JP2004250729A - Cast roll material and roll for rolling seamless steel pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cast roll material for rolling a seamless steel pipe, having superior slipping resistance and inhibiting occurrence of the surface damage, and to provide a roll for rolling the seamless steel pipe. <P>SOLUTION: The cast roll material has a composition comprising 1.0-2.0% C, 0.1-1.0% Si, 0.2-2.0% Mn, 0.5-2.5% Cr, 0.5-2.5% Mo, 3.5-7.0% V, 0.1-2.0% Nb, while satisfying -0.2≤C-(0.24×V+0.13×Nb)≤0.2 (wherein, C, V and Nb denotes the contents (mass%) of respective elements), and the balance Fe with unavoidable impurities. A layer useful as a roll has preferably a hardness Hs of 29 to 43. The cast roll material can further include one or two elements selected among 1.5% or less W, 2% or less Co, 0.1% or less Ti and 0.1% or less Al. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００３１】
本発明例はいずれも、従来例の１．５ 倍以上のロール寿命延長が達成されている。一方、本発明の範囲を外れる比較例は、噛み込み不良の発生（ロールＮｏ．８、Ｎｏ．１０ ）、あるいは圧延途中でスリップが発生（ロールＮｏ．９、Ｎｏ．１３ ）し、従来例に比べても短いロール寿命となっている。
【００３２】
【発明の効果】
本発明によれば、継目無鋼管圧延用として耐スリップ性に優れ、表面損傷を抑制でき、長寿命を有する、継目無鋼管圧延用ロール材および継目無鋼管圧延用ロールを安価に提供でき、産業上格段の効果を奏する。
【図面の簡単な説明】
【図１】ロール材硬さと有効Ｃ量との関係を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a roll for seamless steel pipe rolling, and more particularly to prevention of slip generated during piercing and rolling of steel pipe and improvement of roll life.
[0002]
[Prior art]
In the manufacture of seamless steel pipes by the Mannesmann method, a rolling material (round bar) that is a material to be drilled is sufficiently imparted with a rotary forging effect to perform piercing and further stretching. It has been required to have a property of biting and sufficiently grasping a material to be perforated. Such a demand is particularly strong against the peer-surroll.
[0003]
When the rolling roll loses the biting and gripping properties of the rolled material and slips between the rolled material, rolling defects such as biting failure and rolling stoppage occur, and the continuous rolling process There is a problem that it leads to a big trouble such as a mill stoppage in the factory.
For such a problem, for example, in Patent Document 1, C: 1.10 to 1.85%, Si: 0.3 to 1.2%, Mn: 0.4 to 1.5%, Ni: A high carbon alloy cast steel containing 0.5 to 2.0%, Cr: 0.5 to 2.0%, and the balance being substantially iron is subjected to heat treatment after hot forging, and spherical carbide is 35 to 35%. A method for producing a forging roll for seamless steel pipe rolling, which has a metallographic structure occupying 55 area%, has been proposed. In the technique described in Patent Document 1, by performing hot forging and heat treatment on the adamite roll material, the Shore hardness Hs of the roll surface is suppressed to 29 to 34, and the net-like carbide disappears. It is said that 2 μm of spherical carbide precipitates on the matrix, improving both wear resistance and biting property.
[0004]
Patent Document 2 proposes a method for preventing the slip of the piercer roll. In the technique described in Patent Document 2, the current value of the motor that drives the piercer roll is detected by a sensor, and when the signal from the sensor is equal to or lower than the predetermined current value, the occurrence of slip is predicted, and the piercer roll and the round steel material It is said that slip can be prevented by spraying an anti-slip agent on the surface. Patent Document 3 proposes a hot rolling method in which a special lubricant is interposed between the rolling roll and the material to be rolled to reduce the slip between the material to be rolled and the rolling roll. .
