BRPI0611407A2 - roll to laminate a seamless pipe or tube - Google Patents

Abstract

ROLL TO LAMINATE A SEWING PIPE OR PIPE. The present invention relates to a roll for rolling a seamless tube including a roll neck portion and a cylindrical roll portion. The surface layer of the cylindrical roll portion includes by mass 1.5% to 2.5% C, 1.3% to 3.5% Si, 0.1% to 2.0% Mn, 0, 5% to 8.0% Ni, 0.1% to 2.0% Cr, 0.2% to 5.0% Mo, 0.1% to 5.0% V, 0.1% to 5.0 % W, and 0.1% to 5.0% Nb, 0.05% to 2.0% Co, the balance consisting of Fe and impurities, and graphite having an area ratio of 0.5% to 5, 0%. Therefore, the roller according to the invention has a high wear resistance and a good bite characteristic.

Description

Invention Patent Descriptive Report for "PARALLEL ROLLING A SEWED PIPE OR PIPE"

Technique Field

The present invention relates to a roll, and more specifically a roll to roll a seamless pipe or tube for use in drilling and rolling a seamless tube.

A roll used in a rolling process in which a material is processed in a prescribed manner must have a wear resistance so that the roll has an improved service life. To improve the surface quality of a workpiece, the roller must have a grip resistance. As a roller having improved wear resistance and grip strength, a high speed tool steel roller as described by JP 3219987 B has been developed. The high speed tool steel roll has a very high surface hardness and is mainly used for plate rolling.

On the other hand, a seamless pipe or tube lamination roll (hereinafter referred to as a seamless tube) used to produce a Mannesmann-type seamless tube must have a high bite characteristic. As shown in Figure 1, when for example material is pierced by a perforator, a pair of perforating rollers 1 contacts material 2 and bites material 2. The bitten material is drilled axially by a plug 3 as it is turned in the circle direction !. When punch rolls 1 contact material 2, the contact area of punch rolls 1 and material 2 is very small. Therefore, material 2 is not easily grasped and is likely to slide. Therefore, a seamless tube rolling roll such as a punch roll and a long roll should have a good bite characteristic.

A conventional seamless tube rolling roll has a reduced hardness to its roll surface to achieve an improved bite characteristic. However, if the hardness of the roller surface is decreased, the wear resistance is decreased, and the service life of the roller is shortened. When a high alloy steel or a stainless steel is drilled and specifically rolled, the amount of wear of the seamless pipe Iami-nation roll increases. Therefore, the seam tube roll should have both a good bite characteristic and high wear resistance at the same time.

JP 10-81937 A discloses a seamless tube forging roll which has a good bite characteristic and high wear resistance. The described roller has large spherical carbides in the die. As roll wear progresses, spherical carbides are exposed on the surface, and the roller surface reaches a prescribed hardness state, which enhances the bite feature.

However, it would not be possible to improve the bite characteristic only by exposed spherical carbides.

Description of the Invention

It is an object of the invention to provide a seamless pipe rolling roll which has a high wear resistance and a good bite characteristic.

The inventor considered that if a prescribed amount of graffiti were generated in the matrix of a roll, the bite characteristic would be improved. If a roll that has graphite generated in the matrix is used, the graphite is exposed on the surface as the surface wears away. Graffiti exposed on the surface easily detaches and is removed from the surface. Therefore, the roller surface has appropriate irregularities. Irregularities perfect the bite feature of the roller.

Meanwhile, the inventor considered that in order to improve wear resistance, the generation of high hardness composite carbides would be crucial. If the die wears out, the high hardness composite carbides exposed on the surface contact a workpiece and may restrict the roll from being worn. The inventor considered that the addition of V, W, and Nb in the formation of high hardness carbides would be necessary.

Based on the above technological concept, the following invention has been completed. A roll for rolling a seamless tube according to the invention includes a roller neck portion and a cylindrical roller portion, the surface layer of the cylindrical roller portion. , includes by mass 1.5% to 2.5% C, 1.3% to 3.5% Si, 0.1% to 2.0% Mn, 0.5% to 8.0% Ni, 0.1% to 2.0% Cr, 0.2% to 5.0% Mo, 0.1% to 5.0% V, 0.1% to 5.0% W, and 0.1% to 5.0% Nb, 0.05% to 2.0% Co, the balance consists of Fe and impurities, and the surface layer of the cylindrical roll portion includes graphite having an area ratio of 0.5% to 5.0 %.

Here, the seamless tube rolling roll means a roll-up for drilling and rolling a seamless tube. Examples of a talroll include a cone-type or cylindrical-type punch roll, an elongator roll, a mandrel roll, a reducing roller, and a sizing roller.

