JPH08309408A - Manufacture of seamless pipe excellent in resistance of piercing plug - Google Patents

Abstract

PURPOSE: To manufacture a seamless pipe made of a high alloyed steel, etc., with high rolling efficiency. CONSTITUTION: A billet made of an alloyed steel containing Cr or Ni with at least 5wt.% or over or an alloy whose main components are Cr, Ni or Mo, is pierced by using a piercing plug made of Mo, Mo alloy or a heat resisting steel. A plate is joined on an end face on a side on which the piercing of the billet is started, or plates are jointed on both end faces. The billet with a plate (or plates) joined in this way is hot-pierced by using a piercing plug to process a hollow base stock. By rolling the attained hollow base stock, a seamless pipe is manufactured. Consequently, the resistance of the plug is improved, the life of the plug is extended, the frequency of a plug replacement is reduced, and the reduction in the consumption unit of a tool is attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention is particularly applicable to 13Cr steel, S
Seamless steel pipe made of high alloy steel such as stainless steel such as US304 and SUS316, and N of 25 wt.% Or more, for example
When manufacturing seamless metal pipes made of high alloys containing i as a main component (hereinafter, seamless steel pipes and seamless metal pipes are collectively referred to as "seamless pipes") The present invention relates to a method for manufacturing a seamless pipe having a long life of a piercing plug and capable of achieving a longer life.

[0002]

2. Description of the Related Art Generally, a seamless tube is prepared by forming a round or square billet into a hollow shell by mannesmann punching, press punching, hot extrusion, or the like.
The hollow shell prepared in this way is stretched by a rolling machine such as an elongator, a plug mill or a mandrel mill, and finally subjected to a step of sizing with a sizer or a stretch deducer (hereinafter referred to as "continuous rolling process"). Become a product.

A piercing plug used for Mannesmann piercing or press piercing is constantly in contact with a billet heated to a high temperature of about 1100 to 1300 ° C., and further, is subjected to a high load, and therefore is damaged during piercing. Conventional drilling plugs can withstand hundreds of drillings, for example when drilling billets made of carbon steel (non-high alloy steel),
r steel, high alloy steel typified by stainless steel such as SUS304 and SUS316, or N of 25 wt.% or more
Cr and N typified by high alloys containing i as a main component
When a billet made of a high alloy containing i or Mo as a main component (hereinafter referred to as “high alloy steel”) is perforated, it is severely damaged as shown in FIGS. 4 and 5, and is severely damaged once or several times. There are even cases where it is not possible to drill itself. Figure 4,
FIG. 5 is a side view showing an example of a damaged piercing plug. In FIGS. 4 and 5, 1 is a piercing plug main body, 5 is a melt-down deformation of the tip, 6 is a body wrinkle flaw, and 7 is a head. It is seizure of perforated material on the part. As described above, in the case of drilling a billet made of carbon steel, if a drill plug which can be used for several hundred passes is applied to the billet made of the above high alloy steel or the like, the life is extremely shortened. Therefore, the adverse effect caused by this not only causes an increase in the basic unit of the tool but also causes a reduction in the rolling efficiency due to the replacement of the damaged tool, which causes an increase in the production cost and even a situation where the manufacturing is impossible.

[0004] In order to solve the deterioration of the plug durability at the time of perforating a billet made of the above high alloy steel or the like, many techniques as shown in the following (1) to (4) have been proposed.

(1) Mo (molybdenum) for the perforated plug
For example, a material with higher strength at high temperature than alloy steel is used to prevent plug damage due to deformation.

(2) By applying a lubricant from a part of the plug surface between the pipe and the plug, damage due to seizure is prevented.

(3) A hardener or the like is adhered to the surface of the plug by various surface treatments to prevent seizure and wear and to improve durability.

(4) In order to use the oxide scale as a lubricant, the thickness of the scale or the atmosphere for heat treatment of the plug is changed so as to increase the adhesiveness, thereby improving the durability.

