JPS626633B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a Fe--Cr--Al based oxidation-resistant alloy that has good oxide film adhesion and excellent workability. Fe containing 10-26% Cr and 1-6% Al by weight%
The surface of Cr-Al alloys becomes dense when heated at high temperatures.
It has the characteristic of forming a protective film mainly composed of oxides of Cr and Al to prevent further oxidation, and is used in heating elements, resistors, and structures that require oxidation resistance. Oxidation resistance is mainly due to selective oxidation of Cr and Al on the surface.
Determined by the sustainability of the supply and the properties and adhesion of the oxide film. Sustainability of supply is determined by the base metals Cr and Al.
The content of Cr and Al improves as the content of Cr and Al increases. Therefore, when used at temperatures above the red-hot temperature, the content of Cr and Al is increased to emphasize oxidation resistance, even if workability is sacrificed to some extent. In addition, the adhesion of the oxide film is
In addition to Zr, it is known that addition of rare earth elements can improve the performance. Car cigarette lighters are used in a red-hot state, so Fe-Cr- contains 18 to 26% Cr and 3 to 6% Al.
Al-based steel is used, but for this purpose, adhesion of the oxide film in cold conditions is also required. In other words, a cigarette lighter is made by bending a ribbon-like material into a spiral shape, then applying oxidation treatment to create a dense and uniform oxide film several micrometers thick, which also serves as electrical insulation between each layer, and finally applying a tightening process. Therefore, this processing causes cracks in the coating, and the coating is likely to peel off. If rare earth elements such as Ti or Zr are simply added to conventional Fe-Cr-Al alloys, the above-mentioned cracks and peeling will occur during oxidation treatment or seaming, and oxidation will progress abnormally in those areas during use. The disadvantage was that many accidents occurred due to melting. The object of the present invention is to provide an oxidation-resistant Fe--Cr--Al alloy that has improved and stabilized adhesion of a protective oxide film and has excellent workability. The present invention has a weight percentage of Cr18~26%, Al3~6%, Si
≦1.5%, Ti≦0.5%, C≦0.1%, and N≦0.1%
Fe-Cr containing %Ti/(%C+%N) of 3 to 7, having good adhesion of an oxide film consisting of the remainder Fe and unavoidable impurities, and having good workability. -Al-based alloy. Next, Table 1 shows the chemical composition and %Ti/(%C+%N) of the inventive steel examples and comparative steels (%Ti, %C, and %N represent the weight percentages of Ti, C, and N, respectively). .Hereinafter, this formula will be simply written as Ti/(C+N))
Also shown are the results of evaluating the adhesion and processability of the oxide film using the methods described later.

[Table] The adhesion of the oxide film was evaluated by oxidizing test pieces that had been cold worked to a thickness of 0.25 mm and width of 1.6 mm under the same conditions, and then annealed to remove stress. It was dried, wound around a mandrel with a diameter of 10 mm, unwound, washed and dried again, and evaluated based on the weight difference (amount lost) after each washing and drying. From Table 1, the adhesion of the oxide film is Ti/(C+
It can be seen that when the ratio of N) is less than about 2.5, as seen in the comparison steel (H), the adhesion becomes poor, and when it is about 3 (invention steel (A)) or more, sufficient adhesion is exhibited. Table 2 shows the results of a life test on cigarette lighters manufactured from the same cold-worked materials as in (H), (E), and (L) of Table 1.

[Table] From this table, the life cycle of comparative steel (J) (Ti/(C+N) = 2.46) is significantly lower than that of other (E) and (R), and it is almost the same as the adhesion evaluation mentioned above. It can be seen that they show similar trends and that there is no significant difference in the number of lifetimes between (e) and (li). Next, the workability was evaluated by the elongation in a tensile test and the number of bends until breakage in a repeated bending test. Since the results of the repeated bending test showed almost the same tendency as the elongation in the tensile test, only the elongation measurement results in the tensile test will be explained here. FIG. 1 shows the average and variation range of elongation values of tensile test pieces cut from each of the molten steels shown in Table 1, plotted against the Ti/(C+N) ratio of each molten steel. From the figure, the elongation is Ti/(C
It can be seen that when the ratio of +N) is about 7 or more, it decreases rapidly and the range of variation also increases. In particular, it can be seen that when this ratio is about 8, almost no elongation is shown. In addition, A, B... in the figure are A, B in Table 1,
Corresponds to... As mentioned above, in Fe-Cr-Al alloys, the Ti/(C+N) ratio is closely related to the adhesion of the protective oxide film and the workability of the base material, and this ratio is within the range of 3 to 7. It can be seen that by adjusting this, it is possible to improve the adhesion and stability of the protective oxide film, prevent a decrease in workability, and reduce the range of variation. Next, the reason for limiting the content of each element in the steel of the present invention will be described. Cr is the main element that forms a stable and dense protective film together with Al. If the Cr content is low, the formation of an effective protective film will be insufficient, and the continuity of supply due to diffusion from the base material will decrease compared to the normal peeling of the protective film, resulting in a long period of time at high temperatures exceeding the heat generation. It becomes unusable. On the other hand, if Cr is contained excessively, embrittlement is likely to occur due to precipitation and separation of the σ phase. Therefore, in the present invention, the Cr content is set to 18 to 26%. It has already been mentioned that Al is an element that forms a protective film together with Cr. Even when the Al content is low
It is almost the same as the case of Cr. On the other hand, excessive Al content impairs processability. Therefore, in the present invention
The Al content was set to 3 to 6%. Si constitutes a part of the oxide film and contributes to improving oxidation resistance, but excessive content embrittles the base material, so in the present invention it is set at 1.5% or less. C and N are elements that are inherently harmful to the steel of the present invention, and if they are contained in excess, they will make the material brittle and impair workability.
Further, it is desirable that the amount is small because it reduces the effect of adding Ti, which improves the adhesion of the oxide film. However, in terms of steel manufacturing, it is difficult to extremely reduce the content of these elements, resulting in high costs. Therefore, in the present invention, both amounts are set to 0.1% or less. Ti is an important element that improves the adhesion of the oxide film, but if it exceeds about 0.5%, it embrittles the material and impairs its workability. Therefore, in the present invention, the content is adjusted according to the C+N content within a range of 0.5% or less.
The content is determined so that Ti/(C+N) is 3 to 7. As mentioned above, the Fe-Cr-Al alloy of the present invention contains an appropriate amount of Ti depending on the C+N content, which improves the adhesion of the oxide film without impairing workability. As a result, it has excellent properties including high oxidation resistance and good workability.

[Brief explanation of the drawing]

Figure 1 shows Ti/(C+
It shows the elongation (%) of the tensile test against the ratio of N).

Claims (1)

[Claims] 1 Weight% Cr18~26%, Al3~6%, Si≦1.5
%, Ti≦0.5%, C≦0.1%, and N≦0.1%, and with %Ti/(%C+%N) of 3 to 7, the adhesion of the oxide film consisting of Fe and inevitable impurities is good. An Fe-Cr-Al alloy that is characterized by having good workability.