JPS62127160A - Turbine rotor for super charger of internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the generation of the defect of non-metallic inclusion and to reduce the weight and moment of inertia by making the material by the Ni base super heat resistant alloy containing Al and Ti and making the material regulating the contents of oxygen and nitrogen. CONSTITUTION:A hub part 2 is made hollow and the thickness thereof is taken <=two times of the maximum thickness at the root of a wing part 1 in the turbine rotor that the wing part 1 and hub part 2 are integrally cast. The material is taken as the Ni base super heat resistant alloy containing <=10 and 15ppm oxygen and nitrogen respectively. In this way the generation of the non-metallic inclusion defect is prevented, the hub part can be made hollow, the weight and moment of inertia are reduced and the internal combustion engine excellent in responding property is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a turbine rotor for a supercharger (hereinafter referred to as a turbine rotor) used in an internal combustion engine of an automobile or the like.

[Conventional technology]

A supercharger for an internal combustion engine rotates the turbine rotor by blowing exhaust gas from the engine onto it, pressurizes combustion air with an impeller attached to one end, and supplies it to the engine, especially for automobiles. For engines that undergo frequent rapid acceleration, the moment of inertia 14 is required to be reduced so as to respond quickly.

This turbine rotor is heated to a maximum temperature of about 900° C., has a rotational speed of 200,000 RPMK, and operates under high stress due to centrifugal force. For this reason, a Ni-based super super heat-resistant alloy containing precipitation hardening elements such as Al+Ti is usually used from the viewpoint of high-temperature strength, and since the shape is complicated, the lost wax FFL close casting method is usually adopted.

Since this turbine rotor operates under high temperature and high stress as mentioned above, casting defects such as non-metallic inclusion defects and pinhole defects are likely to cause rotor destruction, and it is important to completely eliminate these defects. It is difficult. For this reason, the entire turbine rotor is divided into several stages, such as fatal parts and semi-fatal parts, and standards for the type, size, number, etc. of defects are set for each part. The connecting part between the n-wing part and the hub part, which is strictly inspected and sorted by the manufacturer, is a high-stress part and is therefore one of the critical parts, and defects in the core part greatly affect the yield of the product.

Reducing the wall thickness of the hub of the turbine rotor by using an intermediate seat is effective in reducing the moment of inertia, but it also makes the shape more complicated and creates high stress areas at the connection with the blades. However, it has not been put to practical use because of the need to reduce the wall thickness in areas where casting defects are likely to occur.

[Problem that the invention seeks to solve]

The present invention provides a turbine rotor having a hollow hub portion with reduced thickness and a small moment of inertia by considering the material and preventing the occurrence of defects due to non-metallic inclusions.

[Means for solving problems]

The turbine rotor of the present invention has a hollow blade portion, the wall thickness of which is less than twice the maximum wall thickness of the root of the blade portion, and the material is A.
It is a Ni-based super super heat-resistant alloy containing 1 and 60 wt% or more of Ni, and the oxygen and nitrogen content is 10 and 15 ppm or less, respectively. Super heat-resistant alloys are produced by casting, and these alloys contain Al and UTi, which are active against oxygen and nitrogen, as precipitation hardening elements, and these elements are oxides.

According to the experiments conducted by the present inventors using an alloy containing 260 wt% Ni, Al, and T1, it is easy to form nitrides and cause nonmetallic inclusion defects. In order to keep it within a practically acceptable range, the oxygen and nitrogen content of the molten metal should be 10 and 15 PPm or less, respectively, and the molten metal should be kept at 10 PPm or less until solidification is completed.
It was found that it is necessary to maintain the temperature at or above wHf.If these standards are exceeded, oxides and nitrides may be generated on the surface of the molten metal, and as will be described later, inclusions may occur especially in the hub part after casting. Harmful defects are likely to occur due to agglomeration, etc.

The wall thickness at the tip of the blade of a turbine rotor is usually about 0.3 fi, and in order to provide sufficient hot water circulation to this thin casting space, it is necessary to heat the mold to a high temperature. However, due to this mold heating, it takes a long time to complete solidification in the hollow hub part, and trace amounts of oxides or nitrides float to the surface.
Trap in the core part.

, which tend to aggregate and become harmful defects. For this reason, as mentioned above, it is necessary to lower the oxygen and nitrogen content of the bath water.

The thinner the inner thickness of the hub, the greater the effect of reducing the weight, especially the moment of inertia.If the cast product is sound, it is estimated that the inner thickness of the hub can be reduced to the same level as the wall thickness of the root of the wing. Considering the possibility of trapping nonmetallic inclusions, etc., the wall thickness of the hub portion was set to be less than twice the maximum wall thickness of the root of the wing portion.

〔Example〕

A prototype turbine rotor of the present invention shown in FIG. 1 was manufactured. A is a front view thereof, and B is a sectional view taken in a plane including the fine details. The turbine rotor includes a hub portion 2 having a blade portion 1 and a hollow portion 3.
It is an integrally cast product consisting of.

As shown in C, the wall thickness of the wing portion 1 is gradually increased from the tip toward the hub portion 2 so that the stress is the same. In the present invention, the maximum wall thickness at the root of the wing section refers to the maximum interval at which the naturally extended curved surface forming this wall thickness intersects the outer diameter surface of the hub section, and the fillet radius is shown in Figure 6. This is the dimension ti excluding the influence of R and the like.

In this embodiment, the tip wall thickness tl of the wing portion 1 is 0.3. Wing part 1
The wall thickness of the base is 2.5 + m on the inlet side of the waste scrap, and 4 m on the outlet side.
ms, the maximum wall thickness is tzz4m, and the wall thickness of the knob part is t
3=4■.

As shown in Fig. 2, a core 6'f consisting of a core part 4 corresponding to the hollow part and a baseboard part 5 is made of ceramic and placed in a separately manufactured mold, and then inserted into the mold. A wax model was made by injecting molten wax, and a mold was made using the usual lost wax method.

I that has been thoroughly refined to contain 7 ppm of oxygen and 10 ppm of nitrogen.
A master alloy equivalent to nconet 713C was melted in a vacuum induction melting and casting machine, and poured into a mold manufactured as described above and heated to 1050°C at a temperature of 1500°C. The degree of vacuum was 10 mHg or more from the start of melting to the completion of solidification. Maintained.

Product parts were cut and separated from the obtained cast body by toe cutting, and treatments such as cutting and removing the riser part, grinding each cut surface, removing the core, and sandblasting were performed. As a result of X-ray and penetrant testing of this product, no harmful defects were found in all products. The gas analysis results were 7 ppm of oxygen and 10 ppm of nitrogen.

〔Effect of the invention〕

As described above, the material of the turbine rotor of the present invention is A.
The Ni-based super super heat-resistant alloy containing Ti and Ti prevents the occurrence of non-metallic inclusion defects as it is a material with a controlled content of oxygen and nitrogen, thereby making the hub part hollow.
The weight and especially the moment of inertia are reduced.

This makes it possible to create an internal combustion engine with excellent response characteristics.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a turbine rotor of the present invention, and FIG. 2 is a diagram of a core used in an example. Ge / Figure (79) (l Jino 2nd ')

Claims (1)

[Claims] In a turbine rotor for an internal combustion engine supercharger in which a blade part and a hub part are integrally cast, the hub part is hollow, its wall thickness is less than twice the maximum wall thickness of the root of the blade part, and the material is Al and Ti. and Ni containing 60 wt% or more of Ni and containing oxygen and nitrogen of 10 and 15 PPm or less, respectively.
A turbine rotor for an internal combustion engine supercharger, characterized by being made of a base super heat-resistant alloy.