JPH06212362A - Ferrochrome alloy for durable heating wire - Google Patents

Abstract

PURPOSE:To obtain an ferrochrome alloy for a durable heating wire having a service life longer than that of the conventional one by specifying an alloy compsn. contg. C, Si, Mn, Cr, Al and rare earth metals and in which P and S are regulated, and the balance Fe. CONSTITUTION:This is a ferrochrome alloy for a durable heating wire having an alloy compsn. contg. <=0.10% C, <=1.5% Si, <=1.0% Mn, 17.0 to 26.0% Cr, 2.0 to 6.0% Al and 0.01 to 0.10% rare earth metals and in which the content of P is regulated to <=0.04% and that of S to <=0.005%, and the balance substantially Fe, and in which wire cutting is hard to generate under severe using conditions. This can be attained by retarding the progress of oxidation with grain boundaries as a path by the fixing of S into the grains by the reduction of impurities and the addition of rare earth metals. In the same alloy, according to uses, the contents of Cr and Al are selected: e.g. (1) 17.0 to 21.0% Cr-2.0 to 4.0% Al, (2) 20.0 to 25.0% Cr-4.0 to 6.0% Al and (3) 23.0 to 26.0%, Cr-4.0 to 6.0% Al.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved ferrochrome alloy for heating wires, and provides a ferrochrome alloy having a longer life than ever before.

[0002]

2. Description of the Related Art Ferrochrome alloys commonly used for heating wires are high Cr-high Al FCHW1 alloys and low Cr-low Al FCHW2 alloys, which are selected according to the required volume resistance value. Although used, the demand for ferrochrome alloys with medium Cr-high Al is increasing recently.

As the use of heating wires expands, the operating conditions often become more severe, and even under mild operating conditions, longer life is always desirable.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a ferrochrome alloy for heating wire, which has a longer life than conventional ones.

[0005]

The ferrochrome alloy for long-life heating wire according to the present invention has, in general terms, C: 0.10%.
Hereinafter, Si: 1.5% or less, Mn: 1.0% or less, Cr:
17.0 to 26.0%, Al: 2.0 to 6.0% and RE
M: 0.01 to 0.10% is contained, P: 0.04% or less and S: 0.005% or less, and the balance has an alloy composition consisting essentially of Fe. .

The Cr content and / or Al content of this ferrochrome alloy is selected according to the application. The typical ranges of those standards are listed below in conformity with existing standards. Cr: 17.0 to 21.0% -Al: 2.0 to 4.0% Cr: 20.0 to 25.0% -Al: 4.0 to 6.0% Cr: 23.0 to 26. 0% -Al: 4.0-6.0%

[0007]

The inventors presumed that the main cause of the disconnection that determines the life of the heating wire is the progress of oxidation through the crystal grain boundaries, and intended to strengthen the grain boundaries. As measures for strengthening the grain boundaries, one is to reduce the above-mentioned impurities and the other is to fix S in the grains by adding REM.

The standard for ferrochrome alloys for heating wires has no particular provision for impurities P and S. In the products on the market, it is the actual situation that S is contained in the range of 0.008 to 0.010%, but it is necessary to regulate this to 0.005% or less and to add 0.01% or more of REM. Fixes S in the form of REM-sulfide. RE
Since M-sulfide has a high freezing point, when the alloy is melted, it precipitates as fine particles early in the solidification process and does not collect at the grain boundaries.

The effect of the addition of REM can be obtained in a trace amount of 0.01% due to the reduction of S. However, in order to ensure this, it is necessary to add REM in an amount of 0.02 to 0.05%. preferable. If the amount added is too large, the amount of inclusions increases and the cleanliness is lowered, so the addition is limited to within 0.10%.

[0010]

Example A ferrochrome alloy having the alloy composition (% by weight, balance Fe) shown in the table was melted. REM is La and C
It is a mixture of rare earth elements whose main component is e. N in the table
o. Items marked with * are comparative examples, and unmarked examples are examples of the invention.

[0011] Table No. C Si Mn Cr Al P S REM life value 1 * 0.02 0.49 0.32 19.2 3.4 0.02 0.008 - 80 2 * 0.03 0.53 0.79 19.4 3.4 0.02 0.002 - 110 3 0.01 0.46 0.26 19.5 3.8 0.03 0.003 0.02 420 4 * 0.01 0.88 0.30 20.2 4.0 0.02 0.002 − 360 5 * 0.02 0.42 0.41 24.0 4.9 0.01 0.009 − 320 6 * 0.03 0.54 0.86 24.1 4.8 0.04 0.002 − 430 7 0.02 0.51 0.29 23.9 4.7 0.02 0.001 0.05 500 8 0.01 1.39 0.33 25.0 4.9 0.03 0.003 0.02 642 9 * 0.03 0.61 0.29 25.1 5.6 0.02 0.001 − 480 10 0.02 0.49 0.38 24.9 5.4 0.02 0.001 0.03 960 Establish a heating wire for testing from each alloy, JISC-252
Select the U method specified in 4, that is, the test method in which the heating wire is bent and held in a U shape, and the temperature is 1300 ° C by applying electricity in the atmosphere.
Was repeated, the cycle of cutting off the current and cooling to room temperature was repeated, and the number of cycles until the disconnection was recorded.
The value is also shown in the column of life value in the table.

From the data in the table, it can be seen that the life is slightly improved by reducing the amounts of P and S, and that the effect is REM.
It can be seen that the addition becomes remarkable.

[0013]

The ferrochrome alloy for heating wire of the present invention is
Standard lifespan values (70 or more for No. 1-4 FCHW2 equivalent products, 1 for No. 9 and 10 FCHW1 equivalent products)
(More than 00) and shows a long life approaching the next order.

If this is used, a long-life heating wire can be manufactured, so that maintenance of various industrial electric heating furnaces and heaters of household electric appliances becomes easy. The heater of a 200V household electric appliance, which is becoming widespread, can be made to have a small diameter, a high calorific value, and a long life.

In addition, the ferrochrome alloy of the present invention can be utilized not only as a heater but also as a material for an automobile exhaust purification mesh because of its long life.

Claims (4)

[Claims] 1. C: 0.10% or less, Si: 1.5% or less, Mn: 1.0% or less, Cr: 17.0 to 26.0%,
Al: 2.0-6.0% and REM: 0.01-0.1
Contains 0%, P: 0.04% or less, and S: 0.00
A ferrochrome alloy for long-life heating wire, which has an alloy composition of 5% or less and the balance being substantially Fe. 2. Cr: 17.0 to 21.0%, Al:
The ferrochrome alloy according to claim 1, which is 2.0 to 4.0%. 3. Cr: 20.0 to 25.0%, Al:
The ferrochrome alloy according to claim 1, which is 4.0 to 6.0%. 4. Cr: 23.0 to 26.0%, Al:
The ferrochrome alloy according to claim 1, which is 4.0 to 6.0%.