kglmm2, thusfullyconformingtotheabove-mentioned requirements. In contrast, the conventional Cu-Ni-Fe alloy has as small a Young's modulus as 13,000 to 14,000 kg/m m2, thus fai ling to fully meet the aforesaid requirements.
It was experimentally discovered thatwhen a magnetic scale composed ofthe alloy of this invention comprising 11.5% byweight of Co, 33% by weight of Cr, 0.5% by weight of Ti and Fe asthe remainderwas formed with a length of 750 mm and a diameter of 2 mm and both ends of said magnetic scale were supported, the maximum extent of 6 of sagging atthe central portion of said scale indicated 0.55 mm. In contrast, the conventional magnetic scale prepared from an alloy comprising 22% by weight of Ni, 8% by weight of Fe and Cu as the remainderwas prepared with the same measurements as mentioned above.
This magnetic scale indicated a maximum sagging 5 of 1.0 mm atthe central portion when both ends of said conventional magnetic scale were supported.
As described above, the magnetic medium ofthis invention has been proved to be suitablefor use with a magnetic scale in respect of coercive force Hc, residual magnetic flux density Br, workability, thermal expansion coefficient,segregation and Young's modulus. In addition, the subject magnetic medium offers the advantagesthattheCr-Co-Fe base alloy has a hardness Hv of 350 - 600, a level far higherthan the hardness (240 - 260) of the conventional Cu-Ni-Fe base alloy; and the subject magnetic medium is noticeably improved in abrasion resistance, thereby preventing the space betweenthe magneticscale and magnetic head from being changed as a result of abrasion.
The conventional Cu-Ni-Fe alloy has a Curie point of 4805C, and decreases in the coercive force Hc and residual magnetic flux density Br with a temperature rise. In contrast, the Cr-Co-Fe base alloy of this invention is characterized in that it has a higher Curie pointthan 650 C, and no change appears in the magnetic properties such as the coercive force Hc and residual magnetic flux density Br up to a temperature of 4505C. Consequently, a magnetic scale composed ofthe Cr-Co-Fe base alloy of this invention ensures instrumentation at an elevated temperature.
The attached Table 1 shows six examples ofthe Cr-Co-Fe base alloys ofthis invention in which the main components are varied in their content, together with one control.
Table 1
Proportions (9 by weight) Samples Cr CO Ti or '0 Fe 1 20 25 Ti - 1 the remainder 2 25 12 Ti - l Exam- 3 33 11 Cu - 2 pies 4 35 5 Ti - 1 5 34 16 a 6 10 35 Ti - 1 Ni Fe Cu Control (9 by (6 by as the wit.) wt.) remainder 20 20 Referring to Table 1 above, Samples 1-4 represent the alloys ofthis invention. Sample5 has a composition falling within the range ofthe invention, but has a thermal expansion coefficient falling outside ofsaid range. Sample 6 has a composition slightlyfalling outside of said range. Sample 7 or Control represents the conventional Cu-Ni-Fe base alloy. The properties of the seven samples shown in Table 1 above are indicated in Property Tables 1 and 2 below.
Property Table 1
Sample Coercive force HC Residual magnetic flux No. (oersted) density Br (kilogausses) 1 600 - 740 8.8 - 10.1 2 500 - 630 14 - 15 3 750 - 850 11 - 12 4 430 - 480 9.5 - 11.0 5 700 - 800 9.5 - 18.5 6 380 - 450 9.8 - 11.2 7 600 - 800 6.0 - 6.5 Property Table 2
Sample rd Thermal expansion No.Hardness coefficient (/C) Young's modulus 1 400 - 460 11.5 x 10-6 22,000 - 23,000 2 400 - 420 10.5 X 10-6 22,000 - 23,500 3 480 - 500 10.6 s 10-6 22,000 - 23,500 4 320 - 350 11.3 X 10-6 22,000 - 23,000 8 360 - 400 13.3 : 10-6 21,000 - 22,000 6 400 - 460 12.2 x 10-6 22,000 - 23,000 7 230 - 255 13.5 - 14.5 10-6 11,000 - 14,500 Note: Even when an additive, for example, Ti was changed to another additive, no noticeable difference appeared in the properties ofthe resultant alloy, providing substantially the same results as the data given in PropertyTables 1 and 2.

