JPS6070155A - Ni alloy for exhaust valve - Google Patents

Abstract

PURPOSE:To obtain an inexpensive Ni alloy for an exhaust valve requiring no stelliting build-up by providing a composition consisting of Ni, specified amounts of Ca, Si, Mn, Cr, Al, Ti, Nb, Fe and one or more among B, Zr and Mg. CONSTITUTION:The composition of an Ni alloy for an exhaust valve is composed of, by weight, <0.1% C, 0.5% Si, 0.1% Mn, 52-63% Ni, 18-25% Cr, 0.5- 2% Al, 1.5-3.5% Ti, 0.3-1.5% Nb, one or more among <0.2% B, <0.2% Zr and <0.05% Mg, and the balance Fe with impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a relatively inexpensive alloy that does not require stellite overlay and is used as a material for exhaust valves of automobile engines.

Traditionally, 2L-4N steel has been used for the exhaust valves of automobile engines, but recently, with the increase in engine output,
2l-4N steel often lacks high-temperature strength. To deal with this situation, exhaust valves made of 2L-4N with Stellite overlay and exhaust valves made of Ni base metal known as Inconel 751 have been put into practical use, but these Both have the disadvantage of being expensive. Therefore, inexpensive alloys with a Ni content of 50 or less were developed, as described in Japanese Patent Application Laid-Open No. 56-20148, etc., but the inventors' research revealed that these low-Ni alloys It has become clear that the corrosion resistance against lead is insufficient, leaving a major problem in practical use.

The present invention has sufficiently high high temperature strength that no Stellite overlay is required, and its corrosion resistance against lead oxide is equivalent to that of an exhaust valve with Stellite overlay or an exhaust valve made of Inconel 751, and the price is lower than these. The purpose of this invention is to provide an alloy for exhaust valves.

The present invention has a weight ratio of 040.1% or less, St O, 5%
Below, Mn 1.0% or less, Ni 52-60%, Cr
18-25 tchi, At 0.5-2.0%, Ti 1.5-3
．． 5%, NbO, 3-1.5%, and further 0.0
An exhaust gas containing one or more of the following: 2- or less BSo, 2% or less Zr, and 0.05% or less Mg, with the remainder being essentially Fe except for impurities. This is a Ni-based alloy for valves.

A small amount of C is necessary in the alloy of the present invention to impart creep rupture ductility, but if it exceeds 0.1%, MC
The content is limited to 0.1% or less since excessive mold carbide deteriorates hot and cold workability.

Si is added to the alloy of the present invention as a deoxidizing agent, and if it exceeds 0.5%, it is harmful to hot workability, high temperature strength, and corrosion resistance to lead oxide, so it is limited to 0.5% or less. do.

Like SL, Mn is also an element added as a deoxidizing agent in the alloy of the present invention, but if it exceeds 1.0%, the high temperature strength decreases, so O Ni is limited to 1.0% or less. The invention alloy has the following effects: (1) producing a gamma prime phase, (2) stabilizing austenite, and (3) increasing corrosion resistance against lead oxide.

In particular, regarding the action (3), there is a transition point at 52 to 53 inches of NiH, and below this transition point, corrosion resistance to lead oxide is unstable, and in some cases, a significantly large amount of corrosion may be exhibited. , above this transition amount, the corrosion resistance against lead halide becomes stable and good. Therefore, in the alloy of the present invention, the lower limit of the Nl content is limited to 52%, but the upper limit of the Ni content is limited to 60% in order to lower the Ni content by at least 10% compared to Inconel 751 in order to keep the price as low as possible. .

Cr is an essential element for imparting oxidation resistance and sulfidation resistance to the alloy of the present invention, especially Inconel 7.
In order to provide sufficient sulfidation resistance, which is the problem with 51, it is desirable to contain at least 18% C.
Since r destabilizes austenite and precipitates a Cr-rich α' phase, lowering high temperature strength (especially creep rupture strength), it is limited to 18 to 25 degrees.

In the alloy of the present invention, At is an essential element for precipitating the gamma prime phase from the austenite matrix and strengthening the alloy, and in order to achieve a sufficient strengthening effect, at least 0.5% must be added. However, if it exceeds 2.0%, hot working becomes extremely difficult, so it is limited to 0.5 to 2.0 inches.

Like At, T1 is an essential element for precipitating the gamma prime phase in the alloy of the present invention to strengthen the alloy, and T1 is required to be at least 1°5 thick in order to obtain a sufficient effect. If it exceeds 3.5%, hot workability will deteriorate significantly, so it is limited to 1.5 to 3.5%.

In the alloy of the present invention, Nb forms a gamma prime phase like At and Ti, but when a small amount of Nb is dissolved in solid solution, the gamma prime phase is strengthened and the high temperature strength of the alloy is increased, so its effect is fully exhibited. Therefore, a minimum of 0.3% is necessary, but if it exceeds 1.5%, the gamma prime becomes unstable, so it is limited to 0.3 to 1.5%.

B5Zr and Mg are both effective elements for strengthening austenite grain boundaries and increasing high-temperature ductility.In particular, the present alloy containing Nb as a gamma prime-forming element has higher high-temperature strength than an alloy that does not contain Nb. is high, but the ductility is low, so it is at least necessary to contain a certain amount of at least one or two or more of these elements. However, if these elements are contained in excessively large amounts, the initial melting temperature will be lowered and the hot workability will be deteriorated.
Hereinafter, it is limited to 0.296 or less and 0.05% or less.

