JPH06243B2 - How to drill seamless pipes made of difficult-to-process materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a method for perforating a seamless pipe, particularly a heated difficult-to-process material that is used in the process of producing a seamless pipe by the Mannesmann pipe making method. The present invention relates to a method for punching a real billet.

[Conventional technology]

The Mannesmann pipe making method has been widely practiced as a method for producing hot seamless pipes, but in this method, a round steel piece (solid billet) heated to a predetermined temperature is first pierced by a piercing rolling machine. A hollow shell is manufactured by rolling, and the hollow shell is reduced in wall thickness with a stretch rolling machine such as an elongator, plug mill or mandrel mill, and reheated if necessary, and then drawn or rolled. This is a method of obtaining a seamless pipe of a predetermined size by mainly reducing the outer diameter by a machine.

Various structures have been proposed for piercing and rolling mills used in the manufacturing process of seamless pipes, but two main rolls and plugs, two plate guide shoes and disc rolls that are outer surface restricting tools, and A so-called two-roll piercer, which is a combination of three main rolls and a plug, is commonly used.

By the way, in such a piercing-rolling process, the plug is constantly exposed to high temperature and high load due to constant contact with the heated solid billet and the hollow shell, so that the plug is easily worn and deformed as compared with the main roll and the disc roll. But,
Currently most widely adopted, eg JIS-SKT3, SKT
4, Ni-Cr system such as SNCM616, SKE62 and its equivalent steel, Ni
-Cr-Mo system or Ni-Cr-Mo-W system low alloy tool steel (hereinafter
Ni-Cr alloy steel) is subjected to scale treatment at a high temperature of 900 to 1000 ° C, and the surface of the plug is tens of micrometers and hundreds of micrometers
When a large amount of carbon steel or low-alloy steel is rolled using a plug that has produced a scale film of μm, it can be rolled hundreds of times even though the plug is made of a material whose high-temperature strength is not so high.

Furthermore, as another method of extending the life of the plug, a so-called water-cooled plug, in which cooling water is circulated in the plug, or a method of ejecting a hot lubricant between the plug and the inner surface of the hollow shell to efficiently perform lubrication ( (JP-A-51-133167), or a method of manufacturing the entire plug or the tip with a molybdenum alloy or ceramics having excellent high temperature strength (JP-A-62-163167).
-207503, JP-A-63-104707, JP-A-63-203205)
Etc. have been proposed.

[Problems to be Solved by the Invention]

By the way, in such a conventional method, for example, Cr
When used to pierce and roll high-Cr steels, stainless steels, Ni-based alloys, or Ti and Ti alloys containing 2% by weight or more, it is possible to simply scale Ni-Cr alloy steels as described above. Even if a plug that has just been treated has an internal water-cooled structure and a lubricant injection structure, the plug is significantly melted and deformed, resulting in a short life. In addition, the method of strengthening only the tip of the plug by using molybdenum alloy or ceramic has a great effect of preventing wear and deformation of the tip, but the function of preventing melt damage of the body is weak and the effect of extending the life of the plug is not sufficient. .

In addition, the cost of the plug is extremely high in the method of constructing the whole with molybdenum alloy, etc., and also prepare an inexpensive plug made of Ni-Cr alloy steel as described above for materials such as carbon steel that are easy to process. There is a problem that the number of plugs that must be owned and managed in the factory must be increased, which is economically inconvenient.

The present inventor has conducted an experiment to obtain a plug having a long life even if it is applied to piercing and rolling for a difficult-to-process material. As a result, the detailed mechanism thereof is unknown, but the following fact has been found.

As a result of applying to a difficult-to-process material using a plug in which a scale layer is adhered by a scale treatment to the surface of the plug made of the Ni-Cr alloy steel described above, melting loss, deformation, and seizure of the plug occur in just a few passes. There was a portion where the scale layer adhered by the scale treatment was scarcely left on the surface, and melting loss and deformation of the plug were mainly observed in this portion.

