JP5300962B2 - Electrical resistor material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric resistor material of high electric resistivity reduced in temperature dependency of the electric resistivity, and capable of restraining a noise caused by a magnetic field generated when a current flows. <P>SOLUTION: This electric resistor material contains 0.1% or less of C, 5% or less of Si, 6% or less of Mn, 9-32% of Cr, 6-25% of Ni, 0.2% or less of N, 0-3% of Mo, 0-4% of Cu, 0-5% of Al, 0-0.4% of Ti, 0-0.4% of Nb, and 0-0.005% of B, and is regulated to bring an A value defined by Expression (1) into 78 or more, and to bring a B value defined by Expression (2) into 14 or more (wherein, A=0.008&times;(%Cr)<SP POS="POST">3</SP>-0.43&times;(%Cr)<SP POS="POST">2</SP>+8.03&times;(%Cr)+6.8&times;(%Si)+10.9&times;(%Al)+0.56&times;(%Mo)+0.92&times;(%Ni) (1), and B=(%Ni)+(%Cu)+0.6&times;(%Mn)+9.69&times;(%C+%N)+0.18&times;(%Cr)-0.11&times;(%Si)<SP POS="POST">2</SP>(2)). <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to an electric resistor used for a main resistor, a power resistor represented by a neutral grounding resistor of a generator, a main resistor of a resistance control vehicle, a vehicle resistor such as a brake resistor, and the like. It relates to equipment.

  It is desirable that the resistor has a constant resistance value without being affected by environmental changes such as temperature. However, the temperature of the resistor is increased by Joule heat generated by energization, and the temperature may be increased to around 400 ° C. in a power resistor or a vehicle resistor through which a large current flows. In a resistor using a metal resistor material, the electrical resistance may increase due to temperature rise, and the original characteristics may be impaired. Therefore, a high electrical resistance material having a small temperature dependency of electrical resistance is used for a power resistor and a vehicle resistor.

  Conventional high electrical resistance materials include Fe-Cr-Al alloys such as FCH1 and FCH2. Since FCH1 and FCH2 contain 17 to 26% Cr and 2 to 6% Al, the electrical resistivity is high and the temperature dependence of the electrical resistivity is also small. However, since it is ferromagnetic, a magnetic field is generated by the current flowing through the resistor, and the resistor itself vibrates and generates noise. Vibration and noise caused by the generated magnetic field can be prevented by using nonmagnetic resistor materials such as NCH1, NCH2, and NCH3. However, NCH1, NCH2, NCH3, etc. are hard workable materials that have high deformation resistance at high temperatures and are prone to scorching during hot rolling, and are also expensive materials because they contain a large amount of Ni.

  In contrast, SUS304 stainless steel contains 18% by mass of Cr, so the electrical resistivity is 70 μΩ · cm, which is higher than that of ordinary steel, but the electrical resistivity is more temperature dependent than that of conventional electrical resistance materials. The nature is great. SUS304 stainless steel is non-magnetic when annealed, but becomes ferromagnetized by processing. As a result, when used as an electric resistor, a large noise is generated due to the generated magnetic field. In addition, when the amount of alloy components such as Si and Al is increased in order to improve the electrical resistivity, the steel sheet becomes hard and bending workability is lowered, and the tendency to ferromagnetization is promoted.

  The present invention has been devised to solve such a problem. By adopting an alloy design that enables an increase in electrical resistivity and a decrease in magnetic permeability, the electrical resistivity is high, and the electrical resistance An object of the present invention is to provide an electrical resistor material that has a small temperature dependency of the rate and that suppresses noise caused by a magnetic field generated when a current flows.

In order to achieve the object, the electrical resistor material of the present invention has C: 0.1 mass% or less, Si: 5 mass% or less, Mn: 6 mass% or less, Cr: 9-32 mass%, Ni: 6 ~ 25% by mass, N: 0.2% by mass or less, Mo: 0-3% by mass, Cu: 0-4% by mass, Al: 0-5% by mass, balance Fe and inevitable impurities composition, The A value defined in (1) is adjusted to 78 or more, and the B value defined in Equation (2) is adjusted to 14 or more.
A = 0.008 × (% Cr) ³ −0.43 × (% Cr) ² + 8.03 × (% Cr) + 6.8 × (% Si)
+ 10.9 × (% Al) + 0.56 × (% Mo) + 0.92 × (% Ni) (1)
B = (% Ni) + (% Cu) + 0.6 × (% Mn) + 9.69 × (% C +% N)
+ 0.18 × (% Cr) −0.11 × (% Si) ² (2)
This electrical resistor material may further contain one or more of Ti: 0.4% by mass or less, Nb: 0.4% by mass or less, and B: 0.005% by mass or less.

