Nippon Steel Sumitomo Metal Corporation

Sumitomo Metal Industries, Inc.

Nippon Steel Corporation

Akihito Yamane

Yuji Arai

Kunio Kondo

Kenichi Sasaki

Hisashi Amaya

Toshiyuki Hata

Yuichiro Yamamoto

Taizo Makino

Kouji Nakaike

Hiroyuki Iwamoto

Chihiro Kozuka

Tooru Egoshi

Shigeru Kidani

The railway axle according to this disclosure has a pair of fitting portions and which each include a fitting portion hardened layer and a base metal portion, and a center parallel portion which includes a center parallel portion hardened layer and the base metal portion. The base metal portion has the chemical composition described in the description. In a region having the Vickers hardness of 480 HV or more in the center parallel portion hardened layer, a dislocation density ρ obtained based on a CoKα characteristic X-ray diffraction result is 2.5×10mor less, a half-value width B of the (211) diffraction plane is 1.34 degrees or less, and the dislocation density ρ and the half-value width B of the (211) plane obtained by X-ray diffraction satisfy Formula (1).(−4.8×10+8.5×10)/ρ≥1.00  (1)

Railway axle

A manufacturing method of a seamless metal pipe includes: preparing a plurality of mandrel bars in which lengths of work portions which come into contact with a hollow shell during elongating are different from one another; selecting a mandrel bar including a work portion having a length corresponding to the number of stands used in thickness reduction, among the plurality of mandrel bars; inserting the mandrel bar selected in the selecting into the hollow shell; and performing the elongating on the hollow shell into which the mandrel bar is inserted. Moreover, in the elongating, outer diameter reduction is performed by one of a preceding-stage stand group and a succeeding-stage stand group and the thickness reduction is performed by the other of the preceding-stage stand group and the succeeding-stage stand group, or the thickness reduction is performed by both of the preceding-stage stand group and the succeeding-stage stand group.

Manufacturing method of seamless metal pipe, mandrel mill, and auxiliary tool

A manufacturing method of a seamless metal pipe includes determining whether a preceding-stage stand group is used in outer diameter reduction or in thickness reduction of a hollow shell; and performing elongating on the hollow shell, into which a mandrel bar is inserted, based on the determination. In addition, in the elongating, when the preceding-stage stand group is used in the outer diameter reduction, the hollow shell is rolled in a state where an inner surface of the hollow shell does not come into contact with the mandrel bar in the preceding-stage stand group, and the hollow shell is rolled in a state where the inner surface of the hollow shell comes into contact with the mandrel bar in the succeeding-stage stand group.

Manufacturing method and manufacturing apparatus of seamless metal pipe

A mandrel mill a method for manufacturing a seamless pipe by using the mandrel mill includes a plurality of roll stands in which three grooved rolls R are disposed in each roll stand such that an angle formed by pressing directions is 120&#xb0; and the pressing directions of the grooved rolls R are alternately shifted by 60&#xb0; between adjacent roll stands, wherein a central angle &#x3b8; defining a circular arc that constitutes a groove bottom profile of the grooved roll R disposed at least in the first and second roll stands is set at less than 60&#xb0;. The mandrel mill can adequately suppress the problem of the mandrel bar not being able to be pulled out from a pipe after drawing and rolling, without resulting in an increase in facility cost and deterioration of maintainability.

Mandrel mill and method for manufacturing seamless pipe or tube

A rolling standin accordance with the invention is a rolling stand provided with three grooved rolls for rolling a tubular or bar shaped material to be rolled, in which three grooved rolls Rto Rare arranged in such a manner that an angle formed by pressing directions of any two adjacent grooved rolls of the three grooved rolls Rto Rcomes to 120 degrees. With regard to a cross sectional shape of each of the grooved rolls Rto Rformed by cutting each of the grooved rolls in a plane which includes a center line of a rotating axis of each of the grooved rolls Rto Rand is orthogonal to a pass line of a material to be rolled, any one grooved roll Ris provided with a first straight portion Lextending vertically to the pressing direction in both side flange portions, and the other two grooved rolls Rand Rare provided with a second straight portion Lopposing to the first straight portion Land extending in parallel to the first straight portion Lin the flange portions.

