JP5799667B2 - Surface protectant for piercing and rolling tools - Google Patents

Description

  The present invention relates to a surface protective agent for piercing and rolling tools such as plugs used in the manufacture of seamless steel pipes, and more particularly to improving the durability of piercing and rolling tools.

  Conventionally, the Mannesmann type pipe manufacturing method has been widely used as a method for manufacturing a seamless steel pipe. In this method, a rolled material (round steel slab or round slab) heated to a predetermined temperature is first subjected to a piercing and rolling process by a piercing and rolling machine to be a hollow material, and then an elongator, a plug mill, a mandrel mill, or the like This is a method of obtaining a seamless steel pipe having a desired size mainly by reducing the outer diameter with a drawing mill or other forming machine after reducing the wall thickness by using a stretching mill and reheating as necessary.

  As a piercing and rolling mill, a so-called Mannesmann piercer combining two inclined rolls and a piercing plug and two guide shoes, a so-called three-roll piercer combining three inclined rolls and a piercing plug, or two A so-called press roll piercer is known that combines a perforated roll and a perforated plug. In the piercing and rolling process using such a piercing and rolling machine, the piercing plug is exposed to a high temperature and high load environment for a long time due to constant contact with a high temperature rolling material or hollow material, resulting in wear, erosion, etc. Prone to occur. For this reason, conventionally, a plug for drilling has been subjected to a scale treatment at a high temperature to form an oxide scale film with a thickness of several tens to several hundreds of μm on the plug surface, thereby preventing the plug from being worn.

  Recently, however, there has been an increasing demand for seamless steel pipes made of high alloy steel such as 13Cr steel and stainless steel, which have high hot deformation resistance and are difficult to form oxide scale on the surface. When such a high-alloy steel material is pierced and rolled, the oxide scale coating formed on the plug surface is severely worn, and damage to the plug tip, such as deformation and seizure, frequently occurs at an early stage. It is necessary to exchange. For this reason, there has been a problem that the plug cost is increased, and the productivity of the seamless steel pipe is also lowered.

For such problems, for example, Patent Document 1, Patent Document 2, and Patent Document 3 improve the adhesion and wear resistance of the oxide scale film by optimizing the composition of the plug and the scale processing conditions. Thus, a method for extending the life of the plug has been proposed.
However, in the techniques described in Patent Document 1, Patent Document 2, and Patent Document 3, a certain degree of effect for extending the life of the plug is recognized, but a large amount of alloy element is required, or the plug is not scaled. There is a problem that the productivity of the plug is reduced, the mass production of the plug cannot be reduced, the manufacturing cost of the plug is increased, and the life of the plug is reduced. Furthermore, recently, with the increase in demand for seamless steel pipes made of high alloy steel, there has been a demand for longer plug life.

  In response to such a demand, for example, Patent Document 4 proposes a lubricant for piercing-rolling plugs. The lubricant described in Patent Document 4 is, by mass%, one or more particulate substances selected from graphite, mica, bentonite, vermiculite, molybdenum disulfide and boron nitride: 1 to 10 %, Water-dispersed or water-soluble polymer: 1 to 10%, one or more inorganic binders selected from boron oxide, boric acid, alkali metal borates, sodium carbonate and potassium carbonate: 0 Contains ~ 15%, the balance consists of water. In the technique described in Patent Document 4, the lubricant is applied to at least the surface of the tip of the scaled plug, and a plug in which a lubricant film having a predetermined thickness is formed on the surface is used. , Piercing and rolling of seamless steel pipes. Thereby, melting of the tip can be prevented and the plug life is improved.

  Patent Document 5 proposes a tool surface protective material for piercing and rolling. The surface protective material described in Patent Document 5 is 10% to 80% iron oxide, 1 to 60% iron powder, 5 to 40% bentonite or montmorite main aggregate, and a binder. A hat-shaped surface protective material that covers the tool surface and protects the tool surface, including a fibrous structural material and / or a modifying material, and the total of the main aggregate and the modifying material is 20 to 90% It is.

  Patent Document 6 proposes a method of manufacturing a seamless steel pipe with good inner surface quality without deteriorating the biting property during piercing and rolling. In the technique described in Patent Document 6, a scale molten material having a eutectic temperature of 1200 ° C. or less with FeO in the surface scale is applied to a plug that has been heat-treated for scale, and subjected to piercing and rolling.

