AU681219B2 - H-steel manufacturing method - Google Patents

Description

SPECIF I CATI ON Title of the Invention: A METHOD OF MANUFACTURING H-SECTION STEELS The present invention relates to a hot-rolling method for the manufacturing H-section steels having a high dimensional accuracy for use in architecture and building, and more particularly to a hot-rolling method using a group of universal mills for manufacturing H-section steels of various different sizes with a dimensional accuracy comparative to that of welded Hsection steels.

Background Art: A steel frame of a building is generally composed of an assembly of Hsection steels. With a growing tendency toward high-rise buildings, a demand for H-section steels of various different sizes or H-section steels with a high dimensional accuracy has increased. However, partly because the web and flanges of hot-rolled H-section steels stipulated by JIS (Japanese Industrial Standards) change in size with relatively large increments such as 25 mm and mm, respectively, and partly because the hot-rolled H-section steels have relatively large rolling tolerances, welded H-section steels are used in many cases for the aforesaid architectural and building purposes.

Figure 1 is a View showing the cross-sectional shape of H-section steels and dimensions of various parts of the H-section steels. Designated by H as the height of a web, B the width of flanges, ti the thickness of the web, t the thickness of the flanges, and bi and b 2 the length or distance from the web and an end of each flange.

I- The nominal size of an H-section steel is represented by H500 X B200 x 10/16, for example. H500 represents a web height of 500 mm, B200 a flange width of 200 mn, and 10/16 a web thickness of 10 mm and a flange thickness of 16 mm, respectively. Dimensional tolerances stipulated for the welded H-section steels by the Steel Structure Association Standards are smaller than these of the hot-rolled H-section steels (hereinafter simply referred to as "H-section steels"). For example, the tolerance allotted to the web height of 500 mm is mm for the welded H-section steel and ±3.0 mm for the H-section steel.

When the dimensions of webs and flanges are not uniform, an assembled structure is defective from the aesthetical view and may cause a joint failure leading to a reduction of strength. Particularly, when an offset S of the web from the center of flanges (which is obtained by S-(bi-b2)/2 shown in Figure 1 and which is hereinafter referred to as "web offset") becomes large, the strength of the structure is lowered due to an offset load applied thereto.

Accordingly, the web offset is set to be ±2.5 mm for welded H-section steels having a web height not smaller than 300 mm, and ±3.5 mm for welded H-section steels having a web height not smaller than 300 mmn.

According to a conventional H-section-steel rolling process, a cast iron bloom a steel bloom is rolled by a two high breakdown mill (hereinafter referred to as 2Hi-BD mill") down into a rough-rolled section piece having a dog-born shape which in turn is rolled down successively by a series of mills composed of a universal roughing mill (hereinafter referred to as "UR mill"), a two high edger mill (hereinafter referred to as "2Hi-E mill"), and a universal finishing mill (hereinafter referred to as "UF mill"). Between the UR mill and the 2Hi-E mill, the rough-rolled section piece is subjected to an intermediate rolling process achieved by a reciprocating or reverse action, and after that a single pass through the UP mill completes or finishes an H-section steel.

I The 2Hi-E mill has two rolls so grooved as to form a plurality of edger passes or grooves arranged in the widthwise direction of the rolls. When H-section steels of various different sizes are to be produced, three edger passes or grooves having different web heights and/or flange widths (H600 X200, H550 x200 and H500X200 or H200 X100, H300 xi50 and H400X200, for example) are formed in each of the two rolls.

Figure 2 is a view showing a plurality of grooves formed in rolls of the 2Hi-E mill and cross-sectional shapes of rolled materials. In this figure, designated by 5 is an upper edger roll, 6 a lower edger roll, a pass or groove provided for the size of H500 X200, a pass or groove provided for the size of H550 x200, and a pass or groove provided for the size of H600 X200.

In the case where a plurality of H-section steels having the same outside dimension are to be produced, a corresponding number of grooves formed in the rolls must have the same web height and flange width but with different web thicknesses and flange thicknesses. In general, as the web thickness and flange thickness reduce, the dimensional accuracy decreases. However, since the H-section steels having a uniform outside dimension must have a dimensional accuracy comparative to that of the welded H-section steels, a great difficulty has arisen when manufacturing such H-section steels by means of a rolling line using the rolls of the 2Hi-B mill.

Figure 3 is a cross-sectional view of a rolled blank piece 7 which changes to an H-section steel to illustrate a method of manufacturing an H-section steel by an edger mill which is composed of a 2Hi-E mill.

Figure 3(a) is a view showing the condition in which rough rolling is achieved in a UR mill having an upper horizontal roll 1, a lower horizontal roll 2 and a pair of opposed vertical rolls 3 and 4. At this rolling stage, a rough-rolled shape of the H-section steel is produced.

Figure 3(b) is a view illustrative of the condition in which rough rolling is achieved in a 2Hi-E mill having only an upper edger roll 5 and a lower edger roll 6. In this figure, one pass or groove is shown which is selected from one of the three passes or grooves shown in Figure 2. At this rolling stage, the accuracy of various dimensions, such as the flange width, the web center (the center of the web located centrally between the opposed flanges at each end), and the like is secured. In Figure using the rolls 5 and 6, opposite toes 7 of the respective flanges are reduced in cross-sectional shape to correct a web offset of the blank piece being rolled. In this instance, in order to obtain an enhanced correcting effect, the inside surfaces of the flanges are brought into contact with the rolls to prevent lateral displacement of the blank piece being rolled.

Figure 3(c) is a view showing the condition in which finished rolling is achieved in the UF mill having an upper horizontal roll 8, a lower horizontal roll 9, and a pair of opposed vertical rolls 10 and 11. At this finished rolling stage, the inside surfaces of the respective flanges are held in contact with the horizontal rolls 8 and 9, while the outside surfaces of the respective flanges are held in contact with the vertical rolls 10 and 11.

Thus, an H-section steel of a final product size is obtained.

In rough rolling achieved in the UR mill shown in Figure the web center may be offset due to uneven enlargement of the flange width caused by an incorrect biting posture, or misalignment of the upper and lower horizontal rolls. When such a web offset occurs, an attempted correction achieved in the subsequent 2Hi-E mill will cause buckling of the flanges due to heavy pressure applied thereto.

Figure 4 is a front elevational view of the rolls, with a blank piece being rolled shown in cross section, illustrating an example of buckled flanges in the 2Hi-E mill. Since only part of the flanges are severely bent or flexed, reduction of the flange width and correction of the web offset are difficult to achieve. Accordingly, even if finished rolling is achieved in the succeeding UF mill, the unevenly enlarged flange width remains unchanged or uncorrected.

