JPH012708A - Continuous elongation rolling method of pipe and its rolling machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a continuous elongation rolling method of a tube using a mandrel mill and a rolling mill thereof.

<Prior art> Traditionally, when seamless steel pipes are manufactured on a mandrel mill line, as detailed in the 3rd edition of the Steel Handbook 111(2) (Japan Iron and Steel Institute 4%, P970-984), Generally, the manufacturing process is as shown in FIG.

In other words, a round steel piece l as a material is heated in a rotary hearth type heating furnace 2.
After being heated to the required temperature, drilling 8! At step i3, the hollow tube 10A is perforated. This hollow tube 10A has a mandrel bar 4 inserted therein, and a mandrel mill 6 consisting of a row of stands having a pair of grooved rolls 5 arranged in series from seven to nine.
The tube material 10B is stretched and rolled by reducing its outer diameter and wall thickness. After the mandrel bar 4 is pulled out, the tube material 10B is heated in a reheating furnace 7, finished with a stretch reducer 8 into a product 10c with a desired outer diameter and wall thickness, and cooled on a cooling bed 9.

The role played by the mandrel mill 6 in the above series of manufacturing steps will be explained in more detail.

Between adjacent stands, the grooved rolls 5 are arranged so as to cross each other at right angles with the pass line as the axis, as shown in the bus schedule of FIG. The amount of reduction in outer diameter in the mandrel mill 6 is usually 20 to 30 ml, and the amount of reduction in wall thickness is about 7 to 12 mm. Note that the optimum outer diameter reduction amount in the mandrel mill is a dependent variable of the outer diameter of the hollow tube on the inlet side of the mandrel mill, and when expressed as an outer diameter reduction rate, it corresponds to a value approximately between 10 and 25%.

<Problems to be Solved by the Invention> By the way, the above-mentioned conventional technology has a fatal flaw. When manufacturing the final product 10C with the smallest diameter,
This means that the outer diameter reduction rate of the stretch reducer 8 inevitably increases. In general, for stretch reducers, it is advantageous to manufacture products with as many different outside diameters as possible from a main tube with the same outside diameter to improve production efficiency, and stretch reducers are advantageous in that they can do this. This is also one of its features. However, it is a well-known fact among those skilled in the art that in stretch reducer rolling, as the outer diameter reduction rate increases, both the dimensional accuracy and inner surface properties of the product deteriorate. Actual operating conditions are set as a compromise between the mutually contradictory objectives of improving production efficiency and improving product quality. Specifically, the maximum outer diameter reduction rate of the stretch reducer is set to approximately 75% or less to ensure minimum quality and at the same time a certain level of production efficiency. The biggest reason why we are forcing compromise operating conditions that are different from ideal conditions is that it is difficult to change the main tube diameter at the input side of the stretch reducer, that is, the outer diameter of the tube material at the outlet side of the mandrel mill, in a short time. This is due to the fact that it is difficult.

Therefore, if the outer diameter of the tube material 10B on the outlet side of the mandrel mill, which serves as the main pipe of the stretch reducer 8, is required to be two to three levels by calculating backward from the outer diameter of the product, conventionally In order to obtain the tube material 10B on the outlet side of the mandrel mill 6, the outer diameter level of the hollow tube 10A on the input side of the mandrel mill 6 had to be changed accordingly.

The following two methods are currently used to change the outside diameter of the hollow shell on the entry side of the mandrel mill.

■ By changing the outside diameter of the round steel piece, the diameter of the hollow tube at the outlet of the punching machine can be changed.

■ Install a sipe between the drilling machine and the mandrel mill to change the diameter of the hollow tube.

However, all of these methods have drawbacks. First, regarding (2), several levels of round steel pieces with different outside diameters must be prepared, and drilling machine tools (such as drilling plugs and guide shoes) must be prepared for each outside diameter.

