JPH04141520A - Production of thin web wide flange shape h-beam - Google Patents

Abstract

PURPOSE:To produce a thin web wide flange shape H-beam without causing deterioration in material and structure due to flange water cooling and also causing no waviness of a web by previously determining the maximum temp. difference between a flange and a web occurring in the course of cooling down to ordinary temp. with respect to size and cooling water volume density and performing heating so that temp. difference lies within the range free from the occurrence of the waviness of a web. CONSTITUTION:In this invention, at least one or more web heating devices 2 are provided to a thin web wide flange shape H-beam producing line. First, water cooling conditions free from the occurrence of abnormal structure and material in a flange face are computed from size, component, and bloom-passing velocity by means of simulation model, and respective temps. of a flange and a web are determined, by which the required amount of temp. rise of the web is determined from the maximum temp. difference free from the occurrence of the waviness of the web. Subsequently, the amount of applied electric power in web heating is determined. Further, whether buckling is caused or not is checked in the course of web heating, and, in the case of NO, heating is done up to the upper limit, and, as to the shortage, the amount of applied electric power in web heating in a former stage is determined. The above procedures are repeated. In the case where buckling does not occur finally, web heating at one spot suffices but stepwise heating at two spots can be used because of heating capacity. The point is that the production of the thin web wide flange shape H-beam can be done by reducing the temp. difference.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a thin-walled H-section steel, and more particularly, it relates to a method for manufacturing a thin-walled H-section steel.
The ratio of tf′tw>3.0, web height (tW),
A thin-walled web H-section steel that prevents the generation of web waves when manufacturing a thin-walled two-nib H-section steel with a web thickness (HW) ratio of ) 1w, tW > 80 by hot rolling. Regarding the manufacturing method.

Conventional technology H-shaped steel is widely used in steel structures, but depending on the application, it is required to reduce the weight as much as possible even if the rigidity is the same. Therefore, efforts are being made to reduce the weight by reducing the thickness of the web, which has little effect on rigidity, and this lightweight H-section steel is generally called thin-web H-section steel. H-section steel is usually produced by a welding method or a rolling method, and although the rolling method is superior in cost and quality to the welding method, the rolling method has web problems.

The generation of web waves due to the rolling method is due to residual stress caused by the temperature difference during the cooling process between the flange and the web, which generates compressive internal stress in the web that exceeds the buckling limit of the web. Because the web is relatively thick, the web is thin, and the web height is high, it is extremely difficult to reduce the temperature difference between the flange and the web, resulting in large residual stress. It was extremely difficult to suppress web waves because of the low

Therefore, various methods have been proposed to reduce residual stress and techniques related to web heating devices for H-beam steel. for example(
1) JP-A-62-28002, (2) JP-A-63
-176429 Publication, (3) JP-A-63-21692
There is Publication No. 3, etc.

Among these, the techniques (1) and (3) are related to the web heating method between the rough rolling mill and the finish rolling mill 111, and the techniques +21 and (3) increase the web heating temperature to A.
This relates to a method for achieving C+ or higher.

However, tf, -tw>3. When manufacturing thin-web H-beam steel with Q, H, 'tw > 80, web waves will occur with any of the above techniques, and in order to prevent them, it is necessary to further reduce the finishing temperature difference. Or conversely, if the web temperature is not greater than the flange temperature, after finish rolling by the finishing universal rolling mill (UPI), the temperature difference will expand due to the cooling rate difference due to the difference between the web thickness and the flange thickness, and web waves will occur. leading to.

For this reason, a method of installing a water cooling device on one side of the UPI and controlling the water density is disclosed in Japanese Patent Application Laid-open No. 1-2009, for example.
Although proposed in Japanese Patent No. 028, strengthening of flange water cooling causes problems such as increased hardness and decreased toughness of the surface to be cooled, so an alternative method was needed.

Problems to be Solved by the Invention The purpose of the present invention is to solve the above-mentioned problems, and specifically, to provide a manufacturing method that can prevent the generation of webs by a simple means when manufacturing thin-walled web H-beam steel using a hot rolling method. The purpose is to propose a method.

l! Means for solving the problem and its operation, that is, the present invention provides a flange cooling device installed between a rough rolling mill and a finishing rolling mill and on the finish rolling am surface, and a web heating device installed at any of the above positions. When manufacturing web H-section steel, the maximum 1 degree difference between the flange and web that occurs during the cooling process to room temperature is determined in advance for each size and cooling water flow density, and the temperature difference is kept within a range where web waves do not occur. The method is characterized in that the web is pre-heated in advance, and when manufacturing thin-walled web H-beam steel using the above-mentioned equipment, the maximum temperature rise amount and heating width that will not cause buckling during web heating are determined in advance. , the web is heated one or more times so that the temperature difference is within a range that does not generate web waves.

