JPS58171556A - Valve material for internal-combustion engine - Google Patents

Abstract

PURPOSE:To obtain a valve material for an internal-combustion engine provided with high wear resistance, toughness, machinability and superior weldability, by properly blending Fe with C, Si, Mn, Cr, etc. and by further adding V and Nb. CONSTITUTION:This valve material for an internal-combustion engine consists of, by weight, 0.55-0.85% C, 0,08-1.50% Si, 0,08-1.50% Mn, 1.20-3.50% Cr. 0.05-0.50% V, 0.02-0.30% Nb and the balance essentially Fe or further contains one or more among <=0.30% Ti, <=0.30% Ta and <=0.30% Zr. This steel as the valve material is provided with high weldability by the balance of Si, Mu, Cr, etc., and by reducing the C content, the appearance of coarse primary carbide is prevented to inhibit the deterioration of the toughness and to provide sufficient cracking and chipping resistances. The added V and Nb prevent the coarsening of the grains due to superheating during welding and stabilize the hardened structure, hardness and toughness.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a valve material for internal combustion engines that has excellent weldability.

The shaft ends of valves used in internal combustion engines require particularly high wear resistance, and conventionally, materials such as SU) I 3 and 8UH11 are induction hardened and used.

However, in recent years, as the performance of internal combustion engines has improved, 5KH has been applied to the shaft end, which requires wear resistance as a single valve with excellent durability.
9.5UJ2 and other materials were welded together, and 1-pieces (see figure) came to be used. However, there is a need for a substitute material for the above-mentioned materials, which have many weld defects such as weld cracks. The present invention has been made in view of the above, and is a valve material for an internal combustion engine that has good wear resistance, toughness, and machinability required for a valve material, and has excellent f-co weldability.

That is, the steel of the present invention has (1) C: 0.55 to 0.85% by weight, 8
i: 0.80-1.50%, Mn: 0.80-1
．． 50%, Cr: 1.20-8.50%.

V: 0.05-050%, Nb: 0.02-030
A valve material for an internal combustion engine having excellent weldability, characterized in that the remaining portion is substantially composed of Fe.

(2) C: 0.55-0.85%, Si: in terms of weight ratio
0.80-1.50%, Mn: 0.80-1.5
0%, Cr: 1.20-8.50%.

V: 0.05-0.50%, Nb: 0.02-0
．． 30%, TI: 0.30% or less, Ta: 0.30%
Hereinafter, a valve material for an internal combustion engine with excellent weldability, characterized in that the first type of Zr of 0.30% or less contains two or more types, and the remainder is substantially composed of Fe.

The steel of the present invention has good weldability due to the balance of Si, Mn, Cr, etc., reduces the amount of C, and has a component composition that does not contain large primary carbides, which minimizes deterioration of toughness and has sufficient crack resistance. Characteristics and durability have characteristics. Furthermore, the addition of Nb prevents crystal grains from becoming coarse due to overheating during welding operations, resulting in a stable hardened structure, hardness, and toughness.

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

C: 0.55-0.85% At least 0.55% is necessary to obtain sufficient hardness by induction hardening. However, if it exceeds 0.85%, the toughness of the quenched part will deteriorate significantly, and the net-like primary carbide will become noticeable during cast iron casting.

A particularly desirable range is 0.60 to no primary carbide.
It is 0.75%.

Si: 0.80-1°50% At least 0.80% or more is required to increase hardenability and wear resistance of the base by adding Mn in combination, but if it is more than 1.50%, machinability deteriorates. In order to
．． Set it to 5%.

Mn: 0.80-1.50% 0.8% or more is required to improve hardening and properties, but 1.5
If it exceeds 0%, the crystal grains will easily become coarse due to overheating, which not only impairs toughness but also deteriorates machinability, so the upper limit is set at 1.5%. A particularly desirable range is 0.80 to 1.20%.

Cr: 1.20-3°50% The above C and Si improve hardenability and at the same time form carbides, contributing to improving wear resistance.

Within the Mn range, at least 1.2% is required.

However, if it exceeds 3.50%, the formation of net-like primary carbides becomes noticeable and the toughness deteriorates, so the upper limit is set at 3.50%. A particularly desirable range is 1.50 to 3.0%.

V: 0.05-0.5% For grain refinement, at least 0.05% is necessary, but even if more than 0.5% is added, the effect will not be improved much. Economical aspects are also taken into account. However, the upper limit was set at 0.5%.

