JPS6221062B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-resistant casting alloy that has excellent creep strength at ultra-high temperatures of 1200°C to 1300°C, and is primarily intended for use as skid rail materials in steelmaking heating furnaces. Conventional alloys for skid rails used at high temperatures of 1200°C or higher include C0.15% or less, Si1-2%, Mn1-2%, Cr25 disclosed in Japanese Patent Publication No. 54-39207.
~32%, N110~25%, Co25~45%, Mo0.5~3
%, P and S are each 0.04% or less, and the balance is Fe. However, this alloy does not necessarily have sufficient creep strength, and the life of skid rails is often determined by creep strength. The present invention was made with the purpose of providing a heat-resistant cast alloy for skid rails that has significantly superior creep strength at ultra-high temperatures of 1200°C to 1300°C compared to conventional materials, and its characteristics are as follows:
C0.1% or less, Si1.0% or less, Mn1.0% or less, Cr25
~35%, W15~25%, Co5~25%, and the remainder essentially consists of Ni. The reasons for limiting the ingredients of the present invention will be described below. In the alloy of the present invention, a small amount of C is effective because it dissolves in the austenite matrix and has the effect of increasing the high-temperature strength of the matrix, but if it is added in an excessively large amount, it forms eutectic carbides with Cr and W. This is not preferable because it inhibits solid solution strengthening by Cr and W and at the same time lowers the melting point of the alloy. For the above reasons, the upper limit of C is set in the alloy of the present invention.
The content of C is limited to 0.1% or less, and this low upper limit of C is one of the characteristics of the alloy of the present invention. Since Si has the effect of increasing oxidation resistance in the alloy of the present invention, a certain amount is necessary in addition to the deoxidizing effect, but since adding too much will lower the melting point of the alloy, it is limited to 1.0% or less. In the alloy of the present invention, it is necessary to add a small amount of Mn as a deoxidizing agent, but if added in an excessively large amount, the oxidation resistance deteriorates, so it is limited to 1.0% or less. In the alloy of the present invention, Cr has the effect of imparting oxidation resistance and increasing high temperature strength through solid solution strengthening, and requires a minimum content of 25%, but if it exceeds 35%,
It is limited to 25% to 35% because it causes excessively large amounts of body-centered cubic chromium solid solution or intermetallic compounds to crystallize and deteriorates high-temperature strength. In the alloy of the present invention, W is the most important alloying element that imparts ultra-high temperature creep strength without lowering the melting point, and requires a minimum content of 15%, but if it exceeds 25%, the oxidation resistance is extremely degraded. Also, although the price of the alloy increases, the creep strength improvement effect is small.
Limited to 15-25%. Adding a large amount of W is also one of the characteristics of this alloy. Co has the effect of increasing the melting point and creep strength in the alloy of the present invention, and a minimum content of 5% is necessary, but if it exceeds 25%, the oxidation resistance will deteriorate drastically, and the improvement in creep strength will also be saturated. 5-25%
limited to. In the alloy of the present invention, Ni is a basic element constituting austenite and constitutes the essential remainder other than the above alloying elements. Next, embodiments of the present invention will be described. The present invention alloy, conventional alloy, and experimental alloy other than the present invention were melted in an atmospheric high-frequency induction melting furnace and cast into ingots with a nominal weight of 10 kg. The chemical compositions of these ingots are shown in Table 1. No.14, 15, 17, 18 among the alloys in Table 1
No. 3 and No. 20 are conventional alloys, and the others are experimental alloys other than the invention. Appropriate test pieces were cut out from these ingots and heated at 1050℃ - 2.5Kgf/
^mm2 creep rupture test, 1200 and 1250℃ tensile test, 10 cycles of 1250℃ x 16h air cooling in the atmosphere
Oxidation resistance test to measure oxidation weight loss, repeated several times;
A compression creep test was conducted to measure the time until 10% creep deformation occurs at 1250°C and 2 kgf/mm. The results of these tests are shown in Table 2. The following can be seen from Tables 1 and 2. From the left column of Table 2, the present alloy has a higher creep rupture strength at 1050°C than any of the conventional experimental alloys except No. 16.

【table】

[Table] No. 16 is an alloy whose Co content is higher than the limited range for the alloy of the present invention, but the creep rupture strength is almost unchanged compared to No. 15, which has Co within the range of the alloy of the present invention. It can be seen that the oxidation resistance is extremely poor, and that excessive Co content has no effective meaning. Furthermore, when comparing No. 14, 15, 17, and 18 of the alloys of the present invention with conventional alloys No. 3 and No. 20, roughly speaking, the temperature was 1050°C.
The creep rupture life of
Turns out it's 10 times better. As stated above, the alloy of the present invention has dramatically improved high-temperature properties that are about 10 times longer in terms of creep life than conventional alloys, so the present invention provides skid rail parts with significantly improved lifespan than conventional alloys. The industrial value is remarkable.

Claims (1)

[Claims] 1 C0.1% or less, Si1.0% or less by weight,
Mn1.0% or less, Cr25~35%, W15~25%, Co5~
A heat-resistant casting alloy with excellent ultra-high temperature creep strength, consisting of 25% Ni and the remainder essentially Ni.