As an example of the above techniques (1) to (4) and a slight improvement, in (1), Japanese Patent Publication No. 2-133106 (hereinafter referred to as "Prior Art 1"), (2) ), JP-A-2-284708 (hereinafter, referred to as "Prior Art 2"), and (3), JP-A-63-63.
-192504 (hereinafter referred to as "Prior Art 3"), and in (4), JP-B-63-54066 (hereinafter referred to as "Prior Art 4") and the like.

However, in the above-mentioned prior art, there are very few that actually work effectively.

In the prior art 2, it is considered possible to prevent seizure between the agent to be drilled and the plug with at least one perforation, but it is very difficult to supply a further lubricant. Also, in other lubricant supply methods, such as supplying lubricant from the plug head through the bar that supports the plug, the plug tip that is the lubricant flow path is damaged,
Alternatively, there is a problem that the pipe material is clogged in the flow path, and it is difficult to withstand continuous use in an actual machine.

On the other hand, a perforated plug made of low alloy steel, for example, 3Cr-1Ni (hereinafter referred to as "conventional component"), which is considered to have the most applications at present, is heat-treated before perforation, and its surface scale is adjusted. The technology used as a lubricant is
It is useful in that the durability can be improved without changing from the conventional drilling method. However, its service life is at most about 10 passes, which is far below that of ordinary steel drilling, and it is impossible to realize a significant reduction in tool unit consumption and improvement in rolling efficiency.

Further, the perforation technique 1 using Mo as the plug material has many advantages such as a high effect of preventing the plug deformation itself and anticipation of seizure resistance, but Mo is expensive and 400 ° C. It has a property of being extremely brittle in a low temperature range up to a certain degree, and there are many problems in industrial use such as this and cracking due to thermal stress are likely to occur.

The prior art 3 has a wear-resistant layer so that damage to the plug can be suppressed, but since it is a hard material, it easily cracks due to repeated thermal stress.
It is hard to say that the technology for using actual equipment is established in that the surface treatment layer peels off.

Therefore, as a means of realizing the extended life of the perforated plug and manufacturing at low cost, Mo or Mo alloy, or ceramics having high wear resistance is arranged at the tip of the plug, and the body portion is provided. A conventional plug that has been subjected to an oxidation treatment or a surface treatment is disclosed in JP-A-62-207503 (hereinafter referred to as "Prior Art 5") and JP-A-62-244.
505 (hereinafter referred to as "Prior Art 6").

The piercing plugs disclosed in Prior Art 5 and 6 (hereinafter referred to as "composite plugs") are all Mo
Of the perforated plugs that are expensive if they are made of a high-strength metal simple substance, only the plug tip portion that receives a high stress load is the high-strength material, and the other parts are mainly made of inexpensive alloy steel,
The purpose is to reduce the cost of the tool, and the cost per drilling is reduced to near that of the conventional one, and the effect is high by the amount corresponding to the improvement of rolling efficiency.

However, since the thermal stress caused by friction between the billet material and the plug body cannot be reduced during processing, cracking due to thermal stress cannot be suppressed. In addition, since the oxide scale applied to the plug body is no different from the conventional technology, if the body is damaged by piercing, even if the head is healthy and piercing is possible, the inner surface quality and accuracy can be improved. Is significantly deteriorated, and as a result, the manufacturing cost cannot be reduced.

[0018]

The problems of the prior art described above are summarized as follows.

When the perforated plug is made of a conventional component, alloy steel such as low alloy steel, the strength of the plug decreases due to the heat mainly received from the material to be perforated or the heat generated by the processing heat of the material during the perforation. A high load causes meltdown-like deformation.

With the alloy steel piercing plug, when piercing a material (billet) which is unavoidably damaged,
Surface hardening wear-resistant plugs and heat-resistant alloys mentioned above, Mo, Mo
The use of a plug made of an alloy or the like does not lead to an improvement in plug durability mainly due to surface cracking, and in the case of a composite plug, the problem cannot be solved mainly due to damage to the body. Therefore, a method for extending the life of a perforated plug, which has the effects of reducing manufacturing costs and improving rolling efficiency, has not yet been established.

