JPS58500B2 - Tainetsugoukin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-resistant alloy with excellent high-temperature strength.

Conventionally, centrifugally cast tubes such as HK40 (0,4C-25Cr-2ONi) have been used in the chemical industry, especially in cracking furnaces and reforming furnaces in ethylene plants, but it is impossible to manufacture small-diameter, thin-walled tubes with cast alloys. Moreover, since the length of the product is limited, there is a drawback that the number of welded parts that are unstable in strength increases.

Furthermore, in the chemical industry, higher temperatures are necessary for efficiency, and Incoloy 800 (20Cr-3ONi-Ti-At), which is currently in practical use as a forged and drawn pipe for the chemical industry,
However, in order to stabilize operations and improve efficiency in the chemical industry, there is a strong demand for the development of a forged material that has high temperature strength and can be used to produce long, narrow-diameter tubes.

The present invention was completed as a result of intensive research by the present inventors in order to meet the above-mentioned needs, and its purpose is to provide a solid solution strengthened forged heat-resistant alloy that has superior high-temperature strength than conventional forged alloys.

That is, the gist of the present invention is that C, 0.01 to 0.3
%, SiO, 01-1.0%, MnX 0.01-2.0
%, Cr, 10-30%, M2.0.003-0.05
%, Mo13-25%, W, 3-25%, or both (however, if both Mo and W are included, the total of No and W is 3-25%.

) and the remainder is Ni (however, Ni, 10% or less is Fe).
can be replaced with

) and unavoidable impurities, or the above components further include B, 0.001 to 0.05%,
It is an austenitic i-thermal alloy containing one or both of Zr 10.001 to 1.0, and has an austenitic structure in which C is dissolved as a solid solution, and has high high-temperature strength.

In the present invention, in order to form an austenitic structure in which C is dissolved as a solid solution, a solution treatment is necessary, and the solution treatment temperature is 1200
If the temperature is below .degree. C., the resulting heat-resistant alloy will not have satisfactory heat resistance unless C is sufficiently dissolved into a solid solution, and even if the treatment time is 1 minute, the solution of C will not be sufficiently promoted.

Next, the reason for limiting the components of the present invention will be explained in detail below.

C is an effective component for improving heat-resistant properties such as tensile strength and creep rupture strength required for a heat-resistant alloy, and is 0.0
1% or more is required, but if it exceeds 0.30%, the amount of C remaining in solid solution increases during heat treatment, resulting in a decrease in high-temperature strength.

Si is necessary as a deoxidizing agent for molten steel, but its composition is 1.
．． If it exceeds 0%, weldability will deteriorate, and if it is less than 0.01%, it will cause a decrease in strength, so the range is from 0.01 to
It was set as 1.0%.

Mn is added as a deoxidizing agent and to improve processability, but excessive addition deteriorates heat resistance properties, so it should be added in the range of 0.01 to
It was set at 2%.

Cr shows excellent effects on improving oxidation resistance and toughness, but 1
If it is less than 0%, oxidation resistance is poor, and if it exceeds 30%, it is difficult to obtain a stable complete austenite phase.

Mg is effective in improving workability when added in an amount of 0.003% or more, but if it exceeds 0.05%, workability and weldability decrease.

Both Mo and W are effective in improving high-temperature strength mainly as solid solution strengthening, but when added in excess, workability deteriorates.
It destabilizes the structure of the alloy and precipitates a brittle phase, and if it is too small, solid solution strengthening cannot be achieved sufficiently, so when adding Mo and W alone, 3 to 25% each was added, and both Mo and W were added. M in case.

It is necessary to similarly limit the total amount of W and W to a range of 3 to 25%.

Considering the economic aspect, Fe can be partially replaced with Ni, but if excessively added, a brittle phase will precipitate, so the amount of Fe that can be replaced with Ni was set to 10% or less.

If 0.001% or more of B is contained in the austenitic heat-resistant alloy, it is effective in improving high-temperature strength, but if it exceeds 0.05%, hot workability and weldability deteriorate.

Like B, Zr improves heat resistance when added in an amount of o, ooi% or more, but if it is excessive, coarse carbides are formed and strength is reduced, so the limit is 0.001 to 1.0%.

Next, the present invention will be explained in detail by way of examples.

Example 1 The present invention and a conventional alloy that does not belong to the alloy composition of the present invention were tested for creep rupture strength at 1000°C and short-time tensile strength at 1000°C as comparative examples.

In the case of the present invention, the solution treatment conditions were a temperature of 1250°C for 15 minutes, Incoloy 800 and Inconel 625 were used for comparison.
InternationalNickelCompan
y), the former is Fe-Cr-Ni alloy, the latter is Ni
-Cr-based alloy.

These component compositions are shown in Table 1 (1) and (2), and 10
Table 2 shows the tensile test results at 00°C and the 103hr and 104hr creep rupture strengths at 1000°C.

These test results show that the creep rupture strength of the alloys of the present invention is considerably improved over the conventional alloys and comparative alloys (alloys X and Y).

Among the results in Table 2 above, the results for Mo and W added steel are shown in FIG. 1, and the results for B and Zr added steel are shown in FIG.

To M Regarding the effect of W, 103hr shown in Figure 1,
104hr creep rupture strength and M.

This is clear from the relationship diagram with +W amount.

The respective symbols in FIG. 1 are as shown in the table below.

Furthermore, as shown in FIG. 2, the effect of boron (B) addition was observed on alloys A, F, and W of the present invention and alloy E.

Comparisons between alloys R, S, and V and alloys H1, M, and RlT indicate the effects of Zr addition.
, U clearly shows that there is a significant strength improvement effect.

In Fig. 2, ◯ indicates the addition of Zr alone, ., B indicates the combined addition of Zr (B≈0.004%).

As described above, the present invention makes it possible to provide a promising heat-resistant alloy that has higher high-temperature strength than conventional alloys.

[Brief explanation of the drawings] Figure 1 is a diagram showing the creep rupture strength of Mo and W added steel.
FIG. 2 is a diagram showing the creep rupture strength of B, Zr-added steel.

Claims (1)

[Claims] 1C, 0.01-0.3%, Si, 0.01-1.0%
, 4Mn, 0.01-2.0%, Cr, 10-30%,
Mg, 0.003-0.05% and Mo, 3-25%,
W, either one or both of 3 to 25% (however, if both M and W are included, the total of Mo and W is 3 to 25%)
A heat-resistant alloy containing 1), the remainder being Ni (however, Ni (10% or less can be replaced with Fe)) and inevitable impurities, and having an austenitic structure in which C is dissolved as a solid solution. 2C, 0.01-0.3%, Si, 0.01-1.0%
, MnX0.01-2.0%, Cr110-30%, M
P, 0.003-0.05% and Mo13-25%, W
, 3 to 2.5% or both (however, Mo and W
If both are included, the total number of Mo and W is 3 to 25. ), and further contains B, 0.001 to 0.05%, Zr,
Contains either or both of 0.001 to 1.0%, with the remainder consisting of Ni (however, 10% or less of Ni can be replaced with Fe) and unavoidable impurities, and has an austenitic structure in which C is solidly dissolved. Heat resistant alloy.