JPH03198902A - Skew rolling method of seamless tube - Google Patents

Abstract

PURPOSE:To obtain a thin small diameter tube without squarishness, wrinkly flaws on the inner surface of tube and flaws on the outer surface of tube by forming elongating rolling under specific conditions using a plug with a rolling part of which the outside diameter is gradually reduced according to the moving direction of a tubular material as plug. CONSTITUTION:Inclined rolls 1 and guide shoes are alternately arranged around the X-X line of the pass line of a hollow shell H and rolled tube H' and the plug 2 is situated on the pass center of the hollow shell H and rolled tube H'. In this case, elongating rolling is performed under the following conditions: 0 deg.<beta<=16 deg., Rg<=0.85d, 1.0RG<=G<=1.2Rg, 0 deg.<=theta1-thetaP<=8 deg., 0 deg.<=alpha<=theta1+4 deg., 0 deg.<theta2<=4 deg., where, beta: tilt angle, d: outside diameter of tubular material before rolling, Rg: the opening degree of inclined roll, G: the opening degree of guide member for tubular material, theta1: the face angle of the inlet of inclined roll theta2: the face angle of the outlet of inclined roll, d: the face angle of the inlet of guide member for tubular material, thetaP: the face angle of the rolling part of plug.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for inclined rolling of seamless pipes in which a pipe material is subjected to elongation rolling accompanied by diameter reduction.

[Conventional technology]

The Mannesmann plug mill method is the most commonly used method for manufacturing seamless pipes. In this pipe manufacturing method, a billet is first heated to a predetermined temperature in a heating furnace, then passed through a piercer (piercing mill), and a bullet-shaped plug is inserted into the center of the billet to create a hollow shell. The hollow shell is then subjected to elongation rolling in a subsequent mill, and then polished using a reeler and sipe, and then subjected to a refining process including shape correction and sizing to obtain a seamless pipe as a product.

Various methods have been known to stretch and roll the above-mentioned hollow shells, but in particular, there is a tilt rolling method using tilted rolls, a stretch rolling method using a mandrel bar such as an Athocel mill or a Desocha mill, or an inner surface regulating tool. There are methods such as empty rolling that does not use plugs or mandrel bars. Among these methods of elongation rolling, which involves reducing the diameter of the pipe material to be rolled, there is a method using a plug (Japanese Patent Publication No. 5B-56651), a dry rolling method (
JP-A-61-144204, JP-A-63-112
No. 007) and the like are known.

[Problem to be solved by the invention]

However, when stretch rolling with diameter reduction is performed using the former method,
As the reduction ratio of the outer diameter increases, the tube after rolling becomes angular, defects on the outer surface of the tube, wrinkles on the inner surface of the tube, etc. Not only does the body length of the inclined roll become longer, the equipment becomes larger and the equipment becomes larger. It is expensive, requires significant modification to apply to existing equipment, and uses guide shoes and day scrolls as pipe material guide members, making mutual positioning complicated.
Moreover, when the drawing ratio becomes large, there is a problem that the material of the tube material enters the joint between the two, causing surface flaws. In addition, in the latter method, when the outside diameter reduction ratio is increased, angularity occurs in the tube material after rolling, resulting in misrolling, and depending on the steel type, there is a problem in that wrinkles occur frequently on the inner surface of the tube. When the present inventors conducted an experiment on the relationship between the wall thickness/outside diameter ratio of the borrow shell and the outside diameter reduction ratio when using the latter method, the results shown in FIG. 5 were obtained.

That is, a plurality of hollow shells made of 12Cr-Fe steel with different wall thickness rg/outer diameter ratios are prepared, and these are
Stretching with diameter reduction by changing the outer diameter reduction ratio (tube outer diameter after hollow shell outer diameter rolling/hollow shell outer diameter Rolling is performed and squareness in the pipe after rolling,
The presence or absence of defects on the inner surface of the tube was investigated.

Figure 5 is a graph showing the relationship between the wall thickness/outer diameter ratio and the outer diameter reduction ratio of a hollow shell, with the wall thickness/outer diameter ratio on the horizontal axis and the outer diameter reduction ratio (%) on the vertical axis. This is an indication. In the graph, the X mark indicates that the angular phenomenon occurred in the pipe material after rolling, the ・ mark indicates that wrinkle flaws occurred on the inner surface of the pipe, and the ○ mark indicates that neither angular flaws nor wrinkle flaws occurred. are shown respectively.

As is clear from this graph, when the wall thickness/outer diameter ratio of the hollow shell is small, angular formation is likely to occur, and conversely, when the wall thickness/outside diameter ratio is small, angular formation is less likely to occur, but when the outside diameter drawing ratio It can be seen that wrinkles occur on the inner surface of the tube as the tube rises.