As described above, when a seamless pipe is manufactured from a billet made of a high alloy steel or the like by a continuous rolling process using the Mannesmann piercing method or the like, the durability of the piercing plug is significantly extended as compared with the conventional one. Therefore, a technology that can reduce the manufacturing cost is desired.

Therefore, in view of the above situation, an object of the present invention is to use an inexpensive high alloy steel or the like without affecting the rolling efficiency even when manufacturing a seamless pipe from a billet made of the high alloy steel or the like. It is possible to manufacture seamless pipes,
It is an object of the present invention to provide a method for manufacturing a seamless pipe having excellent durability of a piercing plug.

[0023]

According to the first aspect of the present invention,
A billet comprising an alloy steel containing at least 5 wt.% Or more Cr or at least 5 wt.% Or more Ni, or an alloy containing any one of Cr, Ni and Mo as a main component is used. The steel plate is joined to the end surface on the side where the piercing of No. 1 is started, or both end surfaces are joined, and the billet joined to the steel sheet is a piercing plug made of any one of Mo, Mo alloy and heat-resistant steel. Then, hot piercing is performed to prepare a hollow material, and the obtained hollow material is rolled to produce a seamless pipe.

According to a second aspect of the present invention, in the first aspect of the present invention, a plug body made of any one of Mo, Mo alloy and heat-resistant steel, and formed on the surface of the plug body, It is characterized by using a perforated plug made of a hard layer having high strength and / or abrasion resistance even at high temperatures.

According to a third aspect of the present invention, in the first aspect of the invention, the plug body is made of any one of Mo, Mo alloy and heat-resistant steel, and is formed at the tip of the plug body. Another feature is that a perforated plug including a plug head made of any one of Mo, Mo alloy, and heat resistant steel is used.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the plug body is made of any one of Mo, Mo alloy and heat-resistant steel, and is formed at the tip of the plug body. In addition, a plug head made of any one of Mo, Mo alloy and heat-resistant steel, and a high strength and / or resistance even under high temperature formed on the surface of the plug body and / or the plug head. It is characterized by using a perforated plug made of a hard layer having abrasion resistance.

The invention according to claim 5 is the invention according to claim 2 or 4.
In the invention described above, the hard layer includes stellite, a ceramic obtained by adding WC to stellite, a ceramic obtained by adding a mixed composition of WC and Co to stellite, and a compound of Cr and C added to stellite. The feature is that it is any one of the ceramics.

[0028]

The function of the present invention will be described in detail below.

First, regarding the perforated plug made of Mo or Mo alloy, which has been difficult to use due to damage such as cracking, the life extension effect of joining steel plates is as follows.

The inventors of the present invention have found that the plug is cracked and damaged by repeated thermal stress.
The surface temperature of the head of a perforated plug made of an alloy was measured by a model perforator under the same perforation conditions as the actual machine. At this time, for comparison, a similar test was performed on a plug made of a low alloy steel and used for perforating a conventional alloy steel and having been subjected to an oxidation treatment. The results are shown in FIG. In FIG. 6, ○ indicates a perforated plug made of Mo or Mo alloy (non-treated metal skin plug), and ■ (black square) indicates a plug subjected to oxidation treatment of low alloy steel (plug with oxide scale). Each is shown. As shown in FIG. 6, the surface temperature of the untreated metal skin plug is always higher than that of the oxide scale plug having a scale on the surface. This can be said regardless of whether the plug material is heat-resistant steel or Mo alloy, regardless of the plug material, but when it was cooled to room temperature by air cooling or mist cooling and drilled several times, Surface cracks as known from. In the present invention, heat-resistant steel means "1100 ° C.
High temperature tensile test according to JIS G 0567, the tensile strength is more than 30 N / mm ² .