Japanese Unexamined Patent Publication No. 08-193241 JP 07-60314 A Japanese Patent Laid-Open No. 2000-190008 JP 2001-234189 A Japanese Patent Laid-Open No. 2002-224713 JP 2002-248507 A

  However, even with the technique described in Patent Document 4, when a plurality of piercing and rolling operations are continuously performed, there is a problem that seizure occurs on the plug and continuous rolling cannot be performed. In addition, the technique described in Patent Document 5 has a problem that it takes a lot of time to mold the protective material, and the surface protective material tends to drop off from the tool surface immediately before or during piercing and rolling. Furthermore, in the technique described in Patent Document 6, there is a problem in that the plug is damaged at an early stage and the life of the plug cannot be further increased.

  The present invention advantageously solves the problems of the prior art, can easily protect the surface of a piercing and rolling tool such as a plug, and can further extend the life of the piercing and rolling tool. It aims at providing the surface protection agent of a tool.

  In order to achieve the above-mentioned object, the present inventors diligently studied various factors that affect the life of a piercing and rolling tool (plug). In piercing and rolling tools (plugs) with an oxide scale coating formed on the surface, the tool life is limited by the wear rate of the oxide scale coating, and seizure and melting occur when the oxide scale coating formed on the surface disappears. Loss occurs and is discarded. For this reason, in such a tool, it came to mind that an oxide scale becomes the most important in order to hold | maintain a tool surface.

  In view of this, the inventors have come up with the idea that, in order to prolong the service life of the piercing and rolling tool, an oxide scale film formed in advance on the surface of the tool may be appropriately supplemented. Then, the inventors have conceived that it is effective to apply a surface protective agent having a specific composition as a simple replenishment method of the oxide scale coating. And, as a surface protective agent, if iron oxide powders such as wustite and magnetite and low melting point compound powders are mixed in a solvent to form a slurry (tool surface protective agent for piercing and rolling), it is simple. And it discovered that the oxide scale film of the tool surface for rolling could be replenished reliably.

  And according to the further examination, by applying the above-mentioned solution to the rolling tool surface, the iron oxide powder in the solution becomes an oxide scale film on the tool surface by the action of the low melting point compound contained in the solution. Fused to replenish the oxide scale film, or further, the oxide scale film is reinforced by the lubricating action of the low melting point compounds contained in the solution, reducing the wear of the oxide scale film and preventing tool lubrication and heat insulation from deteriorating. It was found that the tool life for piercing and rolling can be extended.

Such a solution (surface protective agent) only needs to be applied to the surface of the rolling tool, and can protect the rolling tool without requiring special drying and molding steps. It has been found that there is an advantage that it can greatly contribute to the improvement of productivity of piercing and rolling.
The present invention has been completed based on the above findings and further studies. That is, the gist of the present invention is as follows.
(1) A surface protective agent for a seamless steel pipe piercing and rolling tool in which a main agent and a curing agent are mixed in a solvent to form a slurry, and the seamless steel pipe piercing and rolling tool is coated with an oxide scale coating on the surface. In the formed piercing and rolling tool, the main component includes 4 to 40% of low melting point compound powder in mass% with respect to the total amount of the main component, the remainder is made of iron oxide powder, and the low melting point compound powder is Li and , Na, Si, Ba, Al, Ca, K, and at least one selected from the group consisting of Na, Si, Ba, Al, Ca, and K, the melting point is 600 to 1000 ° C., and the solvent is an aqueous solvent or an alcoholic solvent. Surface protectant for seamless steel pipe piercing and rolling tool.
(2) A surface protective agent for a seamless steel pipe piercing and rolling tool according to (1), wherein the iron oxide powder is wustite powder, magnetite powder, or a mixed powder thereof .

  According to the present invention, on the surface of the piercing and rolling tool on which the oxide scale film has been formed in advance, or on the surface of the piercing and rolling tool on which the oxide scale film has been re-formed on the surface of the piercing and rolling tool that has been subjected to piercing and rolling, The life of the tool for piercing and rolling is significantly improved by simply applying a surface protective agent having a specific composition on the surface of the tool for piercing and rolling at an appropriate time for piercing and rolling a plurality of times before use. There are remarkable effects in the industry. In addition, according to the present invention, it is possible to greatly contribute to the productivity improvement of the high Cr steel seamless steel pipe, and to reduce the manufacturing cost.

It is explanatory drawing which shows typically the damage state of the tool for rolling (plug).

The surface protective agent of the present invention is a surface protective agent for protecting the surface of a tool for piercing and rolling used in piercing and rolling in the production of a seamless steel pipe.
The surface protective agent for the piercing and rolling tool of the present invention is a mixture of a main agent and a curing agent in a solvent, and exhibits a slurry form. In the surface protective agent of the present invention, the main agent is mainly composed of iron oxide powder and contains 4 to 40% of low melting point compound powder in mass% with respect to the total amount of the main agent.

