JPH02268909A - Plug for manufacturing seamless steel tube - Google Patents

Abstract

PURPOSE:To improve the life of a plug and to manufacture a hollow piece excellent in inside quality by composing the plug of the surface layer coming into contact with a material to be pierced made of specified composite material and a core material made of other material. CONSTITUTION:In the plug 1 for the manufacture of a seamless steel tube, the surface layer 3 coming into contact with the material to be pieced has a composite structure of Mo or Mo alloy where ceramic particles are dispersed and the inner core material 4 is made up of other material such as hot tool steel. As a result, since brittleness in the room temperature is avoided and growth of the particles is prohibited by compounding ceramic particles composed of Mo, the life of the plug 1 is improved drastically. This material is provided with very excellent wear resistance, erosion resistance, seizure resistance to the piercing and rolling of high alloy material and besides, it is not broken and improved in life. Further, since the metal flow of the material to be worked can be maintained and seizure flaws do not occur, the hollow piece having good inside quality can be manufactured stably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a plug used in the manufacture of seamless steel pipes.

[Conventional technology]

In the manufacturing process of seamless steel pipes, the drilling process, rolling process (elongator, plug mill), polishing process (reeler)
Various shapes of plugs are used. During drilling or rolling, the surfaces of these plugs are subjected to high pressure and high shear forces at high temperatures, which often causes wear, erosion, seizure, etc.

As a result, not only the life (durability) of the plug was shortened and there was a problem with its durability, but also the quality of the inner surface of the obtained steel pipe was adversely affected. Therefore, several inventions have been made to improve the durability of plugs.

In general, the steel pieces used as materials for seamless steel pipes include low-alloy steel and high-alloy steel. Conventionally, 0.
A plug is used in which an oxide layer is formed on the surface of a plug body made of 3%C-3%Cr-1%Ni-based low alloy steel.

For example, in Japanese Patent Publication No. 5B-19363, by applying heat treatment, and in Japanese Patent Publication No. 59-13924,
In the publication, an oxide layer is formed on the surface of the plug body by thermal spraying a powder mainly composed of iron oxide. According to the plug, the chromium content is 2.25w.
When preparing a 4-8 m hollow piece from a steel billet made of low-alloy steel up to t%, it can withstand 500-1500 drillings and extend the plug life.

However, when drilling a piece of high-alloy steel such as Cr steel with a chromium content of 1113 wt% or more or austenitic stainless steel, it is important to note that these steel pieces have high high-temperature strength and that chromium oxides are present on the surface of the steel piece. As a result, the supply of iron oxide from the rope to the plug surface is cut off, resulting in severe seizure of the plug, and as shown in FIG. 4, the plug 1 undergoes severe melting and seizure. Therefore, the lifespan of a plug is only about five times at most, and in some cases, it is often necessary to stop using it after one puncture.

Furthermore, although the plug is designed to be ideal for metal flow of material during drilling, the plug tip wears out during drilling, resulting in retraction of the plug tip. As a result, the time it takes for the material to come into contact with the plug tip increases, which increases the plug tip reduction ratio, increases the possibility that the material will cause rotary forging cracks, and causes a decline in the inner surface quality of the hollow piece.

Recently, there has been a movement to use plugs made of various heat-resistant alloys to drill holes in these high-alloy steel billets. The material of this plug is a material with high temperature strength and high seizure resistance.
Molybdenum is often applied.

However, in the case of plugs made of molybdenum, not only are the material costs expensive (the machining costs are high due to the difficult-to-cut materials and the complicated shape of the plugs, resulting in high plug production costs). There was a problem that it was very expensive.Furthermore, molybdenum has a specific gravity 1.3 times that of steel, so a plug made of molybdenum is heavy.
This leads to a decrease in work efficiency. Furthermore, because molybdenum has a thermal conductivity more than three times that of steel, it causes a large temperature rise in the mandrel bar that supports the force applied to the plug at the rear of the plug, or in its mounting area, causing deformation of the mandrel bar. This caused problems such as seizure with the plug.

One method for solving this problem is to coat the plug surface with a molybdenum layer. For example, JP-A-61-2
In JP-A No. 86077, thermal spraying and hot isostatic pressure treatment were used to obtain the results of JP-A-62-50009 and JP-A-62-
Publication No. 238011 proposes that the surface of the plug be coated with a molybdenum thermal spray layer or powder layer by hot isostatic pressure treatment after being encapsulated in a capsule.