Thus, the web offset can never be corrected.

In the 2Hi-E mill, the inside surfaces of the flanges are brought into contact with the rolls, with the flanges inclined outwardly. Accordingly, for a thin flange, a buckling problem is unavoidable when a pressure is exerted on a toe 7 of such a thin flange. An H-section steel rolling line including the 2Hi-E mill is therefore unable to manufacture H-section steels with high dimensional accuracy.

A variety of means or measures have been proposed to improve the product dimensional accuracy of H-section steels at the rolling stage of the edger mill. For example, on page 304, Figures 26a to 26c of WALZWERKSWESEN (J.

PUPPE und G. STAUBER, DUESSELDORF VERLAGSTHALEIZEN M. B. A) published in 1934 as a handbook of section steel rolling, universal-type edger mill composed of four rolls (hereinafter referred to as "UE mill") is shown in cross section. In this example, a flange buckling problem such as shown in Figure 4 can be prevented by the action of vertical rolls, and for this reason, an enhanced effect in correcting the web offset can be attained.

The disclosed UE mill has, however, never been used in practice in any of Europe, the U. S. A. and Japan for the reason described below. In this UE mill, one pair of horizontal rolls and one pair of vertical rolls are held in full contact with a blank piece being rolled, so each size of blank piece requires one pair of horizontal rolls, thus leading to an increased number of

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stocked roll sets. This problem becomes significant when H-section steels having a uniform outside dimension are to be manufactured.

The size of an H-section steel used as a steel frame of a high-rise building is determined according to the load applied thereto. Accordingly, various types of H-section steels having different nominal sizes are produced.

In practice, however, H-section steels having one and the same nominal size may have different web lengths and flange widths. When such dimensionally nonuniform H-section steels were used in combination, a difficulty in making a joint would occur, as well as injure the beauty of the resulting steel frame.

The manufacturing of H-section steels of different nominal sizes requires grooved roll mills or universal mills which are selected in accordance with the desired web heights. Numerous rolling methods have been proposed for the purpose of reducing the number of rolls. The present inventor has already proposed a method of reducing the web height by means of a UP mill (Japanese Patent Laid-open Publication No. 2-84203, U.S. Patent No. 4958509, British Patent No. 2222796, Australian Patent No. 625679 and Korean Patent No. 51420) and a method of reducing the web height either in a UR mill or in UF mill (Japanese Patent Laid-open Publication No. 4-258301, U.S. Patent No. 5287715, Australian Patent No. 640553, European Patent Laid-open Publication No. 0498733 and Korean Patent Application No. 92-1775). Japanese Patent Laid-open Publication Nos. 59-133902, 60-82201, 60-83702, 60-118301 and 62-93008 each disclose a method of reducing the web height in intermediate rolling or finish rolling. On the other hand, a method of enlarging the web height in intermediate rolling or finish rolling is disclosed in Japanese Patent Laid-open Publication Nos. 63-30102, 63-72402, 63-168204, 61-262403 and 62-161403.

Furthermore, Japanese Patent Laid-open Publication Nos. 61-262402 and 61-262404 disclose a method of reducing or enlarging the web height.

i I In any of the disclosed methods of reducing and/or enlarging the web height, the toes of each flange are not subjected to reduction in crosssectional area by means of the rolls; rather, the flanges are allowed to enlarge or spread in the widthwise direction. Consequently, when the web height is reduced in particular, a phenomenon is observed that the material flows from the web portion to the flange portion, creating more than 4% enlargement of the flange width which exceeds an allowable tolerance of the flange width.

Thus, the conventional methods have a problem whereby the web offset can increase even when the web height is changed, as the case may be, and canceling out the correcting effect provided by the edger mill.

The H-section steels of the, type having a uniform outside dimension are defined as a series of H-section steels which is uniform in the web height H and flange width B but differs from one another in the web thickness ti and *0 flange thickness t 2 as shown in Figures l(a) and l(b).

To manufacture the uniform outside dimension type H-section steels, grooved roll mills and universal mills which are designed to meet the desired 0 00 web thicknesses and flange thicknesses of the H-section steels are necessary.

Owing to a reduction of the web thickness and flange thickness, the product weight can be reduced. However, reduction in product weight increases production cost. Accordingly, the welded H-section steels have been used heretofore in place of the uniform outside dimension type H-section steels.

The present invention seeks to provide a method of manufacturing highly dimensionally accurate H-section steels by hot rolling, In a particularly preferred aspect the invention relates to a method of manufacturing by hot-rolling various types of H-section steels having different nominal sizes or a series of H-section steels having a uniform outside dimension with a dimensional accuracy comparative to that of the welded H-section steels.

Thus according to the present invention there is provided a method of manufacturing an H-section steel, of the type wherein a group mills (UT) including a universal roughing mill (UR) and a universal edger mill (UE) each composed of four rolls and disposed closely one behind the other is used at least at a final stage of an intermediate rolling process, wherein the improvement comprises: horizontal rolls of the universal edger mill having a width smaller than the width of horizontal rolls of the universal roughing mill so that opposite toes of the respective flanges of a rough-rolled section piece are reduced in a cross-sectional area by and between the horizontal rolls of the universal edger mill while outside surfaces of the respective flanges are confined by vertical rclls of the universal edger mill.

the In a preferred embodinment the intermediate rolling process recited in the preceding paragraph is followed by finished rolling achieved by the use of a universal finishing mill (UF) disposed close to the mill group (UT), The universal finishing mill may be composed of a universal mill including horizontal rolls having a variable width.

In a second aspect, the present invention provides a method of 25 manufacturing an H-section steel of the type wherein a group of mills (UT) including a universal roughing mill (UR) and a universal edger mill (UE) each composed of four rolls and disposed closely one behind the other is used at least at a final stage of an intermediate rolling process, wherein horizontal rolls of the universal roughing mill have, a definite width, horizontal rolls of the universal edger mill are divided to two and have a variable width and the horizontal rolls and vertical rolls of the universal edger mill jointly define a groove so that opposite toes of the respective flanges of a rough-rolled section piece are reduced, but web are not reduced in a cross-sectional area by and between the horizontal rolls of the universal edger mill while inside and outside surfaces of the respective flanges are confined by the horizontal and vertical rolls of the universal edger mill.

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a~LU Preferably the intermediate rolling process recited in the preceding paragraph is followed by finished rolling achieved by the use of a universal finishing nill (UF) disposed close to the mill group (UT).

The universal finishing mill may be of the type inciniucng horizontal rolls having a variable width.

