JPS5940212B2 - Co-based alloy for engine valves and valve seats of internal combustion engines - Google Patents

Description

Detailed Description of the Invention The present invention has excellent high-temperature hardness, thermal shock resistance, and lead oxide corrosion resistance, and is particularly suitable for overlay welding of engine valves and valve seats of internal combustion engines, and for these. The present invention relates to a Co-based alloy suitable for use in castings.

Conventionally, overlay welding of engine valves and valve seats for internal combustion engines has been performed in accordance with American Welding Society Standard 5.13.
RCoCr-A (C: 0.9-1.4%, Si: 2.
0% or less, Mn: 1.0% or less, W: 3.0 to 6.0%
, Cr: 26-32%, Ni: 3.0% or less, Fe: 3
．． 0% or less, Mo: 1.0% or less, C.

and unavoidable impurities: remainder) and 5.13 RCoC
r B (C: 1.2-1.7%, Si: 2.0%
Below, Mn: 1.0% or less, W near, 0 to 9.5%, C
r: 26-32%, Ni: 3.0% or less, Fe: 3.0
% or less, Mo: 1.0% or less, Co and unavoidable impurities: remainder, or more weight %)
base alloys) 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 better characteristics. , all of which have high temperature hardness with a Vickers hardness of 285 or higher at a temperature of 800°C in the overlay welding state, and if the water cooling operation is repeated after being held at a temperature of 700°C for 15 minutes, cracks will occur in the overlay welded part. Thermal shock resistance where the number of operations is 7 or more before occurrence;
and weight loss after 1 hour immersion in molten lead oxide heated to 915°C is 0.09 g/cyrf,/h
It is now required to have lead oxide corrosion resistance of r or less.

It goes without saying that these characteristics are similarly required for engine valve castings and valve seat castings for internal combustion engines manufactured by casting.

However, although the above-mentioned conventional Co-based alloys satisfy the above-mentioned requirements in terms of high-temperature hardness, they do not have properties that satisfy these requirements in terms of thermal shock resistance and lead oxide corrosion resistance. Currently, when used for overlay welding of engine valves and valve seats, or for casting, it does not have a sufficiently satisfactory service life.

From the above-mentioned viewpoints, the present invention provides a Co-based alloy that solves the problems of the conventional Co-based alloys, and has C: 1.0 to 3.5% in weight %, Si: 0.
1~2.0%, Mn: 0.1~2.0%, W: 5~
20%, Cr: 20-40%, Ni: 25%-50%
and, if necessary, one or two of Fe: 1 to 30% and Mo: 2 to 9%, and Co
and unavoidable impurities: It has an excellent high-temperature hardness that satisfies the above conditions required for overlay welding and casting materials for engine valves and valve seats of internal combustion engines, especially high-performance engines, and unavoidable impurities: thermal shock resistance,
and lead oxide corrosion resistance, and furthermore, if it contains Fe, the thermal shock resistance is further improved, and if it contains Mo, the high temperature hardness is further improved.

This is a characteristic of Co-based alloys.

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) C The C component has the effect of forming carbide with Cr, W, MO, etc. and improving the hardness at room temperature and high temperature, but if its content is less than 1.0%, the above effect is However, if the content exceeds 3.5%, the thermal shock resistance will decrease, so the content was set at 1.0 to 3.5%. b) Si In order to ensure the desired deoxidizing effect, castability, overlay weldability, melt flowability, etc., a minimum content of 0.1% is required; on the other hand, it is not allowed to contain more than 2.0%. Since further improvement effects cannot be expected even if the content is reduced to 0.1 to 2
．． It was set as 0%.

(c) Mn In addition to deoxidizing and desulfurizing effects, the Mn component has an effect of improving overlay weldability, but if its content is less than 0.1%, the desired effect cannot be obtained in the above effects, On the other hand, even if the content exceeds 2.0%, no further improvement effect can be expected, so the content was set at 0.1 to 2.0%.

(d) W The W component has the effect of forming 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 cannot be obtained in the above action, and on the other hand, if the content exceeds 20%, overlay weldability and machinability will deteriorate, so the content was set at 5 to 20%.

(e) 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 the content should be 20% or more, but if the content exceeds 40%, it will become brittle, so it is not recommended to contain more than 40%. must not.

(f) Ni The Ni component has the effect of improving the thermal shock resistance and lead oxide corrosion resistance of the alloy when coexisting with the Cr component, but if its content is less than 25%, the lead oxide corrosion resistance is particularly affected. Corrosion weight reduction required for: 0.099/cr
It is not possible to secure less than tt/hr, while 50
If the content exceeds 25% to 50%, the high temperature hardness tends to decrease.
It was determined that

(g) Fe The Fe component has the effect of further improving the thermal shock resistance of the alloy, but if its content is less than 15%, the desired effect cannot be obtained; on the other hand, if it is contained in an amount exceeding 30%. Since the high-temperature hardness decreases and it becomes impossible to maintain a Vickers hardness of 285 or higher at 800°C, the content is set at 1 to 30%.

(h)M.

The Mo component has the effect of further improving the high-temperature hardness of the alloy, but if its content is less than 2%, the desired effect will not be obtained, while if it is contained in excess of 9%, the toughness will decrease. Since the content will decrease by 2~
It was set at 9%.

Next, the Co-based alloy of the present invention will be explained using examples.

First, by a normal melting and casting method, the alloy welding rods 1 to 1 of the present invention were
23. Comparative alloy welding rods 1 to 7 whose compositions are outside the scope of the present invention, and the above-mentioned conventional C.

Conventional alloy welding rods 1 to 1 with a composition corresponding to the base alloy
2 were produced respectively.

The compositions of these welding rods are shown in Table 1.