Rolling stand

[Problem to be Solved] A device for adjusting the rolling positions of rolling rolls and restraining poor roll-biting of the front edge part of a pipe material rolled by a three-roll mandrel mill includes pressing-down devices(P1 to P6) for moving rolling rolls Rto Rin the rolling direction and a control unitfor controlling the pressing-down devices. Immediately after the front edge part of a pipe material T has begun to be rolled by the rolling rolls disposed on at least one rolling stand of the rolling rolls Rto R, the control unitcontrols the pressing-down deviceto move the rolling rolls in the closing direction. Preferably, the rolling rolls disposed on at least one rolling stand of the rolling rolls Rto Rin the closing direction are moved at a speed of 16 mm/sec or higher using the pressing-down device

Method for adjusting rolling positions of rolling rolls constituting three-roll mandrel mill and method for manufacturing seamless pipes or tubes

A multi-roll mandrel mill comprises a plurality of grooved roll bodies as a roll pass for elongation rolling of a shell and a plurality of roll stands, each having roll shafts and roll chock portions for driving the grooved roll bodies for driving the grooved roll bodies, wherein bearings are internally contained in each grooved roll body. Optimizing the design of roll chock portions for every setup is achieved by a tube-making setup of the mandrel mill, wherein at least one of either or both of the roll shafts and the roll chock portions is replaced with a part(s) having a different shape(s) in addition to changing of the grooved roll bodies. The optimization of the design is effective in preventing underfill and overfill.

Multi-roll mandrel mill and method of producing seamless tubes

The present invention provides a mandrel mill and the like that is capable of not only enhancing the elongation ratio of the pipe or tube, but also suppressing a pinhole defect from occurring. The first means of the present invention provides a mandrel mill comprising a plurality of rolling stands in which two grooved rolls R, Rare disposed, respectively, the mandrel mill being characterized in that the roll diameter ratio for the first rolling stand and the second rolling stand is set at a value of 4.6 or over. The second means of the present invention provides a mandrel mill comprising a plurality of rolling stands in which three grooved rolls R, Rand Rare disposed, respectively, the mandrel mill being characterized in that the roll diameter ratio for the first rolling stand and the second rolling stand is set at a value of 2.8 or over.

A retract mandrel mill, comprising a mandrel mill and an extractor, the mandrel mill including a mandrel bar and being configured to roll a tube blank into which the mandrel bar is inserted, the extractor being configured to extract the mandrel bar from the tube blank that has been rolled in the mandrel mill, wherein the distance between the mandrel mill and the extractor is adjustable, and a method for rolling a tube blank by using the retract mandrel mill. As the result of the adjustable distance, even when a tube blank which is shorter than usual is rolled, there is no need to add an extra extension to the length of the tube blank to be elongation-rolled, and the wear of the mandrel bar can be suppressed so that the tube blank can be rolled efficiently and with high yields.

Retract mandrel mill and method for rolling tube blank

A pipe in which polygonization is substantially eliminated is manufactured by a reducer with a grooved roll with a groove having a groove bottom zone including the center of the groove in the roll axial direction and flange zones adjoining both sides of the groove bottom zone. The groove surface has a friction distribution in the roll axial direction such that the frictional force with respect to a material being rolled in the groove bottom zone is larger than the frictional force with respect to a material being rolled in the flange zones. This friction distribution can be achieved by working the groove surface so that the surface roughness of the groove bottom zone becomes greater than the surface roughness of the flange zones or by applying a lubricity modifier which differs with respect to amount and/or type between the groove bottom zone and the flange zones.