The present invention has been made in view of the above circumstances, and its purpose is to achieve rolling with high dimensional accuracy without causing defects or angularity on the inside or outside of the tube even when stretch rolling is performed at a high diameter reduction rate. The purpose of the present invention is to provide a method for inclined rolling of seamless pipes.

[Means to solve the problem]

The method for inclined rolling of a seamless pipe according to the present invention involves moving the pipe material spirally using a plurality of inclined rolls and a pipe material guide member arranged alternately around the pass line of the pipe material, and rolling the pipe material between the inclined rolls and the pipe material. In a seamless pipe inclined rolling method in which a pipe material is subjected to elongation rolling with a diameter reduction using a positioned plug, a plug having a rolling part whose outer diameter is gradually reduced according to the moving direction of the pipe material is used as the plug, and the following method is used. It is characterized by stretching and rolling under certain conditions.

0°〈β≦16゜Rg ≦0.85d 1.0Rg≦G≦1,211g 0°≦θ, -〇, ≦8゜0≦α≦01+4゜0<θ2≦4゜However, β: Inclination angle d : Outer diameter of the tube material before rolling Rg : Opening degree G of the inclined rolls : Opening degree θI of the tube material guide member : Inclined roll artificial face angle θ2 : Inclined roll exit face angle α : Inlet face angle θP of the pipe material guide member : Plug rolling part angle Face angle [effect] The reasons for numerical limitations on the inclination angle β, the opening degree Rg of the inclined roll, the opening degree G of the tube material guide member (hereinafter referred to as guide), etc. are as follows.

[Oo〈β≦16°] The inclination angle β is O because it is necessary to provide a propulsive force to the pipe material.

In addition, if the inclination angle β is 16° or more, the wall thickness reduction rate per half rotation by the plug and the inclined rolls becomes large, and the angle between the inclined rolls and the pipe material during the biting of the tube material or during rolling increases. This is due to the increase in slip between the rollers, the occurrence of misrolls, and the occurrence of outer surface bottoms (slip flaws) due to the increase in the number of rolling edges in the guide direction.

[Rg≦0.850d] This is the opening degree of the inclined roll necessary to perform diameter reduction with a diameter reduction ratio of 0.9 or less.

[1, ORg≦G≦1.2Rg] If the guide opening degree G is less than 1 or OR8, the amount of reduction of the guide with respect to the outer diameter of the pipe material will be large, which will not only cause the bottom of the outer surface to occur due to seizure of the guide, but also cause damage to the guide. This is because slip occurs due to an increase in frictional force, resulting in a state in which rolling is impossible. Furthermore, if the guide opening exceeds 1.2Rg, the ellipticity of the pipe material at the gorge portion of the inclined rolls will be large and the rolling state will become unstable, and the angle at which the pipe material is bitten by the inclined rolls will become large, making rolling impossible. In addition, the thickness unevenness rate worsens and angularity occurs.

[0°≦θ1−θ2≦8°] This is because when the value of θ1−θ is less than 0°, the gap between the inclined roll and the plug is small, resulting in poor biting of the tube material. Also, if the values of θ and -θ exceed 8", the condition is the same as not using the inner surface regulating tool, and the inner surface wrinkles that occur when the inner diameter of the pipe material is reduced cannot be erased, and they remain as they are.
This is because angularity is more likely to occur.

[0°≦α≦θ1 +4°] If the guide inlet face angle α is less than 0°, when the peripheral wall of the pipe material rolled down by the inclined roll bulges and deforms in the guide direction, the pipe material may not be caught between the guides. Due to the occurrence of Furthermore, if the guide face angle α exceeds θ, +4°, rolling becomes unstable and the thickness unevenness rate worsens.

[0〈θ2≦4゛] If the inclined roll exit surface angle θ2 is set to 0° or less, not only angularity will occur in the pipe material, but also misrolls will occur due to slipping. Moreover, if the inclined roll exit face angle θ2 exceeds 4°, a spiral step will occur on the surface of the tube material, resulting in deterioration of dimensional accuracy.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof.

FIG. 1 shows a partial cross-sectional plan view showing the implementation state of the method for inclined rolling of seamless pipes according to the present invention, FIG. 2 is a side view of FIG. 1, and FIG. 3 is the m-m cotton of FIG. 1 is a cross-sectional view of the roll gorge section according to 1. 1 is a barrel-shaped inclined roll;
2 is a plug, 3, 3 is a guide shoe which is a pipe material guide member, H
indicates a hollow shell, and H' indicates a tube after rolling (hereinafter referred to as a rolled tube).

