Structural Reliability Analysis and Design Optimization of Hot-Rolled H-beam Steel Universal Mill

PAN Lu( )， LUO Xianguo()， CHEN Chongfeng()， ZHANG Chenglin()

1 Department of Mechanical Engineering， Anhui Technical College of Mechanical and Electrical Engineering， Wuhu 241000， China2 Anhui Top Additive Manufacturing Technology Co.， Ltd.， Wuhu 241200， China3 Wuhu Machine Engineering School， Wuhu 241200， China4 School of Engineering Science， University of Science and Technology of China， Hefei 230026， China

Abstract: The structure of a hot-rolled H-beam steel universal mill was optimized， including bearing chocks(upper and lower) and mill frame. To verify the reliability of the optimized structure， the parameters of rolling mill and parts were analyzed by finite element， including the maximum stress， strain and maximum displacement. The results showed that the maximum displacement of the mill frame and the bearing chock was 0.049 mm， and the maximum stress was 2.659 MPa. The maximum stress of the mill was 3.181 MPa. There were no obviously elastic deformation and plastic deformation， which satisfied the structural requirements. The reliability of the optimized mill structure was verified.

Key words: mill； structure analysis； stiffness； reliability analysis; stress; finite element analysis

Introduction

H-beam steel is a steel similar to the letter H. It belongs to an economic section steel. H-beam steel has two major categories: hot rolling and welding，which is mainly used for bridge construction， industrial steel structures， high-rise buildings and so on[1-3]. Hot-rolled H-beam steel is an efficient construction profile. In 1902， hot-rolled H-beam steel production equipment and production line were applied in Luxemburg firstly. At present， the main hot-rolled H-beam steel production lines in China mainly included Maanshan Steel， Baotou Steel， Anshan Steel， Laiyang Steel， Rizhao steel and so on.

The rolling mill designed in this paper was imported from abroad， and the mill frame and bearing chocks were badly damaged and rolling force was smaller than before. To save cost， the size of the mill frame and bearing chocks was reduced. The optimized rolling mill was shown in Fig. 1(b).

In this paper， the mill structure was optimized according to the requirements of the new product， and main parts of the hot-rolled H-beam steel universal mill were redesigned， including the mill frame and bearing chocks.

1 Structural Design

The rolling blank was continuous casting blank， and specifications of blank were shown in Fig. 1 (a). According to the company’s specifications and rolling parameters， the rolling force of mill was calculated to be 11.436 tons[4-6]. Figure 1 (b) showed a simplified and optimized three-dimensional model of Hot-rolled H-beam steel universal mill[7，8].

This paper mainly focused on the structural reliability of the mill and its parts (the mill frame， the upper bearing chock and the lower bearing chock)， and the simplified three-dimensional models were shown in Fig. 2.

(a) Rolling blank/mm

(b) Three-dimensional model

(a) Mill frame

(b) Upper bearing chock

(c) Lower bearing chock

2 Finite Element Analysis of Rolling Mill Structure

Rolling mill was one of the most important equipments in rolling production line. The rolling mill was mainly composed of mill frame， roller， roll adjustment device， bearing and bearing chocks， balance device and roll exchange device. During rolling， the rolling piece was directly contacted with the roller， and the rolling force was transmitted to the bearing， the bearing chocks and the mill frame. Therefore， the rolling mill parts must have sufficient strength and stiffness to avoid excessive elastic deformation or even plastic deformation[9-11].

The material of the mill frame is high quality carbon structural steel， and its elastic modulusE=2.09×1011Pa，μ=0.3， yield strengthσs=250 MPa. The material of the bearing block is cast steel， elastic modulusE=1.92×1011Pa，μ=0.3， yield strengthσs=740 MPa.

2.1 Finite element analysis of mill frame and bearing chocks

The maximum rolling force of mill was 11.736 tons. The mill had two mill frames and symmetrical arrangements， so the force of each mill frame was 5.718 tons. To simplify the calculation， the bolt connection of the rolling mill was neglected and set as body connection. The 3D models shown in Fig. 2 were directly imported into finite element software. After determining the material properties and constraints； the rolling force was applied[12-14].