In one preferred embodiment, a final pass through the universal edger mill effects a reduction in web height.

Brief Description of the Drawings Figure 1 is a view illustrating dimensions of various parts of two Hsection steels shown 'n cross-section; Figure 2 is a view showing a plurality of passes or grooves formed in rolls of two high edger mill and cross-sectional shapes of materials being rolled; Figure 3 is an explanatory view illustrating a conventional method for the manufacturing of I--section steels, with rolls shown in front elevation and a blank piece being rolled shown in cross section; Figure 4 is a front elevational view of rolls in a conventional edger mill, with a blank piece being rolled shown in cross section, exemplifying a 20 dflange buckling problem and a web offset problem caused in a conventional 20 edger mill;

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Figure 5 illustrates various H-section-steel manufacturing lines or systems used for carrying out methods of the present invention, in which Figure is a view showing an H-section-steel manufacturing line having a UR mill and a UE mill installed closely one behind the other, Figure 5(b) is a view showing another H-section-steel manufacturing line in which a UR mill, a UE mill and a UF mill equipped with horizontal rolls having a variable width are installed closely one behind another, Figure 5(c) is a view showing an Hsection-steel manufacturing line in which a UR mill and a UE mill equipped with horizontal rolls having a variable width are installed closely one behind the other, and Figure 5(d) is a view showing an H-section-steel manufacturing line including a UR mill, a UE mill and a UF mill installed closely one behind another wherein the UE mill and the UF mill are each equipped with horizontal rolls having a variable width; Figure 6 is a front elevational view of rolls in a universal edger mill (UE mill) used in a rolling method of this invention, showing the positional relationship between each roll and a blank piece being rolled shown in cross-section; Figure 7(a) is a front elevational view of rolls in a universal edger mill used for rolling a blank piece shown in cross-section, and Figure 7(b) is a front elevational view of rolls in a universal finishing mill equipped with two-piece horizontal rolls having a variable width used for rolling a blank piece shown in cross-section; Figure 8 is a front elevational view of horizontal rolls and vertical rolls in a universal edger mill (UE mill), with a blank piece being rolled shown in cross-section, illustrating an example of two-piece horizontal rolls having a variable width; Figure 9 is a cross-sectional view of a rough-rolled section piece I I before it is subjected to test rolling; Figure 10 is a graph showing measured values of the web offset plotted in the longitudinal direction of the rough-rolled blank H-section piece of FIG.

1 and an intermediate blank piece processed therefrom by rolling; Figure 11 is a graph showing the results of a measurement taken to determine the flange width when the web height is reduced according to the method of the present invention; Figure 12 is a table showing the dimensional accuracy of various Hsection steels obtained in Examples of this invention and manufacturing tolerances stipulated for hot-rolled H-section steels and welded H-section steels; Figure 13 is a view showing a plurality of passes or grooves formed in rolls used in a two high breakdown mill (2Hi-BD mill); Figure 14 is a table showing a pass schedule achieved when roughrolled section pieces are rolled by the 2Hi-BD mill; Figure 15 is a table showing a pass schedule achieved when a roughroiled H-section piece is rolled in the line shown in Figure Figure it is a view showing a pass or groove formed in grooved rolls of a two high edger 11ll (2Hi-B mill), with a blank piece being rolled shown in cross section; Figure 17 is a table showing a pass schedule achieved by a conventional 2Hi-E mill used as a Comparative Example in place of the universal edger mill (UE mill) of the mill line shown in Figure 5(d) for manufacturing an H-section steel; and Figure 18 is a graph showing variations of the web offset in the longitudinal direction of H-section steels.

L- L- I 81 Best Mode for Carrying out the Invention: Methods of the present invention, such as defined above, for the manufacturing of an H-section steel will be described below in greater detail.

Figure 5 illustrates various H-section-steel manufacturing lines used for carrying out the methods of the present invention, whereby Figure 5(a) shows an H-section-steel manufacturing line including a UR mill and a UB mill installed closely one behind the other, Figure 5(b) is a view showing another H-section-steel manufacturing line in which a UR mill, a UE mill and a UP mill equipped with horizontal rolls having a variable width are installed closely one behind another, Figure 5(c) is a view showing still another H-section-steel manufacturing line in which a UR mill and a UE mill equipped with horizontal rolls having a variable width are installed closely one behind the other, ,.and Figure 5(d) is a view showing an H-section-steel manufacturing line including a UR mill, a UE mill and a UF mill installed closely one behind another wherein the UE mill and the UP mill are each equipped with horizontal rolls having a variable width. The term "installed closely" is used herein to refer to a condition in which two adjacent roll stands are installed in series without interposition of a table roll.

1. Use of a universal edger mill (UB mill) having a horizontal roll width smaller than that of a universal roughing mill (UR mill): Figure 6 is a front elevational view of rolls in a universal edger mill (UE mill) used in a rolling method of this invention, showing the positional relationship between each roll and a blank piece being rolled shown in cross section. The UE mill is of the universal type having an upper edger horizontal roll 12, a lower edger horizontal roll 13, and two opposed vertical rolls 14 and ~I~IIPC~C~31

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The horizontal rolls 12, 13 of the UB mill have a roll width L smaller than that of horizontal rolls of the UR mill used provided to perform the preceding rolling process, so that there is defined, jointly between opposed sloped portions or shoulders 21 of the respective roller bodies of the horizontal rolls and the inside surface 22 of a corresponding one of the flanges of a blank piece being rolled, an annular space or gap 16 having a thickness or distance 6 by virtue of which the inside flange surfaces 22 of the blank piece being rolled are kept free from restraint by the horizontal rolls. Ends or toes 7 of the flanges are reduced in cross-sectional area by and between the horizontal rolls 12, 18 while the flange outside surfaces 23 are kept under restraint by the vertical rolls 14, Since the respective flanges of the blank piece being rolled are restrained on their outside surfaces by the vertical rolls while the inside surfaces of the respective flanges are kept free from restraint, it is possible to prevent the flanges from becoming buckled as shown in Figure 4 whel subjected to a force or pressure tending to compress the flanges. With this arrangement, the web offset can be corrected with improved efficiency. By virtue of the space defined between the horizontal rolls and the inside surface of each flange of the blank piece being rolled, it is possible to manufacture yv two or more H-section steels of different web heights on the same UE mill.

Description will be given of a mill arrangement in which the UE mill shown in Figure 6 is used in place of the UE mill of the manufacturing line shown in Figure As shown in FIG. a continuously cast slab or bloom (not shown), heated to about 1,250 "C in a heating furnace (not shown), is passed through a 2Hi-BD mill to roll a beam blank which forms a rough H-section steel piece.