Two inclined rolls 1 and two guide shoes 3 are alternately arranged around the pass line XX'h of the hollow shell H1 rolled tube H', and two inclined rolls 1. (2) The plug 2 is positioned in the inner region surrounded by the guide shoes 3, 3 and above the pass center of the hollow shell H2 rolled pipe H'.

Inclined roll 1. 1 is provided with a short cylindrical gorge part 11 in the middle part in the axial direction, and on both sides of the gorge part 11, there are inlet surfaces each having a substantially truncated conical shape whose diameter decreases toward both ends in the axial direction. 12. The outlet surfaces 13 are disposed on the left, right, above, or below the pass line XX of the hollow shell H8 rolled tube H' at predetermined crossing angles and inclination angles, respectively, and are respectively driven by arrows by a drive source (not shown). In addition to being rotationally driven in the direction shown in FIG. Note that the inclined rolls 1, 1 are not limited to barrel-shaped rolls, but may also be cone-shaped rolls.

The plug 2 has a cylindrical portion 2a having a maximum diameter at its tip, and a rolled portion 2b having a substantially truncated conical shape whose diameter is gradually reduced from the cylindrical portion 2a toward the base end, that is, in the direction of movement of the hollow shell H. The rolling part 2b has a reeling part 2c in the form of a cylinder with a smaller diameter at the base end, and a hollow shell H3 is formed by a mandrel bar M fitted inside the base end of the reeling part 2c. It is supported on the pass center of the rolled tube H'.

The angle that the entrance surface 12 of the inclined roll 1 makes with respect to the bath center, that is, the entrance surface angle θ1, the angle that the exit surface 12 makes with respect to the bath center, that is, the exit surface angle θ2, and the rolled part 2b with respect to the axis of the plug 2. , that is, the plug face angle θP, are set so that the relationships 0°≦θ, −θ, ≦8°0°<θ2≦4° are established.

The proximal end of the mandrel bar M moves forward (not shown).

It is connected to the thrust block 6 of the reversing device, and allows the plug 2 to be moved forward and backward along the bus center. Incidentally, the mandrel bar M may be connected to the tip of the plug 2 by extending the inlet side of the inclined roll 1.

The guide shell 3 is formed into an elongated plate shape, and the hollow shell H
The surface facing the first rolling tube H' is formed into a concave surface, and can be moved toward and away from each other by a drive device (not shown). The angle .alpha. which the entrance surface of the guide shoe makes with respect to the pass line XX line is set so that the relationship between the entrance surface angle .theta.1≦α and 0°≦α≦θ1+4° of the inclined roll 1 is established.

In addition, as shown in FIG. 4, other tube material guiding members such as guide rollers 3, 3' having an entrance face angle may be used in place of the guide shoes 3, 3.

In such an embodiment, prior to the start of operation, the thrust block 6 is operated to roll the plug 2 into the porous seat (2) with its rolled portion 2b facing the inlet surface 12 of the inclined rolls 1, 1. Position and hold it above the bus center. Moreover, in this state, the inclination angle β of the inclination roll 1.1
is within the range of 0°≦β≦16°, preferably 3°≦β≦1
The gap between the inclined rolls 1, 1, that is, the opening degree Rg of the inclined rolls, and the gap between the guide shoes, that is, the opening degree G of the guide shoes, is set within the range of 1. ORg≦G≦1.2
12g, and furthermore, the relationship between the guide shoe opening G and the outer diameter d of the hollow shell H is set such that Rg≦0.
The settings are made so that the relationship 85d holds true.

Next, the heated hollow shell 11 is transferred from the direction of the outlined arrow along the pass line The plug 2 is caused to spirally move along the pass line XX, and the plug 2 is fitted into the center thereof. Thereafter, it is subjected to intermittent rolling action by the inclined rolls 1 and 1 and the plug 2 every half rotation, and is elongated into an elliptical shape, and as it progresses downstream in the rolling direction, it is gradually formed into a circular shape, and the diameter is reduced. It is then formed into a rolled tube H'.

In this rolling process, during the diameter reduction process using the inlet surface 12 of the inclined roll 1, the rolled portion 2b of the plug 2 faces the inlet surface 12 of the inclined roll 1.1 from the inner surface of the tube at an appropriate surface angle.
To prevent wrinkles from forming on the inner surface of the tube when the outer diameter of the tube is reduced by contacting the inner surface of the tube before wrinkles occur on the inner surface of the tube.

