JP2560771B2 - Lamination method of thin steel sheets - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial field of application) The present invention relates to a method for strengthening the binding force of a thin steel plate laminated product, and is used for a lubricating oil pump rotor for automobiles and the like. .

(Prior Art) Thin steel sheets punched by press working are laminated and used as a mold.

When the press die 1 is formed, as shown in FIG. 5, thin steel plates 1a, 1b, ... Are laminated and pressed from above and below in a vacuum furnace to be joined by diffusion bonding to firmly It is used as a simple mold.

(Problems to be Solved by the Invention) However, the method of pressurizing with a press and heating in a furnace has the following problems in the case of mass production.

The dimensional tolerance of the thickness of thin steel plates with a thickness of 2.0 mm or less is 5
% To 10%, and when the thin steel sheets are stacked and formed, the dimension of the product in the thickness direction greatly varies.

When the product having the variation in the dimension in the thickness direction is pressurized by a single press machine in a normal batch furnace, the state shown in FIG. 6 is obtained.

That is, when the whole is pressed down by the press 3 as shown in (a), the relatively thick product 4a as shown in (b).
There is a risk that the pressing force will become excessive and the cross-sectional shape will be deformed.

For this reason, there is a method of providing a cushioning material between the press and the product, but it is extremely difficult to select a material satisfying the function as a cushioning material in a furnace heated to about 1000 ° C.

As shown in FIG. 7, the products 5a, 5b, ...
There is also a method of using press machines 6a, 6b, ... for each ke, or measuring the laminated thickness of the laminated plate in advance, dividing into several groups according to the product thickness, and performing heat treatment for each group. However, these methods are not suitable for manufacturing products to be mass-produced.

In the case of laminating thin plates, the plate materials are basically independent for each one, and the strength is remarkably reduced as compared with a structure of the same shape integrally formed. Range or inevitably limited.

An object of the present invention is to manufacture a thin steel plate laminated product in which thin steel plates are laminated to increase the bonding force between the plate materials to a large extent.

[Structure of Invention]

(Means for Solving the Problems) Technical means taken to solve the above technical problems are as follows. That is, in a laminating method of forming a half boss with a circular punch / die on a part of a thin steel plate of 2.0 mm or less and stacking the thin steel plates having the half boss, the thin boss is fitted to the thin steel plate. Is a laminated steel sheet forming method for strengthening the bonding force by heating the material in a vacuum furnace to a temperature equal to or higher than the recrystallization temperature of the material and then cooling the material to laminate the material.

(Operation) The technical means functions as follows. That is, there is a relationship of dφ> Dφ where the diameter of the convex portion of the half boss of the thin steel plate is dφ and the diameter of the concave portion is Dφ. Preliminary bonding is achieved by stacking several plate members, but in this case, they are formed. In the product, internal stress exists in the vicinity of the half boss portion (both uneven portions) during the half boss forming step and the laminating step, and residual stress in the direction in which the plate materials are bonded to each other exists in the half boss portion. By simply leaving the product in the vacuum furnace without pressurizing the product due to this internal stress and the new surface generated by the plastic deformation of the half boss part, the interface of the boss part disappears and almost complete bonding can be achieved. The force is drastically improved, and it can be used for pump rotors, gear parts and the like.

(Example) An example is described above.

In FIGS. 1 to 4, 11 is a half boss 12 formed on a part of a thin steel plate of 2.0 mm or less by a round die punch.

The diameter of the convex part of the half boss is dφ, the diameter of the concave part is Dφ, and d> D
Is.

The thin steel plates 11a, 11b, ... Are fitted with the half bosses superposed on each other as shown in FIG.

When molded in the above process, internal stress is generated in the vicinity of the half boss portion as shown in FIG. 4, P ₂ acts outward on the convex portion, and P ₁ acts on the inner portion in the concave portion, that is, the half boss portions are mutually There is residual stress in the direction in which the plate materials are joined.

Next, it is put in the vacuum furnace 13 to heat it to the recrystallization temperature of the thin steel sheet, and then cooled in the furnace. As a result, due to the internal stress and the plastic deformation of the half boss portion, the interface of the boss portion disappears, and the joint is almost completely completed and strong joint is performed.

〔The invention's effect〕

The present invention has the following effects. That is, (1) the bonding strength is dramatically improved as compared with the conventional laminated molded product.

(2) The equipment is much simpler than the conventional diffusion bonding by pressurization that is used in the laminated die molding.

(3) The heat treatment deformation of the cross-sectional shape of the product is small because no pressure is applied.

(4) Since the process is simpler than the conventional diffusion bonding (pressurizing in a furnace), it is easy to implement.

[Brief description of drawings]

Fig. 1 is a cross-sectional view of a semi-bossed thin steel plate, Fig. 2 is a cross-sectional view of a plurality of thin steel plates of Fig. 1 stacked, Fig. 3 is an inside view of a furnace, and Fig. 4 is a half-bossed portion. FIG. 5 is an explanatory view of stress in FIG. 5, FIG. 5 is an explanatory view of a conventional example, FIG. 6 (a) and (b) are explanatory views of a conventional stacking process of a plurality of products, and FIG. 7 is another conventional example. FIG. 11 …… Thin steel plate, 12 …… Half boss, 13 …… Furnace.

Claims (1)

(57) [Claims] 1. A method of forming a half boss on a part of a thin steel plate, and fitting the half boss to stack the thin steel plates, wherein the half bosses are fitted to stack the thin steel plates, and then a vacuum furnace is used. A method for laminating thin steel sheets, which comprises heating the thin steel sheet material to a temperature equal to or higher than the recrystallization temperature of the steel sheet, followed by furnace cooling.