What Is a Walking Beam?

Walking beam is one of the most commonly used coil transport equipment in rolling mills. The steel coils coming out of the hot-rolled coiler are generally transported through a walking beam, and then transported to the finished product warehouse through a fast chain and a slow chain. Cold rolling, galvanizing, and even the exit and exit of the line also use walking beams to transport steel coils. The walking beam is divided into an entrance walking beam and an exit walking beam according to the arrangement position. The walking beam is generally located underground. A fixed saddle with a saddle-shaped welding structure is arranged on the walking beam. Each fixed saddle is arranged at a certain distance. The moving beam will move the steel coil from a fixed saddle every cycle. Go to the next fixed saddle. The walking beam is realized by a lifting mechanism and a traverse mechanism to convey materials step by step. Stepping can be achieved by an eccentric turning mechanism in individual cases.

Walking beam is one of the most commonly used steel coil transportation equipment in rolling mills. Steel coils from hot-rolled coilers are generally transported through walking beams, and then transported to the finished product warehouse by fast chain and slow chain. Cold rolling, galvanizing, and even the exit and exit of the line also use walking beams to transport steel coils. The walking beam is divided into an entrance walking beam and an exit walking beam according to the arrangement position.

The walking beam is generally located underground. A fixed saddle with a saddle-shaped welding structure is arranged on the walking beam. Each fixed saddle is arranged at a certain distance. The moving beam will move the steel coil from a fixed saddle every cycle. Go to the next fixed saddle. The walking beam is realized by a lifting mechanism and a traverse mechanism to convey materials step by step. Stepping can be achieved by an eccentric turning mechanism in individual cases.

In modern hot rolling, cold rolling and strip processing line workshops, walking beams are one of the indispensable important process equipment. An inductive analysis of various walking beams common in the steel industry was made, and the main parameters in the design were calculated. In addition, a new "T" beam optimization scheme is also introduced, which has a good reference value for the selection and design of walking beams ^[1]

According to the production process requirements of the workshop, the steel coil has two states: vertical coil and horizontal coil. Whether it is standing or lying, it does not have any influence on the body structure and working principle of the walking beam, but the saddle type and lifting stroke are slightly different.

The stepping beam realizes the stepped conveyance of the steel coil on the fixed saddle through the periodic movement of the moving beam "up-forward-down-backward". The movement of the walking beam is divided into two parts: translational movement and lifting movement. The translational movement is generally driven by a translation hydraulic cylinder device. According to the type of the lifting mechanism, the walking beam can be divided into vertical type, link type, slope type and eccentric wheel type. The vertical stepping beam is lifted directly by the hydraulic cylinder, and the lifting stroke can be made larger. The stroke generally used can reach 380mm, but when it is greater than 400mm, the rigidity of the piston rod of the hydraulic cylinder is higher, and the moving beam runs stably. The performance is reduced, and the two hydraulic cylinders need to be synchronized when lifting. The hydraulic cylinders need to be equipped with linear displacement sensors or pull-line encoders. The hydraulic control and automatic control systems have higher requirements for the transportation of steel coils with light and medium loads. The connecting rod type walking beam is moved by the connecting rod to realize the lifting of the moving beam, and the connecting rod guarantees the synchronization of the lifting of the moving beam. The hydraulic circuit and control system are relatively simple, and it is often used for the transportation of steel coils with light and medium loads. The ramp-type walking beam is lifted by wheels and ramps, which can bear a large load and is mostly used for the transportation of billets in heating furnaces. The eccentric wheel type walking beam is lifted by the eccentric wheel mechanism. The lifting distance of the moving beam is a function of the swing angle of the eccentric wheel. When the hydraulic cylinder moves at a constant speed, the rising speed of the moving beam is slow-fast-slow change, starting and stopping at low speed. The impact is relatively small, the operation is stable, and the eccentric wheel walking beam has a good bearing capacity and simple maintenance. The lifting stroke is mostly used for 50 to 280mm. When the stroke is greater than 300mm, the bearing diameter of the eccentric wheel is 950mm, which increases the cost of the bearing specification Therefore, the lifting stroke of this type of walking beam should not be too large.