The iron oxide powder that is the main ingredient is preferably wustite (FeO) powder, magnetite (Fe ₃ O ₄ ) powder, or a mixed powder thereof .
The “low melting point compound powder” contained in the main agent is a powder mainly composed of a low melting point compound having a melting point in the range of 600 to 1000 ° C. If the melting point is less than 600 ° C., the oxide scale is softened at a low temperature and the action as a surface protecting agent is insufficient. On the other hand, when the melting point exceeds 1000 ° C., it becomes difficult to fuse the iron oxide powder with the oxide scale on the tool surface, and the surface protective agent is easily peeled off. For this reason, the melting point of the low melting point compound was limited to the range of 600 to 1000 ° C.

Examples of the low melting point compound include compounds containing Li and one or more of Na, Si, Ba, Al, Ca and K. Specifically, the low melting point compound powder is made of glass, casting flux. 1 or more of carbonates or natural stones or compounds containing one or more of Li, Na, Si , Ba, Al, Ca and K (premelt) Then, after mixing or fusing, a pulverized product may be used. As the premelt product, for example, those used as a flux for continuous casting are suitable. The centrifugal casting flux preferably contains, for example, SiO ₂ , CaO, Na ₂ O, Li ₂ O, K ₂ O, Al ₂ O ₃ , or MnO or MgO. Note that when a substance containing C or B is used as the low melting point compound, it causes embrittlement of the inner surface of the steel pipe, so care must be taken.

Further, the low melting point compound powder contained in the main agent is preferably -180 mesh. When the particle size is larger than 180 mesh, the mixing with the iron oxide powder tends to be inhomogeneous during the preparation of the protective agent. For this reason, it is preferable to limit the particle size of the low melting point compound powder used to -180 mesh.
By mixing the low melting point compound in the iron oxide powder as the main agent, the fusion with the scale previously formed on the surface of the piercing and rolling tool is promoted, and the lubricating effect of the surface protective agent can be further increased. Such an effect becomes remarkable when the content of the low melting point compound is 4% or more. On the other hand, even if it is contained in a large amount exceeding 40%, the effect is saturated, and furthermore, the iron oxide and the low melting point compound are fused to excessively lower the softening temperature, so the surface protection function is lowered and the tool life is likely to be lowered Become. For this reason, the content of the low melting point compound in the main agent is limited to the range of 4 to 40%.

The solvent is water or alcohol. The main agent and the curing agent are mixed in a solvent to form a slurry. In addition, solvent: 20-90 mass parts is mix | blended with respect to 100 mass parts of main agents so that the specific gravity of a surface protection agent may be 60-95 Baume degree ((degree B'e)). As a result, the surface protective agent can be easily applied to the surface of the piercing and rolling tool.
Moreover, it is preferable that a hardening | curing agent shall be 2-20 mass parts with respect to 100 mass parts of main agents.

  As the curing agent, water-soluble acrylic resins, vinyl acetate resins, ethylene acetate resins, styrene resins, clay, water glass, etc., solvent-based ones such as polyethylene resins, ester resins, Examples of the thermosetting resin include a urethane resin, an epoxy resin, an alkyd resin, and rubber, and examples of the thermosetting resin include a phenol resin, a urea resin, and a melamine resin. Further, there is no problem even if a reinforced resin reinforced with carbon fiber or glass fiber, an oil-containing resin, or the like is used.

In order to stably apply the slurry, in addition to the solvent and the main agent and curing agent described above, the surfactant, antifoaming agent, preservative, thickener and the like are appropriately added to the surface protective agent. It is preferable to contain.
The surface protective agent of the present invention is in a slurry state, and the method of applying to the rolling tool may be any of spray coating, brush coating and the like, and is not particularly limited. The surface protective agent is preferably applied at least at the tip portion, that is, in the region of 1/3 or more of the tool length from the tip of the piercing and rolling tool. This is because the tip of the piercing and rolling tool is exposed to a particularly severe environment. The coating amount of the surface protective agent is not particularly limited as long as the region where the tool and the material to be rolled are in contact is covered, but the coating thickness is 0.2 to 3 mm in terms of economy and protection function. It is preferable that