Regarding (2), installing sipes itself requires enormous construction costs, and applying it to existing equipment is technically difficult due to constraints such as securing equipment space.

The present invention has been made in order to solve the above-mentioned problems, and is a continuous tube suitable for rolling tube materials with different outer diameters from hollow blank tubes of the same outer diameter using a mandrel mill. The object of the present invention is to provide a stretching and rolling method and a rolling mill therefor.

<Means for Solving the Problems> As a result of intensive study on means for increasing the outer diameter reduction rate in mandrel mill rolling, the present inventor found that strong reduction is possible with an elliptical shape. I ended up completing it.

That is, the present invention, when rolling a hollow shell using a mandrel mill composed of a plurality of stands, rolls the hollow shell into an elliptical shape, and then compresses it by strongly compressing the long diameter side of the elliptical shape. A method for continuous elongation and rolling of pipes characterized by performing radial elongation rolling, and a rolling mill for a mandrel mill comprising a plurality of stands for elongating and rolling a hollow tube using Caliba rolls, the mandrel mill comprising: Continuous drawing pressure t of a pipe, characterized in that the hole shapes of at least two stands of Caliba rolls on the upstream side of the pipe have elliptical shapes each having a different major axis direction.
It is i.

The configuration of the present invention will be specifically explained below.

The configuration of the grooved roll having an elliptical shape used in the present invention will be explained based on FIG. 1.

FIG. 1 is a front view schematically showing a grooved roll;
(a) is for the first stand, and (b) is for the second stand. In this figure, members that are the same as those in the conventional example are given the same reference numerals and explanations will be omitted.

As shown in FIG. 1(a), the groove shape of the groove roll 5A of the first stand is an ellipse, with the groove width A-B being the major axis and the groove bottom interval C-D being the long axis. Corresponds to the short axis. At this time, the ellipticity α1 (-
It is desirable that Wl/H1) be between 1.01 and 3.00.The reason for limiting the lower limit value is that it is a value necessary to prevent roll edge flaws, as is conventionally known.
In addition, the upper limit value is a practical range in which no collapse (buckling) phenomenon of the tube wall occurs when applying strong pressure from the long axis side of the elliptical shape in the next stand, and a practical range that does not cause the tube wall to collapse (buckling) when inserted into the hollow tube 10A. It is determined by the geometric roll groove bottom spacing limited by the diameter of the mandrel bar 4.

Next, the shape of the grooved roll 5B of the second stand is the same as that of the first stand.
As shown in Figure 3), it is also elliptical, but the hole width is A-
B corresponds to the short axis, and the hole-shaped groove bottom interval C-D corresponds to the long axis.

The ellipticity αt obtained from this major axis W and minor axis H2
(=Wz/Hz) is preferably 0.35 to 1.50.

For the lower limit value, the maximum ellipticity (
αl -3,00) shape is determined based on the conditions to avoid roll edge defects on this stand, and the upper limit is Determined based on the condition that the tube wall in contact with the roll gap does not buckle.

Although the above explanation was made using the 20-roll type, for example, the vertical drive rolls 5B, 5 as shown in FIG. 1(C)
It is also possible to apply the present invention to a 40-type roll stand having idle rolls 5C, 5C between B.

Effect〉 45 to the pass line level PL to the hollow tube 10A
After performing flattening rolling using the elliptical groove roll 5A of the first stand tilted to make it oval, the ellipse of the second stand is tilted by 90” with respect to the groove roll 5A of the first stand. By applying strong pressure from the long diameter side of the elliptical shape using the hole-shaped roll 5B, it is possible to significantly reduce the outer circumference of the hollow tube 10B.As a result, the outer diameter reduction rate in the mandrel mill 6 can be maximized. Since the ratio of the outside diameter of the tube material on the outlet side to the outside diameter of the hollow tube on the input side of the mandrel mill can be increased to about 50%, the ratio is about 0.90.
It is possible to set it arbitrarily between 0.50 and 0.50. As a result, it is possible to practically consolidate the outer diameter of the hollow shell tube on the entrance side of the mandrel mill to one level.

