JPH0424101A - Vehicle wheel - Google Patents

Abstract

PURPOSE:To secure such a vehicle wheel that is high in corrosion resistance and rich in a high-grade feeling as well as very excellent in the degree of freedom to form or the like from the standpoint of designability by forming a disk part with stainless cast steel, and a rim part with stainless steel, respectively. CONSTITUTION:A disk part 1 is formed into a disk form by means of stainless cast steel with a specified chemical composition. In this disk part 1, an axle hole 2 and plural pieces of mounting holes 3 are installed in the central part. In addition, a design surface 4 is installed on an outer surface of the disk part 1, forming various forms and/or patterns. On the other hand, as for a rim part 5, a plate consisting of a malleable material, for example, stainless steel (SUS304) is formed into a hollow cylindrical form by means of roll forming. Then, the disk part 1 and the rim part 5 are unified in one by means of welding, forming a wheel. Thus, the disk part 1 is founded with stainless cast steel, through which anticorrosion and strength are improved and, what is more, even those of geometrical forms are made castable.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a wheel for, for example, a passenger car, or a vehicle wheel. The present invention relates to a so-called two-piece vehicle wheel that is integrally fixed to a rim portion and has improved corrosion resistance and strength.

[Conventional technology]

Conventionally, vehicle wheels use a so-called steel disc type made of pressed steel for both the disc part that connects to the vehicle and the rim part that attaches the tire, and most of them have an integral structure by welding. Vehicle wheels for large vehicles such as trucks and buses are mainly of the steel disc type mentioned above.9 However, wheels for passenger cars and racing cars are designed to improve riding comfort, fuel efficiency, and handling stability. To achieve this goal, vehicle wheels using light alloys such as aluminum alloys and magnesium alloys have become popular. Especially in recent years, it has become more upscale.

Due to individualization and fashion orientation, the outer surface of the disc part,
In other words, items with plating, decoration, painting, etc. applied to the design surface,
Alternatively, there are those made of thin stainless steel plates glued together. Furthermore, even when such stainless steel thin plates are used, there is an increasing demand for various shapes, patterns, etc. to be expressed not only two-dimensionally but also three-dimensionally.

[Problem to be solved by the invention]

Among the vehicle wheels mentioned above, those made of aluminum alloy, which are relatively widely used, have a problem in that they have low corrosion resistance against antifreeze agents sprayed on road surfaces in winter. That is, the gloss of the two wheels is lost due to the sodium chloride and/or calcium chloride contained in the antifreeze agent.

This will end up ruining your fashion sense. Also, just plating, painting, etc. on the design surface gives it a luxurious feel.

There is a problem in that the sense of profoundness, solemnity, etc. is still unsatisfactory. On the other hand, even with the method of bonding a thin stainless steel plate to the design surface mentioned above, it is difficult to express a three-dimensional design and the degree of freedom regarding the shape etc. is extremely low, making it impossible to meet the diversifying needs of recent years. There is a problem.

On the other hand, in order to improve the corrosion resistance of the wheel, it is also conceivable to cast the wheel using stainless steel having a two-phase structure in which a ferrite phase and an austenite phase coexist. Stainless steel cast steel is widely used as a structural material, and JIS 5C3II (JIS 5C3II) is a typical steel type.
0, IC-25CIC-25Cr6Ni-2. In addition, those with Cu added to improve strength (see JP-A-53-113215), those with Cu and N added (see JP-A-54-121223)
, and those with Nb added to improve corrosion resistance (
In stainless steel cast steel, the carbon content is specified to be 0.1% by weight or less in order to ensure particularly excellent corrosion resistance.

However, it is extremely difficult to cast vehicle wheels using cast stainless steel as described above, and there is a problem that it cannot be solved simply by changing the casting material from aluminum alloy to stainless cast steel. In other words, in recent years, there has been an extremely strict demand for vehicle wheels to be thin and lightweight, and the thickness of the component parts has been reduced to an almost limitless level. Therefore, it is usually extremely difficult to cast a casting with a wall thickness of 2 to 3 mm using stainless steel with a carbon content of less than 0.11% by weight, as there is a problem with the flowability of the metal throughout the thin wall. be. In addition, stainless steel cast steel has a carbon content of 0.1% by weight.
In order to cast in
There is also the problem that manufacturing costs are extremely high.