[Problems to be Solved by the Invention] These proposals solve the problems of the molybdenum plugs mentioned above. However, molybdenum and molybdenum alloys are very brittle at room temperature, so they can easily break due to the impact force applied during the initial stage of drilling, and as the drilling process progresses, the structure becomes coarser due to heat transmitted from the material to be drilled, reducing its strength. There was a problem in that it led to this, and eventually it was destroyed.

In their research on molybdenum plugs, the inventors also recognized this brittleness at room temperature as a problem, and took several measures to improve it, but there were many disadvantages as well.

The present invention addresses the problems of melting damage and seizure seen in plugs made of low-alloy steel and heat-resistant steel, thermal effects on the mandrel bar and reduction in workability due to high specific gravity seen in plugs made of molybdenum, and plugs with a molybdenum layer. To provide a seamless steel pipe manufacturing plug that solves problems such as brittleness at room temperature and cracks caused by coarsening of the structure, and can stably manufacture hollow pieces with a long life and good inner surface quality. The purpose is to

(Means for Solving the Problems) The present invention has been made to achieve the above object, and the present inventors have developed a plug made of a composite material in which ceramic particles are dispersed in molybdenum or a molybdenum-based alloy. This goal was successfully achieved by comprising a surface layer in contact with the core material and a core material made of another material.

The shape of the plug is usually approximately bullet-shaped, and the bottom surface is provided with a fitting hole, a fitting protrusion, etc. for attaching a mandrel.

It is also known that the head is hemispherical or umbrella-shaped. The shape of the plug of the present invention is not limited to these, and may be any known shape.

This plug consists of at least a surface layer that contacts the object to be drilled, and a core material that is in contact with the inner surface of the surface layer. The surface layer may be provided over the entire outer surface of the plug or only in areas susceptible to damage by perforation.

By providing unevenness on the surface that contacts the surface layer of the core material, the uneven portion can absorb shear due to the reaction force received from the rotational force of the object to be drilled during drilling, thereby preventing deformation and cracking of the tip of the plug. A shallow unevenness such as a shot blast surface is insufficient for this uneven shape, and a round, triangular or square crater shape or a circular, triangular or square groove shape with a certain depth is preferable. Protrusions or protrusions may be used instead of the above-mentioned depressions and grooves, but in this case there is a disadvantage of increasing the thickness of the surface layer. The size of the unevenness, that is, the diameter, width, and depth, also depends on the size of the plug, but the relative value to the plug diameter is 0.
．． Although a sufficient effect can be found at about 0.005 to 0.5, it is practically preferable to use about 0.05 to 0.2.

Although the distribution of the unevenness may be irregular, it is preferable that the unevenness be arranged at equal intervals. Further, it is preferable that the corner portions of the grooves be rounded to avoid stress concentration.

The core material has a linear expansion coefficient of 3.5X1 from room temperature to 1300°C.
It does not matter whether it is a metal, alloy, or ceramic as long as it is 0-' to 13X10-6/'C, but if the core material is to have an uneven shape, use a material with a higher coefficient of thermal expansion than molybdenum or molybdenum-based alloys, that is, 20° It is preferable to use a material having a thermal expansion coefficient of 4.8xlO-6/'C or higher at C and 7.4xlO-"/"C or higher at 1300°C. For example, 5K
Hot work tool steels such as 061, Nimonic and N
Superalloys such as imoiyal and TiB with even higher high temperature strength
There are ceramics such as Zr0t and Zr0t. If a material with a larger coefficient of thermal expansion than molybdenum is used for the core material and the uneven shape is made into a square groove, the groove will have radial cuts, so it will be difficult to cool down after TIP (during production). Due to the difference in thermal expansion coefficient between molybdenum and the core material, compressive stress acts on the interface between the two on the side surfaces of the groove, which has the advantage of firmly shrink-fitting the two.

Methods for finishing these materials into uneven core materials include a machining method in which the billet is simply cut out, a casting method, and a powder metallurgy method in which powders of these materials are molded and then sintered.

