JPH0234202A - Manufacture of hot rolled h-shape steel - Google Patents

Abstract

PURPOSE:To reduce remaining stresses in the web by forming a recessed groove continuing in the length direction on the central part of flange outside faces of an H-shape steel by a universal rough rolling, forming a projected rib at both sides of the recessed groove in the flange width direction, and then the projected ribs are drafted by a finish rolling mill. CONSTITUTION:A projected part 1A protruded from a flat face at the central part in the vertical direction of a vertical roll 1 in a universal rough rolling mill (UR mill) and recessed parts 1B at both upper and lower sides of the projected part 1A in the vertical direction are formed. A recessed groove 3 continuing in the length direction in the central part of flanges 2F of an H-shape steel 2 is formed by many rolling passes in the UR mill. Projected ribs 4 are formed on both sides of the groove 3, respectively. Then, the UR mill drafts a pair of the upper and lower ribs 4 to fill the groove 3 with metal. A difference between finishing temps. of the web and flange central part is reduced, and remaining stresses in the web are markedly reduced. Thus, no waving is generated even in a thin web and a manufacturing limit is expandable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing hot rolled H-section steel, particularly thin-walled web H-section steel.

[Prior art and the problem to be solved by this invention] When manufacturing H-beam steel using a universal rough rolling mill (hereinafter referred to as UR mill) and a universal finishing rolling mill (hereinafter referred to as UF mill), the conventional flat outer periphery is When a vertical roll with a surface is used, the thickness ratio of the web and flange does not change much until the URI bus-inlet side shape U-F is completed, and the flange remains thicker than the web, resulting in a thinner web. Due to the large temperature drop, the temperature difference between the web and flange during finishing is more than 150"C.

In particular, in the production of thin web H-section steel, this temperature difference is 200°C or more.

Internal stress is generated between the web and the flange due to this difference in finishing temperature and the difference in cooling rate after finishing (the temperature decreases slowly in a thicker flange with a higher temperature), and the web becomes in a state of large internal compressive stress. When using H-beam steel, especially when it is used as a beam material, a thinner web is required to reduce weight. I couldn't do it.

Various manufacturing methods have been proposed for thin web H-beam steel.
One method to prevent web waving has been proposed to reduce the temperature difference between the web and the flange by heating the web from the outside during rolling or by strongly cooling the flange. This results in large losses, and it is difficult to heat or cool symmetrically in the vertical and horizontal directions, and there are problems such as particularly instability in finish rolling.

In addition, as a processing method at an intermediate stage of rolling, the vertical roll shape of the UR mill is made into an uneven shape to form a recess along the longitudinal direction at the center of the outer surface of the flange to prevent the center of the web from shifting (Japanese Patent Laid-Open No. 61-74702 However, in order to increase the effect of widening the flange width, a method has been proposed in which small diameter sections are provided at the top and bottom of the vertical roll and a bulge section is provided at the tip of the flange (Japanese Patent Publication No. 41641/1983). In either case, the purpose is to control the biting position (posture) and widen the flange width, and the temperature difference and thickness difference between the web and the flange are not considered.

This invention was made in view of the above-mentioned circumstances, and its purpose is to reduce the wall thickness at the center of the flange during rough rolling of H-beam steel and to promote cooling, thereby reducing the gap between the web and the flange. An object of the present invention is to provide a method for manufacturing a hot rolled H-section steel that can reduce the temperature difference between the two and significantly reduce the residual stress in the web.

[Means to solve the problem]

As shown in Fig. 3, the vertical roll 1 of the UR mill has a convex part IA that protrudes beyond the normal flat surface F at the center in the vertical direction, and concave parts IB that are concave relative to the flat surface F on both sides of this convex part in the vertical direction. In the multi-pass rolling of the UR mill, the first
As shown in the figure, a longitudinally continuous groove 3 is formed in the center of the flange 2F of the H-section steel 2, and longitudinally continuous protrusions 4 are formed on both sides of the groove in the flange width direction.

Next, in a UR mill, the pair of upper and lower protrusions 4 are rolled down to fill the grooves 3 with metal.

The recess depth h of each pass in the UR mill is equal to the product flange thickness 1. It is smaller, preferably 0.1 tr or less. Further, the cross-sectional area S1 of the pair of protrusions 4 is preferably 1.3 times or more the cross-sectional area S0 of the groove 3.