It is an object of the present invention to solve the problems existing in the above-mentioned prior art, and to provide a vehicle wheel that has high corrosion resistance, has a luxurious feel, and has an extremely high degree of freedom in terms of the shape of the design surface, etc. It is.

[Means to solve the problem]

In order to achieve the above object, one aspect of the present invention is as follows.

A vehicle wheel in which a rim part formed in a hollow cylindrical shape made of a malleable material is fixed to the outer periphery of a disc part integrally formed in a disc shape made of a cast material. Each is made of stainless steel. A technical method was adopted.

In the present invention, stainless steel cast steel is used as a chemical component in weight ratio.

C: 0.1-0.3% Si: 1.5% or less.

Mn: 1.5% or less.

P: 0.04% or less.

S: 0.04% or less Ni: 3. O~13,0%.

It is desirable to have a two-phase structure containing Cr: 20.0 to 30.0%, the balance consisting of iron and inevitable impurities, and the amount of ferrite in the matrix structure being 40 to 90%.

Further, the stainless steel cast steel may be subjected to solution heat treatment in which the stainless steel is held at 1000 to 1150° C. for a certain period of time and then rapidly cooled.

Furthermore, M is added as a chemical component to the stainless steel cast steel at a weight ratio of 1.
O 3.0% or less, Nb 1.0% or less, or Cu
Any of 3.0% or less can be contained.

In addition, the above stainless steel cast steel has M as a chemical component at a weight ratio of 9.
O3.0% or less and Nb1.0% or less, or these can contain Cu3.0% or less.

Next, the chemical composition of cast stainless steel and the reason for limiting the amount of ferrite will be described. In addition, all contents are weight %.

C (Carbon'): 0.1-0.3% Carbon is the element that has the greatest effect on castability.

0.1% or more is required to obtain good castability.

However, if it exceeds 0.3%, Cr carbides will precipitate, reducing corrosion resistance and mechanical properties, increasing hardness, and worsening machinability.

Si (Silicon) 7 1.5% or less Silicon is effective in deoxidizing molten metal and improving castability, but as the content increases, toughness decreases, so it should be kept at 1.5% or less.

Mn (manganese): 1.5% or less Manganese, like silicon, is effective as a deoxidizing agent for molten metal and improves the flowability during casting. However, since a large amount of content lowers corrosion resistance, the content is limited to 1.5% or less.

P (phosphorus): 0.04% or less If phosphorus is contained in an amount exceeding 0.04%, it acts as an impurity and reduces corrosion resistance, so the content should be 0.04% or less.

S (sulfur): 0.04% or less Sulfur is MnS
Although improvement in machinability can be expected due to crystallization, since it acts as an impurity and reduces corrosion resistance, the content is limited to 0.04% or less.

Nickel in Ni): 3.0 to 13.0% Nickel is an austenite forming element and improves toughness and corrosion resistance. In order to ensure an austenite ratio of 10% or more in the two-phase structure, at least 3.0% or more is required. In addition, in order to control the austenite percentage to 60% or less, it is necessary to set it to 13% or less.

Cr (Chromium): 20.0-30.0% Chromium is an essential element to obtain high corrosion resistance and high strength. Although it depends on the relationship with the amount of nickel, if it is less than 20.0%, it becomes a mixed structure of martensite, ferrite, and austenite, which significantly deteriorates the corrosion resistance and also reduces the mechanical toughness. Corrosion resistance improves as the amount of chromium increases, but when it exceeds 30.0%, toughness decreases due to precipitation of sigma phase and further hardness increases, resulting in deterioration of machinability.

Mo (molybdenum): 3.0% or less Molybdenum further improves corrosion resistance when used in combination with chromium. Molybdenum is also a ferrite-forming element, and if it is contained in a large amount, the amount of nickel used will increase in order to maintain the amount of ferrite within the specified range, resulting in higher costs. Furthermore, molybdenum is also an expensive metal, so the upper limit was set at 3.0% from the economic point of view.