14,, ,The beam blank is passed back and forth through a universal mill group (UT) r p eh gr '13 1 composed of a UR mill and a UE mill. By making 7 to 15 such passes in a reciprocating or reversing action (intermediate rolling), the beam blank is so shaped or corrected as to attain the desired dimensions. Thus the dimensioned beam blank is then passed through a U mill which completes an H-section steel of the desired final shape.

When an H-section steel having a size of H700 x B200 is to be manufactured, the UR mill employs horizontal rolls having a width L of 676 mm which is provided for the H700 x B200 size, while the UE mill employs horizontal rolls having a width of 566 mm which is smaller than that of the horizontal rolls of the UR.mill. With the horizontal rolls thus employed, it is possible to manufacture H-section steels of different sizes which vary from H700 x B200 to H700 x B200. In this instance, since rolling in the UE mill is achieved in such a condition that a space 6 #50 mm) is defined between the inside surface of each flange and the horizontal rolls, the flanges are prevented from becoming buckled with the result that a finished H-section steel does not involve a web offset. Further, by closely installing the UR mill and the UE mill, the dimensional accuracy of a leading end portion ad a trailing end portion of an H-section steel can be improved.

II. Use of a universal finishing mill (UF mill) installed close to the mill group (UT): As shown in Figure the UB mill, in which the inside surface of each flange of the blank piece being roll is held out of contact with th;e horizontal rolls, is installed close to the UR mill, and the UF mill Is installed close to the UE mill. With this arrangement, it is possible to improve the dimensional accuracy of a leading end portion and a trailing end portion of the blank piece being rolled. Since the UF mill can also be used in the intermediate rolling process, one pass through the UR mill and the UF mill will complete a reduction of the thickness two times with the result that the rolling efficiency can be improved by 50% or more as compared with the method shown in Figure In addition, the length of the rolling line is relatively short so that the overall building length of a rolling plhnt can be reduced considerably.

III. Use of a universal finishilg mill having horizontal rolls made variable in width: Figure 7(a) is a view showing the width of rolls in the UE mill shown in Figure 6, and Figure 7(b) is a front elevational view of rolls of the universal finishing mill (UF mill) with a blank piece shown in cross section.

In Figure reference character 17 denotes a two-piece horizontal roll having a variable width, and 18 denotes a vertical roll.

The UF mill having the variable-width type horizontal rolls shown in Figure 7(b) may be installed close to the UE mill shown in Figure 5(b) to achieve rolling in a manner described below.

In the case where the horizontal rolls of the UR mill have a roll width of 676 mm (which is equal to an inside dimension of the web of an Hsection steel of the H700 X B200 size), and the horizontal rolls of the UE mill having a width of 566 mm, as shown in Figure if the horizontal rolls of the UF mill has a width variable from 676 mm to 576 mm, then it becomes possible to roll three types of H-section steels having different sizes: H700 x B200, H650 x B200 and H600X B200. Adjustment of the UR mill and the UF mill causes a reduction in the direction of thickness of the web and the flange, while adjustment of the UB mill causes a reduction in the widthwise direction of the flanges. More specifically, a final pass through the UBimill I causes a reduction in web height by 50 mm, and after that a final pass through the UF mill, which is achieved after the width of the horizontal rolls is reduced from 676 mm to 626 mm, converts the blank piece into an H-section steel having a size of H650 x B200.

Similarly, when the web height is reduced by 100 mm in a final pass through the UE mill, and when a final pass achieved through the UF mill with a horizontal roll width changed from 676 mm to 576 mm, it is possible to produce a rolled H-section steel of a size of H600 x B200, The foregoing embodiment relates to the manufacturing of H-section steels having different web heights; however, by properly arranging the mill line, the method of the present invention is able to produce similar H-section steels which are uniform in an outside dimension but differ from one another in flange width, web thickness and/or flange thickness. Since the horizontal roll width of the UE mill is smaller than that of the UR mill, there is a space defined between the inside surface of each flange and the horizontal rolls.

This arrangement is able to obviate the need for providing a separate roll mill used excliSively for the purpose of changing the web height.

In the method described above at the preceding section I or II in conjunction with the mill arrangement shown in Figures 5(a) or it is preferable that a process is achieved to reduce the web height via a final pass made through the UE mill, thereby increasing the degree of freedom in size of H-section steel products which can be manufactured by the same roll set.

IV. Use of a universal edger mill (UE mill) having horizontal rolls made variable in width: Figure 8 is a front elevational view of horizontal rolls of the type having a variable width and vertical rolls of an UE mill with a blank piece 16 11iii being rolled shown in cross section. The variable-width type horizontal rolls 19 can attain a desired width change on the on-line basis and hence does not require a space 16 (defined partly by horizontal rolls shown in Figure 6) for reducing the web height in a final pass of the intermediate rolling.

Accordingly, the horizontal rolls and the vertical rolls jointly define a groove so that the horizontal rolls attain a reduction in cross-sectional area of the toes of flanges while the inside and outside surfaces of the flanges are confined by the horizontal and vertical rolls. With this arrangement a further improvement in the dimensional accuracy can be attained. The variable-width type horizontal rolls, when used in manufacturing a wide variety of H-section ,Rceels of different sizes, provide a substantial reduction in the number of stocked horizontal roll sets of different sizes and a subsequent reduction of roller exchange time. Furthermore, the horizontal rolls are particularly useful when incorporated in a mill line arranged to manufacture H-section steels requiring a uniform outside dimension with high dimensional accuracy.

When the UE mill having the variable-width type horizontal rolls shown in Figure 8 is incorporated in the mill line of Figure the toes of the flanges and the inside and outside surfaces of the flanges are confined by rollers of the UE mill. Accordingly, throughout the length of a rolled product, an enhanced web-offset correcting effect and an enhanced flangeirregular-enlargement correcting effect can be obtained, thus making it possible to manufacture H-section steels with high dimensional accuracy.

In addition to the improved dimensional accuracy, approximately gain in rolling efficiency can be obtained in the same manner as described above with reference to Figure 5(b) when the UE mill having the roll arrangement ,shown in Figure 8 is used in the mill line of Figure The general 2Hi'-E mill has two horizontal rolls so grooved as to form

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a plurality of edger passes or grooves arranged in the widthwise direction of the rolls. In the case of rolls having a body length of 2,500 mm, for example, each of the rolls has three edger grooves of different sizes which are provided for H-section steels of H600 x 200, H550 x 200 and H500 x 200, respectively.

