JPS591782B2 - Iron/chromium/aluminum electric heating alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement of an iron-chromium-aluminum electric heating alloy containing 0.01% or more of carbon and 0.02% or more of nitrogen.

Iron-chromium-aluminum alloys are widely used as electric heating materials along with nickel-chromium alloys, and compared to nickel-chromium alloys, they have superior oxidation resistance at high temperatures, longer lifespans, and lower specific electrical resistance. It has many characteristics such as high production costs and low raw material prices.

Iron-chromium-aluminum electric heating alloys are generally At2.
5 to 8% Cr, 20 to 30% Cr, and the balance Fe (weight %, same hereinafter), and those in this range are difficult to oxidize at the high temperatures used, have good mechanical properties, and are easy to plastic work. It has the necessary conditions for an electrothermal alloy, such as high electrical resistivity, and generally the higher the content of aluminum or chromium, the higher these characteristic values will be.

Therefore, if the operating temperature is high, for example, JIS C252
O, 4-8% aluminum, 20-3% chromium, such as FCHWI, FCHRI or Kanthal (trade name) alloy
0% is generally put into practical use. However, the characteristics of iron-chromium-aluminum electric heating alloys depend not only on the content of aluminum and chromium, but also on the trace impurities contained therein.
It is also well known that high quality,
The production of high-performance iron-chromium-aluminum electrothermal alloys requires advanced technology.

Among these, the inclusion of trace impurities has an unfavorable effect on the properties of the electrothermal alloy, and in particular, the inclusion of trace amounts of carbon and nitrogen significantly impairs the mechanical properties of the electrothermal alloy, making plastic processing such as wire drawing and bending difficult. Make it. Moreover, the oxidation resistance properties are also adversely affected. The effects of this small amount of carbon and nitrogen will be discussed later. This is especially noticeable when the content of chromium or aluminum is high. In iron-chromium-aluminum electrothermal alloys, carbon and nitrogen are mixed in from the raw materials during alloy melting, or are introduced into the molten metal from the melting atmosphere.

For example, by using high-purity raw materials and melting and casting in a vacuum or argon atmosphere rather than in the air, we can produce iron-chromium-aluminum alloys with low carbon and nitrogen content and high chromium and aluminum content. However, it is economically difficult to reduce the amount of carbon mixed in to 0.01% or less using currently commercially available raw materials. Furthermore, if melting and casting is performed in the atmosphere, it is difficult to reduce the nitrogen content to 0.020/) or less. However, as mentioned above, carbon and nitrogen adversely affect the mechanical properties, oxidation resistance, and lifespan of iron, chromium, and aluminum alloys.
It is a good idea to minimize these impurities by using high-quality raw materials, which are economically disadvantageous, or by melting and casting in a vacuum or argon atmosphere using special melting equipment. Since the amount is reduced, it is unavoidable that the manufacturing cost will increase.

The purpose of the present invention is to provide an iron-chromium-aluminum-nium alloy that has excellent properties as an electric heating material even though it contains a certain amount of carbon and nitrogen. , niobium 0.1-0.3 (fl) in an iron-chromium-aluminum alloy consisting of 0.0196% or more carbon, 0.02% or more nitrogen, and 0.1% or less in total, and the remainder substantially iron as impurities. and zirconium 0.0
The present invention relates to an iron-chromium-aluminum-based electric heating alloy with improved mechanical properties, oxidation resistance, and life value, characterized by containing 5 to 0.25%.

As mentioned above, using raw materials that are currently economically available,
When melting in the atmosphere, it is difficult to reduce the carbon and nitrogen contents of the present alloy to 0.01% or less and 0.02% or less, respectively, but the alloy of the present invention contains carbon and nitrogen in this way. Since it shows excellent mechanical properties and oxidation resistance even when it is heated, it is possible to use inexpensive raw materials and perform atmospheric melting, making it an extremely economical iron, chromium, and aluminum electric heating device. It is an alloy.

