JPH0441682A - Suction and exhaust valve for internal-combustion engine made of titanium aluminide - Google Patents

Abstract

PURPOSE:To render high toughness as well as superior strength and heat resistance by coating the surface of the core material of a valve made of titanium aluminide having a specified compsn. with a Ti or Ni shell. CONSTITUTION:The compsn. of the core material of a valve made of titanium aluminide is composed of 25-75atomic% Ti and 25-75atomic% Al. Al least part of the surface of the core material is coated with a Ti or Ni shell to obtain a suction and exhaust valve for an internal-combustion engine. A small amt. of one or more among Cr, Mn, V, Co, Zr, Y, Mo, Nb, Hf, Ta, W, Ce, Nd, Si, B, O, C and N may be incorporated into the Al in the compsn. of the core material as required. The pref. thickness of the shell is 0.1-50% of the thickness of the valve head. The durability of the valve can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to titanium aluminide intake and exhaust valves for internal combustion engines.

[Prior Art] Currently known titanium aluminide has excellent strength and heat resistance, but has the drawback of low toughness. For this reason, it has low durability and is unsuitable as a material for intake and exhaust valves in internal combustion engines.

[Problems to be Solved by the Invention] An object of the present invention is to provide intake and exhaust valves for internal combustion engines made of titanium aluminide, which have excellent strength and heat resistance as well as high toughness.

[Technical Means for Solving the Problems] In order to solve the above problems, the present invention provides a valve core material having the shape of a valve, made of titanium aluminide having the following composition, and at least a part of the surface of this valve core material. Cover T
: or N;.

25at%≦Ti≦75at% 25at%≦Al≦75at% [Function] The above titanium aluminide intake and exhaust valves for internal combustion engines are made of titanium aluminide and have a valve core material in the shape of a valve that has excellent strength and heat resistance. The Ti or Ni outer skin that covers at least a portion of the surface of the valve core material has excellent toughness, so the valve as a whole has excellent strength, heat resistance, and toughness, making it suitable for internal combustion engines. Demonstrates excellent functions as a membrane and exhaust valve.

L Example J This invention will be explained below with reference to drawings showing examples. 1st
The figure shows a first embodiment. 1 in Fig. 1 (A) is the valve core material, which is made of titanium aluminide with Ti -36wt%A] and is cast at 1600°C into a shape similar to the valve.
By cutting, it is formed into a size that is much smaller than the desired valve. This valve core material 1 is sealed in an N can 2 in a vacuum as shown in FIG. 1 (b). Next, as shown in FIG.
jSu HIP (hot isostatic pressure treatment). This HIP brings the N1 can 2 into close contact with the entire surface of the valve core material 1, resulting in a valve-shaped body 4 having N1 as the outer skin 3.

This valve-shaped body 4 is subjected to a homogenization treatment at 1300'CX for 24 hours, and cut into a desired valve shape.

FIG. 2 shows a second embodiment. 11 in FIG. 2(A) is a cylindrical core material, and this core material 11 is r*-33wt%At-3
Mix li powder and Al-Mn alloy powder so that wt% Mrl, put in an Al can, degas at 500℃, and then heat to 68φ.
This extruded material was extruded to a diameter of 26 mm and cut into a length of 25 m. The core material 11 is covered with a Ti can 12 with one end closed and the other end open so as to have an outer diameter of 30φ to form a covering 13. As shown in FIG.
I got it. Therefore, the valve-shaped body 15 is composed of a valve core material 15a and a Ti outer skin 15b. Note that, as shown in FIG. 2(b), the upper and lower surfaces of the valve core material 15a are not covered with the outer skin 15b. This valve-shaped body 15 is
After HIPing at 200° C. for 2 hours at 1300 atmospheres in Ar gas, homogenization treatment was performed at 1200° C. for 24 hours, and the desired valve was cut.

Although not shown as a third embodiment, a shape similar to a valve shape is shown in FIG.
i -36wt% A + was melted and cast at 1600°C,
It is molded by cutting to be much smaller than the valve shape.
It is also possible to thermally spray Ti onto the surface to a thickness of 1 m and then finish it into a desired shape.

3.4.5 each show an embodiment of a valve body different from the valve body 4 of FIG. 1 and the valve body 15 of FIG. 2. The valve-shaped body 16 in FIG. 3 (fourth embodiment) is T1 or N except for the upper end surface of the stem of the valve core material 16a.
In the valve-shaped body 7 of FIG. 4 (fifth embodiment), the entire face portion and part of the stem portion of the valve core material 17a are covered with a Ti or Ni outer skin 17b. . In the valve-shaped body 18 of FIG. 5 (sixth embodiment), only the lower surface of the face portion of the valve core material 18a is made of T1 or Ni.
It is covered with an outer skin 18b.

FIG. 6 shows a valve-shaped body 19 of a seventh embodiment.