In addition, when a stainless steel hollow shell in which oxide scale was positively generated on the surface by heating at about 1200 ° C in the atmosphere for a long time was stretch-rolled by an inclined rolling mill, the hollow shell was formed on the plug surface of the rolling mill. Although it was observed that a large amount of scale had been transferred, it was confirmed that the scale layer adhered by the scale treatment was significantly worn, and that the melting and deformation of the plug itself was not suppressed at all. It was

Furthermore, the plug made of the above Ni-Cr alloy steel is 900 ℃ ~ 1000 ℃
Wear the scale on the plug surface after use with a plug that has been subjected to scale treatment with, and then subjected to piercing and rolling of stainless steel as it is, and a plug that has been previously subjected to several passes of carbon steel and then subjected to piercing and rolling of stainless steel. When the situation and the melting and deformation conditions of the plug itself were compared, in the former case, scale wear was remarkable and the melting and deformation of the plug itself was observed.
In the latter case, scale wear was slight, and neither melting loss nor deformation of the plug itself was observed.

From such a fact, the above-mentioned Ni which is a conventional inexpensive material is
-When drilling and rolling difficult-to-process materials such as high Cr steel and stainless steel using a plug made of Cr alloy steel, carbon steel,
It was confirmed that it is effective to use it after subjecting the low alloy steel to piercing and rolling.

The present invention has been made on the basis of such knowledge, and the purpose thereof is to construct a plug without using an expensive high-temperature high-strength material, reduce damage and deformation of the plug, and extend the life of the plug. Another object of the present invention is to provide a method for perforating a seamless pipe made of a difficult-to-process material.

[Means for Solving the Problems]

In the seamless pipe piercing method according to the present invention, piercing and rolling is performed using the plug used for piercing and rolling carbon steel or low alloy steel containing 5% or more of Cr in advance.

[Action]

As a result, the method of the present invention can extend the service life of the plug, although the detailed mechanism thereof is unknown as described above.

〔Example〕

 The present invention will be specifically described below with reference to the drawings.

FIG. 1 is a partially cutaway plan view showing an embodiment in which the method of the present invention is applied to a two-roll piercer using a disc roll as an outer surface restricting tool, and FIG. 2 is a portion taken along line II-II in FIG. FIG. 3 is an enlarged sectional view, and FIG. 3 is a side view taken along the line III-III in FIG. 1, in which 1 and 2 are main rolls, 3 and 4 are disc rolls, 5 is a plug, B is a solid billet, and H is H. Shows a hollow shell.

The main rolls 1 and 2 have gorge portions 1g and 2 at the middle portion in the axial direction.
g, the diameter is gradually reduced toward the tip side from here, and the diameter is gradually increased toward the rear single side to form a frustoconical shape, respectively, and a path through which the solid billet B and the hollow shell H pass. Line-X-X lines are arranged to face each other, and the end portion on the entry side where the solid billet B is loaded is inclined at a required angle β (referred to as an inclination angle) about the pass line X-X and the pass line X- Approach toward the X-ray side, the required angle γ with respect to the pass line XX line
They are arranged so as to be inclined (referred to as a crossing angle) and have an entrance side surface angle α ₁ and an exit side surface angle α ₂ , which can be rotationally driven in the arrow direction by drive sources (not shown).

The disc rolls 3 and 4 are arranged so as to be respectively located between the main rolls 1 and 2 on both sides (left, right or upper, lower) of the pass line X-X, and a solid billet B and a hollow shell H.
The material is prevented from rolling outwardly on the outer peripheral surface of the to prevent the material from bulging outward, and can be rotationally driven to assist the propulsion of these materials.

The base end of the plug 5 is rotatably supported by the tip of the cored bar 6, and the end of the plug 5 is disposed on the pass line X-X with the end of the plug 5 facing the entry side of the solid billet B.

The solid billet B is fed in the direction of the blank arrow while being heated to a predetermined temperature, and the tip portion thereof is caught between the main rolls 1 and 2. As a result, the solid billet B is regulated by the disc rolls 3 and 4 in the middle of the two main rolls 1 and 2, and the plug 5 is rotated while being rotated around the axis and moving in the axial direction. The hollow shell H is formed by being penetrated and pierced and rolled.

And in the method of the present invention, the solid billet B contains 1% of Cr.
In case of difficult-to-process materials such as high Cr steel containing more than 2% by weight, stainless steel, Ni-based alloys, Ti and Ti alloys, carbon steel or low alloy steel containing 5% or less of Cr The plug used for piercing and rolling the actual billet, that is, the pre-rolling plug is used.