  The electric resistor material of the present invention has an A value of 78 or more incorporating the influence of each alloy component on the electrical resistivity in the Fe-Cr-Ni system, and a B value incorporating the influence of each alloy component on demagnetization. Since the alloy design is such that the electrical resistivity is 14 or more, the electrical resistivity is high, the temperature dependence of the electrical resistivity is small, and the noise caused by the magnetic field generated when a current flows is also suppressed. Therefore, it is used as a resistor in various fields including a power resistor and a vehicle resistor through which a large current flows.

The graph which showed the relationship between the electrical resistivity in room temperature, and the average temperature coefficient in the temperature range of 20-400 degreeC. Graph showing the effect of B value on permeability μ

  The present inventors have investigated various electrical resistor materials that exhibit high electrical resistivity and low temperature dependence of electrical resistivity, have low noise during use, and have good hot workability and bending workability. I searched for new materials. In a power resistor, a vehicle resistor, and the like that are heated to around 400 ° C. by flowing a large current, the temperature dependence of the electrical resistivity is small, specifically, the electrical resistance in a temperature range of 20 to 400 ° C. The average temperature coefficient of the rate is required to be 1.0007 / ° C. or less.

As a result of investigating the relationship between the electrical resistivity and the average temperature coefficient in the temperature range of 20 to 400 ° C., as shown in FIG. 1, in order to make the average temperature coefficient 1.0007 / ° C. or less, the electrical resistivity is 85 μΩ.・ It was found that it was necessary to make it more than cm. On the other hand, in order to prevent noise caused by magnetic field generation, the electrical resistor material is required to be non-magnetic.
Therefore, when the relationship between the component / composition and the electrical resistivity R was investigated in detail for the austenitic Fe—Cr—Ni alloy in which non-magnetism was easily obtained, the electrical resistivity R was expressed by the following equation. Elucidated.
R = 0.008 × (% Cr) ³ −0.43 × (% Cr) ² + 0.83 × (% Cr) + 6.8 × (% Si)
+ 10.9 × (% Al) + 1.0 × (% Mo) + 0.92 × (% Ni) +7.4
Therefore, when the A value defined by the above formula (1) is 78 or more, an electrical resistivity R of 85 μΩ · cm or more is obtained.

  The permeability μ is generally used as a nonmagnetic index. The resistor is bent into a fold-like shape so that the resistor material is placed in a fixed space, but noise generation of the resistor is suppressed when the magnetic permeability μ is 1.010 or less even after the bending. The amount of strain generated by bending into a wrapping shape corresponds to a maximum cold rolling rate of 20%. Therefore, the relationship between the alloy component and the magnetic permeability μ was investigated for the sample as annealed and the sample cold-rolled at a rolling rate of 20%. As a result, as shown in FIG. 2, it was found that the permeability μ can be arranged by the B value defined by the above formula (2). From the relationship between the magnetic permeability μ and the B value, if the B value is set to 14 or more, the magnetic permeability μ is 1.010 or less even when cold rolling is performed at a rolling rate of 20%. It can be said that non-magnetism is maintained even after bending into a shape.

The Fe-Cr-Ni alloy used for the electrical resistor material of the present invention employs an alloy design that satisfies A value ≧ 78 and B value ≧ 14 as described above. The content and action / effect will be described.
C: An alloy component effective for maintaining non-magnetism, but if it exceeds 0.1% by mass, the alloy becomes hard and bending workability decreases.
Si: An alloy component effective for increasing electric resistance, but if an excessive amount of silicon exceeding 5% by mass is contained, bending workability deteriorates due to hardening.

Mn: An alloy component effective for maintaining non-magnetism, but excessive Mn content exceeding 6% by mass causes an increase in the amount of refractory erosion during refining.
Cr: An alloy component effective for increasing the electrical resistivity and improving the corrosion resistance and oxidation resistance at high temperatures, and the effect of adding Cr becomes remarkable at 9% by mass or more. However, when an excessive amount of Cr exceeding 32% by mass is included, surface flaws are likely to occur during hot rolling, and toughness and workability also deteriorate. Preferably, the upper limit of the Cr content is set to 20% by mass.
Ni: An alloy component effective for demagnetization and high electrical resistance, and the increase in hardness of the material is small even if the amount added is increased. In order to ensure workability, at least 6% by mass is required. However, when the Ni content exceeds 25% by mass, deformation resistance at high temperatures is increased, and cracks starting from grain boundaries on the plate surface are likely to occur during hot rolling. Preferably, the upper limit of the Ni content is set to 15% by mass.