Claims (2)

1. Amagneticmediumfora magneticscale comprising: a Cr-Co-Fe base alloy prepared from 15 to 40% by weight of Cr, 5 to 35% by weight of Co, 0.1 to 5% by weight of any one or more of Ti, V, Zr, Nb, Mo,W, Mn, Ni, Si, Cu, Zn, Ge and Ta, except Mo alone, and Fe as the remainder, said magnetic medium having a coercive force Hc of 300 to 1,000 oersteds, a residual magnetic flux density Br of 7,000 to 15,000 gausses, hardness Hv 350 to 600, thermal expansion coefficiency of 9.5 to 11.5x 10- / C, Young's modulus of 20,000to 23,000 Kg/mm2 and segregation pitch of 10 microns or shorter.
2. A magnetic medium used with magnetic scale, substantially as hereinbefore described with referenceto Examples.
GB08518273A 1984-08-30 1985-07-19 Magnetic medium used with magnetic scale Expired GB2163778B (en)

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GB2163778A true GB2163778A (en) 1986-03-05
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2177420A (en) * 1985-07-04 1987-01-21 Sokkisha Magnetic medium used for magnetic scale
US20130299562A1 (en) * 2011-01-14 2013-11-14 Sabastian Piegert Cobalt-based alloy comprising germanium and method for soldering

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH03134502A (en) * 1989-10-06 1991-06-07 Robert Bosch Gmbh Distance measuring apparatus

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1367174A (en) * 1970-12-28 1974-09-18 Inoue Japax Res Magnetic-meterials
GB1435684A (en) * 1974-05-02 1976-05-12 Inoue Japax Res Magnetic materials
EP0003466A1 (en) * 1978-01-19 1979-08-08 Ugimag S.A. Process for the thermal treatment of Fe-Co-Cr alloys for permanent magnets
GB1551717A (en) * 1977-04-21 1979-08-30 Arnold Eng Co Magnetic alloy and processing therefore
US4174983A (en) * 1978-07-13 1979-11-20 Bell Telephone Laboratories, Incorporated Fe-Cr-Co magnetic alloy processing
EP0024686A2 (en) * 1979-08-24 1981-03-11 Western Electric Company, Incorporated Article comprising a magnetic component consisting essentially of an alloy comprising Fe, Cr and Co
US4324597A (en) * 1977-12-27 1982-04-13 Mitsubishi Seiko Kabushiki Kaisha Magnetic alloy
US4496402A (en) * 1981-03-10 1985-01-29 Sumitomo Special Metals Co., Ltd. Fe-Cr-Co Type magnet body of columnar structure and method for the preparation of same

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1367174A (en) * 1970-12-28 1974-09-18 Inoue Japax Res Magnetic-meterials
GB1435684A (en) * 1974-05-02 1976-05-12 Inoue Japax Res Magnetic materials
GB1551717A (en) * 1977-04-21 1979-08-30 Arnold Eng Co Magnetic alloy and processing therefore
US4324597A (en) * 1977-12-27 1982-04-13 Mitsubishi Seiko Kabushiki Kaisha Magnetic alloy
EP0003466A1 (en) * 1978-01-19 1979-08-08 Ugimag S.A. Process for the thermal treatment of Fe-Co-Cr alloys for permanent magnets
US4174983A (en) * 1978-07-13 1979-11-20 Bell Telephone Laboratories, Incorporated Fe-Cr-Co magnetic alloy processing
EP0024686A2 (en) * 1979-08-24 1981-03-11 Western Electric Company, Incorporated Article comprising a magnetic component consisting essentially of an alloy comprising Fe, Cr and Co
US4496402A (en) * 1981-03-10 1985-01-29 Sumitomo Special Metals Co., Ltd. Fe-Cr-Co Type magnet body of columnar structure and method for the preparation of same

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2177420A (en) * 1985-07-04 1987-01-21 Sokkisha Magnetic medium used for magnetic scale
GB2177420B (en) * 1985-07-04 1989-07-12 Sokkisha Magnetic scale
US20130299562A1 (en) * 2011-01-14 2013-11-14 Sabastian Piegert Cobalt-based alloy comprising germanium and method for soldering
US8763885B2 (en) * 2011-01-14 2014-07-01 Siemens Aktiengesellschaft Cobalt-based alloy comprising germanium and method for soldering

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Publication number Publication date
DE3526675A1 (en) 1986-03-06
GB2163778B (en) 1988-11-09
GB8518273D0 (en) 1985-08-29

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