The inventive seamless tube rolling roll includes a graphite having an area ratio of 0.5% to 5.0% in the die. The exposed graphites on the surface easily detach from the roll, so that Irregularities form on the surface, which enhances the bite characteristic. The seamless tube rolling roll according to the invention further includes high hardness MC-type composite carbides such as V carbides, W carbides and Nb carbides. Therefore, high hardness composite carbides can improve wear resistance.

The surface layer of the cylindrical roll portion preferably has a Shore hardness of 30 to 50 ° C.

Thus, the Shore hardness (Hs) of the surface layer is from 30 to 50, so that wear resistance can be further improved. If the Shore hardness of the surface layer is 30 to 50, graphite forms irregularities on the surface of the roll and therefore the bite characteristic can be ensured.

Brief Description of the Drawings

Figure 1 is a view showing how a material is punched by punch rolls.

Best Mode for Carrying Out the Invention Now, one embodiment of the invention will be described in detail.

1. Roll Structure

A seamless tube lamination roll according to the embodiment includes a roll neck portion and a cylindrical core portion. The seamless tube rolling roll is used to punch and cut a seamless tube. More specifically, examples of such a roller include a cone-type or cylinder-type perforating roller, an extender roller, a mandrel roller, a reducing roller, and a sizing roller.

In the seamless tube roll, the roll neck portion and cylindrical roll portion may be integrally formed as an integrated roll or as a composite roll in which the inner part (inner layer) and the surface layer part (inner layer) outer) of the cylindrical portion roll are made of different types of steel. The preferred surface layer has a depth of at least 1% of the radius of the cylindrical roller portion of the roller surface, more preferably at least 5% of the radius of the cylindrical roller portion of the roller surface. In the composite, the surface layer preferably has a depth of at least 50% of the outer layer thickness of the outer layer surface.

2. Chemical Composition

At least the surface layer of the cylindrical portion of the seamless tube rolling roll has the following chemical composition. Here, the surface layer of the cylindrical roll portion refers to the surface layer portion of the cylindrical portion used for perforating or laminating a workpiece and has a prescribed depth of the surface of the cylindrical roller portion.

In the following description, "%" for elements indicates "% mass".

C: 1.5% to 2.5%

The carbon is crystallized as graphite and enhances the bite characteristics of the roller. The carbon combines with V, W, and Nb as will be described to form high hardness MC-type composite carbides, which improves the wear resistance of the roll. Excessive C content however causes the composite carbides to be excessively generated, which diminishes the bite characteristic of the roller. Excessively generated graffiti decreases wear resistance and weakens the matrix. Excessive C content also decreases thermal crack resistance. Therefore, the C content is from 1.5% to 2.5%.

Crystallization of graphite in the matrix may be restricted by a carbide forming element (such as V, W, and Nb) that consumes the Contained in the molten metal relative to the other elements. In consideration of the balance between the quality of graphite to be generated in the matrix and the quantity of high hardness carbides, a preferred C content is 1.9% to 2.5%.

Si: 1.3% to 3.5%

Silicon deoxides the molten metal. Silicon also enhances the flowability of the molten metal. Silicon is a necessary element to make graphite crystallize or precipitate. Excessive Si content however causes graphite to be excessively generated which decreases wear resistance. In addition, excessive Si content decreases mechanical properties such as toughness. Therefore, Si content is 1.3% to 3.5%, preferably 1.3% to 2.2%.

As will be described, 0.2% to 1.0% of the entire Si content is preferably added during casting. The rest of the Si content is added to the molten metal prior to casting.

Mn: 0.1% to 2.0%

Manganese deoxides the molten metal. Manganese combines with S in steel to form MnS and prevents the matrix from becoming brittle. Excessive Mn content however decreases tenacity. Therefore, the content of Mn is from 0.1% to 2.0%.

Ni: 0.5% to 8.0%

Nickel enters the matrix in a solid solution state and improves strength. Nickel also accelerates the crystallization of graphite. Excessive Ni content, however, generates excessive graphite and decreases wear resistance. Therefore, the Ni content is 0.5% to 8.0%, preferably 0.9% to 4.0%.

Cr: 0.1% to 2.0%

Chromium enters the matrix in a solid solution state and improves strength. Chromium combines with C to precipitate high hardness M7C3 composite carbides, which improves wear resistance and toughness. Excessive Cr content however excessively generates M7C3 type carbides, so that graffiti and MC type carbides are prevented from being generated. As M7C3 type carbide has a lower hardness than carbide quelch MC-type compound, and therefore a Crexcess content may decrease wear resistance. Therefore, the Cr content is from 0.1% to 2.0%.