Niobium in Nb): 1.0% or less Niobium also improves corrosion resistance when used in combination with chromium. If it exceeds 1.0%, niobium carbide will precipitate and the toughness will drop sharply. Therefore, the upper limit was set at 1.0%.

Cu (copper'): 3.0% or less Copper improves corrosion resistance and strength, but if it exceeds 3.0%, toughness decreases, so the upper limit was set at 3.0%.

Ferrite amount: 40-90% chromium, nickel, silicon, manganese, molybdenum,
Since the amount of ferrite is determined by the content of all of niobium, carbon, and copper, it is necessary that the components be within the above-mentioned ranges. In a rotating bending test of a wheel, if the yield strength is less than 40 kg/■2, cracking will occur.

For this purpose, a ferrite content of 40% or more is required.

On the other hand, elongation of 10% or more is required to prevent cracking in an impact test, and for this purpose, the amount of ferrite must be set to 90% or less.

In the present invention, as means for fixing the disk portion and the rim portion, means such as t@ contact, adhesion, rivets, caulking, etc. can be applied.

[Example] The figure is a longitudinal sectional view showing an example of the present invention. In the figure, reference numeral 1 denotes a disk portion, which is formed into a disk shape from cast stainless steel having chemical compositions as will be described later. An axle hole 2 and a plurality of mounting holes 3 are bored in the center of the disk portion 1.

A design surface 4 is provided on the outer surface of the disk portion 1, and 5 has various shapes and/or patterns (not shown) formed thereon. Next, 5 is a rim part made of extensible material 1 such as stainless steel (
A plate material made of SUS304) is formed into a hollow cylindrical shape by roll forming. The disk portion 1 and the rim portion 5 are integrated by welding to form a wheel.

Next, in order to evaluate various characteristics of the wheel, test materials having the chemical components shown in Table 1 were cast as materials for forming the disk portion 1. First, inventive materials 1 to 6 and comparative material 1
Nos. 01 to 103 are used to compare the differences between the different chromium and nickel contents. Next, present invention materials 7 to 10 and comparative materials 104 to 105 are used to compare the effects of carbon, and the chemical components other than carbon are kept substantially constant. Furthermore, present invention materials 11 to 15 and comparative material 10
Nos. 6 to 107 are used for comparison based on the differences in content of molybdenum, niobium, and copper.

In addition, when casting each sample material, a 50 kg high frequency induction furnace was used to melt the material in the atmosphere.
℃, and poured into a sand mold at about 1600°C to cast the disk part 1 shown in Fig. 1. Castability is judged by the presence or absence of rounding, which is a casting defect.

Next, the above-mentioned cast product was held at 1050° C. for 1 hour and then water-cooled to perform a solid solution treatment, and two types of disc part 1 materials, an as-cast product and a heat-treated product, were processed and finished. The rim portion 5 was formed by roll forming a plate material of 5US304 and welded to the disk portion 1 to produce a wheel.

The wheels manufactured as described above were subjected to various evaluation tests as described below.

First, a corrosion test was performed on each of the above wheels at 5% at 35°C.
The process consisted of 40 cycles of spraying an aqueous sodium chloride solution for 4 hours, followed by drying at 60° C. for 2 hours, and then holding at 50° C. for 2 hours in an atmosphere with a humidity of 95% or higher. After the test was completed, the presence or absence of rust on the disk portion 1 was observed.

Next, stress corrosion tests were conducted on each of the above wheels at 5% of room temperature.
The test was conducted after being immersed in a sodium chloride aqueous solution for 1000 hours, and the presence or absence of cracks in the disk portion 1 after the test was observed.

Furthermore, as a strength test, 205 kg・m was applied to disk part 1.
A moment of 35 Or, p, m is applied to the wheel.

A rotational bending durability test in which the weight is rotated at
A total of 3 types of drum durability tests were conducted, in which a load of 1 kg was applied from the tire and the drum was rotated at 80 b/h per hour.The passing criteria were 200,000 cycles or more for the rotational bending durability test, no cracking for the impact test, and no cracking for the drum durability test. In this case, the distance was set at 1,800 km or more.