Next, using these welding rods, with a TIG automatic welding machine,
On the surface of a stainless steel (SUS316) base metal with dimensions of 120mmφ in diameter x 207n7IL in thickness, an outer diameter of 1
A circular bead measuring 00 mm x width 2 (Jvtm x thickness 5 ynyt) was welded in one layer.

Next, regarding the annular bead on the base metal, the Rockwell hardness C scale at room temperature and the temperature 800
In addition to measuring the Vickers hardness at °C, the alloy that formed the annular bead was heated to 700°C, held for 15 minutes, and water-cooled repeatedly until cracks appeared in the annular bead. A thermal shock resistance test was conducted to measure the number of operations of 15 mmφ×
Diameter 12mmφ x height L2 from 100m71L overlay material
A test piece with dimensions of mrn was cut out and heated to a temperature of 915°C.
After the test piece was immersed for 1 hour in 40 g of molten lead oxide heated to 40 g, a high temperature corrosion test (lead oxide corrosion resistance test) was conducted to measure the weight loss.

These measurement results are also shown in Table 1.

As shown in Table 1, alloys 1 to 23 of the present invention have superior high-temperature hardness, thermal shock resistance, and lead oxide corrosion resistance compared to conventional alloys 1 to 2. It has characteristics that comfortably satisfy the conditions required for engine valves and valve seats in engines.

In addition, looking at the present invention alloys 1 to 5 and the comparative alloy 1, Ni
It can be seen that as the content of the components increases, the thermal shock resistance and lead oxide corrosion resistance improve.

However, in this case, if the Ni content is 25% or less, the improvement in lead oxide corrosion resistance is insufficient.

Similarly, looking at Invention Alloys 6 to 8 and Comparative Alloys 2 and 3, Comparative Alloy 2, whose C content is lower than the range of this invention, cannot obtain the desired high-temperature hardness; Comparative Alloy 3, which is out of the range, exhibits extremely low thermal shock resistance, whereas Invention Alloys 6 to 8 all exhibit excellent properties.

Furthermore, Invention Alloys 9 to 12, in which the Cr content was varied within the range of this invention, Comparative Alloy 4, in which the Cr content was lower than the range of this invention, and Comparative Alloy 4, in which the Cr content was also higher than the range of this invention. Looking at Comparative Alloy 5, Comparative Alloy 4 has significantly inferior high temperature hardness and lead oxide corrosion resistance, while Comparative Alloy 5 has inferior thermal shock resistance. It is clear that all of Invention Alloys 9 to 12 have excellent properties.

Regarding the W component, looking at Invention Alloys 13 to 15 and Comparative Alloys 6 and 7, in which the W content was varied, Comparative Alloy 6, in which the W content was lower than the range of the present invention.
In Comparative Alloy 7, whose high-temperature hardness was on the high side, the thermal shock resistance was significantly deteriorated, whereas Invention Alloys 13 to 13 whose W content was within the range of the present invention
No. 15 shows excellent characteristics.

Similarly, as is clear from the results shown for invention alloys 16 to 19, in which the Fe content was varied within the range of this invention, as the Fe content increases, the thermal shock resistance increases proportionally. This will further improve your sexuality.

Similarly, the results shown in Invention Alloys 20 to 22, in which the Mo content was varied within the range of the present invention, show that as Mo is increased, the high-temperature hardness is further improved in proportion to this. It is clear that

In addition, alloy 23 of the present invention containing Fe and Mo has been shown to have further improved high temperature hardness and thermal shock resistance.

In addition, in the above example, a case was described in which the Co-based alloy of the present invention was used for overlay welding, but even when used for casting, it exhibits the same excellent characteristics as for overlay welding. Of course.

As mentioned above, the Co-based alloy of the present invention has excellent high-temperature hardness, thermal shock resistance, and lead oxide corrosion resistance, so it is suitable for internal combustion engines, especially internal combustion engines that use leaded gasoline. It is suitable for use in overlay welding of valves and valve seats, and for casting.

Claims (1)

[Claims] IC:1. O~3.5%, Si: 0.1~
2.0%, Mn: 0, 1-2.0%, W: 5-20%,
Cr: 20-40%, Ni: 25%-50%, c
Co-based alloy for engine valves and valve seats of internal combustion engines that has excellent high-temperature hardness, thermal shock resistance, and lead oxide corrosion resistance, and is characterized by having a composition consisting of o and unavoidable impurities: the remainder (at least % by weight) . 2C: 1.0-3.5%, Si: 0.1-2
．． 0%, Mn: 0.1-2.0%, W: 5-20%, C
r: 20-40%, Ni: 25%-50%, F
An engine valve for an internal combustion engine having excellent high-temperature hardness, thermal shock resistance, and lead oxide corrosion resistance, characterized by having a composition consisting of e: 1 to 30%, Co, and unavoidable impurities: the remainder (more than % by weight) and Co-based alloys for valve seats. 3C: 1.0-3.5%, Si: 0.1-2
．． 0%, Mn: 0, 1-2.0%, W: 5-20%, C
r: 20-40%, Ni: 25%-50%, M
An engine valve for an internal combustion engine having excellent high-temperature hardness, thermal shock resistance, and lead oxide corrosion resistance, characterized by having a composition consisting of O: 2 to 9%, Co, and unavoidable impurities: the remainder (more than % by weight) and Co-based alloys for valve seats. 4C:1. O~3.5%, Si: 0.1~2
．． 0%, Mn: 0, 1-2.0%, W: 5-20%, C
r: 20-40%, Ni: 25%-50%, Fe: 1
~30%, Mo: 2-9%, Co and inevitable impurities:
A Co-based alloy for engine valves and valve seats of internal combustion engines, which has a composition consisting of the remainder (more than % by weight) and has excellent high-temperature hardness, thermal shock resistance, and lead oxide corrosion resistance.