JPS6034607B2 - Manufacturing method of Ni-based alloy valve body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention uses a precipitation hardening type Ni-based alloy as a material,
The present invention relates to a method for manufacturing a valve body with excellent heat resistance, wear resistance, and high temperature corrosion resistance from this material.

Conventionally, for example, in the manufacture of valve bodies for internal combustion engines (valve bodies, valve fins, and valve seats), heat resistance, wear resistance, and high temperature corrosion resistance are required, so JIS SUH3, SUH
F such as 31 and 21-small (equivalent to SUH35)
e-Cr system, Fe-Ni-Cr system, and Fe-en-M
N-type heat-resistant steel is used.

By the way, in recent years, internal combustion engines have been forced to use low-grade fuel due to energy shortages, but at the same time there has been a trend toward higher performance with higher temperatures. exposed to combustion gases.

When the above-mentioned heat-resistant steel valve body is used under the above-mentioned severe conditions, high-temperature corrosion occurs due to the combustion gas, and furthermore, the combustion ash that adheres between the valve and the valve seat causes severe damage to both components. Problems such as wear and breakage cannot be avoided.

Therefore, from the above-mentioned viewpoint, the present inventors have conducted research to produce a valve body that exhibits excellent heat resistance, wear resistance, and high-temperature corrosion resistance when put into practical use under severe conditions. In weight%, C: 0.01 to 0.10%, Cr: 18.0 to 21.0%, N: 1.2 to 1.9%, Ti: 2.0 to 2.8%, (but Total amount of mountain and Ti: 3.6 to 4.5%), B: 0
．． 001-0.008%, Zr: 0.01-0.15%
, Si: 0.01 to 1.0%, Mn: 0.01 to 1.0%, Ni and unavoidable impurities: the remainder. Temperature at the end of machining: 700~900oo
, After hot working at a working rate of 25 to 75%,
In a valve body manufactured by heat treatment under the conditions of holding at a predetermined temperature within the range of 650 to 825 pm for a predetermined time, the above-mentioned Ni-based alloy ensures excellent high-temperature corrosion resistance and heat resistance, and the above-mentioned relative They found that by hot working and heat treatment at low temperatures, excellent high-temperature wear resistance can be ensured while maintaining high ballistic properties.

This invention has been made based on the above findings, and the reason why the component composition, hot working conditions, and heat treatment temperature are limited as described above will be explained below. A Component composition [a) C Component C is an effective component for deoxidizing molten metal and refining crystal grains, but if its content is less than 0.01%, the desired effect cannot be obtained; If the content exceeds 0.10%, the amount of carbide precipitated becomes too large and hot workability deteriorates, so the content should be adjusted to 0.01 to 0.1%.
It was set at 10%.

(bI The CrCr component has the effect of improving high-salt corrosion resistance, but if its content is less than 18.0%, the desired high-salt corrosion resistance cannot be secured; on the other hand, if it is contained in excess of 21.0%, Since this results in a significant decrease in strength, the content was set at 18.0 to 21.0%.

'c} Mountains and Ti These components include N, which is precipitated and dispersed uniformly and finely in the substrate.
It has the effect of forming an intermetallic compound consisting of i3 (Ti) to improve high-temperature hardness, thereby significantly improving high-temperature wear resistance. and Ti: 2.0%, and AI1 Ti:
When the content is 3.6%, it is not possible to secure the desired high temperature hardness, while when N: 1.9% and Ti: 2.8% are exceeded,
And AI+Ti: If it exceeds 4.5%, the high rutting properties of this alloy will be impaired, so the content should be
AI: 1.2-1.9%, Ti: 2.0-2.0%, respectively.
8%, and N+Ti: 3.6 to 4.5%.

'd' B and Zr These components have the effect of improving heat resistance especially when they coexist, but their contents are less than 0.001% for B and 0.00% for Zr, respectively.
If it is less than 0.01%, the desired excellent heat resistance cannot be ensured, while B: 0.008% and Zr: 0.15%.
If the content exceeds B, the weldability will deteriorate, so the content should be set at B: 0.001 to 0.00, respectively.
008%, Zr: 0.01 to 0.15%.

{e- Si and Mb These components are contained for the purpose of deoxidizing the molten metal, but
The content of Si: less than 0.01% and M
If n: less than 0.01%, the desired sufficient deoxidation cannot be achieved; on the other hand, if Si: 1.0% and Mn: 1
．． If the Si content exceeds 0%, the high-temperature strength will decrease, so the content was adjusted to 0.01% Si.
-1.0%, Mn: 0.01-1.0%.

B. Hot Working Conditions 'a' Final Hot Working End Temperature As mentioned above, in the method of the present invention, high temperature hardness is ensured through hot working and heat treatment at relatively low temperatures.