In addition, most of the wall thickness processing and outer diameter processing are completed up to the gorge portion 11 of the inclined roll 1.1, and there is almost no diameter reduction effect on the exit side of the inclined roll 1, so wrinkles occur on the inner surface of the tube. There's nothing to do.

[, Test Example 1] Next, the results of a comparative test between the method of the present invention (referred to as an example of the present invention) and a method that does not belong to the present invention (referred to as a comparative example) that does not use a plug or a mandrel bar as an inner surface regulating tool will be explained. .

The sample material was a hollow shell made of 545C carbon steel (diameter 60cm).
1, wall thickness 5.4 am), which was heated to 1000°C, and the diameter reduction rate was reduced to 10% according to the present invention example and comparative example.
Stretching and rolling with changes in the range of ~40%, whether or not rolling is possible,
In addition, the presence or absence of defects on the outer surface of the obtained rolled tube was examined.

Other test conditions are as follows.

Inclination angle β: 3°~20° Inclined roll opening: 34~50° Guide shoe opening
:36-53u+gorge diameter of inclined roll:350Fin The results are as shown in Table 1.

Table 1 In Table 1, the X mark in the rolling availability column indicates that at least one of the following problems has occurred: poor biting of the pipe material, rolling stoppage midway, and failure of ash removal from the pipe material, and ○ mark indicates that the above problems have occurred. This shows the case where it was not done. In addition, in the column for the presence or absence of occurrence of external calculus, an x mark indicates a case in which an external calculus occurred, and an ○ mark indicates a case in which no occurrence was observed.

As is clear from Table 1, in the comparative example, not only the rolling itself was inconvenient, but also the outer surface bottom occurred, whereas in the case of the method of the present invention, the rolling itself was carried out smoothly and there was no occurrence of the outer surface bottom. This shows that good elongation rolling can be carried out.

[Test Example 2] The test material was a hollow shell made of 545C carbon steel (diameter: 60
This was heated to 100 O'C, and the diameter was 40 mm and the wall thickness was heated to 100 O'C and the comparative example which did not use a plug or mandrel bar as an inner surface regulating tool was heated to 100 O'C. Stretch rolling was performed to obtain a 4.5n+ rolled tube, and the presence or absence of poor biting of the tube material, internal surface scratches, and occurrence of angularity was examined.

Other test conditions are as follows.

Inclination angle β: 8゛ Inclined roll opening: 36 dragons Guide shoe opening: 39mm The results are shown in Table 2.

In Table 2, in the columns for presence or absence of defective biting, presence or absence of internal wrinkle flaws, and presence or absence of angularity, the ○ marks indicate cases where these did not occur, and the X marks indicate cases where they occurred. ing.

As is clear from Table 2, in the case of the comparative example, inner surface wrinkles and angularity occurred in most cases, while in the case of the present invention, any of the following occurred: poor biting, inner surface wrinkles, and the bottom of the outer tube. It can be seen that smooth elongation and rolling can be performed without occurrence of any problems.

〔effect〕

As described above, in the present invention, small diameter,
The present invention has excellent effects, such as making a thin-walled tube angular, without causing wrinkles on the inner surface of the tube, or bottoming the outer tube, and by changing the shape of the plug, etc., it can be carried out using conventional equipment. .

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional plan view showing the state during pipe production by the method of the present invention, FIG. 2 is a side view showing the state during pipe production, and FIG. 3 is a cross-sectional view taken along line mm in FIG. 1. FIG. 4 is a cross-sectional view when a guide roller is used as a tube guide member, and FIG. 5 is a graph showing the relationship between the wall thickness/outer diameter ratio and the outside diameter reduction rate of the porrow shell.

Claims (1)

[Claims] 1. While the pipe material is spirally moved by a plurality of inclined rolls and pipe material guide members arranged alternately around the pass line of the pipe material,
In the method for inclined rolling of a seamless pipe, in which the pipe material is subjected to elongation rolling with diameter reduction using the inclined rolls and a plug located in the pipe material, the rolling part has an outer diameter gradually reduced according to the moving direction of the pipe material as the plug. 1. A method for inclined rolling of seamless pipes, which comprises elongation rolling using a plug having the following conditions: 0゜<β≦16゜Rg≦0.85d 1.0Rg≦G≦1.2Rg 0゜≦θ_1−θ_P≦8゜0≦α≦θ_1+4゜0<θ_2≦4゜However, β: Inclination angle d: Rolling Previous tube outside diameter Rg: Inclined roll opening G: Opening of tube guide member θ_1: Inclined roll inlet face angle θ_2: Inclined roll outlet face angle α: Inlet face angle of pipe guide member θ_P: Face angle of plug rolling part