JP5312139B2 - High-strength temperature-sensitive magnetic alloy and heating member for induction heating - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention relates to an induction heating heat generating member used for an induction heating heat generating roller provided in a heat fixing device for an unfixed image (toner image) in an electronic copying apparatus, an electrostatic recording apparatus, etc. It relates to a magnetic alloy.

  In an image fixing unit such as an electronic copying machine or an electrostatic recording apparatus, a toner image formed on a recording paper is heated by an image forming unit such as a photosensitive drum, and an unfixed image is placed on the recording paper. A heat fixing device for fixing is provided. There are various types of heat fixing devices, but in recent years, devices using electromagnetic induction heating with excellent heat generation efficiency have been used.

  As such a heat fixing device, Japanese Patent Laid-Open No. 11-327331 (Patent Document 1) discloses a movable belt and a recording paper on which a toner image is formed between the belt (hereinafter simply referred to as “covered”). A pressure roller that presses the recording paper), induction heating is possible, a heating member for induction heating that presses the belt toward the pressure roller, and excitation means for induction heating the heating member. A heat fixing device is described. The induction heating heat generating member generates an induced current by an alternating magnetic field generated by the excitation means (for example, an excitation coil), and generates heat due to Joule heat generated thereby. The pressure roller includes an outer layer formed around a roll shaft with a heat-resistant and elastic resin such as silicon rubber so that an appropriate nip is formed.

  Further, as another heat fixing device using electromagnetic induction heating, an induction heating heating roller, a pair of pressure rollers rotating in opposite directions, and a pair of pressure rollers are sandwiched between the pair of pressure rollers. There is a belt including a belt movably wound around one pressure roller and the heat generating roller, and an excitation unit for inductively heating the heat generating roller. In this apparatus, the recording paper is conveyed through the pair of pressure rollers while being in close contact with the belt, and the belt is heated by a heat-generating roller heated by induction. The recording paper is sandwiched between the heated belt and the pressure roller, and the unfixed toner image thereon is heated by the belt and fixed on the recording paper.

  Further, in order to make the heat fixing device compact, one of the pair of pressure rollers is replaced with the induction heating heat generating roller, and the moving belt is eliminated. In this case, usually, an outer layer made of elastic heat-resistant rubber or resin (including foamed material) such as silicon rubber, fluororubber or fluororesin is provided on the outer peripheral portion of the heat generating roller.

In the heat fixing device, it is inductively heated, various induction heating heating member for fixing an unfixed toner image on a recording paper, but the non-magnetic stainless steel may be such as those plated with copper is used , a maximum relative permeability of dc magnetic properties ([mu] m) is 5,000 or more, a Curie point of the temperature-sensitive magnetic alloy of about 180 to 250 ° C. is suitably used for having a self temperature control characteristics. As such a temperature-sensitive magnetic alloy, for example, a mass% 36% Ni—Fe alloy (Curie point 220 ° C.) is used.

Japanese Patent Laid-Open No. 11-327331

  In the case where the heat generating member for induction heating is formed of a temperature-sensitive magnetic alloy, after being processed into a predetermined shape, annealing in a recrystallization temperature region (referred to as “magnetic annealing”) is performed in order to develop a high magnetic permeability. The For example, in a 36% Ni—Fe alloy, magnetic annealing is performed at a temperature of about 800 to 1000 ° C.

  However, when magnetic annealing is performed on the heat-generating member after processing, high magnetic permeability is developed, but material hardness and strength are inevitably lowered. For example, in the 36% Ni—Fe alloy, the hardness decreases to about 130 Hv by magnetic annealing. Since the induction current generated in the heat generating member by the high frequency alternating magnetic field flows concentrated on the surface of the member due to the skin effect, the thickness of the heat generating member for induction heating may be about 0.03 to 2 mm from the viewpoint of induction heating. As described above, since the hardness and strength are reduced by magnetic annealing, the heat generating member needs to be formed thicker than the thickness required for induction heating. Further, when the heat generating member is formed thin, it is necessary to take measures such as attaching a support member such as stainless steel to the heat generating member. In any case, since the heat generating member or the heat generating member for induction heating with the support member becomes thicker than necessary for induction heating, downsizing is impaired.