Grooved roll for a reducer and a reducer

A mandrel mill is provided which can perform elongation rolling with a markedly increased working ratio and dimensional accuracy on a material which is inherently difficult to roll such as a hollow shell made of stainless steel or a thin-walled material. A mandrel mill for manufacturing a mother tube by performing elongation rolling of a hollow shell comprises a plurality of roll stands, having at least one 4-roll stand for wall thickness reduction of a hollow shell and at least one 2-roll stand including the final stand downstream of the 4-roll stand.

Mandrel mill and process for manufacturing a seamless pipe

(1) A steel pipe that is expanded radially in a state wherein it was inserted in a well such as an oil well, characterized in that the non-uniform wall thickness ratio E(%) before expanding satisfies the following expression {circle around (1)}.0&#x2266;30/(1+0.018&#x3b1;)&#x2003;&#x2003;{circle around (1)} Wherein &#x3b1; is the pipe expansion ratio (%) calculated by the following expression {circle around (2)}.&#x3b1;=[(inner diameter of the pipe after expanding&#x2212;inner diameter of the pipe before expanding)/inner diameter of the pipe before expanding]&#xd7;100&#x2003;&#x2003;{circle around (2)} (2) A steel pipe that should be expanded radially in a state wherein it is inserted in a well, such as an oil well, characterized in that the eccentric non-uniform wall thickness ratio is 10% or less. When the embedding-expanding method is performed with use of the steel pipe of (1) or (2), lowering of collapse strength of the expanded steel pipe is prevented and bending thereof can be decreased.

Steel pipe for embedding-expanding, and method of embedding-expanding oil well steel pipe

A complex Fourier transform is performed on measured values of wall thickness at points in a cross section of a pipe in an axial direction, types of thickness deviation are classified, thickness deviation amount is calculated from the absolute value of the complex Fourier component, the position of a thick or thin portion of thickness deviation is calculated from the phase of the complex Fourier component, and manufacturing conditions of the pipe are adjusted based on these variables. The relationship r&#xb7;exp(j&#x3b8;) between the thickness deviation amount r and phase &#x3b8; of a first-order thickness deviation obtained for cross sections in the axial direction is subjected to a complex Fourier transform as a function of pipe longitudinal direction, the thickness deviation is further classified by the frequency of twist of the thickness deviation, and an action is taken to prevent the thickness deviation according to the classified thickness deviation.

Manufacturing method and manufacturing apparatus of pipe, thickness deviation information derivation apparatus, and computer program

(1) A steel pipe that is expanded radially in a state wherein it was inserted in a well such as an oil well, characterized in that the non-uniform wall thickness ratio E0 (%) before expanding satisfies the following expression {circle around (1)}.0&#x2266;30/(1+0.018&#x3b1;){circle around (1)} Wherein &#x3b1; is the pipe expansion ratio (%) calculated by the following expression {circle around (2)}.&#x3b1;=[(inner diameter of the pipe after expanding&#x2212;inner diameter of the pipe before expanding)/inner diameter of the pipe before expanding]&#xd7;100{circle around (2)} (2) A steel pipe that should be expanded radially in a state wherein it is inserted in a well, such as an oil well, characterized in that the eccentric non-uniform wall thickness ratio is 10% or less. When the embedding-expanding method is performed with use of the steel pipe of (1) or (2), lowering of collapse strength of the expanded steel pipe is prevented and bending thereof can be decreased.

When manufacturing a seamless pipe by carrying out elongation rolling and sizing on a mother tube for forming a seamless pipe, the occurrence of portions of thickness variation in the seamless pipe is suppressed by previously identifying the portions of wall thickness variation where the thickness varies in the circumferential direction of the seamless pipe, and carrying out elongation rolling so that the thickness of the portions of the mother tube corresponding to the portions of wall thickness variation of the seamless pipe are different in thickness at the completion of elongation rolling from that of other portions of the mother tube. As a result, local variations in wall thickness in the circumferential direction of a seamless pipe are prevented.

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Osaka, Japan

Akihito Yamane