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-81937 [Patent Document 2]
Japanese Patent Laid-Open No. 10-180311 [Patent Document 3]
Japanese Patent Laid-Open No. 6-122002
[Problems to be solved by the invention]
However, in the techniques described in Patent Document 2 and Patent Document 3, the anti-slip agent and the lubricant sprayed between the material to be rolled and the rolling roll bite into the steel pipe surface in the downstream process and deteriorate the steel pipe surface properties. There is a problem. In addition, recently, the upgrading of steel pipes has progressed and the composition has become highly alloyed, so that the hot deformation resistance of the material to be drilled has increased. Therefore, even with the technique described in Patent Document 1, the rolling roll and the material to be drilled are also used. As the slip increases, the surface damage of the rolling roll increases and the roll life decreases. For this reason, the roll for seamless steel pipe rolling is strongly required to further improve the slip resistance and to prolong the roll life. Moreover, since the technique described in Patent Document 1 requires a forging process, there is a problem that the manufacturing process becomes complicated and the manufacturing cost increases.
[0007]
An object of the present invention is to solve the problems of the prior art advantageously, to provide a roll material for seamless steel pipe rolling and a roll for seamless steel pipe rolling, which are excellent in slip resistance and can suppress surface damage, at low cost. To do. The term “slip resistance” as used in the present invention includes slippage between the punched rolled material and the rolling roll during biting in the initial stage of rolling, and slippage between the rolling roll and the punched rolled material after biting. This refers to the difficulty of slipping.
[0008]
[Means for Solving the Problems]
In order to achieve the above-described problems, the present inventors first made extensive studies on factors that affect slip resistance and suppression of surface damage. As a result, the amount of mesh carbide is reduced, and a large amount of coarse MC-type carbide, which is a hard material, can be dispersed on the surface layer of the rolling roll. It was found that the improvement of the property and the suppression of the surface damage can be achieved at the same time.
[0009]
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) It is a roll material used for a roll for seamless steel pipe rolling, and in mass%, C: 1.0 to 2.0%, Si: 0.1 to 1.0%, Mn: 0.2 to 2.0%, Cr: 0.5-2.5%, Mo: 0.5-2.5%, V: 3.5-7.0%, Nb: 0.1-2.0% included And the following equation (1) -0.2≤C- (0.24 * V + 0.13 * Nb) ≤0.2 (1)
(Here, C, V, Nb: content of each element (mass%))
And having a composition comprising the balance Fe and inevitable impurities, a cast roll material for seamless steel pipe rolling excellent in slip resistance.
(2) A cast roll material for a seamless steel pipe rolling roll, wherein the hardness in the roll use layer range in (1) is Hs29 to 43.
(3) A cast roll material for seamless steel pipe rolling according to (1) or (2), further comprising, in addition to the above composition, W: 1.5% or less by mass%.
(4) In any one of (1) to (3), in addition to the above composition, the casting roll material for seamless steel pipe rolling further contains, by mass%, Co: 2% or less.
(5) In any one of (1) to (4), in addition to the above composition, in addition to one by mass, one selected from Ti: 0.1% or less, Al: 0.1% or less A cast roll material for rolling seamless steel pipes, comprising two types.
(6) A seamless steel pipe rolling roll comprising the cast roll material according to any one of (1) to (5) as a roll use layer.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
First, the reasons for limiting the composition of the cast roll material of the present invention will be described. Hereinafter, the mass% in the composition is simply represented by%.
C: 1.0-2.0%
C forms a hard MC type carbide and increases the base hardness to improve the slip resistance and at the same time improve the wear resistance and reduce the surface damage of the roll. Such an effect is recognized when the content is 1.0% or more. If C is less than 1.0%, the solidification temperature rises, castability deteriorates, and shrinkage defects are likely to occur. On the other hand, if the content exceeds 2.0%, eutectic carbides are generated and slip is likely to occur, and the risk of heat cracking increases. For this reason, C is limited to a range of 1.0 to 2.0%.
[0011]
Si: 0.1 to 1.0%
Si is an element that acts as a deoxidizing agent, and in the present invention, it is necessary to contain 0.1% or more. On the other hand, even if the content exceeds 1.0%, the above-described effect is saturated, and MC carbides are coarsened and cracks are likely to occur. For this reason, Si was limited to the range of 0.1 to 1.0%.