  The present invention has been made in view of such a problem, and has a maximum relative magnetic permeability of 5000 or more, a Curie point of about 180 to 250 ° C., and a high strength thermosensitive magnetic alloy and induction which are hard to decrease in hardness by magnetic annealing. An object is to provide a heating member for heating.

  The present inventor measured the hardness after magnetic annealing while adding various third elements based on Ni-Fe and having a predetermined maximum relative magnetic permeability and Curie point. As a third element, Nb is very preferable. In addition, the inventors have found that the intended purpose can be achieved within a predetermined amount of Ni, Nb, and Fe, and have completed the present invention.

That is, the temperature-sensitive magnetic alloy of the present invention is composed of Ni, Nb and Fe (including inevitable impurities) as constituent elements, a maximum relative permeability of 5000 or more, a Curie point of 180 to 250 ° C., and a surface hardness of a test load. The Vickers hardness at 4.9 MPa is HV160 or more, and as shown in FIG.
Point A (Ni: 43.0%, Nb: 6.5%, Fe: 50.5%),
Point B (Ni: 41.0%, Nb: 3.5%, Fe: 55.5%),
Point C (Ni: 38.0%, Nb: 3.5%, Fe: 58.5%),
Point D (Ni: 36.5%, Nb: 6.5%, Fe: 57.0%),
It has a chemical composition within the range surrounded by. In this temperature-sensitive magnetic alloy, the surface hardness after magnetic annealing (Vickers hardness at a test load of 4.9 MPa (500 g), hereinafter simply referred to as “hardness”) is preferably HV180 or more .

  In addition, the heat generating member for induction heating according to the present invention is a heat generating member for induction heating such as a heat generating roller for induction heating for fixing a toner image, and is formed of the high-strength thermosensitive magnetic alloy.

According to the temperature-sensitive magnetic alloy of the present invention, since it has a composition in a specific range of Ni-Nb-Fe, it has a Curie point of 180-250 ° C. with a maximum relative permeability of 5000 or more, and hardness after magnetic annealing. Can be made HV160 or more, and as a heat generating member for induction heating such as a heat generating roller for fixing a toner image, the thickness is reduced without a supporting member such as stainless steel as compared with a conventional temperature-sensitive magnetic alloy. Can contribute to downsizing.

It is a composition diagram which shows the composition range of Ni, Nb, and Fe which are the structural components of the thermosensitive magnetic alloy of this invention. It is explanatory drawing which shows the measuring point of a Curie point.

  The inventor of the present invention is assumed to be able to secure a maximum relative magnetic permeability of 5000 or more from the characteristics of the Ni—Fe binary alloy with respect to the Ni—Nb—Fe alloy. The effect of Nb on the Curie point (cp), the maximum relative permeability of the DC magnetic characteristics, and the hardness after magnetic annealing was investigated in detail. As a result, the point A shown in FIG. 1 (Ni: 43.0%, Nb: 6.5%, Fe: 50.5%), preferably (Ni: 42.0%, Nb: 6.0%, Fe: 52.0%), point B (Ni: 41.0%, Nb: 3.5%, Fe: 55.5%), preferably (Ni: 40.0%, Nb: 4.0%, Fe: 56) 0.0%), point C (Ni: 38.0%, Nb: 3.5%, Fe: 58.5%), preferably (Ni: 38.0%, Nb: 4.0%, Fe: 58.%). 0%), point D (Ni: 36.5%, Nb: 6.5%, Fe: 57.0%), preferably (Ni: 37.0%, Nb: 6.0%, Fe: 57.0) %) Was found to satisfy the above three conditions in a well-balanced manner (hereinafter referred to as “the alloy region of the present invention”). In addition, Fe of the said composition is a remainder and contains an unavoidable impurity.