Therefore, if the finishing temperature exceeds 900°C, a recovery phenomenon will occur during the cooling process after hot working.
The hardening effect imparted by hot working is eliminated, making it impossible to secure the desired high-temperature hardness. On the other hand, if the finishing temperature is less than 700°C, a large stress is simply required for hot working. However, since the quality is insufficient and cracks occur in the valve body during hot working, the end temperature was set as a predetermined temperature within the range of 700 to 900 qo.
'b' Working rate If the working rate is less than 25%, the desired high work hardening cannot be imparted to the valve body.On the other hand, in the case of this alloy, if the working rate exceeds 75%, the work hardening phenomenon of 0 occurs. Not only does it increase rapidly and make hot working extremely difficult,
Since the deterioration in rutting was also significant, the processing rate was set at 25 to 75%.

C Heat Treatment Temperature When the heat treatment temperature is raised above 825 oo, the work hardening imparted to the valve body in the hot working process in the previous step disappears, and the precipitation hardening phenomenon does not occur, so it is difficult to maintain a predetermined high hardness. On the other hand, a heat treatment temperature of less than 65,000 degrees Celsius requires a long time for precipitation hardening and is not practical. Therefore, the heat treatment temperature was set at a predetermined temperature within the range of 650 to 825q0.

Next, the method of the present invention will be specifically explained using examples. Example Using a vacuum melting furnace, molten Ni-based alloys having the compositions shown in Table 1 were prepared, and then cast into ingots having dimensions of diameter: 40mm x length: 1500mm, This ingot is heated to a temperature within the range of 1000 to 1200°C and hot forged to a diameter of 100 to 25
Various round bars with varying ranges of shipboard are formed, and then Ni-based alloy materials having various heights Ho are cut out from these round bars under conditions of constant volume. Hot die forging is performed under the conditions shown in Table 1 to create a valve with dimensions of bottom diameter: 30 mm x height H: 10 mm (this type of valve is used under the most severe conditions). ), and subsequently these valves were also treated with the same first
Methods 1 to 10 of the present invention and comparative methods 1 to 5 were carried out by heat treatment under the conditions shown in the table.

Then, methods 1 to 10 of the present invention and comparative method 1, respectively.
Diameter: 1 x height from the valve manufactured by ~5:
A test piece of one shipboard length was cut out, and this test piece was used to measure the Vickers hardness (high temperature hardness) at a temperature of 700 qo in order to evaluate heat resistance and abrasion resistance, and to evaluate high temperature corrosion resistance. , on the surface of the test piece, V205:
A mixed corrosive material (equivalent to the combustion ash of low-grade fuel) consisting of 85% by weight and 15% by weight of Na2S04 was applied at a ratio of 20:9/ground, heated to a temperature of 90,000, and kept at this temperature for 3 hours. A high-temperature corrosion resistance test was conducted under holding conditions, and the corrosion weight loss after the test was measured. Similarly, test pieces having two U-shaped notches were cut out from each of the above valves and subjected to an impact test. These measurement results are also shown in Table 1. In addition, the processing rate of hot forging in Table 1 is (ratio - H)
/Ho×100.

From the results shown in Table 1, the valves manufactured by methods 1 to 10 of the present invention all have high high-temperature hardness while maintaining high toughness, and have excellent high-temperature corrosion resistance. On the other hand, the valve manufactured under comparative method 2 where the final hot forging end temperature is higher than 900 oo, the valve manufactured under comparative method 3 where the processing rate is less than 25%, and the comparative method 5. Valves manufactured under heat treatment temperatures exceeding 82,500°C do not have sufficient hardness at high temperatures.
In addition, the valve manufactured under the conditions in which the final hot forging temperature of Comparative Method 1 is less than 70,000, and the processing rate of Comparative Method 4 is 75
In valves manufactured under conditions exceeding %, forging cracks occurred in all valves due to a significant lack of toughness.

As described above, according to the method of the present invention, a valve made of a Ni-based alloy that has excellent high-temperature corrosion resistance and heat resistance, and also has excellent high-temperature wear resistance (high-temperature hardness) while maintaining high-grade properties. Moreover, this Ni-based alloy valve body has the excellent properties mentioned above, so it is suitable for practical use under harsh conditions where it is exposed to high temperatures and highly corrosive combustion gas. It exhibits excellent performance over an extremely long period of time.

Claims (1)

[Claims] 1 C: 0.01-0.10%, Cr: 18.0-21.0%, Al: 1.2-1.9%, Ti: 2.0-2.8% , (However, total amount of Al and Ti: 3.6 to 4.5%), B:
0.001-0.008%, Zr: 0.01-0.15
%, Si: 0.01 to 1.0%, Mn: 0.01 to 1.0%, Ni and unavoidable impurities: the remainder (weight %) is used as a material. The above material is subjected to hot working at a final hot working end temperature of 700 to 900°C and a processing rate of 25 to 75%, and then heated to a predetermined temperature within the range of 650 to 825°C for a predetermined period of time. N with excellent heat resistance, wear resistance and high temperature corrosion resistance, which is characterized by heat treatment under conditions of retention.
A method for manufacturing an i-based alloy valve body.