This type of high-chromium, high-aluminum containing iron, chromium,
According to the results of investigating the carbon and nitrogen contents and mechanical properties of aluminum electric heating alloys, the total carbon and nitrogen content is 0.0.
Below 3%, the elongation, reduction of area, and number of bends all show approximately constant values, but when this exceeds 0.03%, the variation gradually increases, suggesting that abnormalities in mechanical properties have occurred. , 0.04% or more, the number of occurrences of abnormal values and the range of variation suddenly increase.

The occurrence of such abnormal parts makes wire drawing and rolling difficult, and is extremely undesirable as an electrothermal alloy. It is already known that such small values of elongation, drawing, or bending can be improved by adding a small amount of niobium, but according to the inventor's research, abnormalities in mechanical properties disappear. It has been found that the oxidation resistance or lifetime value, which is a fundamental property of electrothermal alloys, is impaired by the addition of niobium.

As a result of continuing research on methods for improving the mechanical properties, life value, and oxidation resistance of iron-chromium-aluminum alloys containing 0.030/) or more of carbon and nitrogen in total, the inventor discovered that niobium and zirconium By adding these together, we succeeded in obtaining an iron-chromium-aluminum-based electric heating alloy with excellent properties.

Tables 1 and 2 and FIG. 1 show the test results of the present invention in which niobium and zirconium were added together and in which they were not added.

According to Tables 1 and 2, when niobium and zirconium are contained, the C content and N content are high;
Even if C+N)% is 0.061% or 0.062%, there is no abnormal value in mechanical properties, and the life value at 1300°C is lower than that without additives, as in the case of only niobium added. In fact, it can be seen that the value is better than that without additives. Figure 1 shows 1 in the atmosphere.
It shows the relationship between heating time and oxidation weight gain when heated to 200°C.

Samples A, B, C, and D have the same chemical composition as samples A, B, C, and D in Tables 1 and 2, respectively. The oxidation weight gain of samples B and D containing niobium and zirconium is the same as that of sample A, which does not contain these two elements. l! -C, it is less than half that of -C, and it can be seen that the oxidation resistance is significantly improved when niobium and zirconium are contained together. If the niobium content is less than 0.1%, no improvement in mechanical properties will be observed, and if it exceeds 0.301%, it will have an unfavorable effect on oxidation resistance and life. 1 to 0.3Cf11.

Furthermore, if the zirconium content is less than 0.05%, it will not have the effect of improving the life value, and if it is less than 0.25%, the mechanical properties will deteriorate, so the content should be 0.05 to 0.
025%. In addition, in the present invention, 1200
Since we are targeting electric heating alloys that can be used at temperatures above 1300°C, chromium is 20-30% and aluminum is 4-8%.
(f), and in order to enable production by atmospheric dissolution, the carbon content is 0.01% or more, the nitrogen content is 0.02% or more, and the total content is 0.02%.
It shall contain 1% or less as an impurity, and the remainder shall consist essentially of iron.

As explained above, the electrothermal alloy of the present application contains 0.1 to 0.3% and 0.05% of niobium and zirconium, respectively.
~0.25 (: fl) is contained, so the iron-chromium-aluminum alloy contains 0.01% or more carbon and 0 nitrogen.
．． 0.02% or more but less than 0.1(f) in total, its mechanical properties, oxidation resistance properties, or lifespan values are improved and show excellent values, and therefore it has been used conventionally. The practical effects are extremely large, such as being able to use inexpensive raw materials instead of low-carbon and low-nitrogen raw materials, and melting in the atmosphere instead of vacuum melting or argon atmosphere melting. .

[Brief explanation of the drawing]

FIG. 1 is a graph showing an example of the oxidation resistance test results of the electrothermal alloy according to the present invention and a conventional product. B and D...Samples according to the present invention, A and C
...Contrast material not containing Nb and Zr.

Claims (1)

[Claims] 1. Iron-chromium-aluminum system consisting of 20-30% chromium, 4-8% aluminum, impurities of 0.01% or more of carbon, 0.02% or more of nitrogen, and 0.1% or less in total, the balance being essentially iron. Iron/chromium/aluminum with improved mechanical properties, oxidation resistance, and life value, characterized by containing 0.1 to 0.3% of niobium and 0.05 to 0.25% of zirconium in the alloy. Alloy for electric heating.