  That is, in FIG. 1, when Nb is less than the B-C line and its extension line, the hardness after annealing generally decreases, and when the Ni content is low, the Curie point is also below 180 ° C., When the amount of Ni is high, the Curie point exceeds 250 ° C. Moreover, when there is more Nb amount than an A-D line and its extension line, workability will deteriorate on the whole and shaping | molding of a raw material will become difficult. Further, if the amount of Nb is less than that of the AB line, the hardness after magnetic annealing also decreases, and if the amount of Ni is large, the Curie point increases and exceeds 250 ° C. Further, when the amount of Ni is smaller than that of the CD line, the maximum relative permeability is lowered, and the Curie point is also lower than 180 ° C. As long as the characteristics of the temperature-sensitive magnetic alloy of the present invention are not affected, about several percent of the characteristic improving element can be added. In this case, it is only necessary that the ratio of each element amount satisfies the alloy region of the present invention when the total amount of Ni, Nb and Fe excluding the characteristic improving element is 100%.

  The temperature-sensitive magnetic alloy of the present invention melts a Ni—Nb—Fe alloy having the composition of the above-described alloy region of the present invention, and hot-processes a slab obtained by casting the alloy (hot forging or hot Rolling), followed by soft annealing and cold rolling as necessary, and the resulting alloy sheet is subjected to magnetic annealing as final annealing. When the cold rolling is performed in a plurality of steps, intermediate annealing (softening annealing) can be performed between the steps. Since the alloy of the present invention contains Nb which is easily oxidized, the melting is preferably performed by vacuum melting, and the softening annealing and magnetic annealing are preferably heat treatment in a reducing atmosphere such as a hydrogen gas atmosphere. The soft annealing and the intermediate annealing may be performed under the same conditions as the magnetic annealing described later.

  The magnetic annealing is usually performed by heating and holding at a temperature in the range of about 950 to 1150 ° C. for about 0.5 to 2 hours. Since the magnetic annealing temperature increases the crystal grain size by recrystallization, the surface hardness tends to decrease and the Curie point also tends to decrease. On the other hand, the influence on the maximum relative permeability is more sensitive than the hardness and the Curie point, and the maximum relative permeability tends to be greatly improved as the annealing temperature increases. Therefore, it is desirable to set an optimum annealing temperature within the temperature range so as to ensure a maximum relative permeability of 5000 or more.

  When processing into a heat generating member having a predetermined shape, the cold-rolled sheet after annealing is appropriately processed to be processed into a target shape, and then subjected to magnetic annealing. In forming the shape, it may be formed in a plurality of steps while performing intermediate annealing as necessary. In the case of a heating roller for induction heating used in a heat fixing device for toner images, it is usually produced by deep drawing a cold-rolled plate after annealing into a bottomed cylindrical shape, and cutting and removing the bottom after forming. When deep drawing is performed, the molding can be divided into a plurality of steps, and intermediate annealing can be performed during the process. The plate thickness of the heating roller for induction heating is usually set to about 0.03 to 2 mm. The temperature-sensitive magnetic alloy according to the present invention is not limited to the heat-generating roller, and can be suitably used for various induction heating heat-generating members and materials used in toner image heat-fixing devices.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not limitedly interpreted by the said embodiment and the following Example.

  The Ni amount, Nb amount, balance Fe, and inevitable impurity Ni—Nb—Fe alloy shown in Table 1 were vacuum-melted, and the molten metal was cast to obtain a slab. The obtained slab was heated to 1150 ° C. and hot forged in the atmosphere to obtain a forged slab having a cross-sectional shape of 50 mm width × 8 mm thickness, and then softened and annealed by heating at 1100 ° C. for 1 hr in a hydrogen atmosphere. Then, the surface was chamfered and cold rolled to obtain a cold rolled sheet having a width of 50 mm and a thickness of 2 mm. This rolled plate was further subjected to intermediate annealing by heating and holding at 1000 ° C. for 1 hr, and then processed into a thickness of 0.5 mm (plate width 50 mm) by cold rolling, and the magnetic annealing temperature shown in Table 1 (annealing time 1 hr) And magnetic annealing.

  Tissue observation specimens were collected from each sample of the Ni—Nb—Fe alloy plate produced as described above, and the average crystal grain size was identified from the structure standard diagram by optical microscope observation (100 times) in accordance with the provisions of JIS G0511. did. Moreover, a hardness measurement test piece was collected from each sample, and Vickers hardness (test load 4.9 MPa) was measured. Moreover, the Curie point measurement test piece and the magnetic permeability measurement test piece were sampled from each sample, and the maximum relative permeability of the Curie point and DC magnetic characteristics was determined. The maximum relative permeability (μm) was measured in accordance with the provisions of the old JISC2531 (1987 edition).