Next, the surface of the core material thus produced is coated with a composite material in which ceramic ink particles are dispersed in molybdenum or a molybdenum-based alloy. The base material molybdenum or molybdenum-based alloy may be any material that has excellent lubricity and strength properties at high temperatures, and in addition to pure molybdenum, for example, TZM (0
,5 decaytχTi-0,07reχZr-0.05wtXC
-Ba1. Mo), TZC (1,0 decaytχTi-0
, 14ivtχZr-0, 1wtχC-Ba1. Mo)
, ZtlM(0,72wtXZr-0,14wtX
tlf-0,05wtχC-Ba1. Mo), Ml
(C(1, OwtχHf-0,05WtχC-Ba1.
Mo) etc. can also be used.

Ceramic particles can be made of one or a combination of various oxides, carbides, nitrides, and borides; is preferred.

Examples of preferred ceramic particles include ZrO□, Ce,
Oly, o,, Ah(h, TiO2, Lag's, Sm
103, etc. The particle shape may be general granular, fibrous, or the like. The particle size of ceramic particles is about 0.01 to 5n in the case of granular particles, preferably 0.0
Approximately 2 to 1n is appropriate. In addition, the amount of dispersion is 1% by volume.
It is preferably about 20%, preferably about 5 to 10%.

Dispersion of the ceramic particles in the ceramic molybdenum or molybdenum base metal is carried out by homogeneous mixing with particles of molybdenum or molybdenum-based alloy. The grain size of the molybdenum or molybdenum-based alloy is suitably about 0.5 to 10 μm, preferably about 1 to 5 μm.

Coating methods include cutting the billet by machining and then joining it to the core material by HIPIP fitting, as well as sintering, which solidifies and joins molybdenum or molybdenum-based alloy powder in which ceramic particles are dispersed. Examples include the HIP method, the Canning HIP method, and the explosive molding method (impact molding method), but any other solidification techniques may be applied. Among these methods, the Canning HIP method is briefly explained as follows. First, the powder is subjected to cold isostatic pressing (CIP).
Molded using a molding method such as Next, this is inserted into a metal capsule, thoroughly dried by vacuum heating and degassing, and then vacuum sealed in the capsule and subjected to IP treatment.

After joining, the outer surface is finished if necessary and the parts are ready for use.

The plug of the present invention can be applied not only to a plug for drilling a steel billet as described above, but also to a plug used for an elongator, a plug mill, a reeler, etc.

[Function] Molybdenum is generally brittle at room temperature, so it may break at the initial stage of drilling, or grains grow during drilling, resulting in a decrease in strength and eventually breakage. It avoids brittleness at room temperature and suppresses grain growth to prevent brittleness.

〔Example〕

Embodiment 1 A state in which a plug 1 according to an embodiment of the present invention is attached to a mandrel bar 2 is shown in FIGS. 2(a) and 2(b). This shows the case of a piercer plug as an example; (a) is a side view thereof, and (b) is a side view of section 8-A in FIG. 1(a).

In this plug 1, the surface layer 3 that contacts the object to be drilled is ZrO□
It has a composite structure of molybdenum in which particles, Y2O3 particles, and Ah03 particles are dispersed, and the internal core material is hot work tool steel (
SKD61). The plug has a warhead shape with the tip of a cone rounded into a substantially hemispherical shape.

The plug 1 is attached to the tip of a cylindrical mandrel bar 2. A fitting hole 5 of a predetermined depth for attachment to the mandrel bar 2 is bored in the bottom of the plug I. on the other hand,
A protrusion 6 is provided at the tip of the mandrel bar 2, and the plug 1 and the mandrel bar 2 are fitted through the fitting hole 5 and the protrusion 6.

In this example, a test was conducted to see how much improvement there would be compared to a case where the coating layer was a composite material of molybdenum in which Zrot particles, Y2O3 particles, and A1z03 particles were dispersed.

A core material with an outer diameter of 26 mm and a length of 60 n+m was prepared for a model test plug with an outer diameter of 32 mm and a length of 76 a+m.

The coating layer is pasted on the surface of the core material by wet mixing various ceramic particles with an average particle size of 0.02 μm with molybdenum powder with an average particle size of 1N in 10% by volume, and then solidifying and bonding the dried powder using the Canning HIP method. Ta.

Details of the manufacturing conditions of the plug are shown in Table 1.

Table 1 Plug Manufacturing Conditions Model drilling tests were conducted on these four plugs using a small drilling machine. The material to be drilled was a round steel piece made of 13% CrtFfl with a diameter of 40 rtm and a length of 200° C. and a temperature of 1250° C., and was processed into a hollow piece with a diameter of 42+ ma, a thickness of 6 ann, and a length of 400 rtm. Note that the test was conducted without preheating the plug. Table 2 shows the service life and damage state of the plug as a result of the model drilling test.

