JPH07155807A - Skew rolling method of seamless tube - Google Patents

Abstract

PURPOSE:To prevent the generation of failure of biting, to increase the degree of freedom in the setting of rolling and to improve yield and productivity in piercing. CONSTITUTION:In a skew rolling method of a seamless tube, face angles on the inlet side of rolling rolls 31A, 31B are varied in the pass-line direction, the face angle alpha1 on the inlet side in the region where a material to be rolled begins to contact the rolling rolls 31A, 31B is made relatively smaller and the face angle alpha1 on the inlet side in the region where the material to be rolled is advanced toward the gorge part after that is made relatively larger.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inclined rolling method for a seamless pipe such as a seamless steel pipe.

[0002]

2. Description of the Related Art The manufacturing process of seamless steel pipe is basically
It consists of a piercing step of making a hole in the raw round billet, a drawing and rolling step of thinning and drawing the pierced hollow shell, and a finishing rolling step of squeezing the drawn and rolled hollow shell to a predetermined outer diameter.

FIG. 4 is an explanatory view showing a piercing / rolling process in the manufacturing process of the seamless steel pipe. 1A and 1B are rolling rolls, and the rolling rolls 1A and 1B are constant in their mutually opposite rotation axes with respect to a pass line through which a round billet 2A as a raw material and a hollow rolled raw pipe 2B that has been pierced and rolled pass. Are inclined at a lead angle β of 1 and are rotatable in the same direction. A pair of disc shoes 3A and 3B are arranged on both sides of these rolling regions to suppress the hollow shell 2B that bulges during piercing and rolling.

In recent years, for the purpose of piercing and rolling high alloy steel such as stainless steel, the rolling roll is changed from the conventional barrel type (the rolling diameter of which gradually decreases on the rolling-out side from the gorge portion) to the cone type (rolling). (The diameter of the roll gradually increases toward the exit side), so that this cone type rolling roll is tilted at an inclination angle β, and a cross-type piercing rolling machine is also used at a cross angle γ. It's coming.

For example, in Japanese Examined Patent Publication No. 60-59042, the cone rolls 11A and 1B as shown in FIGS. 5 and 6 are kept in proper ranges of the inclination angle β and the crossing angle γ, and at the same time, the disc roll shoes 13A and 13B. By applying a pressing force in the direction of travel,
A piercing and rolling method is disclosed which is characterized by achieving a metal flow equivalent to that of the hot extrusion method. 5 and 6, 12A is a round billet, 12B is a hollow shell, and 14 is a plug.

Generally, in piercing and rolling in which barrel type rolls are arranged at an inclination angle β, the roll diameter gradually decreases on the exit side from the gorge portion and the peripheral speed becomes slower, so that the cross-sectional area is pierced and the forward speed decreases. Is applied to the material to be rolled, and as a result, the material to be rolled is twisted and additional shear strain is generated in the cross section.

On the other hand, the cone-shaped rolls are inclinedly arranged at a constant advance angle β, and the entrance side angle α with respect to the pass line.
_In piercing rolling in which ₁ and the flank angle α ₂ are cross-arranged at the crossing angle γ, by setting β, α ₁ , α ₂ , and γ in the optimum range, twisting of the material to be rolled and It is possible not to generate the additional shear strain of. this is,
This is because the roll diameter gradually increases toward the rolling-out side and the peripheral speed increases, so that there is no brake on the material to be rolled.

Therefore, when piercing and rolling a high alloy steel such as a stainless steel which is inferior in hot deformability, twisting of the material to be rolled and additional shear strain in the cross section are not generated so that the inner and outer surfaces The occurrence of flaws can be prevented.

[0009]

During piercing and rolling, the material to be rolled advances while rotating in the circumferential direction.
It is necessary to receive from the rolling roll a thrust in the forward direction that overcomes the drag force that impedes the forward movement that is received from the plug due to drilling. This thrust is applied to the rolling roll in the contact area between the rolling roll and the rolling material, which exists when the rolling material is rolled down from the position where the rolling material first contacts the roll to the gorge portion of the rolling roll. To the material to be rolled.

On the other hand, the rolling rolls in the meantime generally have a roll profile having an inclination of α ₁ called the entrance side angle with respect to the pass line. Saikoku Sho 60
-59042 is based on the assumption of a rolling roll having a single α ₁ as the entrance side angle, although no specific numerical value is stated.

However, if the entrance side angle α ₁ is too large, the material to be rolled is drastically reduced when the rolling bites, and the drag force from the rolling roll required for deformation exceeds the thrust in the forward direction transmitted from the rolling roll. A biting failure that the material to be rolled is not bitten occurs. On the other hand, if α ₁ is too small, Mannesmann cracking occurs and the inner surface defects frequently occur because the number of times the material to be rolled is entangled by the rolling roll before contacting the plug increases. Therefore, it is said that the entrance side surface angle α ₁ has an appropriate range.