<Example> [Example 1] Outer diameter: 115. Om x wall thickness: 13. Using Oam's hollow tube with a 20-ru 28-stand mandrel mill,
Outer diameter: 90. The present invention was applied to rolling a tube material with Omm x wall thickness = 3.0 mm. The pass schedule of the mandrel mill at this time is shown in Figure 2. The hole shape and dimensions of these rolls and the rolling results are also shown in Table 1. The diameter of the mandrel bar used here was 82.0a.
It is u*.

As is clear from Table 1, the total outer diameter reduction rate is approximately 48.6
%, which is significantly larger than that of the conventional example.

In addition, conventionally, the pipe material having the above dimensions has an outer diameter of 11
0. OMtX wall thickness: 11. It was manufactured from a 0mm hollow tube.

[Example 2] Outer diameter: 110.0 mm × wall thickness: 11.0 mm hollow tube was made with the roll hole type arrangement shown in Table 2, outer diameter: 60 mm.
．． The present invention was applied to rolling a tube material of 0 m111 x wall thickness: 3.0 mm. The rolling results are also shown in Table 2.

The diameter of the mandrel bar used here was 52. Oaw
It is n.

As is clear from this table, the total outer diameter reduction rate is 45.5%.
It is.

In addition, the outer diameter of the tube material in the case of rolling in the conventional example using a hollow tube having the above dimensions is up to 90.0 mm at most.

Furthermore, assuming that the outer diameter of the final product on the outlet side of the trench reducer is 30.0 mm, the outer diameter reduction rate is 66.7% when using a mother pipe with an outer diameter of 90 nm. When using a main tube with an outer diameter of 60.0 mm, the outer diameter reduction rate is approximately 50.0%, so the latter, which has a smaller outer diameter reduction rate in the stretch reducer, has a higher dimensional accuracy of the product than the former. Those skilled in the art can easily understand that the inner surface properties are excellent and the inner surface properties are excellent.

It should be noted that the pipe material rolled by the method of the present invention has the same level of dimensional accuracy and durability of the inner and outer surfaces as those of the pipe material rolled by the conventional method.

<Effects of the Invention> As explained above, according to the present invention, pipe materials with different outside diameters can be drawn and rolled from a hollow blank pipe with the same outside diameter, so it is possible to consolidate the material dimensions. , a reduction in material costs can be expected.

Furthermore, since the outer diameter reduction rate of the stretch reducer can be reduced, it is possible to improve product quality.

[Brief explanation of drawings]

FIG. 1 is a front view schematically showing the main parts of the grooved roll used in the present invention, and FIG. 2 is a partial front view schematically showing an example of the pass schedule of the mandrel mill according to the present invention.
FIG. 3 is an explanatory diagram schematically showing the manufacturing process of a seamless steel pipe using a mandrel mill line, and FIG. 4 is a plan view schematically showing a pass schedule of the mandrel mill.・
1... Material (round steel piece), 5... Hole roll. 6...Mandrel mill. 10A...Hollow tube, 10B...Pipe material patent applicant Kawasaki Steel Co., Ltd. Figure 4 Figure 2

Claims (2)

[Claims] (1) When rolling a hollow shell using a mandrel mill composed of multiple stands, the hollow shell is rolled into an elliptical shape, and then the long diameter side of this elliptical shape is strongly rolled down to reduce the diameter and stretch-roll. A method for continuous elongation and rolling of a pipe, characterized by carrying out the following steps. (2) A rolling mill for a mandrel mill consisting of multiple stands for elongating and rolling a hollow shell using Caliba rolls, wherein the hole shapes of the Caliba rolls in at least two stands on the upstream side of the mandrel mill are different in the major axis direction. A continuous elongation rolling machine for a tube, characterized in that it has an elliptical shape.