JPH09182932A - Production of connecting rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an integrally formed connecting rod, which is easy for breaking/splitting a large end part by taking a forging stock from a rolled material so that metal flow of the integrally formed connecting rod is directed to the direction along a breaking face. SOLUTION: A billet 1 is rolled in the longitudinal direction to a long size platy rolled stock 2. The rolled stock 2 is cut into strips in the direction orthogonal to the longitudinal direction, a strip like rolled stock 3 obtained by cutting to strip has metal flow directed to the plate width direction. The strip like rolled material 3, while coinciding its longitudinal direction to the rod longitudinal direction, is subjected to hot forging in the plate width direction. A bur 4 is removed after forging, an integrally formed connecting rod 5 is obtained. The integrally formed connecting rod obtained has metal flow directing to the traverse width direction over whole length. By this method, a part to be split of both sides of a large end part has metal flow parallel to the face to be split, breaking and splitting are easily executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a split split connecting rod, and more particularly to a method for manufacturing a connecting rod integrally molded product before split splitting.

[0002]

2. Description of the Related Art A connecting rod, which is one of the main parts of an automobile engine, is divided into a rod end and a cap end at a large end for connection with a Clark shaft. The components were conventionally manufactured in separate steps. However, reflecting the recent severe economic situation, the two are integrally molded, the large end of the molded product is broken and split into the rod side and the cap side, and the split split surface is combined without machining the split split surface. Type connecting rods are being developed.

In the split split type connecting rod, it is necessary that the material forming the connecting rod-integrally molded product is excellent in the breaking property. From this viewpoint, a sintered product or a sintered forged product that is forged after sintering is generally used as the integrally formed product of the connecting rod.

[0004]

However, the mechanical properties of the sintered product and the sintered forged product are essentially inferior to those of the rolling forged product manufactured through melting, rolling and forging. Nevertheless, sinters and sinter forgings are used because the excellent mechanical properties of rolling forgings make fracture splitting of the large end difficult.

In view of such a situation, the present applicant has recently used a connecting rod integrally molded article having high strength and excellent breakability.
A low ductility non-heat treated steel was developed and a patent application was filed in Japanese Patent Laid-Open Nos. 7-153030 and 7-185598. However, with other steels, it is still difficult to achieve fracture splitting with a flat fracture surface, which means that despite the excellent mechanical properties of the rolling forged product, its application to fracture splitting type connecting rods is difficult. It is the biggest cause of delay.

It is an object of the present invention to provide a connecting rod manufacturing method for manufacturing a connecting rod integrally molded product which is a roll-forged product having excellent mechanical properties and which is excellent in breakability at the large end.

[0007]

[Means for Solving the Problems] In a rolling forged product, a metal flow occurs along with the rolling. When a connecting rod integrally molded product is manufactured by a rolling forging method, conventionally, a process as shown in FIG. 1 has been considered in accordance with the manufacturing of a normal connecting rod. In other words, the rolled rod 8 is forged in the diametrical direction with the longitudinal direction of the rolled rod 8 aligned with the longitudinal direction of the connecting rod to form the connecting rod integrally molded product 10. Reference numeral 11 is a burr generated around the integrally formed connecting rod product 10.

At this time, the metal flow of the rolled rod 8 is oriented in its longitudinal direction. Therefore, the connecting rod-integrated molded product 10 has a metal flow oriented in the rod longitudinal direction. As a result, in the part to be divided at the large end of the conrod-integrated molded product 10, the metal flow is orthogonal to the face to be divided.

The inventors of the present invention have considered that one of the causes of difficulty in fracture splitting of a rolling forged product is the right-angled intersection of the metal flows on the planned split plane, and variously changed the material sampling method from the rolled material. Then, the magnitude of the influence of the direction of the metal flow on the fracture property of the large end was investigated. As a result, if the direction of the metal flow in the part to be split at the large end is along the part to be split, the large end can be easily formed even if the well-known high strength / ductile tempered steel for connecting rod is used. It was found that the material was fracture-divided and a flat division surface was obtained.

The connecting rod manufacturing method of the present invention was developed on the basis of such findings, and in manufacturing a connecting rod integrally molded product on the premise that the large end portion is fractured and divided into the rod side and the cap side, the connecting rod is manufactured. It is characterized in that the metal material in at least a portion corresponding to the split portion of the integrally molded product is forged into a connecting rod in a direction along the split surface.

In the connecting rod manufacturing method of the present invention, the material of the rolled material does not matter. When the high-strength, low-ductility non-heat treated steel developed by the applicant is used, the fracture division of the large end portion becomes easier. 0.48C-0.3Si-0.9Mn-0.2Cr
When a known high-strength / high-ductility heat-treated steel for connecting rods such as -0.15 Pb is used, fracture splitting at the large end is possible. It is also possible to use a non-ferrous metal such as an aluminum alloy or a titanium alloy.

The direction of the metal flow in the portion corresponding to the dividing portion is preferably parallel to the dividing surface from the viewpoint of facilitating fracture division, but is inclined at an angle of 30 ° or less with respect to the dividing surface. However, there is no problem in practical use. In the fractured split connecting rod that is the subject of the present invention, the joining is performed again on the split surfaces, so this inclination does not affect the joining accuracy.

The direction of the metal flow with respect to both surfaces of the connecting rod-integrally molded product does not matter at all. In the embodiments described below, the case is shown in which the direction is parallel to or perpendicular to both surfaces of the molded product, but there is no problem even if it is inclined with respect to both surfaces.