Nb: 0.02-0.30% Along with ■, it is a major element in the steel of the present invention, and it refines crystal grains, prevents coarsening of crystal grains at high temperatures, and improves toughness. I need. However, if 0.30% or more is added, coarse NbC
The upper limit of 0.30% was set as the upper limit of f-cots that are formed and impair the high toughness that is a characteristic of the steel of the present invention. A particularly desirable range is 0.02~
It is 0.2%.

Ti: 0.80% or less, Ta: OJO% or less, Zr: 0
．． 30% or less These elements form carbides and contribute to preventing coarsening of crystal grains, but adding more than 0.3% of any of them actually reduces toughness, so the upper limit for each is set at 0.8%.

Next, the present invention will be explained in detail based on examples.

Example 1 After melting an alloy having the composition shown in Table 1 in an electric furnace, the alloy 2 was cast into a steel ingot, followed by blooming and rolling.

A rolled material (020XL) was obtained after the annealing process.

Table 1 0-1 1! 1. 5 1 8 (1) Weldability The above-mentioned 20×L rolled material was processed into a 020×20 specimen and butt friction welded with a 5UH3 material of the same size to eliminate cracks in the welded area and the invention material (base material). Table 2 shows the cracking of f.

According to Table 2, the steels of the present invention exhibit very good weldability as evidenced by the presence or absence of weld cracking. This makes it clear that it is suitable if the valve is manufactured in a welded construction.

Table 2 (2) Wear resistance and toughness of the rolled material in the longitudinal direction
TX5L) and Charpy test (10 x 1OX55L) were cut out, and the worn surfaces and notch surfaces were induction hardened, and then the abrasion resistance and toughness tests were conducted, and the results are listed in Table 3.

According to Table 3, the steel of the present invention has wear resistance equivalent to that of the comparative steel, and shows a rather good impact value.

Table 3 Table 5 (Note 3) (Test conditions) Test piece dimensions: 50WX30TX150L welding rod: J
IS DF 8B-B Welding rod diameter 3.2 Welding current: 105A Preheating: 3oo0C Post heat: 400'C (Note 4) ○ mark 2 Weld cracks present x n: No weld cracks Table 5 Weld crack occurrence As is clear from the presence/absence, the steel of the present invention exhibits very good weldability. This makes it clear that it is suitable if the valve is manufactured in a welded construction.

(2) Wear resistance and toughness A Charpy test piece (1OX10X55L) was cut out from near the surface of the above-mentioned 060XL rolled material that had been induction hardened, and a wear test piece <2owxtOTX5L) was tested for wear resistance and toughness. It is shown in Table 6.

According to Table 6, the impact resistance of the steel of the present invention is almost the same as that of the comparative steel, but the wear resistance is irritatingly superior.

Table 6 (Note 5) (Test conditions) Rotating disk: 80M21 (SA) Friction speed: 0.97 m/see Distance: 200 m Final load: 6.5 kg/w (Note 6) 10R, C notch test piece (3) Machinability Table 7 shows the machinability of the rolled material 060XL before induction hardening using a drilling test. 7th
As is clear from the table, the machinability of the steel of the present invention shows a tool life comparable to that of the comparative steel.

As explained above in Table 7, the steel of the present invention does not cause any cracking in the weld zone or base metal during welding. Furthermore, since it exhibits excellent wear resistance, toughness, and machinability, it is a suitable material for use in internal combustion engine valves and exhibits a long life. As described above, the industrial contribution of the steel of the present invention is extremely large.

[Brief explanation of the drawing]

The figure shows an f-co valve in which the shaft ends are butted and welded together. l: Valve 2: Shaft end Applicant: Daido Steel Co., Ltd. Agent Yoshio Kawaguchi

Claims (2)

[Claims] (1) C: 0.55-0.85% by weight, S
i: 0.80-1.50%, Mn: 0.80-1
．． 50%, Or: 1.20-3.50%. V: 0.05-0.50%, Nb: 0.02-0.30
A valve material for an internal combustion engine having excellent weldability, characterized in that the remaining portion is substantially composed of Fe. (2) C: 0.55-0.85%, Si: in terms of weight ratio
0.80-1.50%, Mn: 0.80-1.50%,
Or: 1.20-150%. V: 0.05-0.50%, Nb: 0.02-0.30
%, TI: 0.30% or less, Ta: 0.30% or less,
Zr: A valve material for an internal combustion engine with excellent weldability, characterized in that it contains one or more of two or more of Zr at 0.30% or less, and the remainder substantially consists of Fe.