In the case where the 2Hi-E mill shown in Figure 3(b) is used, if the horizontal roll width is fixed and not variable, one set of horizontal rolls must be stocked for each of the desired product sizes. However, if the horizontal roll width is variable within a range of 100 mm at maximum, Hsection steels having three different sizes of H600 X 200, H550 x 200 and H500 X 200, for example, can be rolled by a single set of horizontal rolls of the variable-width type. Thus, the number of variable-width type horizontal roll sets to be stocked can be reduced to a value which is s a: 4g the number of grooved rolls of the general 2Hi-E mill shown in Figure 2.

The 2,500-mm-body-length rolls used in a 2Hi-E mill are more than tons in weight. On the other hand, the universal horizontal rolls are about 7 tons in weight, and even when a mechanism for changing the horizontal roller width is provided, the price of the universal horizontal rolls is about 2/3 of that of the rolls of the 2Hi-E mill.

To make the rolls variable in width, an arrangement disclosed in Japanese Utility Model Laid-open Publication No. 3-111404 (corresponding to U.S. Patent No. 5154074 and European Patent No. 443725), for example, may be used, which includes a movable sleeve roll having on its outer peripheral surface projections and connected by a sliding key to an arbor, a nut threaded over an externally threaded distal end portion of the sleeve and having circumferentially equidistant projections each adapted to be engaged in a space 4z *etween two adjacent ones of the projections on the sleeve roll, and a split 18 key axially interconnecting the sleeve roll and the nut at their opposed ends including the projections.

It is possible according to the present invention to achieve intermediate rolling using the mill group in which the UE mill having the variable-width type horizontal rolls is incorporated. The intermediate rolling may be followed by finished rolling by using the UF mill disposed close to the mill group in a manner described in the preceding section II. It is further possible according to the present invention to replace the UF mill by the universal mill equipped with the variable-width type horizontal rolls as described in the precedent section III.

The UE mill of the type having a variable horizontal roll width is able to roll H-section steels of various different sizes with high dimensional accuracy.

Various effects attained by the H-section-steel manufacturing methods of the present invention will be described below in conjunction with Preliminary Experiments 1 and 2, Examples 1 through 6, and a Comparative Example.

(Preliminary Example 1) Using model mills, an experiment was conducted to determine a web-offset correcting effect attainable when a UE mill having a horizontal roll width smaller than that of a UR mill was used to keep the inside surface of each flange free from forcible contact with the horizontal rolls of the UE mill.

Figure 9 is a view showing the cross-sectional shape of a roughly rolled blank section piece used with the model mills. To secure accurate measurement of rolled dimensions with minimum unit of 0.1 mm, the blank section piece is formed from stainless steel because stainless steel does not produce any scale at rolling temperatures.

The blank section piece was produced by cutting from a 500-mm-length stainless steel H-section with an initial web offset of 1 mm 21.5)/2=1)1.

Rolling conditions were set as follows.

Rolling temperature: 900 °C Number of pass: one Flange width reduction rate: 6% Type of edger mills used: 2Hi edger mill of the type having grooved rolls: horizontal rolls were, brought into contact with the inside surface of each flange.

Horizontal roll width: 84 m Universal edger mill: horizontal rolls and vertical rolls arranged to confine the inside and outside surfaces of each flange, respectively.

Horizontal roll width: 84 mm (identical to the method disclosed in "WAKZWERJSWESEB" specified under the heading "Prior Art".) Universal edger mill: Horizontal roll width: 64 mm so inat there was a width space of 6=10 mm defined between the inside surface of each flange and the horizontal rolls.

Each of the rolling processes specified above was followed by rolling in a UF mill equipped with horizontal rolls having a variable width, so as to attain a slight reduction in thickness of the web and flange portions at a reduction rate of The finish-rolled product was measured to determine the web offset.

Figure 10 is a graph showing measured values of the web offset plotted in the lengthwise direction of the blank section piece and two rolled products

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produced as a result of the foregoing Experiment.

As is apparent from the solid lines indicated by in Figure rolling in the 2Hi edger mill as specified above in the preceding paragraph caused the flanged portion (on the side of bi=23.5 mm) to buckle outwardly to such an extent which could be recovered only by the subsequent finished rolling in the UF mill, and accordingly no substantial web-offset correcting effect was observed. The web offset was substantially the same as the initial web offset of the blank section piece, as indicated by the solid lines The dash-and-dot lines shown in Figure 10 clearly indicated that as a result of rolling achieved in the conventional edger mill as specified above in the preceding paragraph the web was displaced toward a central portion of the flange by about 1 mmn, so that the web offset was corrected or reduced from 1 mn to 0.01 mm. In the case of the universal edger mill used in the method of this invention specified above in the preceding paragraph the flange portions were prevented from bucking outwards with the result that the web was displaced toward the center of the flanges by about 1 mm, and subsequently the web offset was corrected or reduced from 1 mm to 0.02 mm, as indicated by the solid lines shown in Figure 10. As understood from the above description, the weboffset correcting effect attained by the inventive method was substantially the same as that obtained by the conventional method in which the edger mill was used.

(Preliminary Experiment 2) Using the universal edger mill specified above at the paragraph and the blank section piece shown in Figure 9, an experiment was conducted to change the web height.

In Preliminary Experiment 2, the web height was reduced from 100 mm to 88 mm (a reduction of 12 mm), and the flange width was reduced from 50 mm to 47 I mm (a reduction of 3 mmn). Rolling in the universal edger mill was followed by finished rolling in the UF mill achieved in the same manner as Preliminary Experiment 1.

Figure 11 is a graph showing measured values of the flange width taken in the lengthwise direction of the blank section piece before and after the blank section piece was passed through the UF mill. In this figure, the broken lines represent variations of flange width observed after rolling in the UE mill, while the solid lines represent variations of the flange width observed after rolling in the UF mill. As is apparent from Figure 11, variations of the flange width are not large even when a reduction in flange width is attained, and variations of the flange width observed after the UF mill is not greater than (47.09 mm 46.79 mm) which is superior in dimensional accuracy to the welded H-section steels The reason being, since the toes of the flanges undergo a reduction in cross-sectional area while the web height is being reduced, a reduction in web height causes the material in the web portion to be squeezed or to flow in the rolling direction. Thus, the caused material flow has no effect on the change in flange width.