Table 2 Model drilling test results As shown in Table 2, the specimen of the present invention succeeded in drilling more than ten holes without preheating.

In this way, the effect of compositing molybdenum with ceramic particles has been fully demonstrated.

Embodiment 2 A plug I, which is another embodiment of the present invention, is connected to a mandrel bar 2.
Figures 2 (a) and (b) show the state in which it is installed.

This is an example of the case of a poorer plug (
a) is its side view, (b) is the AA in Fig. 2 (a)
FIG.

This plug 1 has a surface layer 3 that contacts the object to be drilled.
It has a composite structure of molybdenum in which particles, Y2O1 particles, and AhOs particles are dispersed, and the internal core material 4 is made of a material with a higher coefficient of thermal expansion than molybdenum. In addition, the core material 4 is
A groove 7 having an uneven shape as shown in FIG. 2(b) is formed on the surface. The plug has a warhead shape with the tip of a cone rounded into a substantially hemispherical shape. The plug l is attached to the tip of a cylindrical mandrel bar 2. The bottom of the plug 1 has a fitting hole 5 of a predetermined depth for attaching to the mandrel bar 2.
is drilled. On the other hand, a protrusion 6 is provided at the tip of the mandrel bar 2, and the plug 1 and the mandrel bar 2 are fitted through the fitting hole 5 and the protrusion 6.

The method for manufacturing the plug is as follows. In this example, the shape of the core material 4 is also bullet-shaped like the plug, but several grooves 7 are formed in the axial direction.

In this example, we investigated how much improvement is achieved when the coating layer is made of a composite material of molybdenum in which ZrO1 particles, YzOs particles, and AhO:+ particles are dispersed, compared to the case where pure molybdenum is coated. We tested to see how much improvement there would be if we did so.

A core material with an outer diameter of 26 mm and a length of 60 mm was prepared for a model test plug with an outer diameter of 32 mm and a length of 76 fflffi.

The core material has a width of 2.5 mm and a length of 60 mm on its outer circumference.
Six Il grooves were carved at equal intervals, and the corners were rounded.

The coating layer was coated on the surface of the core material by wet mixing various ceramic particles with an average particle size of 0.02Q with molybdenum powder with an average particle size of 1 μm at a volume percent of 10Q, and then solidifying and bonding the dried powder using the Canning HIP method. After that, plug 1 was manufactured by finishing processing.

In addition, instead of grooving the core material as in the comparison,
Those with a nickel intermediate layer between the coating layer and the core material,
A core material whose surface was subjected to shot blasting treatment to make the interface between the molybdenum coating layer and the core material irregular was prepared and compared with the plug of the present invention.

Table 3 Plug Manufacturing Conditions A model drilling test was conducted on these seven plugs using a small drilling machine. The material to be drilled is made of 13% Crjil and has a diameter φ
A round steel piece measuring 40M, length 200mm, and temperature 1250°C was processed into a hollow piece with diameter φ42, thickness 6 ornaments, and length 400mm. Note that the test was conducted without preheating the plug. Table 4 shows the service life and damage state of the plug as a result of the model drilling test.

Table 4 Model Drilling Test Results As shown in Table 4, the specimen of the present invention had a very long life without being preheated before use, and was able to successfully drill tens of times as many holes as Nα10 and Nα11.

In this way, the effectiveness of compositing molybdenum with ceramic particles and grooving the core material was fully demonstrated.

Example 3 Next, an example in which the present invention is applied to a plug mill plug is shown in FIGS. 3(a) and 3(b). (a) is a side view of the plug, and (b)
) is a side sectional view of the core material 4.

Like the piercer plug, this plug 1 also has a surface layer 3 in contact with the rolled material made of molybdenum, and an internal core material 4 made of a material having a higher coefficient of thermal expansion than molybdenum. In addition, uneven grooves 7 shown in FIG. 3(b) are formed on the surface of the core material 4 so that the bonding interface has sufficient bonding strength against shearing due to the axial force received from the rolled object during rolling. ing. The plug 1 has a substantially truncated conical shape.

The plug 1 is attached to the tip of a cylindrical mandrel bar 2. A through hole 8 of a predetermined diameter is bored in the center of the plug 1 to be attached to the mandrel bar 2. On the other hand, the tip of the mandrel bar 2 is threaded so that the plug 1 and the mandrel bar 2 can be fixed with bolts 9.

