JPS62177310A - Manufacture of crank shaft - Google Patents

Abstract

PURPOSE:To obtain selective assembling among arms and pins and to enhance the quality in manufacturing crank shafts of various kinds and sizes, by fitting a crank pin into a hole, which is provided in advance in a crank arm, and welding the fitted part before assembling. CONSTITUTION:A crank arm 1 and a crank pin 3 are manufactured separately. To manufacture a crank shaft, the pin 3 is inserted into a hole, which is provided to the crank arm 1 in advance at the position for the pin 3 first, and then the joined part is welded into one body. An alternative method is not provide a circular arc part, which is concentric with the crank pin 3, to the position for the pin for installation of the crank pin 3 and the to weld the joined part. In addition, the shape of the crank pin 3 is formed in such a manner that different-diameter-parts are provided at both ends of the pin 3 and that the diameter 'a' of the welded part is larger than that 'b' of the working part. With this contrivance, since the welded part is situated at a position apart from the surface of the crank pin working part, the surface of the working part is not affected by the welding. In addition, the welded length is lengthened, thereby lowering the stress per unit length.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing crankshafts for use in marine and other engine parts.

[Background Art] In recent years, ships have become increasingly specialized for various purposes, and the shapes and sizes of crankshafts installed therein have also become more diverse. On the other hand, with the advent of low-speed rotation to increase propeller efficiency in order to save energy, and with the advent of fuel-efficient diesel engines, there is a need to reduce the weight of the crankshaft. Conventional crankshafts are either fully integrated, in which the crank arm and crank pin are manufactured as one unit, or semi-assembled, in which the journal and crank arm are shrink-fitted. Therefore, due to the complexity of the shape, much time was required for forging and mechanical cutting. Moreover, since the wall thicknesses of the crank arm and crank pin are different, in order to maintain sufficient and the same strength for each, we used high-carbon steel with high hardenability, high-carbon Ni-Cr steel, or Cr-M steel. O steel is often used, which, together with the complexity of the shape, makes the heat treatment complicated and takes a long time. For these reasons, it has been difficult to respond to the aforementioned market demands.

[Problems to be Solved by the Invention] As described above, the present invention can cope with diversification of shapes and sizes, is easy to perform hot processing such as forging and rolling, machine cutting, and heat treatment, and is furthermore flexible in terms of material quality. The objective is to manufacture a lightweight crankshaft with excellent hardness and little excess thickness.

[Means for solving the problem] As a countermeasure to this problem, the present invention manufactures the crank arm and the crank pin separately, and inserts a hole pre-drilled at the position of the pin in the crank arm as shown in FIG. 1(A). After inserting and fitting the crank pin, the fitting part can be integrated by melt welding, or as shown in Fig. 1(B), A groove in the shape of a part of a circular arc is pre-processed, the crank pin is fitted into the groove, and the fitting part is then fused and welded to integrate the crankshaft. Furthermore, this is a method of manufacturing a crankshaft using the above-described method, using crank pins having concentric shapes of different diameters as shown in FIGS. 1(C) and 1(D).

[Function] The production method according to the present invention is based on the above idea,
The crank arm and crank pin, which were conventionally integrated, are manufactured separately and then combined to form a single unit, thereby obtaining various advantages.

That is, in the manufacturing method constituting the present invention, the crank arm and crank pin are first manufactured by separately performing hot working such as forging and rolling, and machining. The steel type, heat treatment method, and
All you have to do is select the conditions, etc., and you can use one with the same chemical composition or one with a different composition hot-formed by forging or rolling, but after fitting the crank pin into the hole in the crank arm. In order to perform fusion welding of the fitting portion, welding characteristics 1 such as weld cracking resistance and mechanical properties of the welded portion are combined. Hot forming methods such as forging and rolling of crank arms and crank pins, and machining methods are as follows:
Although not particularly limited, means are selected that are free of internal and surface defects in the steel.

Regarding the shape of the crank pin, Fig. 1 (A) and (B) shows a simple cylindrical type, and Fig. 1 (C) and (D) shows a stepped cylindrical type with concentric different diameter parts. did.