(Example 1) The UE mill shown in Figure 6 was installed in the mill line shown in Figure The IJE mill had horizontal rolls provided for the H800 x B300 product and having a horizontal roll width of 750 mm. Using the rolling equipment or system, an experiment was conducted to manufacture three types of H-section steels: the first type having a web height of 900 mm, a flange width of 300 a web thickness of 12 mm, and a flange thickness of 25 mm (hereinafter represented as H9000 X B300 x 12/25). the second type being H850 x B300 x 12/25, and the third type being H800 x B300 x 12/25. In the mill line shown in Figure the UR mill was spaced by 3 m from the UE mill, and the UF mill was spaced by 120 m from the UE mill.

At first, for the manufacturing of the H900 x B300 H-section steel, the horizontal roll widths of the UR mill and the UF mill were 850 mm. Following that, 7 (seven) passes in a tandem reversing action through the UR and UE mills and a final pass through the UF mill completed the H900x 8300 H-section steel.

In the UE mill, rolling was accomplished with a space 6 50 mm) defined between the inside surfaces of the respective flanges of a blank piece being rolled and th 'rizontal rolls.

Accordingly, in manufacturing the H850x 8300 H-section steel, the horizontal roll widths of the UR and UF mills were set to 800 mm. A total of 7 passes in a tandem reversing action through the UR and UE followed by a final pass through the UF converted the blank piece into an H850 x B300 H-section steel. At that time, rolling in the UE mill was carried out with a space 6# mm) defined between the flanges' inside surfaces of the blank piece being rolled and the horizontal rolls.

In the manufacturing of an H800 x 8300 H-section steel, the UR mill and the UF mill were set to have the same horizontal roll width of 750 mm.

Subsequently, 7 (seven) passes in a tandem reversing action through the UR and UE mills and a final pass through the UF mill completed the H800x B300 Hsection steel. In the UE, rolling was accomplished with no space defined between the inside surfaces of the respective flanges of the blank piece and the horizontal rolls.

By virtue of the UE mill having a smaller horizontal roll width than the UR mill, three H-section steels of different sizes, namely, H900 x B300, H850 x B300, and H800 x B300 could be manufactured by only one UE mill.

Figure 12 is a table showing manufacturing tolerances of the hot-rolled H-section steels manufactured according to Examples 1 6 and those of welded Hsection steels. As is apparent from the same figure, the H-section steels according to Example 1 have a dimensional accuracy which is well within the allowable manufacturing tolerances of the welded H-section steels.

(Example 2) Using the system including the mill-line arrangement shown in Figure an experiment was made to manufacture an H850 x B300 x 12/25 H-section steel. In this Example, horizontal rolls installed in the corresponding mills were selected as follows: UR mill with horizontal rolls having a width L of 850 mm designed for the H900x B300 product, UE mill with horizontal rolls having a roll width L of 750 mm designed for the H800 x B300 product, and UF mill with horizontal rolls having a width L of 800 mm signed for the desired H850 x B300 product. Subsequently, 6 passes in a tandem reversing action through the UR and UE mills converted a blank piece into an intermediate blank piece having a shape designed for the H900 x B300 product. At that time, rolling in the UE was achieved while maintaining a space (6=50 mm). In the seventh pass through the UE mill, the web height was reduced by 50 mm, so that a shape suitable for the manufacturing of the H850x B300 product was produced. Then, by making a final pass through the UF, an H850 x B300 H-section steel was produced.

Since rolling in the UE mill was achieved while keeping the space 6 constant, a reduction in web height could be readily achieved by a final pass through the UE mill. The resulting H-section steel had a dimensional accuracy which is well within the allowable dimensional tolerance of the corresponding welded H-section steel, as shown in Figure 12.

(Example 3) Using a system having such a mill-line arrangement as shown in Figure s an experiment was made to manufacture an H850 x 8300 x 12/25 H-section 24 steel. In this Example, installation of the horizontal rolls was made according to the following combination: UR mill with horizontal rolls (850 mm in width) designed for the H900 x B300 product, UE mill with horizontal rolls (750 mm in width) designed for the H800 x B300 product, and UP mill with horizontal rolls (having a fixed width of 800 mm) designed for the desired x 8300 product. The UR mill, UR mill and UF mill were uniformly spaced at intervals of 3 m.

Accordingly, a blank piece was given 6 passes through the UR, UB and UP mills in a reversing action, during that time the UP mill did not take part in the rolling action, while th. UR and UE mills engaged in the rolling action to perform hit~Teediate rolling to produce an intermediate blank piece of a shape suitable for the H900X B300 product. At that time, rolling in the UE mill was achieved while keeping a space 6=50 mm). In the following seventh pass through the UB mill, a 50 mm reduction in web height of the intermediate blank piece was attaintd in order to provide the same blank piece with a shape suitable for the production of the H850 x B300 product. Subsequently, a final pass through the UF mill completed an H850 X B300 H-section steel.

By virtue of the rolling process achieved while keeping the space in the UE rill and while keeping the UP mill out of rolling action, the web height could be reduced by a final pass through the UE mill. Owing to a cfose installation of the three mills, dimensional accuracy of the resulting Hsection steel was superior to that of the H-section steels of Example 2, as shown in Figure 12.

(Example 4) Using the system of the mill-line arrangement shown in Figure an experiment was made to manufacture an H850 x B300 x 12/25 H-section steel.

In this Example, the UF mill was equipped with horizontal rolls of the-> t-7 11 variable-width type which was variable in the width range of 750 to 850 mm. The horizontal roll width of the UF mill was set to 850 mm, and after that, the' blank piece was given 5 (five) passes through the UR, UE, and UF mills in a tandem reversing action. From the first to fourth passes, the UF mill did not take part in the rolling action, while the UR and UE mills engaged in the rolling action to perform intermediate rolling of the H900 x B300 product. In the fifth pass, the UE mill attained a reduction in web height of the order of mm, thereby producing an intermediate product having a shape suitable for the manufacturing of the H850x B300 product. Accordingly, the horizontal roll" width of the UF mill was changed to 800 mm, the intermediate product was subsequently rolled by the UF mill. By the finished rolling achieved in the UP, an H850 x B300 x 12/25 H-section steel was produced. As understood from Figure 12, the H-section steel had a dimensional accuracy which is superior to the dimensional accuracy of the H-section steel of Example 2.

Since a reduction in web height could readily be attained by the final pass through the UE mill, and since the horizontal roll width of the UF mill was variable to confine the flanges of the intermediate product throughout the rolling process, such precise dimensional accuracy as shown in Figure 12 could be obtained.

(Example Using the mill line shown in Figure an experiment was conducted to manufacture three H-section steels of different sizes: H500X B200 x 10/16 X B200 x 10/16, and H600 x B200 x 10/16. At that time, the UR mill, UE mill and UF mill were uniformly spaced at intervals of 3 nL For the manufacturing of H500 X B200 product, a continuous cast slab having a thickness of 300 mm, and a width of 700 mm was used as a blank piece.