Hereinafter, a detailed explanation of the configuration and the operation of the means of the present invention will be as follows.

Present invention 11! investigated a method for preventing the generation of web waves in thin-web H-beam steel by rolling.

The generation mechanism of web waves is as follows: (1) difference in heat shrinkage due to temperature difference between the flange and web in direct image of finish rolling; (2) difference in plastic strain due to difference in cooling rate after finish rolling. Later on, it is necessary to control the temperature difference between the flange and the web. In addition, as a method to control the temperature difference between the flange and the web, a method using water cooling of the flange is generally adopted due to cost considerations, but due to changes in the structure of the water-cooled surface and an imbalance in upper and lower temperatures during cooling, Because there are many problems such as warping and twisting, the current rolling process involves adjusting the material components.

Therefore, we simulated various conditions related to the maximum temperature difference between the flange and the web that occurs during the cooling process to room temperature, and found that the residual stress in the web was 5 kgf,
(As long as it is 1 or less.) Based on the knowledge A, the present invention was established based on this knowledge.

According to the research results of the present inventors, the maximum temperature difference between the flange and the web that occurs during the cooling process to room temperature is determined in advance for each size, cooling water flow density, and cooling fiD time.
By heating in the pre-web stage to a temperature difference that does not generate web liquid or a target residual stress, it is possible to obtain a thin H-section steel with no web waves and low residual stress. It was found that changes in the structure and material of the water-cooled surface can be prevented by increasing the temperature by the amount of relaxation of the flange cooling.

The present invention will be further explained below with reference to the drawings.

FIG. 1 is an explanatory diagram showing the rolling equipment for carrying out the present invention, FIG. 2 is a graph showing the relationship between the ratio of height to web thickness and critical buckling stress, and FIG. 3(a) is 3(b) is a graph showing the relationship between the temperature of the web and the flange and the passage of time, and FIG. 3(b) is a graph showing the relationship between the residual stress and the passage of time, %lF! Figure 4 (a), (bl and tc> each indicate an example of the embodiment of the present invention, and (al
is a graph showing the relationship between time and temperature, (b) is a graph showing the relationship between web temperature and web residual stress, and (C) is a graph showing the relationship between web temperature and web residual stress. FIG. 1 is a perspective view showing an example of a web heating device used in carrying out the present invention.

When manufacturing a thin web H-beam steel with Hw /l w > 80 and tf 'tw > 3.0, the critical buckling stress is plotted on the vertical axis and the web thickness (tw) is plotted on the horizontal axis, as shown in Figure 142. and web height (HW
), and assuming that E=iNong's modulus, ■=Poisson's ratio, b=width where uniform compressive stress acts, and K=constant, the buckling limit of the web is 10 kQf, and ■2 or less. Become. However, if we consider that the web residual stress 'web buckling stress = web wave generation index', theoretically it would be 1.0 to generate a web wave, but the web is restrained by the flange and the restraint condition is different from that of a flat plate. Therefore, 0.6 to 0.7 is usually considered to be the limit for web wave generation, and Hw2・'tW
>80, the web residual stress is 5 kl;l f・'12
Preferably, 5 kl; l f , .2 or less is required. On the other hand, since t, t > t, w for H-beam steel, the cooling rate becomes a flange web, and a temperature difference occurs as shown in Figure 3 (a). If this difference is large, immediately after UF rolling, residual Even if the stress is 0, compression→tension→compression acts on the web as shown in Figure 143(b), and if the critical buckling stress value is low, web fluid (buckling) occurs.

Therefore, in order to eliminate the temperature difference between the flange and the web before UF rolling, a flange water cooling device 1a is installed as shown in Fig. 141.
, 1btfLIF before.

However, in this case as well, if tf, 1-1w, and tw are large, a temperature difference will occur during the LIFI cooling process, as shown in Figure 4 (a), (bl, and (C)). At present, a water cooling system such as 1C in Figure 1 is installed.Since the residual stress is determined by this temperature difference, various simulations have been carried out to determine the flange temperature of the water cooling direct image, the web 2i degrees, and the product dimensions. However, flange cooling is determined by the amount of water or water density and the threading speed (cooling time), but the web is determined only by the threading speed, and the function of temperature control ("JA degree rise") is determined by the threading speed. Therefore, even if the flange water cooling device is reinforced to reduce the temperature difference, problems such as the material and shape during cooling will occur.

Therefore, the present invention is such that the web heating device 2 shown in FIG. It is preferable to also perform flange heating during this web heating. Incidentally, FIG. 5 shows an example of a preferable electromagnetic induction type web heating device proposed by the inventor.

