JP6044997B2 - Nickel-based alloy wastegate valve - Google Patents

Description

  The present invention relates to a valve component made of a nickel base alloy mounted in an engine.

  In recent years, there has been remarkable progress in improving the fuel efficiency of automobiles. For example, the automobile engine has been made smaller and lighter than before, and the shortage of output is combined with a turbocharger to compensate for the shortage of output. Turbo is becoming mainstream. Furthermore, since high output is pursued, valve parts with higher heat resistance are required.

  As a material used for such an engine component, for example, in Patent Document 1, 0.01 to 0.1% C, 0 to 0.5% Si, 0 to 0.5% Mn, and more than 23% by weight%. 25% or less of Cr, 0.5 to 1.5% Nb, 2.0 to 3.0% Ti, 1.0 to 2.0% Al, more than 45% and 50% or less of Ni, 0.1 Nickel-based alloys composed of ˜1.2% Cu, 0.3-2.0% W, etc. are disclosed. The nickel-base alloy is described as being useful as a heat-resistant alloy for valves because it has excellent high-temperature tensile strength at 900 ° C. and high hardness even after prolonged aging treatment at 800 ° C. .

Patent Document 2 discloses that 40 to 49% Ni, 1.2 to 1.8% Al, 2.0 to 3.0% Ti, 0.9 to 7.8% Nb, 1% or less by weight. A nickel-base alloy composed of Mo or the like is disclosed. The nickel-base alloy is described as being useful as a diesel engine component (particularly an exhaust valve component) because of its excellent corrosion resistance and wear resistance.

Japanese Patent Laid-Open No. 4-191344 Japanese translation of PCT publication No. 2004-512428

However, as described above, with the miniaturization and weight reduction of automobile engines, the exhaust gas temperature of the engine may reach around 900 to 1000 ° C. In the valve parts made of nickel-base alloy described in Patent Documents 1 and 2, There was a problem that high temperature strength and high temperature creep properties were insufficient.

Further, when the nickel base alloy described in Patent Documents 1 and 2 has a surface hardness after solution treatment exceeding a predetermined value, workability (particularly caulking processing) is required when valve parts are manufactured using the nickel base alloy. There was also a problem that the property was inferior.

  Accordingly, an object of the present invention is to provide a valve component made of a nickel base alloy having both excellent heat resistance and workability.

In order to solve the above-mentioned problems, the present inventors have intensively studied. As a result, a certain amount of Mo is added to the nickel-base alloy, the Ti and Al contents are kept below a certain amount, and a nickel-base alloy valve. It has been found that by making the surface hardness of a part (waist gate valve) a certain value or less, it is possible to achieve both workability and required heat resistance when manufacturing a waste gate valve . That is, the wastegate valve according to the present invention is, by weight, 0.01 to 0.05% C, 0.1 to 0.5% Si, 0.1 to 0.5% Mn, 0.001 to 0. 0.01% B, 23.5 to 25.0% Cr, 0.7 to 1.3% Nb, 2.0 to 3.2% Ti, 1.2 to 2.2% Al, 45 to 50% Ni 0.3 to 1.0% Cu, 0.5 to 1.5% Mo, 1.0 to 2.0% W, and the sum of the Ti content and the Al content is A nickel-base alloy wastegate valve consisting of 3.9% by weight or less, the balance being Fe and inevitable impurities, wherein the surface hardness of the wastegate valve is 84.6 HRB or less on the Rockwell B scale A wastegate valve made of a nickel-base alloy was obtained.

The waste gate valve made of a nickel base alloy according to the present invention has an effect of having both excellent heat resistance and workability. It can also have excellent high temperature creep properties . Therefore, the nickel-base alloy wastegate valve according to the present invention can withstand a high temperature atmosphere of 900 ° C. to 1000 ° C. for a long time.

It is a mimetic diagram of valve part 1 which is an example of an embodiment of the invention. It is a schematic diagram which shows the positional relationship of the valve component 1, the ring-shaped component 2, and the attachment plate 3 at the time of a crimping process. It is a schematic diagram which shows the state of the valve component molded object 4 which the crimping process of the valve component 1, the ring-shaped component 2, and the attachment plate 3 was completed.

An example of an embodiment of the present invention will be described. The reason why the component range of the nickel-based alloy constituting the automotive valve component according to the present invention is limited will be described in detail below.

The C (carbon) content is 0.01 to 0.05% by weight. C combines with Ti, Nb and Cr to form carbides and improves high temperature strength. In order to obtain such an effect, at least 0.01% by weight or more must be added. However, when added excessively, a large amount of MC carbide is generated to reduce hot workability, so the upper limit was made 0.05% by weight.

