grooveless rolling

　　The method of rolling billets and bars on flat rolls without grooves is also called flat roll rolling, round edge rectangular rolling or grooveless rolling.

　　Square billet, square steel and round steel are generally rolled on rolls with various pass patterns. However, this rolling method has large consumption and reserve of rolls and frequent roll change, which not only seriously affects the improvement of mill productivity, but also increases the production cost. For this reason, many countries in the world have studied the non pass rolling with grooved flat rolls instead of all grooved rolls in the roughing mill and the medium mill in the production of billet and simple section steel, and only the finishing mill still adopts the conventional pass rolling method and has achieved results. At the end of the 20th century, he worked successively in brocken, Australia? The industrial tests of non pass rolling were carried out on the bar mill of BHP company, the wire rod mill of laclide company in the United States and the bloom rolling mill of Shuidao plant in Japan, and were successful. Since the 1980s, Japan, China and other countries have made progress in theoretical research and practical application. The non pass rolling method of bars and billets successfully developed by Kawasaki iron and Steel Company of Japan has been put into industrial production and is being popularized and applied in the rolling production of small and medium-sized steel mills in some countries in the world. Pass free rolling is widely replacing conventional pass rolling.

　　Pass free rolling technology can be used not only for rolling carbon steel, but also for rolling alloy steel; It can be used not only for billet production, but also for rolling square steel, round steel and wire rod; At present, it has been widely used in blooming mill, blooming mill, compact mill, semi continuous mill, tandem mill, continuous mill and other bar and wire mills.

　　Compared with the traditional pass rolling method, the non pass rolling method has the following advantages:

　　(1) Save energy. By adopting pass free rolling, the operation rate of the rolling mill can be significantly increased, thus reducing the shutdown time and reducing the fuel consumption of the heating furnace by 6%; During pass free rolling, the deformation of the rolled piece is relatively uniform, the additional stress generated inside the rolled piece is small, and there is no force exerted by the side wall of the rolling groove on the rolled piece and the friction caused by the roll diameter difference around the rolling groove on the rolled piece. Therefore, the rolling force is reduced by 5%~10% compared with conventional pass rolling, and the electric energy can be saved by about 7%.

　　(2) The finished product is of good quality. The non pass rolling can avoid the quality defects caused by the dislocation of roll and guide device, rolling deviation and overfilling during pass rolling; Pass free rolling can make the metal produce transverse flow, which is conducive to the surface renewal, so that the defects such as hair lines and cracks on the surface can be reduced and the surface layer changes uniformly, which is very important for products requiring uniform distribution of decarburization layer; There is no speed difference on the working surface of the roll, and the relative sliding on the contact surface between the metal and the roll is much smaller than that during pass rolling. Therefore, there is no wear debris of the roll pressing on the surface of the rolled piece, which is particularly beneficial to the production of wire rods as wire drawing blanks. Because the wear debris on the surface of the rolled piece is the main cause of the filament breaking. Due to the improvement of the quality of the wire drawing rod, the production capacity of the fine wire drawing machine can be increased by 6% and the cost can be reduced by 5.5%.

　　(3) High yield and metal saving. During pass free rolling, the deformation of the rolled piece is uniform, so the length of defects at the head and tail of the rolled piece is greatly reduced. Because the length of cutting head and tail is significantly reduced, the yield can be increased by 0.4%~1.0%; During pass free rolling, the guide plate and guard plate are simple, their installation and adjustment requirements are not strict, and the roll movement has no effect on the deformation of rolled piece, so the intermediate rolling waste caused by steel jamming and other reasons is reduced accordingly; Due to uniform deformation, the percentage of rolled pieces without internal defects is also higher than that of conventional pass rolling method. Therefore, a remarkable effect of improving yield and saving metal can be obtained.

　　(4) Save roll and simplify roll repair. The roll diameter used in non pass rolling is smaller than that used in conventional pass rolling, and the difference is twice the depth of the rolling groove, so the weight of the roll is reduced; Because there is no roll ring during flat roll rolling, the utilization rate of roll body length can be increased by 20%~30%; The working diameter of the roll at the contact between the rolled piece and the roll is the same, there is no roll diameter difference formed by the rolling groove, there is no roll surface speed difference in the wide direction of the rolled piece, the roll wear is greatly reduced and more uniform, the roll repair amount is significantly reduced, and the roll life is increased by 3~6 times; Because the roll without pass can be applied to products of various specifications, and the same roll can be applied to different stands, the roll reserve can be greatly reduced (by about 1/3), thus greatly simplifying the roll management; Because the flat roll does not turn the rolling groove, the labor and cost of roll processing are reduced.

　　(5) Improve the production capacity of rolling mill, reduce labor intensity, labor volume and production cost. When rolling without pass, because of the large commonality of rolls, it is often not necessary to change rolls when changing products, and the adjustment of rolling mill is relatively simple, which can reduce the downtime of rolling mill by 37%; When changing the roll, because the requirements for the axial relative position of the roll are not strict, the guide plate and guard plate are simple and easy to adjust, which greatly shortens the time of changing the roll; During rolling, there are few accidents of rolling jam and intermediate rolling waste, and the time to deal with the accidents is also less. Therefore, the operation of rolling mill

　　The production rate is greatly improved, thus significantly improving the production capacity of the rolling mill, which is particularly effective for rolling mills with multiple varieties and small batch production and alloy steel mills with multiple varieties and specifications. In addition, due to the large deformation of pass free rolling, the rolling passes can be reduced and the rolling rhythm time can be shortened, which is also one of the main reasons for the increase of mill output.

　　There are still the following problems to be solved in the application of pass free rolling:

　　(1) Because no pass rolling has no side wall to hold the rolled piece, it is easy to cause off square, and it is impossible to continue rolling in serious cases;

　　(2) Because the corners of the rolled piece are rolled repeatedly without slots, it is sharp and may cause folding defects;

　　(3) On the continuous rolling mill composed of all the horizontal roll stands, it is necessary to turn the steel between the two stands. When the rolled piece contacts the guide device, it is easy to be scratched, and continuous rolling can cause folding defects;

　　(4) In order to make pass less rolling used in actual production, it is necessary to design rolling procedures and guide devices to prevent off square rolling. The design of this guide device should be able to prevent bending, twisting off square deformation and scratching of the surface of the rolled piece at the front and rear ends of the rolled piece;

　　(5) A steel turnover device capable of stably twisting rolled pieces shall be installed between continuous horizontal racks.

　　The main design points of pass less rolling are to ensure that the rolled piece is rolled stably between two rolls, the rolled piece does not overturn or twist, and the diagonal difference of the cross section of the rolled piece or the inclination of the side of the cross section of the rolled piece does not exceed a certain limit value. Therefore, it is necessary to accurately determine the section shape, size and deformation parameters of the rolled piece, and also to determine the difference between the guide plate spacing in the direction of the roll entrance and the width of the rolled piece at the entrance. When no pass rolling is adopted, the inlet guide plate plays a decisive role in the stability of the rolled piece entering the roll and rolling between rolls. The gap between the inlet guide plate and the inlet rolled piece must be reasonably determined.