  The Curie point was measured as follows. As shown in FIG. 2, a test piece S (22 mm wide, 27 mm long) provided with two coils (5 windings) along the length direction is placed in a heating furnace 1, and the temperature of the test piece S is adjusted to a thermocouple. Further, an alternating voltage of 30 kHz is applied to one coil, and the induced electromotive force is measured with the other coil. The induced electromotive force was measured while raising the temperature of the heating furnace, and the temperature when the induced electromotive force began to decrease was taken as the Curie point. In the figure, 2 is a transmitter, 3 is a voltmeter, and 4 is a thermometer.

  The measurement results are summarized in Table 1. The sample numbers in Table 1 are shown in FIG. The acceptable level of each characteristic was a Curie point of 180 to 250 ° C., a maximum relative magnetic permeability of 5000 or more, and a hardness of HV160 or higher, which is about HV30 higher than the conventional level. In the table, “-” indicates that measurement was omitted.

  From Table 1, Sample Nos. 1, 2 and 17 containing no or little Nb, even after setting the magnetic annealing temperature as low as 800 ° C. and 1000 ° C., had a hardness after annealing lower than HV160. Further, Sample Nos. 3 to 5 having a small amount of Ni generally had a Curie point lower than 180 ° C. Further, Sample No. 13 having a low Nb amount and a large Ni amount also did not provide sufficient hardness. Further, Sample Nos. 14 to 16 having an excessive amount of Ni had high Curie points as a whole even when the magnetic annealing was set to a high 1100 ° C. In addition, Sample No. 20 with an excessive Nb amount had a very poor workability because the slab was cracked at the hot forging stage. In contrast, sample Nos. 6-12, 18 and 19 (including those with numbers A and B added) in the alloy region of the present invention have an acceptable level of Curie point and maximum relative permeability. Further, the hardness was HV180 or more, and it was confirmed that it had sufficient strength as compared with Sample No. 1 of the conventional example.

  Further, a Ni—Nb—Fe alloy plate (thickness 0.5 mm) of the composition of Sample No. 9 of the inventive example having a relatively high Nb amount was manufactured in the same manner as described above, and a circular flat blank was collected therefrom. A bottomed cylindrical body having an inner diameter of 30 mm, a thickness of 40 μm and a length of 440 mm was produced by three-stage deep drawing. Between each process of deep drawing, the intermediate annealing which heated and hold | maintained at 1100 degreeC and 0.5 hr was performed in hydrogen atmosphere. After molding, magnetic annealing was performed by heating and holding at 1100 ° C. for 1 hr in the same atmosphere. Thereafter, the bottom portion was cut to obtain a cylindrical heating roller having a length of 430 mm. When this roller was cut in the length direction, developed, and the surface hardness was measured, it was HV203. Moreover, when the test piece was extract | collected and the Curie point and the maximum relative magnetic permeability were measured, they were 191 degreeC and 8000, respectively.

Claims (3)

It is a high-strength thermosensitive magnetic alloy whose constituent elements are Ni, Nb and Fe,
The maximum relative permeability is 5000 or more, the Curie point is 180 to 250 ° C., the surface hardness is HV160 or more in terms of Vickers hardness at a test load of 4.9 MPa,
As shown in FIG.
Point A (Ni: 43.0%, Nb: 6.5%, Fe: 50.5%),
Point B (Ni: 41.0%, Nb: 3.5%, Fe: 55.5%),
Point C (Ni: 38.0%, Nb: 3.5%, Fe: 58.5%),
Point D (Ni: 36.5%, Nb: 6.5%, Fe: 57.0%),
A high-strength thermosensitive magnetic alloy having a chemical composition within the range surrounded by. A heating member for induction heating for fixing a toner image, the heating member for induction heating formed of the high-strength temperature-sensitive magnetic alloy according to claim 1 . The heating member for induction heating according to claim 2 , wherein the heating member for induction heating is a heating roller for induction heating.

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