JPS5937733B2 - Co-based alloy for overlay welding of engine valves and valve seats of internal combustion engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Co-based alloy that has excellent high-temperature hardness and thermal shock resistance and is suitable for use in overlay welding of engine valves and valve seats of internal combustion engines. .

Conventionally, American Welding Association standard 5.13FCoCr- was used for overlay welding of engine valves and valve seats of internal combustion engines.
A (C: 0.9-1.4%, Mn:<1.0%, W:
3.0-6.0%, C: 26-32%, Si■0.
4 to 2.0%, Co: remainder, weight %) and 5.1%
-B (C: 1.2-1.7%, Mn: <1
．． 0%, W: 7.0-9.5%, C: 26-32%,
Co-based alloys (hereinafter referred to as conventional Co-based alloys) such as Si: 0.4 to 2.0%, Co (remaining: weight %) have been widely used.

On the other hand, in recent years, as the performance of internal combustion engines has improved, the engine valves and valve seats are required to have even more excellent characteristics. In general, if both are in the build-up welding state and have a high temperature hardness with a Vickers hardness of 285 or higher at a temperature of 800°C, and if water cooling is repeatedly performed after holding the temperature at 700°C for 15 minutes, the build-up weld will It is now required to have thermal shock resistance that can be repeated 7 times or more before cracking occurs.

However, although the above-mentioned conventional Co-based alloys satisfy the above requirements in terms of high-temperature hardness, they do not have properties that satisfy this requirement in terms of thermal shock resistance, and therefore are not suitable for high-performance engines. At present, when used for overlay welding of valves and valve seats, it does not have a sufficiently satisfactory service life. Therefore, based on the above-mentioned viewpoint, the present inventors have developed a material with excellent high-temperature hardness that satisfies the above-mentioned conditions required for overlay welding materials for engine valves and valve seats of internal combustion engines, particularly high-performance engines. In order to obtain a material for overlay welding that has thermal shock resistance, we conducted research focusing on the above-mentioned conventional CO-based alloy, and found that Fe
They have found that the thermal shock resistance is improved when MO is contained, and the high-temperature hardness is further improved when one or both of MO is contained.

Therefore, the present invention was made based on the above findings, and has a composition consisting of, in weight%, one or two of the following: CO and inevitable impurities: the remainder; It is a CO-based alloy that has excellent high-temperature hardness and thermal shock resistance, and is suitable for use in overlay welding of engine valves and valve seats of internal combustion engines.

Next, the reason why the composition range of the CO-based alloy of the present invention is limited as described above will be explained.

(a) The CC component includes Cr, Cr, MO, etc., and carbides. When the content is less than 1.0%, the desired effect cannot be obtained; on the other hand, when the content exceeds 3.5%, the desired effect cannot be obtained. Since the thermal shock resistance decreases, the content is set at 1.0 to 3.5%.

(b) The WW component has the effect of refining carbides and solid solution strengthening of the matrix, thereby improving the high-temperature hardness and high-temperature strength of the alloy, but if its content is less than 5%, The desired effect could not be obtained from the above action, and on the other hand, 20 (
If the content exceeds fl), overlay weldability and machinability will deteriorate, so the content was set at 5 to 20%.

(c) Cr The Cr component has the effect of solid-solution strengthening the base material and improving high-temperature hardness and oxidation resistance.

However, if the content is less than 20%, the desired effect cannot be ensured, so it is necessary to contain more than 35%.
If the content exceeds the
The content must not exceed %. (d) The MnMn component has a deoxidizing and desulfurizing effect as well as an effect of improving overlay workability, but if its content is less than 0.1%, the desired effect cannot be obtained; Even if the content exceeds 0.0%, no further improvement effect can be expected, so the content was set at 0.1 to 2.001).

(e) S! In order to ensure the desired deoxidizing effect, castability, overlay workability, and melt flowability, a minimum content of 0.1% is required, but even if the content exceeds 2.0%. Since further improvement effects cannot be expected, the content should be reduced to 0.1 to 2.
．． It was set as 0%.

(f) Fe Inclusion of the Fe component allows the alloy to exhibit significantly superior resistance to repeated thermal shock; however, if the Fe content is less than 10%, the desired thermal shock resistance cannot be ensured. On the other hand, if the content exceeds 35(f), the high temperature hardness will decrease, so the content should be increased from 10 to 35(f).
%.