Mo: 0.2% to 5.0%

Molybdenum enters the matrix in a solid solution state and improves high temperature softening resistance. Molybdenocombin with C to form M6C or M2C type carbides, which improves wear resistance. Excessive Mo content however prevents graphite from being produced. Therefore, the Mo content is 0.2% to 5.0%, preferably 0.5% to 4.5%.

V: 0.1% to 5.0%

Vanadium combines with C to produce high hardness MC-type composite carbides, which improves wear resistance. Vanadium serves to refine crystal grains, which improves toughness. Excessive V content however prevents graphite from being produced. Therefore, V content is 0.1% to 5.0%, preferably 0.2% to 4.0%.

W: 0.1% to 5.0%

Tungsten combines with C to form high hardness composite carbides, which improves wear resistance. Tungsten also enters the matrix in a solid solution state to improve high temperature break-in resistance. Excessive W content however prevents graphite from being generated. Moreover, toughness and thermal cracking resistance are decreased, which increases the likelihood of segregation. Therefore, the content of W is from 0.1% to 5.0%.

Nb: 0.1% to 5.0%

Niobium combines with C to form MC hardness composite carbides, which improves wear resistance. Oniobium serves to refine crystal grains to improve toughness and thermal cracking resistance. However, excessive Nb content prevents graphite from being generated. Excessive Nb content decreases attenuation and resistance to thermal cracking. Therefore, the Nb content is from 0.1% to 5.0%, preferably from 0.1% to 4.5%.

Co: 0.05% to 2.0%

Cobalt enters the matrix in a solid solution state to improve the hardness and high temperature softening resistance of the matrix, which improves wear resistance. An excessive Co content however makes the carbides more easily secreted, which decreases the toughness of the matrix. Therefore, the Co content is from 0.05% to 2.0%.

Note that the balance includes Fe but could sometimes contain impurities such as P and S.

Phosphorus and sulfur degrade mechanical properties and therefore the content of these elements is preferably as small as possible. Therefore, the content of P is preferably no more than 0.2% and the content of S is preferably no more than 0.2%.

Note that for various causes in the manufacturing process, impurities other than PeS may be contained.

3. Structure

Graphite Amount

The surface layer of the cylindrical roller portion of the seamless pipe forming roller according to the embodiment includes graphite.

The area ratio of graphite included in the surface layer is 0.5% to 5.0%.

The area ratio of graphite can be measured by the following method. An arbitrary region of the surface of the cylindrical portion of the seamless pipe lamination roller is selected. Using an optical microscope or a scanning electron microscope (SEM), the dografite area ratio in the selected region is measured. The graphite area ratio can be measured for example by image analysis using an unstressed metal structure image or a photograph.

The graffiti exposed on the roller surface detaches easily and is removed from the roller surface. Therefore, irregularities are formed on the roller surface. If the roller surface is worn, the graffiti exposed in the surface layer by sequential wear will stand out and therefore there are always irregularities on the roller surface. The irregularities perfect the biting feature. Graphite has a lubricating function and therefore can prevent a scuff from being generated on the roller surface.

If the area ratio of graphite is less than 0.5%, the amount of graphite is insufficient, and irregularities are unlikely to be formed on the surface. This decreases the bite feature. On the other hand, if the graphite area ratio exceeds 5.0%, the roll matrix becomes brittle and wear resistance is decreased.

The shape of the graphite is not restricted. This can be either spherical or flake.

Toughness

The Shore hardness of the surface layer of the seamless tube rolling roll is preferably in the range of 30 to 50 (Hs). If Shore hardness is too low, wear resistance is decreased, while if Shore resistance is too high the bite characteristic is decreased. If Shore hardness is 30 to 50, high wear resistance as well as graphite bite characteristics can be assured. Note that if the Shore hardness of the seamless pipe rolling roll is outside the range described above, the bite characteristic and wear resistance are improved over the conventional case as long as the above described chemical composition specification is met and a graphite. with the area ratio described above is contained.

Shore hardness of the surface layer can be measured by the following method. A Shore hardness test (JISZ2240) is performed on a plurality of regions on the surface of the cylindrical portion of the seamless pipe termination roll. The average of the measured values obtained in the region plurality is determined as the Shore hardness.

It is only necessary that the specifications for the chemical composition and structure described above are met at least on the surface layer of the cylindrical roller portion, while the cylindrical roller portion may have the chemical composition and structure described above or The whole orol may have the chemical composition and structure described above.

4. Manufacturing Method

The seamless tube rolling roll according to the pattern can be produced as an integrated roll or a composite roll.