The valve shape body 19 has a thickness b-a of the Ti or Ni outer skin relative to the thickness b of the novel head in the valve shape body 16.
is 0.1 to 50%.

In FIG. 6, 198 indicates a valve core material made of titanium aluminide, and 19b indicates an outer skin made of Ti or Ni.

Table 1 shows the characteristics of the first to third examples. Elongation measurements and Charpy tests were performed on the valve stem. From Table 1, the valves of Examples 1 to 3 are made of T having an appropriate thickness and excellent toughness.
It is clear that since the valve has an outer skin of Ni or Ni, it has high toughness and prolongs the life of the actual machine.

In each of the above examples, one or more of the following may be contained as the Al alloy component (81%), and the remainder may be AI.

Cr・0.05-10 Mn...0.05-10 V...0.05-10 Co0.05-10 Z"...0.05-10 Y...0.05-10 Mo ...0.05-10 Nb...0.05-10 1-(f...0.05-10 C a.0.01-10 W...0.01-10 Ce... 0.01-10 Nd...0.01-10 Si...0.001-10 B...0.01-5.0 0...0.01-1.0 C...0 .001~5.O N...0.001~5.0 When producing titanium aluminide, the following points should be noted regarding each of the above components: (a) 25 at% for At, Ti, Fe, and Ni. If there is no vortex or if it exceeds 75 at%, the alloy will not react,
It is difficult to form it into an intermetallic compound.

(b) TCr, 1vln for Cr, Mn, B, C, N
is less than 0.05 at%, B is less than 0.01 at%, C,
If N is less than 0.0018t%, no improvement in ductility is observed. Also, Cr and Mn are 10 at%, and B, C, and N are 5. Q
Above at%, the improvement in ductility is saturated.

(C> Regarding W and Si, no improvement in oxidation resistance is observed when W is less than 0.01 at% and Si is less than 0.0018 t%, and W and Si are less than 10 at%.
%, oxidation resistance becomes saturated.

(d) Co, Zr, Y, Mo, Nb, 1-1f, Ta
, Ce, Nd, O, Co, Zr, Y, MOINb, Hf is less than 0.05 at%, Ta, Ce, Nd, O is less than 0.01 at%, no improvement in strength is observed, and multi-element When the amount exceeds 10 at%, the strength is saturated.

(e) Thickness of the outer skin Tr, the thickness of the outer skin of Nr is 0.1% of the thickness of the valve core material
If it is less than that, there is no effect of increasing toughness. Moreover, if it exceeds 50%, the inherent heat resistance of titanium aluminide will be greatly lost.

[Effects] The titanium aluminide intake and exhaust valves for internal combustion engines of the present invention have the above-mentioned structure, and have excellent toughness and durability in addition to strength and heat resistance. Therefore, it is very suitable as a material for intake and exhaust valves for internal combustion engines.

[Brief explanation of drawings]

FIG. 1 shows a first embodiment, in which (a) shows a front view of the valve core material, (b) shows a front sectional view of the manufacturing process, and (c) shows a front sectional view of the valve-shaped body. FIG. 2 shows a second embodiment,
(a) shows a front sectional view of a core material covered with a Ti can, and (b) shows a front sectional view of a valve-shaped body. Section 3.4.
FIG. 5 each shows a front sectional view of a different example of a valve shape. FIG. 6 shows a special example of FIG. 1... Valve core material 3... Outer skin 4... Valve shaped body 15... Valve shaped body 15a... Valve core material 15b... Outer skin 16.
...Valve shaped body 16a...Valve core material 16b...Outer skin 17.
...Valve shaped body 17a...Valve core material 17b...Outer skin 18.
...Valve shaped body 18a...Valve core material 18b...Outer skin 19.
・・Valve shape body

Claims (3)

[Claims] (1) An internal combustion engine made of titanium aluminide, characterized by comprising a valve core material in the shape of a valve made of titanium aluminide having the following composition, and an outer skin of Ti or Ni that covers at least a portion of the surface of the valve core material. Engine intake and exhaust valves. 25at%≦Ti≦75at% 25at%≦Al≦75at% (2) The titanium aluminide intake and exhaust valve for an internal combustion engine according to claim (1), wherein Al contains at least one of the following elements in At%, and the remainder is Al. Cr...0.05-10 Mn...0.05-10 V...0.05-10 Co...0.05-10 Zr...0.05-10 Y...0 .05-10 Mo...0.05-10 Nb...0.05-10 Hf...0.05-10 Ta...0.05-10 W...0.05-10 Ce ...0.05-10 Nd...0.05-10 Si...0.001-10 B...0.01-5.0 O...0.01-1.0 C. ...0.001-5.0 N...0.001-5.0 (3) Made of titanium aluminide according to claim (1) or (2), wherein the thickness of the Ti or Ni outer skin covering the valve head is 0.1 to 50% of the thickness of the valve head. Intake and exhaust valves for internal combustion engines.