JPS6037856B2 - Manufacturing method of H-beam steel without web waves - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an H-section steel without web waves, and particularly to a method for manufacturing an H-section steel without web waves by adjusting the finish rolling temperature.

As shown in Figure 1, the cross-sectional properties of H-section steel are usually such that the thickness of the flange is thicker than the thickness of the web 2, so the cooling rate of the web 2 during the hot rolling process is slower than that of the flange, resulting in poor finish. At the end of rolling, the flange temperature may be 200° C. or more higher than the web temperature.

Due to the finishing temperature conditions of flange 1 and web 2 at the end of rolling and the difference in cooling rate between flange 1 and web 2 after rolling, flange 1 is relatively shorter than web 2 when cooled to room temperature. As a result, as shown in FIG. 2, tensile residual stress is generated in the flange 1 and compressive longitudinal residual stress is generated in the web 2. As a result, the compressive residual stress of the web 2 exceeds the critical buckling stress, resulting in a defect in the shape of the web waves, which makes the web 2 unusable as a product. Therefore, in order to prevent web waves, it is sufficient to suppress the compressive residual stress of the web to below the critical buckling stress. Many proposals have been made in the past as methods for reducing residual stress, and Japanese Patent Publication No. 41-20330 47-31
481, 47-32164 51-5607, 54-5
0442, Tokusekki Showa 50-13311 beat, etc.

Among these, the one that is superior in terms of work efficiency is Taruko Sho 41-2, which cools the flange or keeps the web warm during rolling.
0336 and the method of Japanese Patent Application Laid-Open No. 13311/1983.
However, in order to use these methods, it is necessary to specifically set the finishing temperatures of the flange and web, and this has not been clearly defined in conventional methods.
An object of the present invention is to solve the problems of the conventional methods described above and to provide a method for manufacturing an H-section steel without web waves, which allows the finishing temperature of the flange and web to be specifically set. The gist of the present invention is as follows.

That is, in a method for manufacturing an H-section steel without web waves in which web insulation or flange water cooling is performed in the process before the final finish rolling of the H-section steel, the web wave evaluation index Wc for evaluating the shape defects of the web waves of the above-mentioned day section steel is The finishing temperature of the flange and web is expressed as a function of the finishing temperature and the cross-sectional dimension as shown below, and the finishing temperature of the flange and web that gives the target web wave evaluation index is determined from the above functional expression, and the This is a method for manufacturing an H-section steel without web waves, characterized by adjusting the temperature of at least one of web heat retention and flange water cooling. WC=a.

10a, -△T; 10a2・△T solution + a3・ln (T “T
W) + a4・ln 10 a5 - Samurai 2 The inventors' research has shown that the magnitude of residual stress is not determined only by the finishing temperature of the flange and web, but changes depending on the height of the flange and finishing temperature and the cross-sectional dimensions. It has been found. Naturally, the critical seat stress is considered to be a function of cross-sectional dimensions, particularly wafer thickness and inner web width. In consideration of the above points, we have established a web wave evaluation index that evaluates the degree of shape defects in web waves, and expressed this as a function of finishing temperature and cross-sectional dimensions. From this evaluation formula, we have determined that flanges and webs can be finished without web waves. The temperature conditions were determined, and a method was found to perform at least one of web warming and flange water cooling in the process before final rolling to achieve these finishing temperature conditions. Through research conducted by the present inventors, it has become clear that the web wave evaluation index Wc can be accurately expressed as a function of the following factors such as finishing temperature and cross-sectional dimensions.

However, Wc is defined by the ratio of the average compressive residual stress of the web to the critical buckling stress, and it is considered that this value is greater than 1 to generate web waves. Wc=F(△Tf, △
Tw, Tf-Twtf/tM Hw/tW)
......{1'Here, Tr, Tw: Finishing temperature of flange and web (0〇) tf, tw: Thickness of flange and web (wind) Hw: Inner web width (sail) T^・,
T^3: Ferrite transformation start and end temperature (0〇)△
Tf: When Tr and T^3 O When Tf<T^3 T^3-Tf △Tw: When Tw and T^, Tw-T^. Tw<T
When ^, 0 Also, steel type (chemical composition), wide width, medium width,
If we fix the type of H-shaped steel such as narrow width, and the size of the cross-sectional dimensions such as large, medium, and small, then the formula (1) becomes '
2} can be approximated by formula.