[For production]

For H-section steel, the temperature drop is greatest in the thinner web during rolling, followed by the area around the tip of the flange, and the smallest temperature drop is at the joint between the flange and web (fillet) or at the center of the outer surface of the flange. Since the temperature in this part is high and the temperature decreases slowly during cooling, internal stress occurs due to the temperature difference between this part and the web.

In the present invention, the cooling rate of the central part of the flange is increased by thinning the central part of the flange due to the groove 3 in the center of the outer surface of the flange, and increasing the heat dissipation area by the groove 3 and the protrusions 4. In H-section steel 5, the finishing temperature difference between the web 5W and the center of flange 5F has decreased from the conventional 200℃ to 100℃ or less. In this case, if the web receives a compressive stress exceeding the buckling limit, it becomes wavy, but in the present invention, the internal stress is reduced due to the reduction in the finishing temperature difference, so web undulation does not occur, and the web thickness limit can be reduced.

Also, regarding the cross-sectional shape, in the UF mill, the protruding strip 4 is rolled down and metal flows vertically, filling the concave groove 3 and expanding the flange width slightly, so that the outer surface of the flange 5F is expanded as shown in Fig. 2. A flat H-shaped steel 5 is obtained.

The recess depth h is smaller than the product flange thickness t, preferably 0.7 t or less, and the uneven area is SI≧1.33.
．． The reason for this is that in order to promote temperature reduction in the center of the flange, it is better to have a larger h, but if it exceeds 0.7 tr, it will be difficult for the metal to fill in the recess even after UF rolling, and there is a risk that the shape will be defective. There are 1. If it exceeds, for example, even if the rough rolling is divided into two stages and the depth of the recess is changed, the thickness will not be sufficient. - direction,
When h is 0.7tr or less, S, ≧1.33. Under these conditions, recesses can be stably filled.

Note that it is preferable that C at the end of rough rolling be 0.2 tt or more in order to improve the cooling effect of the fillet portion.

〔Example〕

This is H2O2 (web height) x flange width) x
This is an example in which an H-section steel with a thickness of 9/22 (web/flange thickness) was rolled using a vertical roll 1 having the dimensions shown in FIG. 3 and according to the rolling schedule shown in Table 1.

Conventionally, the finishing temperature after UF mill rolling was 700/910 (W
/F), the finishing temperature difference was 210°C at 8T, but in the present invention, ΔT = 100''C at 700/800, making it possible to eliminate the occurrence of waviness even in thin webs. It was possible to expand the manufacturing limits of thin web H-section steel.

Furthermore, after the UF milling, the inner and outer surfaces of flange 5F became flat, and the flange width expanded by about 3 cm.

First Table Reduction Schedule [Effects of the Invention] As mentioned above, the manufacturing method of the present invention provides a concave and convex portion on the vertical roll of the OR mill, thereby creating a concave groove in the center of the outer surface of the H-beam flange during universal rough rolling. Since protrusions are formed on both sides and the protrusions are rolled down by a UF mill, the finishing temperature difference between the web and the center of the flange after finishing rolling can be reduced, and residual stress in the web can be significantly reduced.

As a result, even thin webs can be manufactured without causing undulation, and the manufacturing limits of thin web H-beam steels can be expanded.

[Brief explanation of the drawing]

1 and 2 are perspective views showing the H-section steel during universal rough rolling and universal finish rolling of the present invention, and FIG. 3 is a schematic diagram showing the vertical rolls of the OR mill according to the present invention. 1... Vertical roll, IA... Convex part, IB... Concave part, 2...
H-beam, 2F...flange, 2W...web, 3...concave groove, 4...convex strip, 5...H-beam, 5F...flange, 5W...web.

Claims (1)

[Claims] (1) When rolling H-section steel using a universal rough rolling mill and a universal finishing mill, a convex portion is provided in the vertical center of the vertical roll of the universal rough rolling mill, and a concave portion is provided on both sides of this convex portion in the vertical direction. By doing so, after forming a concave groove continuous in the longitudinal direction at the center of the outer surface of the flange of the H-beam steel by universal rough rolling, and forming convex stripes continuous in the longitudinal direction on both sides of the concave groove in the width direction of the flange, the universal rough rolling process is performed. A method for manufacturing a hot-rolled H-section steel, comprising rolling down the convex strip using a finishing rolling mill.