On the other hand, the perforated plug made of pure Mo is preheated before the perforation so that the surface temperature is about 400.degree.
In the case of a plug that was perforated while keeping the minimum temperature, and in the case of a surface-hardened plug having a hard layer formed on the surface by thermal spraying, by performing forced cooling from inside the plug,
No occurrence of defects could be confirmed even after drilling 10 times or more.

From these results, it is necessary to devise measures such as suppressing an increase in the surface temperature of a plug having a hard layer formed on the surface thereof, including a composite plug, and a plug having low thermal stress resistance. all right.

Therefore, the inventors have come up with the use of oxide scale that effectively functions as a heat insulating layer. That is, as a method for realizing this, a conventional pre-oxidation treatment for a perforated plug,
Unlike the plug protection cover that has been subjected to the pre-oxidation treatment shown in FIG. 8, the oxide scale that is the heat insulating layer is not lost with each drilling, and as shown in FIG. This is a method in which oxide scale is supplied to each plug.

The oxide scale supply from the billet side according to the present invention can be carried out in the same manner as the oxide scale film formation treatment by the heat treatment for each perforation. By using this, as shown in FIG. 9, it is possible to suppress an increase in the surface temperature of the perforated plug. In FIG. 9, the mark □ is a plug by the supply of oxide scale from the billet side of the present invention (the plug of the present invention), and the mark ■ (black square) is a plug for oxide scale film formation treatment (plug with oxide scale). Therefore, one is that the application of oxide scale coating, which was only possible with conventional alloy steel plugs such as plugs,
It enables application to plugs made of Mo or Mo alloys that sublime at high temperatures, and is effective in extending the life. Further, oxide scale itself can be generated in billets such as high alloy steels, but the amount of oxide scales is extremely smaller than that of carbon steel or low alloy steel, as represented by stainless steel and heat resistant steel. In this case, the effect cannot be expected only from the billet end face. Therefore, by actively transferring the oxide scale generated from the steel plate joined to the billet end face to the perforated plug and using it for heat insulation, the thermal stress generated in the plug is reduced, the occurrence of cracks is suppressed, and the durability of the plug is improved. It can be extended.

Next, on the surface of the plug, a hard layer having high strength and / or abrasion resistance even at high temperature (hereinafter referred to as "hard layer"), for example, 30Cr-Co based alloy (stellite) or stellite. WC, WC-Co, Cr
_With respect to the plug formed with the layer made of ceramics or the like having the component composition to which ₂ C-based material or the like is added, the reason substantially similar to the contents shown in the first is mentioned. That is, the method of the present invention is effective as a method of suppressing the peeling against the problem that the hard layer cannot be used due to the peeling of the hard layer due to thermal stress, although it has obvious advantages over the conventional plug. I found that. This is the oxide scale
Since it effectively functions as a heat insulating material, it can suppress the thermal stress generated between the surface and the plug base material. In addition to the above, as shown in Table 4, general ceramics can be used as the hard layer.

This also applies to, for example, a composite plug in which a perforated plug is formed in a shape including a plug barrel and a plug head formed at the tip of the plug barrel. It can be said that it is very effective because it can suppress the deformation of the plug body, which is considered to be the only drawback. Further, in such a composite plug, the same applies when the hard layer is formed on the plug body and / or the plug head.

The hard layer formed on the surface of the plug body is formed by thermal spraying, plating, TD (VC) treatment, P
Any of VD (physical vapor deposition method) and CVD (chemical vapor deposition method) can be applied, and the method is not limited.

In the case of a composite plug, use of scale coating treatment by oxidation treatment used for ordinary plugs is also included.

[0039]

EXAMPLES Next, the present invention will be described in more detail by way of examples.

Example 1 As shown in FIG. 7, 13Cr
A billet in which a steel plate 9 made of general carbon steel is joined to an end face of the billet 8 made of steel on which drilling is started (hereinafter referred to as “tip face”) (indicated by a joining portion T in the table), A perforated plug 1 having a shape shown in FIG. 1 using a billet made of normal 13Cr steel without joining steel plates.
Under various perforating conditions by the Mannesmann rolling method using a device having at least two pairs of rolls and at least two shoes, the material being used by variously changing the material within the scope of the invention and outside the scope of the invention. Perforation was performed.
Then, the plug life was investigated for each of the used perforated plugs, and the plug life ratio is shown in Table 1. The plug life ratio was based on Comparative Example 1 using a plug made of conventional steel made of 3Cr-1Ni steel.

