At the time of die forging, the forged blank is forged into a product having a certain geometry in one or more stages of forging. For elongated forgings (i.e., workpieces having a length dimension greater than the cross-sectional dimension of the forged workpiece), forging typically includes several forging steps such as pre-redistribution of the blank mass, cross-section molding, and final forming. In conventional shape forging, the excess material usually becomes the burr of the forging, which needs to be removed before final forging.
In recent years, the hot forging of steel has caused great development and changes in the shape processing technology. In addition to the new forging dies and forging equipment, the improvement of the forging process is also reflected in the improvement of economy and forging quality. Among them, the meaning of burr-free forging is also becoming more and more important.
Precision forging is an economical alternative to traditional complex geometry workpiece forging. For example, connecting rod workpieces, if not precision forging, require complex machining to achieve precision forging. With precision forging, you can economically achieve IT8~IT10 tolerances. Since the burr-free precision forging does not cause burrs, the omission is not only the burring process during forging, but also the metal material occupied by the forged burrs. The prerequisite for this is: the forging process that is compatible with the forged parts. This process includes: quality preforming that is consistent with the quality of the workpiece (such as cross wedge rolling), thicker in a closed forging die, the desired cross-sectional dimensions, and final precision forging.
Forging blanks with small forming, accurate size and constant volume are the basis of normal burr-free die forging. For most steel die forged workpieces, forged blanks are usually cut from steel bar blanking equipment. Compared with sawing, this scissor steel bar shearing device has the characteristics of high speed and high precision, and has high material utilization rate due to the omission of the kerf.
In order to ensure the accuracy of cutting and cutting, it is necessary to review the quality and volume of the blank after blanking in the auxiliary equipment of the steel bar shearing machine, and to carry out the production process parameters such as the slit size and cutting speed of the cutting. Adjustment. Only the blank has a more flat cut surface and is more perpendicular to the axis of the steel bar for better blank cutting quality. The exciter at the cutting edge (Fig. 1) can simultaneously improve multiple process parameters of the trimming surface. In addition to improving the surface quality of the cut surface, it also reduces the angle of inclination of the cut surface of the bar to less than 1 when cutting, reducing the wave on the surface. Such a cutting device with an exciter is particularly suitable for cutting forged blanks that require straightness or that have no defects on the shear plane. Therefore, in precision forging without burrs, it is most desirable to use such a cutting device.
Figure 1 How the steel rod cutting machine works
In a research project conducted by IPH, the effect of the trimming tool shaker on the trimming result was tested (Fig. 2). The purpose of the test is to analyze the effect of low frequency vibration in the auditory range on the quality of the trimmed surface and the reasons for the improved quality of the trimmed surface. In order to achieve this, various kinds of possibilities of the exciter were tested and analyzed, and various excitation methods such as piezoelectric excitation, hydraulic excitation, and mechanical vibration were used.
Figure 2 Using the excitation device to improve the quality of the cut cross section of the steel bar
In the preliminary test, the vibration test of the cutting shears using the hydraulic excitation method pointed out that the quality of the cut section of the bar can be improved by the hydraulic exciter. This improvement further improves the quality of the cross-section forging.
In the measures to improve the quality of the cutting section of the steel bar, the adjustment of the cutting gap plays a decisive role. The cutting gap refers to the horizontal distance between the two edges of the steel bar cutting machine. The adjustment of the cutting gap has a great relationship with the rigidity of the cutting machine, the diameter of the steel bar and the tribological properties of the material being cut. The greatest influence of the trimming gap is the flatness of the cross section and the angle of the trimming surface to the workpiece axis. During the cutting process, an increase in the trimming gap will result in a deterioration in the flatness of the cut surface. The effect of the rigidity of the cutting machine on the increase in the cutting gap has not been verified yet.
In a research project jointly conducted with the Leibniz Forming Process Technology and Forming Processing Equipment Research Institute (IFUM) at the University of Hannover, IPH performed a rigorous test on the collected data, and performed a clipping gap that can obtain a flat cross section. Digital analysis has been used to summarize a method for detecting the appropriate clipping gap of a hydraulically excited steel bar cutting machine. Next, it will be verified to be a dedicated module device and put on the market. For other hydraulically excited steel bar cutting machines, a universal equipment module will be developed and the actual tailoring verification will be carried out. Throughout the test, the research work was assisted and supported by two famous steel bar cutting machine manufacturers. Since the general rule of the slit expansion is summarized, if it is possible to calculate the gap of the hydraulic excitation steel bar cutting machine in the future, the adjustment of the knife gap is simpler and the effect is better.
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