The method of using this web heating device is as follows.

■ First, use a simulation model to calculate the water cooling conditions that will not cause abnormalities in the structure or material of the flange surface from the size, composition, and threading speed, and determine the temperature of the flange and web. (Including residual stress and presence or absence of buckling) ■■The web must be made from the maximum temperature difference that prevents web waves from occurring! ! Find the amount of temperature rise.

■ Determine the power input for web heating from ■.

(2) Check whether buckling occurs during web heating. If no, heat up to the upper limit, and calculate the amount of power input for web heating in the previous stage to account for the shortage.

■ Repeat ■～■.

However, if the answer is YES to (2), the web may be heated at one location, but due to the heating capacity, it may be heated in stages at two locations.

From the above, we found that by cooling the flange to the allowable shearing temperature based on the material and structure, and for sizes that still produce web waves, heating the web at one or more places to reduce the temperature difference, it is possible to It becomes possible to manufacture

Note that the web heating device may be installed before and after the rough universal rolling 813 shown in FIG. 1 and behind the flange water cooling device 1C, and web heating can slow down the flange cooling to prevent the generation of web waves. It is also possible.

Furthermore, it is also possible to set TF<TW by heating before UF.

<Effects of the Invention> As explained in detail above, the present invention provides a thin-walled material by using a flange cooling device installed between a rough rolling mill and a finishing rolling mill and on the finish rolling mVt surface, and a web heating device installed at any of the above positions. When manufacturing web H-section steel, the maximum temperature difference between the flange and web that occurs during the cooling process to room temperature is determined in advance for each size and the highest density of cooling water, and the temperature difference is determined so that the web liquid does not occur. The method is characterized in that the web is pre-heated in advance, and when manufacturing thin-walled web H-beam steel using the equipment, the maximum temperature rise and processing width that will not cause buckling during web heating are determined in advance. , the web is heated one or more times so that the temperature difference is within a range that does not generate web waves.

According to the present invention, when manufacturing a thin web H section steel that combines a flange cooling 8M and a web heating device, the maximum temperature difference between the flange and the web that occurs during the cooling process to room temperature is determined in advance based on the size and the maximum temperature of the cooling water. By determining the temperature rise l and heating width at which buckling does not occur during web heating for each density (or determining the temperature rise l and heating width at which buckling does not occur during web heating), the web is heated within a temperature difference that does not generate web waves, so the flange Thin H-section steel can be manufactured without deteriorating the material and structure due to water cooling and without producing web waves.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a rolling equipment for carrying out the present invention, and FIG.
The figure is a graph showing the relationship between the ratio of height to web thickness and critical buckling stress. Figure 3 (a) is a graph showing the relationship between web and flange temperature and the course of FfI. Figure 3 (b
) is a graph showing the relationship between residual stress and the passage of time, M4
Figure (a). (b) and (C) each show an example of the embodiment of the present invention, (a) is a graph showing the relationship between time and temperature, (
1)) is a graph showing the relationship between web temperature and web residual stress, (C) is a graph showing the relationship between web 711 degrees and web residual stress, and Figure 5 is a graph showing the relationship between web temperature and web residual stress. It is a perspective view showing an example. Codes 1a, ]b, 1C... Flange water cooling device 2
... Web heating device 3 ... Rough universal rolling mill 4 ... Etching rolling mill 5 ... Finishing universal rolling mill 6 ...
H-shaped steel 6f...Flange 6W...
・・Web 7・・・・Induction Heating Equipment Applicant Kawasaki Steel Co., Ltd. Agent Patent Attorney Yoshikatsu Matsushita Lawyer Fumio Soejima Figures 2 and 3 (of) 1015 Riku time rrI < minute) (wa) hour 11 (su) Fig. 4 (ku) (F)) tsu, ]'irou Q'c Fig. 4 (C) Fig. 5

Claims (1)

[Claims] 1) When manufacturing a thin web H-section steel using a flange cooling device installed between a rough rolling mill and a finishing rolling mill and at the rear of the finishing rolling mill and a web heating device installed at any of the above positions. First, the maximum temperature difference between the flange and the web that occurs during the cooling process to room temperature is determined in advance for each size and cooling water flow density, and the web is preheated so that the temperature difference is within the range where web waves do not occur. A method for producing a characteristic thin-walled web H-section steel. 2) When manufacturing a thin web H-section steel using the apparatus according to claim 1, the maximum temperature rise amount and heating width at which buckling does not occur during web heating are determined in advance, and the temperature difference at which web waves do not occur is determined in advance. 1. Place the web so that it is inside.
A method for producing a thin web H-beam steel, the method comprising heating the steel more than once.