However, even under the same entrance side angle condition, the larger the gap at the gorge position of the rolling roll and the closer the plug tip position is to the rolling entrance side, the more likely the defective rolling of the material to be rolled occurs. This is because the larger the gap at the gorge position of the rolling roll and the closer the plug tip position is to the rolling entry side, the smaller the contact area between the rolling roll and the rolling material until it contacts the plug of the rolling material. This is because the forward thrust force transmitted from the rolling rolls is reduced.

Further, when the temperature of the material to be rolled is low, even if the surface of the rolling roll is worn, defective biting is likely to occur. Therefore, even if the above-mentioned proper entrance side angle α ₁ ,
Not all biting defects are present under all rolling setting conditions, and biting defects may occur due to changes in rolling environment conditions, which significantly impairs yield and productivity.

Further, in the production operation, it is required to manufacture hollow shells having the same roll shape, the same plug shape, and various wall thicknesses and outer diameters. For this reason, it is necessary to greatly change the roll gap and the advanced amount of the plug, and changing these conditions often causes defective biting.

Therefore, the condition range in which defective biting occurs is made as small as possible, and the rollable range is made as wide as possible.
It was desired to increase the degree of freedom in rolling settings.

It is an object of the present invention to prevent the occurrence of biting failure in piercing and rolling, increase the degree of freedom in rolling setting, and improve yield and productivity.

[0017]

SUMMARY OF THE INVENTION According to the present invention, a pair of cone type rolling rolls are arranged so as to be inclined with respect to a pass line at a constant advance angle β, and a pass line having an entrance side angle and an exit side angle. With a crossing angle γ, and one of a pair of disc roll shoes, a pair of fixed shoes, and a pair of drive roller shoes is arranged on both sides of the rolling region formed by the both rolling rolls. In the method of seamless pipe inclined rolling by the inclined rolling machine,
By changing the entrance side angle of the rolling roll in the pass line direction, the entrance side angle in the region where the rolled material starts contact with the rolling roll is relatively small, in the region where the rolled material then advances toward the gorge part. Inclination rolling is performed with a relatively large entrance side angle.

[0018]

As a result of a detailed study of the occurrence state of bite failure of the material to be rolled when piercing and rolling with the cone type roll, the present inventors found that the entrance side angles of the cone type roll described above are plural in the pass line direction. It was found that biting defects can be significantly prevented by performing stepwise or continuous changes and setting their angles within an appropriate range, and piercing and rolling can be performed without impairing yield and productivity. It was

That is, the diameter D _R of the gorge portion of the cone type rolling roll 1A as shown in FIG. 7 is 700 mm, the roll barrel length L _R is 600 mm, and the roll length L ₁ from the entrance side end to the gorge portion is 250 mm. , Incoming side angle α ₁ is 3 °, outgoing side angle α ² is 3
°, crossing angle γ is 15 °, inclination angle β is 20 °.
A billet having a diameter D _B of 116 mm was used as a material to be rolled by changing the roll gap E and the advanced amount L of the plug to make holes, and the occurrence of defective biting was investigated. FIG. 9 shows the result of the dimensionless arrangement of the roll gap E and the billet diameter D _{B and} the ratio of the advanced plug amount L and the billet diameter D _B.

On the other hand, the cone type rolling roll 1A as shown in FIG. 8 has a gore diameter D _R of 700 mm, a roll barrel length L _R of 600 mm, and a roll length from the entrance end to the gorge portion. L ₁ is 250 mm, the entrance side angle α ₁ on the gorge side is 3 °,
Deflection angle α ₂ is 3 °, crossing angle γ is 15 °, inclination angle β is 20 °
With a piercing and rolling mill with an entrance side angle α ₁ ′ of 2.5 ° from the entrance end face to 200 mm, a roll gap E and a plug advanced amount L are changed by using a billet having a diameter D _B of 116 mm as a material to be rolled. After punching, the occurrence of defective biting was investigated. Fig. 1 shows the results of the dimensionless arrangement based on the ratio of the roll gap E to the billet diameter D _{B and} the ratio of the advanced plug amount L to the billet diameter D _B.
It shows in 0. The area of defective biting is narrowed and the rollable area is greatly expanded.

Therefore, in the method of inclined rolling of a pipe, a pair of cone type rolling rolls are inclinedly arranged at a constant advancing angle β, and are cross-arranged at γ with respect to the pass line so as to have an emergent side angle α _2. The entry side angle α ₁ ′ with respect to the pass line on the roll entry side where the billet as the material first comes into contact with the roll, and then the pass line on the roll entry side where the billet is pressed down while advancing to the gorge By providing the entrance side angle α ₁ (0 <α ₁ '<α ₁ ) with respect to, it is possible to narrow the area in which the leading edge biting failure occurs, and it is possible to increase the degree of freedom in rolling setting.