[0012]
Mn: 0.2 to 2.0%
Mn is effective for fixing S which inhibits wear resistance as MnS, detoxifying and stabilizing. Moreover, Mn has the effect | action which accelerates | stimulates formation of the scale which protects the roll surface. In order to obtain such an effect, the content of 0.2% or more is necessary. However, even if the content exceeds 2.0%, the effect is saturated and an effect commensurate with the content cannot be expected, which is economically disadvantageous. For this reason, Mn was contained in the range of 0.2 to 2.0%. In addition, Preferably it is 0.2 to 1.5%.
[0013]
Cr: 0.5 to 2.5%
Cr is an element that has the effect of improving the heat resistance of the base and suppressing the occurrence of heat cracks and plastic flow at high temperatures. In the present invention, it is necessary to contain 0.5% or more. On the other hand, if the content exceeds 2.5%, a chromium-based eutectic carbide is generated, the roll surface is smoothed, slip is likely to occur, slip resistance is lowered, and heat cracks become prominent. For this reason, Cr was limited to the range of 0.5 to 2.5%. In addition, Preferably it is 0.5 to 2.0%.
[0014]
Mo: 0.5 to 2.5%
Mo is an element that has the effect of increasing the high temperature strength of the base, suppressing the plastic flow at high temperatures and improving the wear resistance. In the present invention, it is necessary to contain 0.5% or more. On the other hand, if the content exceeds 2.5%, eutectic carbides are generated, the roll surface is smoothed, slip is likely to occur, slip resistance is lowered, and heat cracks become prominent. For this reason, Mo was limited to the range of 0.5 to 2.5%.
[0015]
V: 3.5-7.0%
V is an effective element for forming a coarse hard MC type carbide effective for slip prevention, and is one of the important elements in the present invention. An appropriate amount of coarse hard MC type carbide effective for slip prevention crystallizes when V is contained in an amount of 3.5% or more. However, if it exceeds 7.0%, MC carbide becomes coarse and excessive. , Segregates during casting, lowers the fluidity of the molten metal, and hinders castability. For this reason, V was limited to the range of 3.5 to 7.0%.
[0016]
Nb: 0.1-2.0%
Nb is an element having an action of solid-dissolving in MC-type carbides to strengthen the carbides and suppressing gravity segregation of MC-type carbides. Containing is required. On the other hand, if the content exceeds 2.0%, MC carbides are excessively coarsened, which promotes segregation of MC type carbides. For this reason, Nb was limited to the range of 0.1 to 2.0%.
[0017]
In the present invention, it is important to adjust the content of each component so as to satisfy the following formula (1) after the contents of C, V, and Nb are within the above-described range.
−0.2 ≦ C− (0.24 × V + 0.13 × Nb) ≦ 0.2 (1)
(Here, C, V, Nb: content of each element (mass%))
(0.24 × V + 0.13 × Nb) means the amount of C consumed for the formation of MC type carbide by V and Nb, and {C− (0.24 × V + 0.13 × Nb)} is MC It represents the amount of C that dissolves in the base without being consumed in the formation of carbides and affects the hardness of the roll material. Hereinafter, in the present invention, {C− (0.24 × V + 0.13 × Nb)} is also referred to as an effective C amount.
[0018]
When the effective C amount is less than -0.2, the base hardness is lowered, the wear resistance is deteriorated, and the roll life is shortened. On the other hand, if the effective C amount exceeds 0.2, the roll material hardness becomes too hard, and eutectic carbides appear and slip is likely to occur. For this reason, the amount of effective C was limited to the range of -0.2 to 0.2. The relationship between the effective C amount and the roll hardness is shown in FIG.
[0019]
FIG. 1 shows the results obtained by the following experiment.