(g) The V, horse, and MO components have a homogeneous structure that forms fine carbides that are difficult to coarsen, and also stabilizes and strengthens the alloy structure by alloying with Cr and W, thereby further improving the high-temperature hardness of the alloy. However, when the content of maple is less than 0.5% and MO: less than 3%, the desired effect cannot be obtained, while on the other hand: 5.0% and MO: 90
If the content exceeds 1), the toughness will decrease, so the content should be set to V: 0.5 to 5.0%,
MO: Set at 3-9%.

(h) CO The inclusion of the CO component provides the alloy with excellent high-temperature hardness and oxidation resistance, so in order to ensure these properties, at least 10%, preferably 200%
1) The above content is desirable.

Next, the CO-based alloy for overlay welding of the present invention will be explained with reference to examples. First, by applying the usual melting casting method and wire rod processing method, welded alloys 1 to 24 of the present invention, each having the final component composition shown in Table 1, and a comparison with a component composition outside the scope of the present invention. Alloy welding bars 1 to 10, and the above conventional CO-based alloys (American Welding Society Standard 5.13RC
Conventional alloy welded bars 1 and 2 having compositions corresponding to 0Cr-A and B) were manufactured, respectively.

Next, using each of the above-mentioned inventive alloy welded strips 1 to 24, comparative alloy welded strips 1 to 10, and conventional alloy welded strips 1 and 2, welded by an automatic welding machine (02+C2H2 gas), a diameter of 1.
20 pieces φ x thickness 201! On the surface of the base metal made of stainless steel (SUS3l6) with the dimensions of IR, the outer diameter is 10071I.
! A circular bead measuring 1 ton x 201 gt in width was welded in one layer.

Next, the Rockwell hardness (C scale) at room temperature and the Vickers hardness at a temperature of 800°C were determined for each annular bead on the base metal, and the annular bead was formed on the base metal. , temperature 70
A thermal shock resistance test was conducted in which the operation of heating to 0° C., holding for 15 minutes, and then cooling with water was repeated, and the number of operations until cracking occurred in the annular bead was measured.

These measurement results are also shown in Table 1. As shown in Table 1, overlay welds (circular beads) formed with conventional alloys conventionally used for overlay welding of engine valves and valve seats of internal combustion engines are relatively superior. Although it has high-temperature hardness, its thermal shock resistance is significantly inferior, and overlay welds made of comparative alloys with compositions outside the scope of the present invention have either high-temperature hardness or thermal shock resistance. It has become inferior and does not have both of these characteristics.

As described above, depending on conventional alloys and comparative alloys, the overlay welds of engine valves and valve seats in high-performance engines require (a) a Vickers hardness of 285 or higher at a temperature of 800°C, and (b) thermal shock resistance. In contrast, with the alloy of the present invention, it was not possible to form an overlay weld that satisfied the conditions of 7 or more heating and water cooling operations until cracking occurred in the steel test. It is possible to form a build-up welded part that fully satisfies the conditions and has excellent properties.

As mentioned above, the CO-based alloy of the present invention has excellent high-temperature hardness and thermal shock resistance, so it is suitable for overlay welding of engine valves and valve seats of internal combustion engines, especially high-performance engines. It exhibits outstanding performance.

Claims (1)

[Claims] 1 C: 1.0-3.5%, W: 5-20%, Cr: 20-35%, Mn: 0.1-2.0%, Si: 0.1-2 .0%, Co and unavoidable impurities: The rest: By containing Fe: 10 to 30% (or more by weight), it has heat resistance while maintaining excellent high temperature hardness. A Co-based alloy for overlay welding of engine valves and valve seats of internal combustion engines, characterized by improved impact resistance. 2C: 1.0-3.5%, W: 5-20%, Cr: 20-35%, Mn: 0.1-2.0%, Si: 0.1-2.0%, Co and Unavoidable impurities: remaining, the thermal shock resistance is improved by incorporating Fe: 10 to 30% into a Co-based alloy consisting of V: 0
．． 5 to 5.0%, Mo: 3 to 9%, an internal combustion engine characterized in that the high temperature hardness is further improved by further containing one or two of the following: Co-based alloy for overlay welding of engine valves and valve seats.