S Figure 14 is a view showing a pass schedule achieved to roll a roughly i\

I

rolled blank section piece using a 2Hi breakdown mill (2Hi-BD mill). Using the,.

2Hi-BD mill having a groove arrangement shown in Figure 13, and using the continuous slab heated to 1250 *C in a heating furnace, a beam blank (roughly rolled blank section piece for a desired H-section steel) having a web height of 720 mm, a web thickness of 60 mm, a flange width of 250 mm, and an average flange thickness of 110 mm was prepared according to the pass schedule shown in Figure 14.

The UE mill used in this Example had variable-width type horizontal rolls and, as shown in Figure 8, was equipped with vertical rolls having a central projection engaged with the outside surface of a corresponding flange.

The central projection had a width of 190 mm, a groove cut in each of the horizontal rolls had a depth d of 93.5 mm, the distance D between opposed sleeve rolls 19' was 0 (zero), and the horizontal roller with was 468 mm. The distance D could be changed either on the on-line basis or on the off-line basis.

In the manufacturing of ,n H550 x B200 x 10/16 H-section steel, the distance between the opposed sleeve rolls was set to 50 mm with the result that the horizontal roll width L was increased to 518 mm. For the manufacturing of an H600 X B200 x 10/16, the D and L were set to 100 mm and 568 mm, respectively. Taking into account the abrasive wear of the horizontal rolls of the UR mill, the horizontal rolls of the UE mill were variable within a width range of 120 mm at maximum.

Figure 15 is a view showing a pass schedule achieved when rolling an Hsection steel in the mill line shown in Figure The setting was made to determine a hoizontal roll width of 468 mm for the UR mill, at that time the, horizontal roll width of the UE mill was set to 468 mm, which was identical to the horizontal roll width of the UR mill. Accordingly, an H500 x B200 10/16 n 7 I H-section steel was mandfactured by executing the pass schedule shown in Figure In the UE mill, the vertical rolls did not undertake a reduction of the flange portion in the direction of the thickness, and an opening identical to the thickness of the leading end (entry side) of the blank piece was maintained.

The vertical rolls had a primary function to protect the flange portions from becoming buckled when subjected to a force or pressure exerted from the horizontal rolls and to prevent the flange from becoming thick at the central portion thereof. To enable the UE mill to attain a reduction in flange width limited below reduction of the flange and the web in the direction of the thickness was achieved in the UR mill at the ratio of 1.5:1,0 With the final pass made through the UF mill which attained rolling with a light reduction, an H-section steel of the desired final shape was produced.

Accordingly, the horizontal roll width of the UR mill was set to 518 mm and the horizontal roll widths of the UE and UF mills were enlarged to 518 mm. With the horizontal roll widths thus set, an H550 x 8200 x 10/16 H-seciion steel was manufactured. Subsequently, an H600 X B200 x 10/16 H-section steel was manufactured under the condition that the horizontal roll width of the UR mill was set to 568 mm, and the horizontal roll widths of the UE and UF mills were enlarged to 568 mIL Changes or variations in dimension of various parts of the obtained H-section steels are shown in Figure 12. With the use of the UR and UP mills each having variable-width type horizontal rolls, and by virtue of rolling achieved in the UB and UF mills while keeping the flanges under restraint, the H-section steels exhibited the dimensional accuracy comparable to that of the welded H-section steels, as shown in Figure 12.

(Example 6) Using the mill line shown in Figure an experiment was made to manufacture three H-section steels having different sizes: H500 x B200, H550 X B200 and H600 x B200. In the mill line shown in Figure the UR mill and the UE mill were spaced by 3 m, and the UE mill and the UP mill were spaced by.

120 m.

The UR mill and the UE mill were equipped with the same horizontal rolls as those used in Example 5 described above, while the UF mill employed three horizontal rolls of different sizes used exclusively for the manufacturing of a corresponding one of the three types of H-section steels.

In the manufacturing of the H600 X B200 product, the UR mill, UE mill and UF mill were each set to have the same horizontal roll width of 568 mm.

Accordingly, the UE mill and the UF mill did not take part in a reduction of the web height.

For the manufacturiag of the H500 x B200 product, the horizontal roll width of the UE mill was reduced from 568 mm to 518 mm when a final pass was made through a mill group of UR and UE to roll the H600 x B200 product.

Accordingly, the web height of the blank piece was reduced by 50 mnO in the UE mill, followed by a finish rolling in the UP mill.

In the manufacturing of the H500 x B200 product, the horizontal roll width of the UE mill was reduced from 568 mm to 468 mm when a final pass was made tirough the UR mill and the UE mill to roll the H600 x B200 product. In the UE mill, the web height of the blank piece was reduced by 100 mm and after that a finished rolling was completed in the UF mill. Dimensional changes or variations of various parts of the thus obtained H-section steels are also shown in Figure 12.

(Comparative Example) Figure 16 is a view showing an arrangement of rolls in a conventional I 2Hi-E mill with a blank piece shown in cross section.

Figure 17 illustrates a pass schedule achieved, as a comparative example, to roll an H-section steel using the conventional 2Hi-E mill in place of the edger mill in the mill line shown in Figure A 2Hi-E mill having an edger groove of 93.5 mm in depth shown in Figure 16 was installed in the mill line of Figure and then the pass schedule shown in Figure 17 was executed to manufacture an 1500 X B200 X 10/16 H-section steel. In a similar manner, an H600 x B200 X 10/16 H-section steel was also manufactured.

Dimensional changes or variations of various parts of the thus obtained H- 1 section steels are shown in Figure 12.

As is apparent from Figure 12, the methods using the conventional 2Hi-E mill are not satisfactory because variations of various dimensions of the Hsection steels exceed the tolerances of the welded H-section steels.

Furthermore, the flange width is increased, at the leading and trailing ends as viewed from the rolling direction, to such an extent w;ich exceeds the tolerance of the welded H-section steel.

Figure 18 shows variations of the web offset taken in the rolling direction in conjunction with the H500 x B200 x 10/16 H-sectin steels obtained by Example 5 and Comparative Example. In this figure, the solid lines represent the web offset observed when rolling is achieved by using the mill line shown in Figure 5(d) in which the UE mill and UF mill are each equipped with horizontal rolls having a variable width, and with the three universal mills installed close to one another. Similarly, the broken lines represent the web offset observed when rolling is achieved when using the conventional 2Hi-E mill.