Drilling conditions: Gorge reduction rate: 7 to 15% Heating temperature: 1050 to 1300 ° C (changed depending on metal type) Used billet diameter; Diameter (outer diameter 40 mmφ, 50 mmφ) Billet metal type; 13Cr steel Joined steel sheet type; General Carbon steel Joined steel plate dimensions; 27 × 27 × 3 mm, 34 × 34 × 3
mm

[0042]

[Table 1]

As shown in Table 1, in Comparative Example 1.2 in which a plug made of pure Mo was used and Example 1 of the present invention, Example 1 of the present invention in which a steel sheet was joined to the tip surface of the billet was a steel sheet. It can be seen that the life of the plug can be extended as compared with Comparative Example 2 in which No. In Comparative Example 2, cracking also occurred. Although not shown in Table 1 of this Example, almost the same results were obtained when the steel plates were joined to both end faces of the billet as when the steel plates were joined to the tip faces.

In Comparative Example 3 and Inventive Example 2 using the plug made of TZM, it is understood that the life of the plug is extended when the steel plate is joined to the tip surface of the billet. Also,
In Comparative Example 3, cracking also occurred.

In both Example 3 of the present invention using the plug made of TZC and Example 4 of the present invention using the plug made of JIS-SUH31, the steel plate was joined to the tip surface of the billet, so that the life of the plug is extended. I understand.

Example 2 Under the same perforation conditions as in Example 1, the plug body 1 was a conventional plug SKD61, and the hard layer 2 having various compositions shown in Table 2 was formed on the surface of the plug body 1. Drilling was performed using a piercing plug having the shape shown in FIG. Then, the plug life of each of the used perforated plugs was investigated, and the plug life ratio is shown in Table 2. The plug life ratio was based on Comparative Example 1.

[0047]

[Table 2]

As is apparent from Table 2, when comparing Comparative Example 4 in which stellite is used as the main component of the hard layer 2 and Example 5 of the present invention, Example 5 of the present invention in which a steel sheet is joined to the tip surface of the billet is shown. It can be seen that the life of the plug can be extended.
When drilling was performed without joining the steel plates, the hard layer 2 was peeled and melted in most cases.
The heat insulating effect according to the present invention eliminates this, and the life of the plug is dramatically extended. In addition, Table 2 of the present embodiment
Although not shown, when the steel plates were joined to both end faces of the billet, almost the same results were obtained as when the steel plates were joined to the tip faces.

WC is added to stellite as the main component of the hard layer 2.
Inventive Example 6 in which -Co was added and Inventive Example 7 in which Cr ₂ C was added to stellite had a longer plug life than Inventive Example 5 composed of stellite alone.

[Embodiment 3] Under the same perforation conditions as in Embodiment 1, a plug barrel 1 made of S45C and a plug head made of TZM fastened to the tip of the plug barrel by a head fastening portion 4 are used. Part 3, plug body 1 and plug head 3
Hard layer 2 having various compositions shown in Table 3 formed on the surface of
Drilling was performed using a piercing plug having the shape shown in FIG. Then, the plug life was investigated for each of the used perforated plugs, and the plug life ratio is shown in Table 3. The plug life ratio was based on Comparative Example 1.

[0051]

[Table 3]

As is clear from Table 3, when comparing Comparative Example 5 and Inventive Example 8 in which stellite was used as the main component of the hard layer 2, inventive Example 8 in which a steel plate was joined to the tip surface of the billet. It can be seen that the life of the plug can be extended.
This is because it was possible to eliminate the decrease in plug life due to peeling of the hard layer. However, Comparative Example 5 in which the steel plate was not joined to the tip surface of the billet was a result that was not much different from the low alloy steel plug. Although not shown in Table 3 of the present embodiment, when the steel plates were joined to both end faces of the billet, almost the same results as when the steel plates were joined to the tip faces were obtained.