The content of Si (silicon) is 0.1 to 0.5% by weight. Si is added as a deoxidizing element. Moreover, the addition of an appropriate amount improves the oxidation resistance. However, if added excessively, ductility is lowered, so the upper limit was made 0.5 wt%.

The content of Mn (manganese) is 0.1 to 0.5% by weight. Mn is also added as a deoxidizing element in the same manner as Si. However, if added excessively, the high temperature strength is lowered, so the upper limit was made 0.5% by weight.

The content of B (boron) is 0.001 to 0.01% by weight. B enhances the crystal grain boundary to increase the creep strength and has the effect of improving hot workability. For this reason, addition of 0.001% by weight or more is necessary. However, if added excessively, a low melting point compound is formed at the grain boundary and hot workability is impaired, so the upper limit was made 0.01 wt%.

The content of Cr (chromium) is 23.5 to 25.0% by weight. Cr is an essential element for improving oxidation resistance and corrosion resistance. Further, when added to some extent, an acicular structure grows and an improvement in creep resistance is recognized. However, when excessively added, the acicular structure becomes coarse and causes performance deterioration, so the content was made 23.5 to 25.0% by weight.

The content of Nb (niobium) is 0.7 to 1.3% by weight. Nb combines with Ni to precipitate an intermetallic compound γ ″ phase of Ni ₃ Nb and improves the high temperature strength. Moreover, it combines with C to produce carbide NbC, which contributes to improvement in high temperature hardness and strength. However, if added excessively, the material becomes brittle, so the content was made 0.7 to 1.3% by weight.

The content of Ti (titanium) is 2.0 to 3.2% by weight. Ti combines with Ni to form an intermetallic compound γ ′ phase of Ni ₃ Ti and strengthens the austenite phase. If the amount of Ti is increased, the amount of the γ phase that is the strengthening phase is increased, and the high-temperature strength is improved. However, if added excessively, the embrittlement phase precipitates and the hot formability of the material is impaired, so the range of addition was limited to 2.0 to 3.2 wt%.

The content of Al (aluminum) is 1.2 to 2.2% by weight. Al is an important element that combines with Ni to form a Ni ₃ Al intermetallic compound γ ′ phase and strengthens the austenite phase. If the amount of Al is increased, the amount of the γ ′ phase that is a strengthening phase increases, and the high-temperature strength is improved. However, if added excessively, the strengthening phase becomes unstable, leading to the precipitation of the embrittlement phase. For this reason, since the hot formability of a raw material is inhibited, the addition range was limited to 1.2 to 2.2% by weight.

The content of Ni (nickel) is 45 to 50% by weight. Ni is indispensable for forming an austenite base that is a matrix. Further, a γ 'phase that is a precipitation strengthening phase is formed, and the high temperature strength is improved. In order to dissolve the strengthening element, a certain amount is necessary, and the lower limit of the addition amount is set to 45% by weight or more. However, when excessively added, the cost of the alloy increases, and the resistance to sulfidation corrosion deteriorates, so the upper limit was made 50% by weight.

The content of Cu (copper) is 0.3 to 1.0% by weight. Cu is added for the purpose of improving sulfide corrosion. When excessively added, hot embrittlement occurs, so the content was limited to 0.3 to 1.0% by weight.

The content of Mo (molybdenum) is 0.5 to 1.5% by weight. Mo is an element that improves high-temperature strength and high-temperature creep characteristics by solid solution strengthening in a temperature range in which a precipitation strengthening phase that achieves hot strength is dissolved. If the content is less than 0.5% by weight, the effect of improving the high temperature strength and the high temperature creep property is not manifested, and if the content exceeds 1.5% by weight, the content is limited because it is harmful to hot workability. .

The content of W (tungsten) is 1.0 to 2.0% by weight. W is an element that improves high-temperature strength and high-temperature creep characteristics by solid solution strengthening in a temperature range in which a precipitation strengthening phase that achieves hot strength is dissolved. If the content is less than 1.0% by weight, the effect of improving the high-temperature strength and the high-temperature creep property is not manifested, and if the content exceeds 2.0% by weight, the hot workability is harmful. Limited.

Next, the reason for defining the surface hardness of the wastegate valve according to the present invention will be described. When caulking is included in the process of manufacturing the wastegate valve , solution treatment is performed in advance in order to improve the workability between the wastegate valve and the counterpart material. However, when the surface hardness of the wastegate valve after the solution treatment exceeds a certain value, the material is not uniformly deformed when the caulking process is performed, and a crack or the like occurs. Therefore, the wastegate valve of the present invention is subjected to a solution treatment in consideration of the conditions of the wastegate valve that can be caulked without problems as will be described later and the machining characteristics that will be described later in order to perform the crimping process in the manufacturing process. The subsequent surface hardness was defined as 84.6 HRB or less on the Rockwell B scale.