Next, examples will be described. Table 1 shows the chemical compositions of samples used to compare the properties of the alloy of the present invention with experimental alloys and conventional alloys. All of these samples are forged or rolled bars.

In Table 1, Nos. 1 and 2 are alloys of the present invention, N[L3~Nα
11 is an experimental alloy, Nα12 to N[L14 are conventional alloys corresponding to Inconel 751, Nimonic 80A and 2l-4N, respectively. Alloys N11 to Nα13 in Table 1 were heat treated at 1050°C x 15m1n oil cooling + 750°C x 4h air cooling, and N[L14 was heated at 1150°C
It was subjected to heat treatment of 30ml water cooling + 800°C x 4h air cooling and subjected to various tests.

Table 2 shows the 0.2% proof stress at 800℃ and 900℃, 80
100 hour creep rupture strength at 0°C, melt p at 920°C
bo and melt (60chi PbO+ 40chi Pb5O+)
It shows the corrosion weight loss inside.

As can be seen from Table 2, all of the experimental alloys except N[L5 have a significantly large corrosion loss in PbO, and this is because these experimental alloys all have a low Ni content of 52 or less. Among the experimental alloys, N15 with an N1 content of 54°6 was good in terms of PbO corrosion loss, but it had poor yield strength at 800°C, creep rupture strength, and 60% PbO+40
% PbThe N of the present alloy in terms of corrosion loss against SO4
[Not as good as L 1 or N112. This demonstrates the effectiveness of the corners in the alloy of the present invention.

(Experimental alloy N (L5 does not contain corners) Invention alloys (NlllLl, Nl12) are Inconel 75
1(N[L12), the yield strength and creep rupture strength are the same, and although the corrosion resistance against PbO is slightly inferior, it is at a level that poses no problem in practical use. On the other hand, 60% PbO+
Since the corrosion resistance against 40% PbSO4 is excellent, it can be said that the balance of corrosion resistance is rather excellent. Of the conventional alloys, Nimonic 80A (N(L13)
It can be seen that although the price is high, the yield strength at high temperatures is low, and 2l-4N steel generally lacks high temperature strength and does not have sufficient corrosion resistance against PbO.

From the above, it is clear that the alloy of the present invention has properties as an alloy for exhaust valves that are almost the same as the conventional alloy Inconel 751, but Inconel 751 (Ni content 70
Since the price is low due to the low Ni content of at least 10%, it is possible to provide a material for exhaust valves of automobile engines that is cheaper than conventional materials, and has great industrial effects. It is.

Agent: Patent Attorney: Takashi Honma Procedural amendment (spontaneous) December 22, 1980 Commissioner of the Japan Patent Office Kazuo Wakasugi 1, Indication of the case 1981 Patent Application No. 178182 2, Name of the invention Ni-based alloy for exhaust valves 3. Relationship with the case of the person making the amendment Patent applicant address 2-1-2 Marunouchi, Chiyoda-ku, Tokyo Name
(508) Norio Kono, Representative of Hitachi Metals, Ltd. (
1 idiot) 4. Column 6 for explanation of agent, contents of amendment as shown in the attached sheet.

Amendment content 1: The claims on page 1 of the specification are amended as follows: C061% or less, Si 0.5%, Mn 1.0
%, average 52-63%, Cr18-25%, A10.
5-2.0%, Ti 1.5-3.5%, Nb013-
Contains 1.5% and further 0.02% or less B, 0.2%
Contains one or more of the following Zr, 0.05% or less Mg, and the remainder is essentially Fe excluding impurities.
A Ni-based alloy for exhaust valves, characterized by comprising:

2. “Ni52-60%” on page 2, line 16
52-63%”.

3. Correct "60%" on page 4, line 7 to "63%".

4. Amend Table 1 on page 7 as shown in Table 1 on the next page.

5, page 8, lines 1 to 2 rNo, 1 and No.

2 is the invention alloy, No. 3 to No. 11 is the experimental alloy,
No, 12-No, 14 J, 1-No.

4 is the invention alloy, No. 5 to No. 13 is the experimental alloy =
Correct as No, 14-No, 16 J.

6, page 8, line 4 [No, 1-No, 13J
Correct as 1No, 1-No, 15J.

7. Change rNo. 14J on page 8, line 6 to “No, 16J.
and correct it.

8. Table 2 on page 9 of the same page is amended as shown in table 2 on the next page.

9. Correct [No, 5J in the first line of page 10 to [No, 7J].

10, page 10, line 5, change [No, 5J to “No, 7J
and correct it.

11, page 10, lines 7 to 8, “No. of the alloy of the present invention”
, 1 or No, 2. ” is not as good as the alloy of the present invention. ] and correct it.

12, page 10, line 10, 1No, 5J as “No, 7
Correct it with J.

'Q knee 13. r (No, 1, No
, 2) Delete J.

14, I'(No, 12)J on page 10, line 13 is corrected to ``(No, 14)J.

15, "The amount of Ni is 10% or more" in lines 5 and 6 of page 11 is corrected to "The amount of Ni is 17% or more, usually about 15%".

that's all °−4d

Claims (1)

[Claims] Weight ratio: C approximately 0.1% or less, St O, 5% or less, M
n 1.0 or less, Ni 52-60%, Cr 18-2
5%, AA O, 5-2.0%, Ti 1.5
~3.5%, NbO, 3-1.5%, and further 0
．． 02% or less B, 0.2% or less Zr, 0.05%
Characteristic N1-based alloy for exhaust valves.