As a main component of the hard layer 2, WC is added to stellite.
Inventive Example 9 in which -Co was added and Inventive Example 10 in which Cr ₂ C was added to stellite had a longer plug life than Inventive Example 8 composed of stellite alone.

The components of the alloys used in this example are summarized in Table 4.

[0055]

[Table 4]

[0056]

As described above, according to the present invention, at least 5 wt.% Or more Cr or 5 wt.% Or more N is used.
By improving the plug durability, which is a problem in the production of a seamless pipe made of an alloy steel containing i or an alloy containing any one of Cr, Ni and Mo as a main component, rolling efficiency can be improved. It is possible to realize the improvement and the reduction of the unit consumption of the tool, and it is possible to manufacture the high-value-added seamless pipe at a low price, thus, the industrially useful effect is brought about.

[Brief description of drawings]

FIG. 1 is a sectional view showing a perforated plug according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a perforated plug according to Embodiment 2 of the present invention.

FIG. 3 is a sectional view showing a perforated plug according to Embodiment 3 of the present invention.

FIG. 4 is a side view showing an example of a damaged perforated plug.

FIG. 5 is a side view showing an example of a damaged perforated plug.

FIG. 6 is a graph showing the relationship between the plug surface temperature change during drilling near the tip of the drilled plug and the drilling time.

FIG. 7 is a perspective view showing a billet in which a steel plate is joined to the front end surface according to the embodiment of the present invention.

FIG. 8 is an exploded perspective view showing a perforated plug having a pre-oxidized plug protection cover.

FIG. 9 is a graph showing the relationship between the plug surface temperature change during drilling near the tip of the drilled plug and the drilling time in comparison between the method of the present invention and the conventional method.

[Explanation of symbols]

 1 piercing plug, piercing plug body or piercing plug body 2 hard layer applied to the surface of piercing plug 3 head member in composite plug 4 head fastening part 5 melt-down deformation of head 6 body wrinkle flaw 7 head Seizure of perforated material 8 Perforated billet 9 Steel plate joined to billet end face 10 Perforated plug protective cover

Claims (5)

[Claims] 1. An alloy steel containing at least 5 wt.% Or more Cr or at least 5 wt.% Or more Ni, or C.
Using a billet made of an alloy containing any one of r, Ni and Mo as a main component, a steel plate is joined to an end face on the side where the perforation of the billet is started, or both end faces, and the steel plate is The joined billet is
A seamless pipe is manufactured by using a piercing plug made of any one of an alloy and a heat-resistant steel, hot piercing to prepare a hollow material, and rolling the obtained hollow material. A method for producing a seamless pipe with excellent durability of a piercing plug. 2. A plug body made of any one of Mo, Mo alloy and heat-resistant steel, and having high strength and / or abrasion resistance formed on the surface of the plug body even at high temperature. The method according to claim 1, wherein a perforated plug consisting of a hard layer is used. 3. A plug body made of any one of Mo, Mo alloy and heat-resistant steel, and any one of Mo, Mo alloy and heat-resistant steel formed at the tip of the plug body. The method of claim 1 wherein a perforated plug consisting of a one-piece plug head is used. 4. A plug body made of any one of Mo, Mo alloy and heat-resistant steel, and any one of Mo, Mo alloy and heat-resistant steel formed at the tip of the plug body. A perforated plug comprising a plug head made of one kind and a hard layer formed on the surface of the plug body and / or the plug head and having high strength and / or abrasion resistance even under high temperature is used. The method of claim 1. 5. The hard layer is made of stellite, a ceramic obtained by adding WC to stellite, and WC to stellite.
5. A ceramic composition obtained by adding a mixed composition of Co and Co, and a ceramic composition obtained by adding a compound of Cr and C to stellite.
The described method.