Nickel-based alloy wastegate valve material according to the present invention (hereinafter, referred to as the present invention material), reference material and the conventional nickel-based alloy wastegate valve material (hereinafter, referred to as conventional material) using a waist automotive After forging into the shape of a gate valve (hereinafter referred to as a valve component), a machining test for cutting the surface of the valve component into a predetermined shape was performed, and the test results will be described. In this test, the inventive material , the reference material, and the conventional material were prepared for each 40 pieces (n = 40), then cut into a predetermined shape, and the presence or absence and number of used carbide tips were used. It was confirmed. The present invention material used for machining tests of this example, the reference material and Table 1 the chemical composition of the conventional material, the present invention product, reference product and the test results of conventional machining shown in Table 2. Here, the valve parts manufactured using the material of the present invention and the reference material are referred to as the product of the present invention and the reference product , respectively, and the valve parts manufactured using the conventional material are referred to as the conventional product.

As a result of the machining test, as for the presence or absence of abnormality of the cemented carbide chip, 40 pieces of the present product and each of the reference products were cut as shown in Table 2, but there were abnormalities such as cracks and cracks in the chip. Was not confirmed. Similarly, no abnormalities such as cracks and cracks were found in the conventional product. Next, the present invention product, for reference materials and chip number used to complete the conventional Each 40 pieces of cutting, the present invention product Contact and conventional products without chip replacement, the chip number used was The number of chips used was one, and the reference product was replaced in the middle, and the number of chips used was two.

Next, the valve parts machined in Example 1 were subjected to a solution treatment at 1035 ° C. for 1 hour, and their surface hardness (unit: HRB) was measured. A processing test was conducted. In this test, as shown in FIGS. 1 to 3, with the valve component (waist gate valve) 1 left stationary (FIG. 1), the ring-shaped component 2 and the mounting plate 3 are inserted from above and at a predetermined pressure. By pressurizing the valve component 1 (FIG. 2), the ring-shaped component 2 and the mounting plate 3 are fixed to the valve component 1 to complete the valve component molded body 4 (FIG. 3). Table 3 shows the surface hardness (unit: HRB) of the invention product , reference product, and conventional product after solution treatment, and the results of the caulking process test.

As shown in Table 3, the surface hardness after solution treatment at 1035 ° C. for 1 hour was 82.4 to 84.6 HRB for the product of the present invention, and 96.1 to 98.5 HRB for the reference product . . On the other hand, the conventional product was 77.5-83.5 HRB . Accordingly, For the present invention products, has excellent crimping characteristics, it was found that also combines excellent mechanical processing properties.

Further, as a result of this test, as shown in Table 3, all of the samples of the present invention and the reference product could be caulked without problems. Similarly, all of the results of caulking using conventional products could also be caulked. The number of samples subjected to caulking was 25 for each of the reference product of the present invention and the conventional product (n = 25). Five samples were extracted from each sample, and the hardness was measured.

Next, using the sample subjected to crimping in Example 2, a tensile test was performed in order to measure the adhesion strength between the product of the present invention , the reference product, and the conventional product and the counterpart component (ring-shaped component). In this test, the valve component and ring-shaped component were separately fixed on the tensile tester using the crimped valve component molded body, and a force was applied in the direction of separating each component. The tensile strength (unit: kN) when the parts were separated was measured.

As a result of this test, as shown in Table 4, the tensile strength of the product of the present invention was in the range of 15 to 23 kN, and the tensile strength of the reference product was in the range of 12 to 23 kN. On the other hand, the tensile strength of the conventional product was 18-22 kN. From the above test results, the nickel-base alloy wastegate valve of the present invention has excellent heat resistance and caulking workability equivalent to those of the reference product and the conventional product , and the once caulked valve parts are strong. It was found to have adhesion.

  1 Valve parts (Westgate valve)

Claims (1)

% By weight, 0.01-0.05% C, 0.1-0.5% Si, 0.1-0.5% Mn, 0.001-0.01% B, 23.5-25. 0% Cr, 0.7 to 1.3% Nb, 2.0 to 3.2% Ti, 1.2 to 2.2% Al, 45 to 50% Ni, 0.3 to 1.0% Cu, 0.5 to 1.5% Mo, 1.0 to 2.0% W is contained, and the total of the Ti content and the Al content is 3.9% or less by weight%. A nickel-base alloy waste gate valve made of Fe and inevitable impurities , wherein the waste gate valve has a surface hardness of 84.6 HRB or less on the Rockwell B scale. Made of wastegate valve .

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