JPH0714538B2 - Method for setting specific roll diameter of rolling roll in manufacturing taper rod - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention sets a specific roll diameter of a rolling roll in manufacturing a coil spring material having a non-linear characteristic or a taper rod used for a connecting rod or the like by rolling. Regarding the method.

(Prior Art) As a method of manufacturing a taper rod by rolling, there is one disclosed in Japanese Patent Laid-Open No. 57-91384.

As shown in FIG. 1, the bar material 1 is first rolled into a flat cross section by a pair of rolling rolls 2 in a first pass, and then the bar material 1 is rolled into a pair in a second pass. As shown in FIG. 2, by the rolling rolls 3, a diameter-reducing taper portion 4 having a diameter that decreases from the front to the rear in the rolling direction and an diameter-increasing taper portion 5 that has a diameter that increases from the front to the rear in the rolling direction. It is rolled into a tapered rod having
Therefore, as shown in FIG. 3, the second pass rolling roll 3 is provided with a hole die 6 whose diameter gradually changes in the circumferential direction.

(Problems to be Solved by the Invention) In the above-described two-pass rolling, if the aspect ratio of the bar cross section after passing the first pass becomes large and the degree of flatness of the cross section becomes too large, the material collapses. As a result, rolling on the second pass becomes impossible. The aspect ratio of the bar cross section after passing the first pass is determined by the gap between the pair of first pass rolling rolls, the specific roll diameter that is the ratio of the diameter of the first pass rolling roll and the bar diameter before rolling, and the like. It has been known.

Therefore, in order to reduce the aspect ratio of the cross section of the bar after passing the first pass, it is conceivable to increase the gap between the pair of first pass rolling rolls. However, when manufacturing a taper rod with a large difference between the maximum diameter and the minimum diameter, it is necessary to increase the area reduction ratio of the material cross section. It is necessary to properly fill the hole shape of the pass rolling roll with the material.

Therefore, it is conceivable to prevent the material collapse due to the increase of the aspect ratio by changing the specific roll diameter.

However, there is no conventional method for specifically setting such a specific roll diameter, and it is the current situation that the experiment must be repeated to obtain the specific roll diameter by trial and error. Such trial-and-error setting is extremely inefficient in manufacturing tapered rods of various diameters.

It is an object of the present invention to solve the above problems that occur when rolling a taper rod having a high surface reduction rate.

(Means for Solving the Problem) The present invention is characterized by solving the problems of the prior art in that a bar 1 is rolled into a flat cross section by a pair of rolling rolls 2 in a first pass. Then, when the bar material 1 is roll-formed by the pair of rolling rolls 3 in the second pass into a taper rod 10 having a taper portion 4 whose diameter decreases from the front to the rear in the rolling direction, the bar before rolling The material diameter is d ₀ , the minimum diameter of the taper rod after rolling is d ₁ , and the area reduction ratio is The diameter of the first pass rolling roll 2 is D _R , and the specific roll diameter is When rolling with R ≧ 0.5, the specific roll diameter is (E is the base of natural logarithm).

(Operation) The aspect ratio of the bar cross section after passing the first pass is the area reduction ratio R
It is qualitatively recognized that the specific roll diameter δ increases as the value of γ increases and the specific roll diameter δ increases.

Therefore, in order to make the aspect ratio of the cross section of the bar material after passing the first pass smaller than the maximum value that can be rolled, it is necessary to reduce the specific roll diameter δ in accordance with the surface reduction rate R.

The present invention is based on the finding that the area reduction ratio R and the specific roll diameter δ have a certain correlation with respect to the predetermined aspect ratio.

That is, if the aspect ratio of the cross section of the bar after passing the first pass is 4 or less, the bar is properly guided to the hole shape of the second pass rolling roll and can be rolled without causing material collapse. It was confirmed by the experiment.

When the surface reduction rate R was less than 50%, the aspect ratio never exceeded 4 in the practical range of the specific roll diameter. If the reduction rate R is 50% or more, In the range of, the aspect ratio never exceeded 4.

(Example) Hereinafter, the Example of this invention is described based on drawing.