The above results are summarized in Table 2.

(The following is a blank space) As is clear from Table 2, the occurrence of rust in the corrosion test and the occurrence of cracks in the impact test were observed in the comparative material 10'l. This is considered to be because, as shown in Table 1, the low Cr content results in a mixed structure of martensite, ferrite, and austenite, resulting in a significant deterioration of corrosion resistance and toughness. Next, since comparative materials 102105 and 106.107 have no elongation, cracking was observed in the impact test. Furthermore, since the comparative material 104 had a low carbon content, a rounding defect, which is a casting defect, occurred. Furthermore, since Comparative Material 103 had a low yield strength, cracking was observed in the one-rotation bending durability test. On the other hand, in Inventive material 1-15, no rounding defects were observed at all, indicating that the castability was extremely good. In this case, not only is there no need to use expensive materials as in conventional stainless steel casting, but there is also the possibility of reducing wall thickness and weight. In addition, no rust was observed in corrosion tests, indicating extremely high corrosion resistance, and when used as a wheel,
Even when driving on roads sprayed with anti-freeze, the design can maintain a calming gloss. Furthermore, no single crack was observed in stress corrosion tests and various strength tests. Therefore, a high-strength vehicle wheel with excellent mechanical properties can be obtained.

In this embodiment, an example of a wheel for a two-passenger car has been described, but the present invention is not limited thereto, and can of course be applied to wheels for a vehicle such as a salon bus, a large trunk for private business use, or the like.

〔Effect of the invention〕

Since the present invention has the configuration and operation described above, it can achieve the following effects.

(1) Since the disc part is cast from stainless steel, corrosion resistance and strength can be greatly improved, and complex shapes can also be cast, greatly increasing the degree of freedom in the design surface shape and pattern. It can be improved.

(2) The structure of the design surface is not limited to the two-dimensional structure of conventional stainless steel thin plates, but can also be made into a three-dimensional design with uneven parts, giving a sense of luxury, solidity, solemnity, etc. As a result, it is possible to fully meet the diverse needs of recent years.

(3) Since a particularly expensive raw material for stainless steel f steel is not required and a material with good castability can be obtained, weight reduction and cost reduction of the disk portion can be expected.

(4) Since it has excellent corrosion resistance, it is possible to maintain a calm luster including the design surface, and it is possible to ensure a luxurious feel.

[Brief explanation of drawings]

The figure is a longitudinal sectional view showing an embodiment of the present invention. 1: Disc part, 5: Rim part.

Claims (7)

[Claims] (1) In a vehicle wheel in which a rim part formed in a hollow cylinder shape made of a malleable material is fixed to the outer periphery of a disc part integrally formed in a disc shape made of a cast material, the disc part is made of cast stainless steel; A vehicle wheel characterized in that each rim portion is formed of stainless steel. (2) Stainless steel cast steel has a chemical composition of C by weight ratio.
: 0.1 to 0.3%, Si: 1.5% or less, Mn: 1.5% or less, P: 0.04% or less, S: 0.04% or less, Ni: 3.0 to 13. 0%, Cr: 20.0-30.0%, the remainder consists of iron and unavoidable impurities, and the amount of ferrite in the base structure is 40-90%. ) Wheels for vehicles listed. (3) The vehicle wheel according to claim (1) or (2), wherein the cast stainless steel has been subjected to solution heat treatment in which the cast stainless steel is held at 1000 to 1150°C for a certain period of time and then rapidly cooled. (4) The vehicle wheel according to any one of claims (1) to (3), wherein the stainless steel cast steel contains 3.0% by weight or less of Mo as a chemical component. (5) The vehicle wheel according to any one of claims (1) to (4), wherein the stainless cast steel contains 1.0% by weight or less of Nb as a chemical component. (6) The vehicle wheel according to any one of claims (1) to (3), wherein the stainless cast steel contains 3.0% by weight or less of Cu as a chemical component. (7) Stainless steel cast steel has Nb1 as a chemical component by weight
．． The vehicle wheel according to any one of claims (1) to (3), containing 0% or less, Mo 3.0% or less, and Cu 3.0% or less.