Integrated Roll Fabrication Method

When a seamless pipe roll roll according to the embodiment is formed as an integrated roll, the seamless pipe roll roll is produced by static casting or forging.

In order to adjust the area ratio of the graphite to be from 0.5% to 5.0%, the following conditions (A) and (B) are preferably met at the time of casting.

(A) During casting, the cooling rate to just above the solid phase line in the phase diagram is set lower than a normal cooling rate. Graphite is produced in the vicinity of the solid phase line, so if the cooling rate is too low, the amount of graphite to be produced can be increased.

(B) During casting, an inoculation is performed. More specifically, during casting, an inoculant (such as ferro silicon) including Si is added. The Si included in the inoculant forms nuclei to generate graphite. Therefore, a desired amount of graphite can be produced during casting.

The addition of Si during casting increases the amount of graphite, although if Si is excessively added during casting, a raw graphite is produced, which decreases the mechanical properties of seamless pipe lamination. Therefore, the amount of Si added during casting is preferably from 0.2% to 1.0%, more preferably from 0.2% to 0.6%.

Silicon is added during casting, the amount of Si aser added to the molten metal prior to casting is less than the target components. In summary, the amount of Si to be added during melting and melting is regulated so that the Si content at the end of the melt is equal to the Si content described in 2.

According to the above method, in order to remove the distortion of the roll and adjust the hardness of the roll, the roll is heat treated after casting or forging. More specifically, the recoating / tempering process is performed. Preferably, annealing is performed at an annealing temperature of 1000 ° C to 1200 ° C, and then the tempering is performed a number of times at a tempering temperature of 450 ° C to 650 ° C. The heat treatment allows the Shore hardness of the seamless pipe lamination roll surface to be 30 to 50.

Composite Roll Fabrication Method

When the seamless tube rolling roll is produced as a composite roll, the outer layer is formed to have a chemical composition and structure described in 2 and 3. The inner layer may be any generally available tough material such as ductile cast iron. , common cast iron, graphite cast iron, spherical graphite cast iron, wrought steel, cast steel, and the like.

The composite roller is produced for example by a centrifugal casting method, a continuous layer deposition method (described by JP 44-4903 B) using radiofrequency heating, a manufacturing method (described by JP 47-2851 A) according to which an outer shell is formed by isostatic hot pressing by a powder metallurgy method, and a layer deposition method (described by JP 57-2862 A) using an electro-slag fusion, or the like. When the outer layer is fused, conditions (A) and (B) described above are preferably met. Heat treatment after sinking is performed in the same way as in the integrated roll manufacturing method.

Example 1

Punch rollers having various chemical compositions and various amounts of graphite have been prepared and examined for their bite and wear resistance characteristics.

A cone-type perforator having the chemical composition shown in Table 1 has been produced. <table> table see original document page 13 </column> </row> <table> <table> table see original document page 14 </column> </row> <table> More specifically, the metals having the chemical compositions of Table 1 were produced by melting using an electric furnace. Then, the molten metals were each made into a steel ingot by a melting method. ingot.

For rolls N— 1 to 16, 0.2% to 1.0% Si by weight was added as an inoculant during casting. Meanwhile, roll N217 was not provided with an inoculant during casting. To the roll Nq 18.1.5% Si from the 2.8% Si container was added during casting.

The ingot produced was forged to form the cone type punch rolls. The formed rolls were annealed and tempered so that the surface layers of the rolls had the Shore hardness values (Hs) shown in Table 1. Shore hardness was measured according to the method described in 3. The measured area ratio (% ) of graphite is provided in Table 1.

Note that each of the punch rollers produced according to the embodiment was an integrated roll and had a throat size of 410 mm.

The rolls in Table 1 were each incorporated into the punch. The transverse angle of each of the rolls in Table 1 was 0 ° to 30 °.

After the rollers were incorporated, ten high alloy (25% Cr-35% Ni) billets having an outside diameter of 70 mm and a length of 400 mm were prepared for each roll, and the rolls were examined for bite characteristic, wear resistance, and grip resistance. Exam results are provided in Table 2.

Table 2

<table> table see original document page 15 </column> </row> <table> Continued. ..

<table> table see original document page 16 </column> </row> <table>

Bite Feature

When the ten billets were drilled, the biting characteristics were visually determined. Determination results are indicated in the "bite characteristic" column in Table 2.

When all ten billets were bitten into a non-slip roll with the roll and punched, it was determined that the bite roll feature was very high ("□" in Table 2). It was determined that the bite characteristic of the roll was high when all billets are bitten and perforated although at least one of the ten billets slipped with the roll ("o" in Table 2). It was determined that the bite characteristic was low when at least one of the ten billets was not bitten by the roll and could not be pierced ("x" in Table 2).