In the present invention, the reason why 0 <α ₁ '<α ₂ is set is as follows. The billet, which is the rolling material, first contacts the roll so that the material to be rolled is suddenly pressed down when the rolling bites and the drag force from the rolling roll required for deformation does not exceed the thrust in the forward direction transmitted from the rolling roll. The entrance side angle α ₁ 'at the position to be set must be smaller than the entrance side angle α ₁ just before the gorge part. Therefore, α ₁ ′ does not exceed α ₁ .

On the other hand, when α ₁ 'has a negative value, the contact area between the roll and the billet disappears at the entrance side angle α ₁ ', and the thrust cannot be expected. Therefore, α ₁ 'is greater than 0.

The effect of the present invention does not depend on the type of shoe used with the rolling rolls, and therefore any of a disc roll shoe, a fixed shoe and a drive roller shoe may be used as the shoe.

In the practice of the present invention, the entrance side angle of the cone type rolling roll is not limited to change in two steps in the pass line direction, but may change in three or more steps, or continuously. May be

[0026]

1 is a plan view showing an inclined rolling mill according to the present invention, FIG. 2 is a side view of FIG. 1, and FIG. 3 is a front view seen from the rolling direction of FIG.

In FIGS. 1 to 3, a pair of cone type rolling rolls 31A and 31B are inclinedly arranged with respect to the pass line at a constant advance angle β, and the entrance side angles α ₁ , α ₁ 'and the exit side angle α are set. cross arranged with cross angle γ with respect to the pass line so as to have a _2, the both rolling rolls 31A, on both sides of the rolling region 31B is formed, a pair of drive rollers shoe 3
3A and 33B were arranged. And both rolling rolls 31
A plug 34 is arranged between A and 31B, and both rolling rolls 3
Round billet 32A with 1A, 31B gorge roll gap
Was tilt-rolled to obtain a hollow shell 32B.

At this time, the entrance side angles of the rolling rolls 31A and 31B are changed in the pass line direction to change the round billet 32A.
Has a relatively small entrance side angle α ₁ ′ in the region where the rolling rolls 31A and 31B start contact, and the round billet 32A is then
The entrance side surface angle α ₁ in the region of advancing toward the edge portion is made relatively large. That is, the roll-entry side surfaces of the rolling rolls 31A and 31B have two stages, and 0 <α ₁ '<α ₁ .

The operation and effect of this embodiment will be described below. That is, a cone type roll with a gorge diameter of 700 mm was placed together with the disc roll shoe under the conditions shown in Table 1,
A billet having an outer diameter of 116 φ was pierced and rolled. Table 1 also shows the presence or absence of defective biting at that time.

[0030]

[Table 1]

According to the method of the present invention, no defective biting occurred at all, even under the condition that defective biting occurred in each of the comparative examples.

[0032]

As described above, according to the present invention, it is possible to prevent the occurrence of biting failure in piercing and rolling, increase the degree of freedom in rolling setting, and improve yield and productivity.

[Brief description of drawings]

FIG. 1 is a plan view showing an inclined rolling mill according to the present invention.

FIG. 2 is a side view of FIG.

FIG. 3 is a front view seen from the rolling direction in FIG.

FIG. 4 is a plan view and a side view showing a conventional barrel-type roll-rolling mill using a disc shoe.

FIG. 5 is a plan view of an inclined rolling mill using a conventional cone type roll.

FIG. 6 is a side view of FIG.

FIG. 7 is a diagram showing a conventional roll shape and size.

FIG. 8 is a diagram showing a roll shape and dimensions according to the present invention.

FIG. 9 is a diagram showing a rollable region when piercing-rolled with the roll shape shown in FIG. 7.

FIG. 10 is a diagram showing a rollable region when piercing-rolled with the roll shape shown in FIG. 8 according to the present invention.

[Explanation of symbols]

 31A, 31B Rolling roll 32A Round billet 32B Hollow shell 33A, 33B Drive roller shoe 34 Plug

Claims (1)

[Claims] 1. A pair of cone-shaped rolling rolls are arranged at a constant advance angle β with respect to a pass line, and are crossed with a cross angle γ with respect to the pass line so as to have an entrance side angle and an exit side angle. A pair of disc roll shoes, a pair of fixed shoes, and a pair of drive roller shoes are arranged on both sides of the rolling region formed by the rolling rolls. In the inclined pipe rolling method, the entrance side angle of the rolling roll is changed in the pass line direction so that the entrance side angle in the region where the rolling material starts contact with the rolling roll is relatively small, and the rolling material then moves to the gorge part. A seamless pipe tilt rolling method, characterized in that tilt rolling is performed with a relatively large entrance side angle in a region advancing toward.