In mass%, 1.3% C-0.5% Si-0.6% Mn-1.5% Cr-1.0% Mo-1.0% Nb-3.5 to 6.0% V system And 1.6% C-0.4% Si-0.4% Mn-1.4% Cr-0.8% Mo-1.3% Nb-4.8 to 7.2% A ring roll having a diameter of 280 mm was prepared by centrifugal casting, and cooled to room temperature (air-cooled) to obtain a test piece material. Test pieces were collected from these ring-shaped test pieces, subjected to tempering treatment, and the hardness was measured. The tempering treatment was 690 ° C. × 20 h (1.3% C-1.0% Nb-V system) and 720 ° C. × 20 h (1.6% C-1.3% Nb-V system). . The hardness measured the Shore hardness Hs based on JISZ2246. From FIG. 1, by adjusting the C, Nb, V content so that the effective C amount is in the range of -0.2 to 0.2, the roll hardness is a hardness range excellent in slip resistance. It can be seen that it can be in the range of Hs29 to 43.
[0020]
In addition to the basic components described above, one or two selected from W, Co, Ti, or Al can be selected and contained as necessary.
W: 1.5% or less W has an action of strengthening carbides and improving wear resistance, and can be contained if necessary. Such an effect is recognized when the content is 0.5% or more. However, when the content exceeds 1.5%, an excessive amount of eutectic carbide is generated, and slip resistance is lowered. For this reason, in this invention, it is preferable to limit W to 1.5% or less. In addition, More preferably, it is 1.0% or less.
[0021]
Co: 2% or less Co has the effect of strengthening the base and suppressing hot plastic flow to prolong the life of the roll. In the present invention, Co can be contained if necessary. Such an effect is recognized when the content is 0.5% or more, but even if the content exceeds 2%, the effect is saturated, and an effect commensurate with the content cannot be expected, resulting in an economical disadvantage. For this reason, Co is preferably limited to 2% or less.
[0022]
One or two types selected from Ti: 0.1% or less and Al: 0.1% or less are both Ti and Al, which are elements having an effect of refining the structure, and are selected as necessary. Can be contained. When Ti and Al each contain more than 0.1%, the fluidity of the molten metal is lowered and the castability is lowered. More preferably, Al: 0.08% or less, Ti: 0.05% or less.
[0023]
The balance other than the above components is Fe and inevitable impurities. As inevitable impurities, P: 0.2% or less, S: 0.1% or less, and N: 0.1% or less are acceptable.
In addition to the above composition, the cast roll material of the present invention preferably has a depth range that can be effectively used as a roll, that is, the hardness in the roll use layer is Hs29 to 43. When the hardness of the roll use layer is less than Hs29, the hardness is too low, wear resistance is reduced, and roll life is reduced. On the other hand, if it exceeds Hs43, the hardness is too high and the slip resistance decreases. For this reason, in the roll material of this invention, it is preferable to limit the hardness of a roll use layer to the range of Hs29-43.
[0024]
Below, the preferable manufacturing method of this invention roll material is demonstrated.
In the roll material of the present invention, it is preferable from the viewpoint of energy cost and manufacturing cost that the molten metal having the above composition is formed into a ring-shaped roll material having a predetermined size by a centrifugal casting method. Any known method can be applied to the centrifugal casting method.
After the molten metal having the above composition is made into a ring-shaped roll material by centrifugal casting, the ring-shaped roll material is used as an outer layer of the roll, and during the solidification of the ring-shaped roll material or after complete solidification, the rotation of the mold is stopped to It can also be statically cast to form a composite roll. Thereby, the inner surface side of the outer layer material is redissolved and the outer layer and the inner layer are welded and integrated to form a composite roll. As the inner layer material to be statically cast, it is preferable to use graphite steel, spheroidal graphite cast iron, or hypereutectoid steel having excellent castability and mechanical properties. Moreover, you may provide the intermediate | middle layer which consists of hypereutectoid steel between an outer layer and an inner layer. When a roll is manufactured by centrifugal casting, the intermediate layer may be centrifugally cast following the centrifugal casting of the outer layer.
[0025]
Moreover, since this cast roll material is rich in toughness, it can be manufactured by making a sleeve roll with only the outer layer and shrink-fitting the shaft material.
After the ring-shaped roll material is centrifugally cast as described above, the ring-shaped roll material is used as a sleeve which is a roll use layer, and the shaft material is fitted into the sleeve by shrink fitting or cold fitting, and assembled. It can also be a roll. As the shaft material, cast steel, cast iron, and forged steel can be used, but carbon steel, CrMo steel, spheroidal graphite cast iron, and the like are preferable from the viewpoint of hardness.