Such direction control of the metal flow is performed by material sampling, preliminary forging, and the like. These will be described in detail in the embodiments described later. It goes without saying that the method of dividing the large end portion of the manufactured connecting rod-integrated molded product may be of any type.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing a manufacturing process of a connecting rod-integrally molded product as an example of the method of the present invention.

In this method, the billet 1 is rolled in the longitudinal direction to form a long plate-shaped rolled material 2. The rolled material 2 is subdivided in a direction perpendicular to the longitudinal direction. The strip-shaped rolled material 3 obtained by the subdivision has a metal flow oriented in the plate width direction. The strip-shaped rolled material 3 is hot forged in the plate thickness direction with its longitudinal direction aligned with the rod longitudinal direction. After forging, the burr 4 is removed to obtain a connecting rod integrated molded product 5.

The connecting rod-integrated molded product 5 thus obtained has a metal flow directed in the lateral width direction over the entire length of the rod. Therefore, at the planned dividing portions on both sides of the large end, the metal flow becomes parallel to the dividing surface, and the fracture division is easily performed.

Using the two types of steel shown in Table 1, a connecting rod-integrally molded product was produced by this method. Steel A is a high-strength, low-ductility non-heat treated steel developed by the present applicant, and steel B is a high-strength, high-ductility tempered steel known as ordinary steel for connecting rods.

[0019]

[Table 1]

The billet has a width of 160 mm and a thickness of 160 mm.
It is. This is rolled to a width of 270 mm and a thickness of 20 mm,
Further, the rolled material was cut in the longitudinal direction by 50 mm each to obtain a strip-shaped rolled material having a length of 270 mm, a width of 50 mm and a thickness of 20 mm. The obtained rolled material was hot forged into a connecting rod integrally molded product.

For comparison, the outer diameter is 34 mm and the length is 270.
A conrod-integrated molded product was manufactured by hot forging from a rolled round bar material of mm.

The large end of each manufactured connecting rod-integral molded product was fractured and divided into a rod side and a cap side by using a dividing jig 6 shown in FIG. That is, the split pieces 6a, 6a having a semicircular cross section of the splitting jig 6 are inserted into the large end portion of the integrally formed connecting rod product, and the weight is dropped onto the wedge 7 inserted between the split pieces 6a, 6a. The large end was split into a rod side and a cap side.

The minimum energy required for fracture in each division was investigated. Also, the inner diameter of the large end portion when both members are fastened after division is measured in the rod longitudinal direction and the rod width direction, and the inner diameter accuracy after division is calculated as (longitudinal direction diameter-
It was evaluated by (width direction diameter). Table 2 shows the survey results.

[0024]

[Table 2]

In the case of the steel A developed by the present applicant, the implementation of the method makes the division easier and improves the flatness of the division surface. In the case of steel B, the comparative method has a large breaking energy and a dividing surface that can withstand practical use cannot be obtained. However, the practice of this method facilitates breaking and a dividing surface that can withstand practical use is obtained.

FIG. 4 is a schematic view showing a manufacturing process of a connecting rod-integrally molded product according to another example of the method of the present invention.

According to this method, when the rolled rod 8 having a circular cross section is hot forged in the diametrical direction to form the connecting rod integrated molded product 10, the rolled rod 8 is placed at the divided position of the large end of the connecting rod integrated molded product 5. Hot forging is performed so that the corresponding part is bent into a Z shape.

In the obtained pre-forged product 9, the metal flow is in the forging direction at the portion corresponding to the divided portion. Then, if the preliminary forged product 9 is forged into a connecting rod shape, a connecting rod-integrated molded product 10 in which the metal flow in the part to be divided at the large end is oriented in the thickness direction of the connecting rod is obtained. Also with such a connecting rod-integrally-molded product, it is easy to break and divide the large end portion.

Although this method has more molding steps than the above-mentioned method, since the metal flow in the portions other than the divided portions can be directed in the rod longitudinal direction, it is easy to secure the strength in the rod longitudinal direction. .

Also in this method, the same comparative test as in the case of the above-mentioned method was conducted. The rolled bar has the same outer diameter 34 as the comparative method.
mm, and the length of 270 mm was used. Table 3 shows the test results
As described above, this method also facilitates fracture division of the rolling forged product in the same manner as the above method.

[0031]

[Table 3]

[0032]

As described above, according to the connecting rod manufacturing method of the present invention, by controlling the direction of the metal flow in the part to be divided, the rolling forging method having excellent mechanical properties is used, It is possible to manufacture a conrod-integrated molded product in which breakage division of a part is easy. Therefore,
This makes it possible to manufacture high-quality split split connecting rods that cannot be obtained with sintered products or sintered forged products.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a manufacturing process of a connecting rod integrally molded product in a conventional method.

FIG. 2 is a schematic diagram showing a manufacturing process of a connecting rod-integrally molded product for one example of the method of the present invention.

FIG. 3 is a perspective view of a division jig used for a comparative test.

FIG. 4 is a schematic view showing a manufacturing process of a connecting rod-integrally molded product according to another example of the method of the present invention.

[Explanation of symbols]

 1 Billet 2,3 Rolled material 5,10 Connecting rod integrally molded product 8 Rolled bar material 9 Pre-forged product

Claims (1)

[Claims] 1. When manufacturing a connecting rod integrally molded product on the premise that the large end portion is fractured and divided into a rod side and a cap side, a metal flow is divided at least at a portion corresponding to the dividing portion of the connecting rod integrated molded product. A method for manufacturing a connecting rod, comprising forging a rolled material in a direction along a surface into a connecting rod.