Wc=ao+a.・△T; 10 too・△T completed + a3・ln
(Tf-TW) 10a Kouma 10a5-Samurai 2-.・--． [21 Here,
ao~, n, , n2 are constants.

(2) From the formula, determine the finishing temperatures Tf and Tw of the flange and web so that Wc is 1 or less. Next, in order to achieve the finishing temperatures Tr and Tw, the web is kept warm by using a heat radiation prevention plate 3 as shown in FIG. 3 in the process before finishing rolling, or by installing a flange water cooling device 4 as shown in FIG. H-section steel without web waves can be manufactured by using water cooling at the flange or by performing at least one of these treatments. EXAMPLE A typical narrow large-sized Japanese section steel as shown below was manufactured.

Steel type SS41 (JISG3101) Web height 9
0 rib flange width 30 rib web formation 16 rib flange thickness 28 ribs, that is, the flange and web before finish rolling,
Finish rolling was performed with various combinations of web and flange finish rolling temperatures, such as web insulation, flange water cooling, or no treatment. It is shown in Figure 5.

On the other hand, the web wave evaluation index in this case can be specifically expressed in the following form. Wc=-1.94-0.0000196△T
f-0.0284ノΔTw+.

-221n (Tf-TW) 11-63n (Beauty) 10o-o
oo383 Samurai 2 -・--・-'31 (In formula 3', if the web wave generation limit Wc = 1, the finishing temperature of the flange and web at that limit can be determined. Figure 5 shows this Wc = 1 line is displayed, the area above this line is in the range of Wc>1, and the area below this line is in the range of Wc<1.As is clear from Fig. 5, the area before finish rolling is In the process, web heat insulation or flange cooling is performed to keep the web within the wave generation limit, that is, Wc<
By adjusting the finishing temperature within the range of 1, it is possible to prevent the occurrence of web waves in H-section steel products.

As is clear from the above examples, the finishing temperature of the flange and web is determined by the web wave evaluation index, and the temperature is adjusted by web insulation or flange water padding.H section steel without web waves is manufactured by the method of the present invention. I was able to do that.

The equation for predicting warpage after cooling of steel sheet piles manufactured by hot rolling can also be expressed as a function of finished knitting degree and cross-sectional size, and the technical idea of the present invention can be widely applied.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the H-beam steel, FIG. 2 is a cross-sectional view showing the distribution of residual stress in the H-beam steel, FIG. 3 is a cross-sectional view showing the heat retention status of the web of the H-beam steel according to the present invention, and FIG. The figure is a sectional view showing the state of water cooling of the flange of the H-section steel according to the present invention, and Fig. 5 is the flange finishing temperature, wet finishing temperature, and web wave generation of the H-section steel in each example of web heat insulation, flange water cooling, and no treatment. FIG. 1...Flange, 2...Web, 3.
... Heat radiation prevention plate, 4 ... Flange water cooling device. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. In a method for manufacturing an H-section steel without web corrugation, in which web insulation or flange water cooling is performed in the process before final finishing rolling of the H-section steel, a defective shape of the web corrugation of the H-section steel is evaluated. The web wave evaluation index W_c is expressed by the following relational expression as a function of the finishing temperature and cross-sectional dimension of the flange and web, and the finishing temperature of the flange and web that becomes the target web wave evaluation index is determined from the above relational expression. A method for manufacturing an H-beam steel without web waves, characterized in that the temperature of at least one of the web insulation and flange water cooling is adjusted to reach the finishing temperature. W_c=a_0+a_1・ΔT^n^1_f+a_2・
ΔT^n^2_w+a_3・ln(T_f-T_w)+
a_4・ln((t_f)/(t_w))+a_5・(
(H_w)/(t_w))^2 where W_c: Web wave evaluation index T_f, T_w: Finishing temperature of flange and web (°C
) t_f, t_w: Thickness of flange and web (mm
)H_w: Web inner width (mm) T_A_1, T_A_3
: Ferrite transformation start and end temperature (°C) ΔT_f:
0 when T_f≧T_A_3 T_A_3−T_fΔT_w when T_f<T_A_3
: When T_w≧T_A_1, T_w-T_A_1T_w
<When T_A_1, 0a_0 to a_5, n_1, n_2
:constant