If the plug is a new one with a scale layer attached to its surface by, for example, a scale treatment, this pre-rolling is 5
Perforated rolling for 10 solid billets, ie 5-10
Do about a pass.

The mechanical strength of the base material is not limited to a new plug, even if it is a used plug in which the stainless steel solid billet is used for only one pass and the scale layer is slightly worn. Unless it is remarkably impaired due to the influence, it can be reused by re-piercing and rolling the carbon steel for several passes.

Furthermore, while applying a pre-rolled plug to difficult-to-form materials, etc., the life of the plug will be extended if the usage is temporarily stopped before the fatal wear occurs and pre-rolling is performed on a carbon steel solid billet or the like. Has an effect on.

Needless to say, the carbon steel used for pre-rolling and the low-alloy steel containing 5% or less of Cr may be prepared only for the purpose of this pre-rolling. Alternatively, pre-rolling may be performed by applying a plug that should be used for producing seamless pipes made of difficult-to-process materials such as high Cr steel and stainless steel when producing seamless pipes made of low alloy steel containing 5% or less of Cr. It is desirable to give it.

[Test Example 1] The inclined rolling mills shown in FIGS. 1 to 3 were used, and the plugs were subjected to a scale treatment, and five solid billets each having a component composition as shown in Table 1 were prepared in advance. Rolling was carried out.

The rolling conditions are as follows.

Solid Billet Dimensions Diameter: 60mm Length: 500mm Temperature: 1200 ° C Inclined roll Gorge part diameter: 450mm Roll barrel length: 200mm Crossing angle: 20 ° Inclination angle: 10 ° Input / exit side angle: 3.5 ° Rotation speed: 60rpm Plug diameter: 44mm Length: 100mm Material: C: 0.2%, Si: 0.5% Mn: 0.5%, Ni: 1.2% Cr: 3.5% Adhesive scale thickness: 200μm Hollow shell dimensions Outer diameter: 62mm (typical value) Wall thickness ： 8mm Length ： 1040mm After that, SUS304 and Ti alloy are pierced and rolled in pairs of two,
The wear states of the plugs were compared.

The results are shown in Table 2.

A plug that was not pre-rolled was also prepared, and piercing-rolling was performed under the same other conditions.

The results of the punching test for the Ti alloy were almost the same.

[Test Example 2] Using the plug A shown in [Test Example 1], the solid billet sample No. 1 shown in Table 1 was again pre-rolled with 5 pieces, and then 2 pieces of SUS304 were punched.

As a result, the deformation at the tip of the plug was increased, but there was almost no change in the body, and it was in a state in which it could be used.

Further, for comparison, plug A not pre-rolled was similarly perforated with two SUS304s, and as a result, a halfway stop occurred at the second plug.

In the above description, a two-roll piercer that uses a cone-type roll as the main roll has been described as an example, but a three-roll piercer that does not use an outer surface regulation tool, the two-roll piercer whose main roll is a barrel-type roll, and the like are also applicable. Needless to say.

〔effect〕

As described above, in the method of the present invention, pre-rolling is performed by drilling carbon steel or a low alloy steel containing 5% or less of Cr in advance with respect to a conventional plug made of an inexpensive material prior to drilling of a difficult-to-work material. It is possible to extend the life of an inexpensive plug only by applying the above, and it is also economically advantageous because it is not necessary to prepare another plug made of a special material or the like.

[Brief description of drawings]

FIG. 1 is a partially cutaway plan view showing an embodiment of the method of the present invention,
2 is a sectional view taken along the line II-II in FIG. 1, and FIG.
It is a side view by the III-III line of a figure. 1, 2 ... Main roll 3, 4 ... Disc roll 5 ... Plug B ... Solid billet H ... Hollow shell

Claims (1)

[Claims] 1. A seamless pipe piercing method for piercing and rolling a solid billet made of a difficult-to-work material using an inclined rolling mill, wherein a carbon steel or a low alloy steel containing 5% or less of Cr is piercing-rolled in advance. A method for perforating a seamless pipe made of a difficult-to-process material, characterized in that piercing and rolling is performed using the plug used for.