Induction Heating Of Workpiece Research Articles

SUBSTANTIATION OF INDUCTION HEATING DURING FLANGING OF TUBULAR WORKPIECES BY ROLLING FORMING

Rolling forming (RF) processes are among the most efficient methods of metal forming. The required profile of the workpiece in rolling processes is formed by local deformation with conical or cylindrical rolls using sound technological schemes. When roll forming pipe billets with a ratio of the height of the initial deformed part to the wall thickness of more than 2.5, the flange seating process is made impossible by the loss of billet stability with subsequent fold formation. This phenomenon makes it impossible to produce wide flanges by drawing. To form workpieces with particularly wide flanges, we have developed a flanging method by rolling stamping. The essence of the flanging method is that at the initial stages of rolling, the top of the conical roll is shifted in the direction of the contact patch. At intermediate stages, to prevent the workpiece wall from turning inside out, the top of the roll is shifted in the opposite direction (along the workpiece axis). The main technological constraints are imposed by the insufficient ductility of the billet material, which can cause fracture. To develop the flanging processes in a reasonable manner, we studied the mechanics of outer flange deformation and methods of controlling material flow. The stress-strain state (SSS) of the material was analyzed using the hardness measurement method and the mesh method. The nature of the change in the stress-strain state in the most dangerous zones of the workpiece was determined, depending on the ratio of the flange diameter to the initial workpiece. Based on the experimental results, a mathematical model of the deformation trajectory of material particles of the outer surface of the flange in the coordinates of deformation intensity - an indicator of the stress state - was constructed. To assess the deformability of the material, a damage summation model with a power law approximation of the damage function was used. The model allows us to determine the ultimate fracture dimensions of the flange, as well as the plasticity resource used at intermediate stages. The condition for the suitability of metals for flanging by rolling stamping for engineering calculations is obtained. The necessity of applying induction heating in the processes of culling by rolling stamping is substantiated. This makes it possible to expand the technological capabilities of flanging processes by developing and using induction heating of workpieces, due to an increase in the plasticity characteristics and a decrease in the strength characteristics of metals in the process of deformation.

Development and optimization of technology and modernization of forging line for bearing rings

The object of research is the forging line L-408 (Ukraine) for the production of workpieces for rings of railway bearings. This line is installed at Kharkiv Bearing Plant (JSC HARP, Ukraine) and consists of a KIN 750 induction heating section, a P-2038A hydraulic three-position press and a KPS 250 ring-rolling unit. Based on the results of the technical audit of the line, it is revealed that the KIN 750 is produced on an outdated hardware base and has a deliberately lower efficiency. In addition, the lack of control over power and frequency during the heating process does not make it possible to optimize the process for energy costs. Also, the presses of all six lines operate from one hydraulic pump station, which provokes its obviously inefficient operation when only part of the lines is involved. In addition, the principle of operation of the P-2038A press in the absence of a hydraulic pressure control system in the executive bodies of the press does not allow for optimal control of hydraulic pumps according to the criterion of minimum electric power consumption. In the course of the study, the finite element method is chosen as the main method of mathematical modeling of induction heating of the workpiece and forging operations. A new induction heating system has been developed and produced, which has undoubted advantages over the previously existing induction heating line, since it is made on a modern elemental base and has the ability to programmatically control power during the heating process. The press is modernized with an autonomous pump station with a capacity of 132 kW (instead of a central station with a capacity of 900 kW). The use of kinetic energy of the slider and traverse gives a radical reduction in energy consumption, especially when several or even more of the six forging lines L-408 are working. Mathematical models and numerical methods developed for modeling controlled induction heating of workpieces and volume press operations have proved their effectiveness in calculating and optimizing the design and operating parameters of the hot forging line. The effects detected by mathematical modeling are fully confirmed during field tests, and the temperatures and pressures themselves slightly differed from the measurement results.

Study on induction heating of workpiece before gear rolling process with different coil structures

The temperature distribution of heated workpiece has a great impact on the subsequent gear rolling process. To get a satisfied temperature distribution, longitudinal magnetic flux (LMF) coil and transverse magnetic flux (TMF) coil were designed. The influences of current density and current frequency on the heating efficiency and the temperature distribution of the workpiece corresponding to two coil structures were investigated by establishing an induction heating model combing the coupling of electromagnetic and thermal fields and the rotary motion of the workpiece. In addition, an induction heating experiment was conducted to verify the model. From the numerical results, a conclusion can be made that compared with TMF coil, the LMF coil can reduce the inner hole temperature and improve the heating efficiency. With proper current density and current frequency, the workpiece heated by LMF coil can obtain a better temperature distribution than that heated by TMF coil.

Enhancement of Machinability of Inconel 718 in End Milling through Online Induction Heating of Workpiece

Abstract. This paper presents the outcome of a study on heat assisted end milling of Inconel 718 using inducting heating technique conducted to enhance the machinability of the material. The heating temperature maintained below the phase transformation temperature was aimed at softening the top removable material layers. The experimental results of both conventional and heat assisted machining were compared. The machinability of Inconel 718 under these conditions was evaluated in terms of tool life, tool wear morphology and chatter. The advantages of Induction heating is demonstrated by an longer tool life and lower chatter. The study showed that preheated machining facilitates up to 80% increase of tool life over conventional machining conducted using TiAlN coated carbide inserts.