[0026]
As described above, the roll produced using the cast roll material of the present invention can be suitably applied as a seamless steel pipe rolling roll such as an elongator roll in addition to the piercer roll.
[0027]
【Example】
A molten metal having the composition shown in Table 1 was melted in a low-frequency melting furnace, and a ring-shaped roll material (outer diameter: 1348 mmφ−inner diameter: 655 mmφ × length 2080 mm) was obtained by centrifugal casting. The casting temperature was 1530 ° C., and the centrifugal force was 150 G as a multiple of gravity. In addition, P was 0.005 to 0.010% and S was 0.008 to 0.015%. After casting, a tempering treatment was performed at 690 to 740 ° C. The obtained ring-shaped roll material was finished to a predetermined size, shrink-fitted to an arbor (shaft material), assembled into a sleeve-type roll, and used as a piercer roll for seamless steel pipe rolling.
[0028]
The roll hardness Hs was measured on the roll surface (rolled surface) of the obtained piercer roll in accordance with JIS Z 2246.
The obtained piercer roll was mounted on a Mannesmann piercing and rolling machine, and piercing and rolling of a high Cr alloy billet (outer diameter: 207 mmφ) containing 9% by mass or more of Cr was performed, and the roll life was measured. The number of rolling rolls up to the point at which reuse became impossible due to biting failure, occurrence of slip, and roll damage was defined as the roll life of the roll. In addition, the case where the roll made from a forged adamite was used was made into the prior art example.
[0029]
The obtained results are also shown in Table 1. The roll life of each roll is the ratio of the number of rolled rolls to the reference value, the roll life ratio = (the number of rolled rolls) / (the number of rolled rolls in the conventional example), based on the number of rolled rolls of forged adamite rolls as a standard example. evaluated.
[0030]
[Table 1]

[0031]
In all of the examples of the present invention, a roll life extension of 1.5 times or more of the conventional example is achieved. On the other hand, the comparative examples which are out of the scope of the present invention are the conventional examples in which the occurrence of a biting failure (roll No. 8, No. 10) or the occurrence of slip during rolling (roll No. 9, No. 13). Compared to this, the roll life is short.
[0032]
【The invention's effect】
According to the present invention, it is possible to provide a roll material for seamless steel pipe rolling and a roll for seamless steel pipe rolling at low cost, which has excellent slip resistance, can suppress surface damage, and has a long service life. Has an exceptional effect.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between roll material hardness and effective C amount.

Claims (6)

It is a roll material used for a roll for seamless steel pipe rolling.
C: 1.0 to 2.0%, Si: 0.1 to 1.0%,
Mn: 0.2 to 2.0%, Cr: 0.5 to 2.5%,
Mo: 0.5 to 2.5%, V: 3.5 to 7.0%,
Nb: 0.1-2.0%
And satisfying the following formula (1), and having a composition comprising the remaining Fe and inevitable impurities, a cast roll material for a seamless steel pipe rolling roll excellent in slip resistance.
−0.2 ≦ C− (0.24 × V + 0.13 × Nb) ≦ 0.2 (1)
Here, C, V, Nb: content of each element (mass%) The hardness within a roll use layer range is Hs29-43, The cast roll material for seamless steel pipe rolling rolls of Claim 1 characterized by the above-mentioned. The cast roll material for seamless steel pipe rolling rolls according to claim 1 or 2, further comprising W: 1.5% or less by mass% in addition to the composition. The cast roll material for a seamless steel pipe rolling roll according to any one of claims 1 to 3, further comprising Co: 2% or less in mass% in addition to the composition. 5. In addition to the composition, the composition further contains one or two selected from Ti: 0.1% or less and Al: 0.1% or less by mass%. A cast roll material for a seamless steel pipe rolling roll according to any one of the above. A seamless steel pipe rolling roll comprising the cast roll material according to any one of claims 1 to 5 as a roll use layer.

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