N: An effective component for maintaining non-magnetism, but containing an excessive amount of N exceeding 0.2% by mass tends to harden the material by solid solution strengthening. N can also be made into the level (0.03 mass% or less) mixed from steelmaking, without adding actively.
Mo: An alloy component added as necessary, and exhibits an effect of increasing the electrical resistivity. However, the addition of an excessive amount of Mo exceeding 3% by mass hardens the material by solid solution strengthening and reduces workability.
Cu: An alloy component added as necessary, effective for demagnetization, and small in solid solution strengthening ability. However, addition of an excessive amount of Cu exceeding 4% by mass lowers the high temperature ductility and causes ear cracks during hot rolling.

Al: An alloy component added as necessary, and exhibits the most effective action for increasing electrical resistivity. However, addition of an excessive amount of Al exceeding 5% by mass generates a large amount of an intermetallic compound with Ni and lowers the high temperature ductility. Preferably, the upper limit of the Al content is set to 2% by mass.
Ti: An alloy component added as necessary, and effective in improving bending workability. However, when an excessive amount of Ti exceeding 0.4% by mass is added, surface flaws are likely to occur in the slab obtained by continuous casting.

Nb: It is an alloy component added as necessary, and is effective in improving the high temperature strength. However, excessive addition of Nb exceeding 0.4 mass% reduces the toughness of the material.
B: When the B value, which is an index of demagnetization, exceeds 17, cracks starting from grain boundaries are likely to occur on the surface of the hot rolled sheet. B exhibits the action of suppressing the occurrence of cracks. However, if B is added in excess of 0.005% by mass, the grain boundary is lowered to lower the hot workability.

A Fe-Cr-Ni alloy having the composition shown in Table 1 is melted in a 30 kg high-frequency vacuum melting furnace and subjected to rough hot rolling, finish hot rolling, annealing / pickling, cold rolling, finish annealing, pickling rolling. A 2 mm thick Fe—Cr—Ni alloy material was produced.
During hot rolling, the occurrence of cracks and ear cracks on the plate surface was investigated. No. In 1 to 8 (steel of the present invention), there were no ear cracks, and almost no surface cracks occurred on the plate. On the other hand, no. In Nos. 11 and 12 (comparative steel), neither ear cracks nor surface cracks occurred. In No. 13 (comparative steel), remarkable surface cracks occurred in the hot rolled sheet.

A test piece was cut out from each Fe—Cr—Ni alloy material, and the electrical resistivity, the temperature dependence of the electrical resistivity, and the magnetic permeability μ were measured as follows.
In measuring the electrical resistivity, the electrical resistance-temperature characteristic test method defined in JIS C2526 was adopted, and the electrical resistivity of each test piece at each temperature was measured. From the measured value, an average temperature coefficient α ₂₀ to ₄₀₀ in a temperature range of 20 to 400 ° C. was obtained.
The permeability μ was measured with a magnetic balance using a test piece cut out from a material cold-rolled at a rolling rate of 20%.

As can be seen from the measurement results in Table 2, the temperature dependence of the electrical resistivity of the Fe—Cr—Ni alloy according to the present invention is 1.0007 / ° C. or less, and the magnetic permeability after 20% cold rolling. μ was 1.010 or less effective for noise suppression.
On the other hand, the comparative material 11 having a small A value and B value has a large temperature dependency of the electrical resistivity, and generates a large noise when used as a resistor. The comparative material 12 having a high A value of 85 has a small temperature dependency of the electrical resistivity, but has a small B value, so that when it is used for a resistor, a large noise is generated due to magnetization. Further, the comparative material 13 having a high B value of 19 is less suitable because the nonmagnetic property is maintained. However, since the A value is small, the temperature dependency of the electrical resistivity is large and is not suitable as a resistor material.

Claims (2)

C: 0.1 mass% or less, Si: 5 mass% or less, Mn: 6 mass% or less, Cr: 9-32 mass%, Ni: 6-25 mass%, N: 0.2 mass% or less, Mo: 0 to 3% by mass, Cu: 0 to 4% by mass, Al: 0 to 5% by mass, balance Fe and inevitable impurities, and the A value defined by formula (1) is 78 or more, formula (2 The B value defined in (4) is adjusted to 14 or more.
A = 0.008 × (% Cr) ³ −0.43 × (% Cr) ² + 8.03 × (% Cr) + 6.8 × (% Si)
+ 10.9 × (% Al) + 0.56 × (% Mo) + 0.92 × (% Ni) (1)
B = (% Ni) + (% Cu) + 0.6 × (% Mn) + 9.69 × (% C +% N)
+ 0.18 × (% Cr) −0.11 × (% Si) ² (2)   The electrical resistor material according to claim 1, further comprising one or more of Ti: 0.4 mass% or less, Nb: 0.4 mass% or less, and B: 0.005 mass% or less.

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