It appears clear from Figure 18 that according to the conventional amethods, a portion of the rolled product which contains a web offset S r ofL r II exceeding ±2 mm (tolerance of the welded H-section steels) is at least 30 of the rolling length; whereas in the case of the methods of the present invention, such a portion cannot be observed. Thus, the methods of the present invention are able to eliminate a web-offset failure.

In a rolling process using a universal mill, an elongation in the rolling direction is not produced at leading and trailing ends of a blank piece being rolled, so that the flange width tends to spread more greatly at the opposite ends than at a central portion. This tendency may be controlled by the edger mill which effects a reduction of the flange toes via each pass achieved in a reciprocating or reversing action. However, in the case of the 2Hi-E mill shown in Figure 16, flange portions are caused to buckle to such an extent which can be recovered by the subsequent rolling in UR mill, and an effect in correcting the web offset can never be obtained.

The bucking of the flange portions can be prevented by a reduction of the flange toes which is attained while the opposite surfaces of the flanges are confined by vertical rolls of the UE mill as shown in Figure 8. When the flange width is reduced, the ce.ntral portion of the flange is deformed first and then undergoes an extension in the rolling direction. Accordingly, the flange width at the leading and trailing ends of the blank piece can be equalized with the flange width at the central portion of the blank piece.

According to the hot-rolling method for manufacturing an H-section steel, the dimensional accuracy can be increased to an extent incomparably higher than that of the method using a conventional 2Hi-E mill, and the web offset can be reduced considerably. Accordingly, the method of this invention is able to manufacture H-section steel having a high dimensional accuracy which is comparative to that of welded H-section steel. Further, since the web height can, be changed during the rolling operation, a plurality of H-section steels having different sizes can be manufactured by using only one mill group and with a dimensional accuracy comparable to that of the welded H-section steel.

Possibility of Industrial Application: The H-section-steel manufacturing method of this invention is capable of improving the dimensional accuracy and reducing the web offset, as compared with rolling methods using the conventional 2H-E mill. In addition, the web height can be readily reduced during the rolling operation with the result that by using only one mill group, H-section Steels of various different sizes can be hot-rolled with high dimensional accuracy comparable to that of the welded Hsection steels.

The invention is applicable to the multi-size, small-quantity production of H-section steels used as steel frames in buildings.

32 32

Claims (8)

1. A method of manufacturing an H-section steel, of the type wherein a group of mills including a universal roughing mill and a universal edger mill each composed of four rolls and disposed closely one behind the other is used at least at a final stage of an intermediate rolling process, characterised in that horizontal rolls of the universal edger mill have a width smaller than the width of horizontal rolls of the universal roughing mill so that opposite toes of the respective flanges of a rough-rolled section piece are reduced in cross-sectional area by and between the horizontal rolls of the universal edger mill while outside surfaces of the respective flanges are confined by vertical rolls of the universal edger mill.

2. A method of manufacturing an H-section steel, of the type wherein a group of mills including a universal roughing mill and a universal edger mill each composed of four rolls and disposed closely one behind the other is used at least at a final stage of an intermediate rolling process, characterised in that horizontal rolls of the universal edger mill have a width smaller than the width of horizontal rolls of the universal roughing mill so that opposite toes of the respective flanges of a rough-rolled section piece are reduced in cross-sectional area byv and between the horizontal rolls of the universal edger mill to achieve the intermediate rolling process while outside surfaces of the respective flanges are confined by vertical rolls of the universal edger mill, and the intermediate rolling process is followed by finished rolling achieved by the use of a universal finishing mill disposed close to the mill group. 25

3. A method of manufacturing an H-section steel according to claim 2, wherein the universal finishing mill comprises a universal mill including horizontal rolls having a variable width.

4. A method of manufacturing an H-section steel, of the type wherein a group of mills including a universal roughing mill and a universal edger mill each composed of four rolls and disposed closely one behind the other is used at least at a final stage of an intermadiate rolling process, characterised in that horizontal rolls of the universal roughing mill have a definite width, horizontal rolls of the universal edger mill are divided to two and have a variable width, and the horizontal rolls and vertical rolls of the universal edger mill jointly define a groove so that opposite toes of the respective flanges of a rough-rolled section piece are reduced and web are not reduced I in cross-sectional area by and between the horizontal rolls of the universal edger mill whilt i side and outside surfaces of the respective flanges are confined by the horizontal and vertical rolls of the universal edger mill.

A method of manufacturing an H-section steel, of the type wherein a group of mills including a universal roughing mill and a universal edger mill each composed of four rolls and disposed closely one behind the other is used at least at a final stage of an intermediate rolling process, characterised in that horizontal rolls of the universal roughing mill have a definite width, horizontal rolls of the universal edger mill are divided to two and have a variable width, and the horizontal rolls and vertical rolls of the universal edger mill jointly define a groove so that opposite toes of the respective flanges of a rough-rolled section piece are reduced and web are not reduced in cross-sectional area by and between the horizontal rolls of the universal edger m'll to achieve the intermediate rolling process while inside and outside surfaces of the respective flanges are confined by the horizontal and vertical rolls of the universal edger mill, and the intermediate rolling process is followed by finish rolling achieved by the use of a universal finishing mill disposed close to the mill group.

6, A method of manufacturing an H-section steel according to claim wherein the universal finishing mill comprises horizontal rolls having a variable width.

7. A method of manufacturing an I-I-section steel according to any one of the preceding claims 1 6 wherein a final pass through the universal edger mill attains a reduction in web height. 25

8. A method as claimed in any preceding claim and substantially as hereinbefore described with reference to the drawings. Dated this tenth day of June 1997 SUMITOMO METAL INDUSTRIES LTD Patent Attorneys for the Applicant: F.B. RICE CO. ZS Tt ~r o Abstract This invention relates to a method of manufacturing an H-section steel used for architecture and building. The method of this invention includes an intermediate rolling process achieved by a group of mills including a universal roughing mill (UR) and a universal edger mill and is chavacterized in that horizontal rolls of the UE have a width smaller than the width of horizontal rolls of the UR so that opposite toes of the respective flanges are reduced in cross-sectional area by and between the horizontal rolls of the UE while outside surfaces of the respective flanges are confined by vertical rolls of the UE, the horizontal rolls of the UE have a variable width, and the horizontal and vertical rolls of the UE jointly define a groove so that the respective flanges are reduced in the direction of thickness. By the method of this invention, H-section steels having a dimensional accuracy comparative to that of the welded H-section steels can be manufactured by hot-rolling while protecting the flanges against buckling.