Figure 3 (a) showed the deformation states of the mill frame before and after applying force. The maximum displacement ofYdirection (force direction) is 0.025 57 mm. TheYdirection displacement distribution was shown in Fig. 3 (b). The maximum equivalent stress of the mill frame was 0.443 1 MPa. The equivalent stress distribution of the mill frame was shown in Fig. 3 (c)[15-16].

(a) Diagram of mill frame

(b) Y direction displacement distribution

(c) Equivalent stress distribution

Similarly， the stress and displacement states of the upper bearing chock and lower bearing chock were shown in Figs. 4 and 5. Figure 4(a) showed the deformation states of the upper bearing chock before and after applying force. Figure 4 (b) showed the deformation states of the lower bearing chock before and after applying force.

(a) Upper bearing chock

(b) Lower bearing chock

Figure 5 (a) showed the displacement distribution inYdirection of the upper bearing chock， and the maximum displacement in Y direction of the upper bearing block was 0.049 mm. Figure 5 (b) showed the equivalent stress distribution map of the upper bearing chock， and the maximum equivalent stress of the upper bearing chock was 2.659 MPa.

(a) Y direction displacement distribution diagram

(b) Upper bearing chock Equivalent stress distribution diagram

Figure 6 (a) showed the displacement distribution inYdirection of the lower bearing chock， and the maximum displacement inYdirection of the lower bearing block was 0.001 mm. Figure 6 (b) showed the equivalent stress distribution of the lower bearing chock， and the maximum equivalent stress of the lower bearing chock was 2.299 MPa.

The results showed that the upper and lower bearing chock had small stress and displacement， high stiffness， no obvious elastic deformations， no plastic deformation， and the results meet the structural requirements.

2.2 Finite element analysis of mill

On the basis of analyzing the main parts of rolling mill (mill frame and bearing chock)， the overall structure and performance of the rolling mill was studied. Figure 7 showed the deformations of the rolling mill (1/2 model) before and after loading force. Figure 8 (a) showed the displacement distribution inYdirection， and the maximum displacement inYdirection was 0.049 mm. Figure 8 (b) showed the equivalent stress distribution of rolling mill， and the maximum equivalent stress of rolling mill was 3.181 MPa. Therefore， the overall displacement and stress of the mill were small， and the overall rigidity was high， which fully meet requirements.

(a) Y direction displacement distribution

(b) Lower bearing chock equivalent stress distribution

Fig.7 Mill deformation diagram of before and after loading force

(a) Y direction displacement distribution diagram

(b) Equivalent stress distribution diagram

3 Conclusions

In this paper， the structure of a hot-rolled H-beam steel universal mill was optimized. With the help of finite element software， the parameters of rolling mill， mill frame and upper and lower bearing chocks were obtained， including stress， displacement and deformation before and after loading force.

(1) The maximum displacement ofYdirection of rolling mill was 0.049 mm and the maximum equivalent stress was 3.181 MPa， so the rolling mill had high stiffness and reliable structure without obvious elastic deformation.

(2) The maximum displacement of mill frame inYdirection was 0.025 57 mm， and the maximum displacement of the upper bearing chock was 0.049 mm inYdirection. The maximum displacement of the lower bearing chock was 0.001 mm inYdirection. Therefore， the main parts of rolling mill had small elastic deformation and high rigidity.

(3) The maximum equivalent stress of the mil frame was 0.4431 MPa， the maximum equivalent stress of the upper bearing chock was 2.659 MPa， and the maximum equivalent stress of the lower bearing chock was 2.299 MPa. Therefore， the stress of main parts of rolling mill was far less than yield strength， and there was no destructive plastic deformation.

(4) Ignoring screw down and bolt connection during the analysis， some other parts of mill needed to be checked to avoid the damage of parts in the rolling process.