The structure of the walking beam is basically composed of fixed parts and movable parts. The fixed parts are mainly composed of track assembly, columns, beams, fixed saddles and guide wheels. The moving parts mainly include box-type movable beams, lifting mechanisms, translation mechanisms and wheels. Groups, etc., the lifting and translation mechanisms are driven by hydraulic cylinders ^[2]

During the design of the heavy coil packaging of a steel plant, according to the specifications of the transported steel coils and the characteristics of the layout of the process equipment, a new type of walking beam was optimized by referring to the structural form of the export walking beam of the acid rolling mill introduced by a steel plant. . Its characteristics are as follows.

1) The new type of walking beam adopts T shaped column instead of mouth shaped column of the conventional walking beam fixed beam, eliminating the frame embedded in the concrete part and simplifying the longer connecting beam between the saddles. The stresses of the verified bolts are far less than the allowable stresses. The strength of the bolts meets the requirements of the working conditions, which simplifies the structure, reduces the quality of the equipment, and saves the cost of equipment manufacturing.

2) The design of the conventional walking beam wheel track, in order to prevent the walking beam from tipping over, there is an equal-length upper pressure rail to restrain the wheel above the track. In this design process, by calculation, under the most unfavorable conditions, the ratio of the weight of the moving beam to the tipping moment of the steel coil is 2.75, and the maximum size of the head or tail of the walking beam can be eliminated by the weight The tipping force distance when the steel coil is rolled, and the margin is large, so the rail pressing and rail pressing beam are cancelled, the design is optimized, and the structure is simplified.

Through the above two optimization designs, optimization schemes, and simplified structures, the equipment quality was reduced from 35t to 25t, and the equipment quality was reduced by 28.5%, which reduced the costs of equipment manufacturing, civil construction, equipment installation and maintenance, and saved project investment. ^[3]

Although there are 4 types of walking beams that are often used, the design of the translational hydraulic cylinder mechanism is basically the same. The analysis of the force of the walking beam lifting mechanism is relatively simple, which is summarized according to the force of the hydraulic cylinder and the work of the hydraulic circuit. Select the appropriate hydraulic cylinder pressure. The analysis of the eccentric wheeled walking beam's force and its movement trajectory are relatively complicated, and it also includes the design and selection of the lifting hydraulic cylinder, so the following takes a typical eccentric wheeled walking beam as an example to analyze the design calculation process of the walking beam .

The determination of the stroke, the movement of the walking beam is a stepping movement, the step size is the stroke of the translation hydraulic cylinder, and also the distance between the fixed saddle and the moving beam saddle. The head of the translation hydraulic cylinder is hinged on the movable beam. When the movable beam is raised and lowered, the translation hydraulic cylinder swings at a certain angle, which will cause the horizontal displacement of the movable beam saddle relative to the fixed saddle, which may cause the steel coil to shake slightly. The horizontal arrangement of the translation hydraulic cylinder is not positioned at the highest point or the lowest point of the moving beam, but the position where the moving beam contacts the steel coil during the ascent, and the midpoint of the upper and lower limits of the moving beam is generally taken. This can reduce the slight sway of the steel coil on the saddle.

Where space permits, try to place the translation hydraulic cylinder under the head or the walking beam, so that the piston rod of the hydraulic cylinder receives the tensile force when the walking beam is rolled. If the hydraulic cylinder pushes the moving beam forward, the piston rod will bear the pressure. Piston rods need to be calculated for stability. However, the working pressure of hydraulic cylinders in most engineering designs is about 10 MPa, which belongs to the low- and medium-pressure working range. However, hydraulic cylinders in the metallurgical industry are all heavy-duty series. After several checks, the stability safety factor Both are large, so the stability calculation of the plunger can be omitted. If you want to check ^[1]

By analyzing the principle, structure and design theory of the walking beam, combined with the practical application of a steel mill rewinding packaging project, the project layout is more reasonable, the structure is more compact, and the investment in the engineering project is saved. In specific engineering projects, according to the principle and structural characteristics of walking beams, by adding lifting or rotating saddles on moving beams and replacing fixed beam saddles with cantilever saddles, various types of walking beams can be derived ^{[ 1]} .