The method for manufacturing the plug is as follows. In this example as well, the core material 4 is made of hot work tool steel (SKD61) or TiBz ceramics.

The core material 4 is provided with several grooves 7 in the radial direction.

In this example, when the coating layer is a composite material of molybdenum in which ZrO, particles, y, o: 1 particles, and Alt03 particles are dispersed, it was tested to see how much improvement is achieved compared to the case where pure molybdenum is coated.

For a plug for actual use with an outer diameter of φ164M and a length of 120o++n, a core material was prepared in which the outer periphery was processed so that molybdenum could be applied to the outer periphery to a thickness of 20no++. In particular, in this part, two square grooves with a width of 10 marks and a depth of 5 marks were carved at equal intervals in the circumferential direction, and the corners were rounded.

The coating layer is coated on the surface of the core material by wet mixing various ceramic particles with an average particle size of 0.02 μm with molybdenum powder with an average particle size of 1 μm at 10% by volume, and then solidifying and bonding the dried powder using the Canning HIP method. After that, plug 1 was manufactured by finishing processing.

In addition, instead of grooving the core material as in the comparison,
The present invention was produced by providing an intermediate layer of 2.ν Kel between the coating layer and the core material, or by subjecting the surface of the core material to shot blasting to make the interface between the molybdenum coating layer and the core material irregular. compared to plug.

Table 5 shows the manufacturing conditions of the plug.

Table 5: Plug manufacturing conditions A rolling test was conducted on these six plugs using an actual drilling machine. The material to be rolled is a cylindrical steel piece made of 13% Cr1il processed into a hollow piece, and the temperature was set to 1100 in advance.
It was heated to ℃ and used. Table 6 shows the rolling cost and damage condition of the 17 plug at its service life limit, as a result of the actual machine test.

Table 6 Actual machine test results As shown in Table 6, the specimen of the present invention had a very long life without being preheated before use, and was successfully rolled several tens of times as much as No. 17.

In this way, it has been proven that combining molybdenum with ceramic particles and grooving the core material is sufficiently effective and can also be applied to plug mill plugs.

〔Effect of the invention〕

As explained above, the plug of the present invention provides the following effects.

(1) Since the brittleness of the molybdenum-based coating layer at room temperature was avoided, the plug of the present invention did not require preheating, resulting in improved workability.

In addition, since the growth of crystal grains in the coating layer is also suppressed, the life of the plug is greatly improved.

(2) It has extremely excellent wear resistance, erosion resistance, seizure resistance, etc. against drilling and rolling of high alloy materials, does not break, and has a significantly extended lifespan.

Further, since the ideal metal flow of the material to be drilled and the material to be rolled can be maintained and seizure defects etc. do not occur, hollow pieces with good inner surface quality can be stably manufactured.

(3) Compared to a structure made entirely of molybdenum, the weight can be reduced, and heat shadows on the mandrel bar can also be avoided.

(4) By providing the core material with an uneven shape, the bondability between the coating layer and the core material was improved, leading to a significant improvement in the lifespan.

Therefore, it has been possible to improve the working efficiency of seamless steel pipe manufacturing and to significantly reduce costs, resulting in industrially useful effects.

[Brief explanation of drawings]

FIGS. 1 and 2 are views showing an embodiment in which the present invention is applied to a piercer plug, and FIG. 1A is a side view thereof, and FIG. Fig. 3 shows an embodiment in which the present invention is applied to a plug mill plug, in which (a) is a side view thereof and (b) is a side sectional view of its core material. 4 is a side view showing an example of damage caused by use of a conventional plug. 1... Plug, 2... Mandrel bar, 3... Surface layer, 4... Core material, 5... Fitting hole, 6... Convex part, 7
...Groove, 8...Through hole, 9...Bolt Patent applicant Nihon Kokan Co., Ltd. Agent Patent attorney Kuninaka Political Affairs (a) (b) Summer figure (a) (b) Fig. 2 (a) Figure 3 Figure 4

Claims (2)

[Claims] (1) Plug for seamless steel pipe manufacturing consisting of a surface layer in contact with the object to be drilled, which is made of a composite material made of molybdenum or a molybdenum-based alloy with ceramic particles dispersed therein, and a core material made of another material. (2) The plug for seamless steel pipe manufacturing according to claim (1), wherein the surface with which the surface layer of the core material contacts is provided with an uneven shape.