Wear Resistance

Among the numbered rollers, the rollers that successfully punctured all ten billets were inspected for amount of wear (μιτι). The inspection result is given in the "wear quantity" column in Table 2. The amount of wear was measured by the following method. The surface of the cylindrical roll portion was measured before and after drilling the ten billets using a three-dimensional shape measuring instrument. Based on the measurement data before and after drilling, the maximum wear depth was obtained, and the maximum wear depth (μιη) was determined as the amount of roll wear. Note that "-" in Table 2 indicates that wear resistance could not be assessed because the bite characteristic was low.

Grab resistance

Among the numbered rollers, the rollers that successfully punctured all ten billets were visually inspected for presence / absence of grip on the roll after perforation. The result of the determination is given in the "grab resistance" column in Table 2. The grip strength was determined to be high when no part of the perforated billets was not deposited on the roll surface after perforation ("o" in Table 2). On the other hand, it was determined that the grip strength was low when a portion of the wrinkles was deposited on the surface of the roll after perforation. Note that the "-" in Table 2 indicates that grip strength could not be assessed because the bite characteristic was low.

Test Results

Referring to Tables 1 and 2, the rollers designated as rollers N-1 through 10 each had a chemical composition and a graffiti area ratio within the ranges of the invention, and therefore these all had a high bite characteristic. wear was small and less than 70 μm and grip strength was high.

The rollers designated as N— 2 to 9 rollers each had a Shore hardness (Hs) within the range of 30 to 50, so the clamping feature was very high and the amount of wear was less than 50 μιτι.

The rollers designated as N-1 to 10 rollers each had a high grip strength.

On the other hand, the rollers designated as N-11 to 18 rollers each had a chemical composition or graphite area ratio outside the ranges of the invention, and thus the bite characteristic and / or wear resistance was low. More specifically, the roller No. 11 had a low Si content and a lower graphite area ratio than the lower limit according to the invention, and thus the bite characteristic was low. Roll # 12 had a low C and Si content, and a lower graphite area ratio than the lower limit according to the invention, and thus the bite characteristic was low. Roll # 13 had a high C content and a graphite area ratio that exceeded the upper limit according to the invention. Therefore, the amount of wear was more than 70 μιτι and the wear resistance was low. Roll # 14 had a high Si content and a graphite area ratio that exceeded the upper limit according to the invention. Therefore, the amount of wear was more than 70 μιτι and the wear resistance was low. Roll # 15 had a low Ni content and a lower graphite area ratio than the lower limit according to the invention. Therefore, the bite characteristic was low. The roller N216 had a high Cr, V, W, and Nb content which forms a high hardness composite carbide and the graphite area ratio was lower than the lower limit according to the invention. Therefore, the bite feature was low.

Roll # 17 had a chemical composition within the range of the invention, but an inoculant was not added during casting, and therefore the graphite area ratio was less than the lower limit according to the invention. Therefore, the bite characteristic was low,

Roll # 18 had a chemical composition within the range of the invention, and the chemical composition was similar to the chemical composition of roll # 9. However, the amount of Si added during casting was as high as 1.5%, so the ratio of graphite area exceeded the upper limits according to the invention. Therefore, the wear resistance exceeded 70 μm and the wear resistance was low.

Although the present invention has been described and illustrated in detail, it is clearly understood that it is by way of illustration and example only and should not be construed as a limitation. The invention may be incorporated into various modified forms without departing from the spirit and scope of the invention.

Industrial Applicability

A seamless pipe rolling roll according to the invention is widely applicable as a roll used for punching and lamination of a seamless pipe. The invention is particularly applicable to a cylindrical or cone-type roller perforator that pierces and rolls in the axial direction while the material is being rotated in the circumferential direction.

Claims (2)

1. Roll for rolling a seamless pipe or tube comprising a roll neck portion and a cylindrical roll portion, the surface layer of said roll cylindrical portion comprising by weight 1.5% by weight. 2.5% C, 1.3% to 3.5% Si, 0.1% to 2.0% Mn, -0.5% to 8.0% Ni, 0.1% to 2.0% Cr , 0.2% to 5.0% Mo, 0.1% to 5.0% V, 0.1% to-5.0% W, and 0.1% to 5.0% Nb, 0.05 % to 2.0% Co, the balance consisting of Fee impurities, said surface layer comprising graphite having an area ratio of 0.5% to 5.0%. A roller according to claim 1, wherein the surface layer of said cylindrical roller portion has a Shore hardness of 30 to 50 ° C.