In the case of a crank pin with concentric different diameter parts, please refer to Figure 1 (C
), the diameter a of the welded part of the fitting is larger than the diameter a of the working part of the crankpin, and the welded part is located away from the surface of the working part of the crankpin. There is an advantage that the surface is not affected by welding, and the length of the fitting weld line becomes longer, so the applied stress per unit length of the weld line becomes smaller. Furthermore, forming the welded portion into a circular arc or a portion thereof has the advantage that processing of the crank pin is easy. The crank pin is fitted into a hole or groove of the crank arm by cold fitting or shrink fitting, and the fitting portion is fused and welded. Types of fusion welding include, for example, welding that uses high energy density such as electron beam welding and laser welding, as well as welding that uses a bevel in the mating part, such as TIG welding, M
Any welding method can be used as long as it can produce a defect-free weld, such as gas-shielded arc welding such as IG welding and CO2 welding, submerged arc welding, and coated metal arc welding, and is not particularly limited. Further, depending on the thickness of the crank arm, it is also preferable to perform, for example, a combination of electron beam welding and other fusion welding methods. When welding, we carefully consider factors related to the strength and soundness of the welded part, such as the material of the crank arm and crank pin, the chemical composition, and the thickness difference in the longitudinal direction of the crank arm, and select appropriate welding materials and welding conditions (preheating conditions, post-heating conditions, etc.). (including thermal conditions).

After welding, heat treatment such as stress relief annealing, hardening, standard tempering, quenching and tempering is performed as necessary.

Although not particularly specified in the present invention, the method of the present invention can also be applied to joining a crank arm and a journal.

In other words, it is also preferable to weld the fitting diameter of the fitting portion of the groove and the journal, which are pre-drilled or machined into a concentric arc shape with the journal.

[Example] Next, an example of manufacturing a crank according to the present invention will be given.
This will be explained in more detail.

Table 1 shows an example of the production of an actual model of a welded part that partially reproduces an actual crankshaft in accordance with the present invention. In the table, Example No.

For No. 2, existing standard materials KSF55 and KSF60 were welded together, and for No. 3, a low carbon quenched and tempered material was used for the crank arm in order to improve weldability.

The welding method used was a combination of electron beam welding and narrow gap MIG welding for Nol and No. 3, as the welded part thickness was large, 300 mm and 24 Onin, respectively, but for N'o2, the welded part thickness was relatively small, 200 mm. , using only the electron beam welding method. The shape of the crank pin used was one having concentric different diameter portions as shown in FIG. 1(C).

Welding was performed using a combination of preheating and postheating, and after welding was completed, the surface of the welded area was cleaned, and post-weld heat treatment (pwHT) was performed.

Welded joints were sampled from the crankshafts manufactured using the method shown in Table 1 and subjected to non-destructive testing. After confirming that there were no defects such as cracks or pin holes in Table 1, Table 2, various welded test pieces were taken. Samples are inspected for strength, toughness, fatigue strength, etc.
Shown in the table. As shown in Table 2, the tensile strength and WIyWl value of the butt weld were both equal to or better than the base metal, and each had KSF55. KSF60
As such, it was judged to be of sufficient value and worth the use.

[Effects of the Invention] As described above, the present invention is characterized in that, in manufacturing a crankshaft, a crank pin is fitted into a pre-drilled hole or groove of a crank arm, and then the fitting part is fused and welded. With the manufacturing method of crankshafts, it is possible to easily manufacture crankshafts of various types and sizes with excellent quality by selecting combinations of crank arms and crank pins, and it is easy to forge, machine cut, and heat treat, and is industrially The above effect is significant.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a fitting part between a crank arm part and a crank pin part of the present invention, (A) is a diagram showing the crank pin being inserted and fitted into the hole of the crank arm, and (B) is a diagram showing the fitting part of the crank pin concentric with the crank pin. (C) is a diagram in which a cylindrical crank pin with a concentrically different diameter portion is fitted into a hole in a crank arm; (D) is a diagram in which a crank pin is fitted into a groove having a part of a circular arc shape; It is a figure which fits the cylindrical crank pin which has a diameter part into the groove part of a crank arm. 1: Crank arm 2: Simple cylindrical crank pin

Claims (3)

[Claims] (1) A method for manufacturing a crankshaft, which comprises inserting and fitting a crank pin into a pre-drilled hole in a crank arm, and then assembling the fitted portion by fusion welding. (2) It has the shape of a part of an arc concentric with the crank pin,
A method for manufacturing a crankshaft, characterized in that the crankshaft is assembled by fitting a crankpin into a groove of a crank arm that has been pre-processed so as to fit the crankpin therein, and then melt-welding the fitting portion. (3) The method for manufacturing a crankshaft according to claim 1 or 2, wherein the crank pin is a crank pin having a concentrically different diameter portion.