In the surface protective agent of the present invention, drying after coating is not essential. In particular, it may be wet or freshly dried, and there is no problem even if the next piercing and rolling is performed without special drying.
The tool for piercing and rolling to which the surface protective agent of the present invention is applied is subjected to a heat treatment for scaling before use, and further to a heat treatment for rescaling after a plurality of times of piercing and rolling, and the surface layer preferably has a thickness of 0.1 to A 2 mm scale layer (iron oxide layer) is formed. By forming a scale layer on the surface of the rolling tool, the heat insulation and lubricity of the scale layer can suppress damage to the rolling tool body to some extent, and it is possible to slightly extend the tool life. As soon as it is subjected to piercing and rolling, the scale layer on the surface of the rolling tool is worn out and the scale layer becomes thin. Finally, as shown in FIG. 1, deformation of the rolling tool, seizure or glare occurs. The rolling tool will be discarded. For this reason, this invention surface protectant is apply | coated to the tool surface for rolling in which the oxide scale layer was formed, and the scale layer of the tool surface for rolling is reinforced.

  The surface protective agent of the present invention contains iron oxide such as wustite and magnetite as a main agent and a low melting point compound powder, and is applied to the surface of the tool to oxidize by the action of the low melting point compound contained in the protective agent. Iron powder is fused with the oxide scale layer on the surface of the tool, and the oxide scale layer is replenished, or the oxide scale layer is reinforced by the lubricating action of the low melting point compound powder, so that the wear of the oxide scale layer is suppressed and the tool is lubricated. And a decrease in heat insulation can be prevented, and the life of the piercing and rolling tool can be extended. In addition, the surface protective agent of the present invention has a slurry form in which the main agent and the curing agent are mixed in a solvent, and can be easily and reliably applied to the surface of the rolling tool, and the surface of the rolling tool is oxidized. The scale layer can be replenished or reinforced.

  A surface protective agent having a slurry form having a composition shown in Table 1 is spray-coated on a plug (a piercing and rolling tool: unused) having a thickness of 0.5 to 1 mm formed on the surface in advance. After the protective agent was applied to the surface, the 13Cr seamless steel pipe material was subjected to piercing and rolling, and four piercing and rolling were performed. The spray coating was performed every two piercing and rolling. Next, of the plugs subjected to piercing and rolling, reusable plugs that were not damaged or seized at the tip were subjected to a rescale heat treatment (cooling after heating at 950 ° C. for 4 hours) to form an oxide scale on the surface. . Next, a surface protective agent having a slurry form shown in Table 1 was spray-applied to the rescaled and heat-treated rolling tool, and then subjected to piercing and rolling of 13Cr-based seamless steel pipe material, and four piercing and rolling were performed. . At the end of each piercing and rolling, the tool surface is observed to visually determine the necessity of the coating treatment, and if necessary, the tool surface is pierced and rolled once or several times. The coating process which spray-coats a protective agent on was performed.

  Such re-scaling heat treatment, coating treatment, and piercing and rolling were repeated until the plug life that was deformed, seized, or glazed and discarded, and the total number of piercing and rolling until the plug life was obtained. . The number of repetitions (n number) under the same conditions was 4, and the average plug life was defined as the plug life (number) by applying the surface protecting agent. In addition, as a conventional example, after performing the heat treatment with scaling, it was subjected to piercing and rolling until defects such as deformation and seizure occurred and were discarded (until the lifetime) without applying a surface protective agent.

  Table 4 shows the obtained results.

  All plugs subjected to piercing and rolling by applying the surface protective agent of the present invention have a plug life of 10 or more, which is more than 3 times that of the conventional example and a longer tool life for rolling. is made of. On the other hand, a plug coated with a surface protective agent outside the scope of the present invention can ensure a longer plug life than the conventional example, but cannot achieve a desired long life.

Claims (2)

A surface protective agent for a seamless steel pipe piercing and rolling tool in which a main agent and a curing agent are mixed in a solvent to form a slurry,
The seamless steel pipe piercing and rolling tool is a piercing and rolling tool having an oxide scale film formed on the surface,
The main agent contains 4 to 40% of low melting point compound powder by mass% with respect to the total amount of the main agent, the remainder is made of iron oxide powder, and the low melting point compound powder is Li, Na, Si, Ba, Al, Ca , One or more selected from K, and a melting point of 600 to 1000 ° C.,
A surface protective agent for a seamless steel pipe piercing and rolling tool, wherein the solvent is an aqueous solvent or an alcoholic solvent.   The surface protective agent for a seamless steel pipe piercing and rolling tool according to claim 1, wherein the iron oxide powder is made of wustite powder, magnetite powder, or a mixed powder thereof.

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