As the first-pass rolling roll 2, a roll having an oval hole shape is used, and as shown in FIG. 4, a bar 1 having a diameter d ₀ before rolling is used.
Is rolled into an oval cross-sectional shape with an aspect ratio (B / H). A flat roll may be used as the first pass rolling roll, and the hole shape is not limited.

The second pass rolling roll 3 roll-forms the bar material 1 that has passed through the first pass into a taper rod 10 as shown in the second illustration above, and the minimum diameter of the taper rod 10 is as shown in the fifth illustration.
Let d ₁ .

In this example, the bar diameter before rolling was d ₀ = 14 mm, the first pass rolling roll diameter D _R was φ50 mm (δ = D _R / d ₀ = 3.6), φ80
mm (δ = D _R / d ₀ = 5.7), φ100 mm (δ = D _R / d ₀ = 7.1),
The one having a diameter of 240 mm (δ = D _R / d ₀ = 17.1) was used. Also, the reduction rate When δ = 3.6, the surface area is reduced to 40%, 50%, and 60% respectively. When δ = 5.7, the surface area is reduced to 60%, and when δ = 17.1, the area is 40%.
%, 45%, 50%, 60% respectively. The material of the bar material was SC steel and SUP steel, the rolling temperature was 900 to 1100 ° C, and the rolling speed was 0.5 to 5 m / min.

FIG. 6 shows the relationship between the area reduction ratio R and the aspect ratio (B / H). In the figure, □ is δ = 3.6, ● is δ = 5.7, and △ is δ =
7.1 and ○ indicate the case of δ = 17.1, respectively. Then, if the aspect ratio is 4 or more, rolling could not be performed because the material collapsed when the bar after passing the first pass was guided to the second pass, but if the aspect ratio was 4 or less, It could be rolled without material collapse.

FIG. 7 shows the relationship between lnδ and R when the aspect ratio is 4 or less. Then, the reduction rate of each rolling result is 50.
R = -0.1lnδ + 0.784 even under a high reduction rate of over 0.1%
It can be seen that the distribution is in the region below the value line represented by the equation. Therefore, even when rolling R ≧ 0.5, Then, the bar after passing the first pass can be guided and rolled in the second pass without causing material collapse.

(Effect of the Invention) According to the present invention, when a taper rod having a surface reduction ratio R of 50% or more is manufactured by rolling, the specific roll diameter is By doing so, the bar material after passing the first pass can be guided and rolled in the second pass without causing material collapse, so the specific roll diameter can be set without trial and error. Therefore, it is possible to improve the production efficiency by rolling the high reduction taper rod.

[Brief description of drawings]

The drawings relate to the embodiment of the present invention, FIG. 1 is a perspective view showing a schematic configuration of a rolling facility for a taper rod, FIG. 2 is a perspective view of the taper rod, FIG. 3 is a sectional view of a second-pass rolling roll, and FIG. The figure shows the cross-sectional shape of the bar before and after passing through the first pass.
The figure shows the cross-sectional shape of the bar before and after passing through the second pass. Fig. 6 shows the relationship between the aspect ratio of the bar after passing through the first pass and the taper rod area reduction rate. Fig. 7 shows the specific roll diameter. It is a figure which shows the relationship between a taper rod area reduction rate. 1 ... bar material, 2 ... first-pass rolling roll, 3 ... second-pass rolling roll, 4 ... reduced-diameter taper portion, 10 ... taper rod.

Claims (1)

[Claims] 1. A bar material 1 is rolled into a flat cross section by a pair of rolling rolls 2 in a first pass, and then the bar material 1 is rolled from a front side to a rear side in a rolling direction by a pair of rolling rolls 3 in a second pass. When roll-forming into a taper rod 10 having a taper portion 4 with a reduced diameter, the rod diameter before rolling is d ₀ , the minimum diameter of the taper rod after rolling is d ₁ , and the area reduction ratio is The diameter of the first pass rolling roll 2 is D _R , and the specific roll diameter is When rolling with R ≧ 0.5, the specific roll diameter is (E is a base of natural logarithm). A method for setting a specific roll diameter of a rolling roll in the production of a taper rod, wherein