РЕЗУЛЬТАТЫ СРАВНИТЕЛЬНОГО ИССЛЕДОВАНИЯ РАБОТОСПОСОБНОСТИ РЕЖУЩИХ ИНСТРУМЕНТОВ ПРИ ОБРАБОТКЕ СПЕЦИАЛИЗИРОВАННЫХ НЕРЖАВЕЮЩИХ СТАЛЕЙ

Abstract

The paper studies the effect of the tool material on the wear resistance of domestic carbide cutting tools when processing stainless steels. It provides some results of the comparative study of various tool materials operating in similar conditions in order to identify the most efficient ones. The purpose of the work is to identify the most rational tool materials for the given operating conditions of a tool and accumulate a database for recommendation development. The consideration is given to external turning by straight turning tools with mechanically fastened cutting plates. The plates are square and quadrangular (the diameter of the circumscribed circle is 17.5 mm) with and without a central mounting hole, with and without a chip groove. During processing the workpiece diameter has changed from 280 to 60 mm. The cutting speed has been maintained within 50-55 m/min by spindle speed variation. The screw-cutting lathe of model 16K25 is used. The cutter feed is chosen to equal 0.21 mm/rev. of a workpiece based on the surface roughness requirements. The cutting depth is assumed to be 0.5 mm for finishing conditions and 1mm for rough machining conditions. In either case, 0.5 mm is considered the maximum allowable value of wear on the rear face. The cutting tools were compared by their wear resistance period, i.e. according to the operation time of the cutting plates with the proper roughness until the wear of 0.5mm is achieved on the rear face. Machining was interrupted every 15 minutes to measure the amount of wear reached. The wear was measured using a multisensor measuring center (video measuring machine) of Micro Vu Sol 161 model. The test results were duplicated and documented. The conducted study has shown that: wear resistance of tool materials varies significantly; the use of coatings on domestic hard alloy of VK8 grade significantly increases the performance of the cutting plates; the technological method of cutting edge finishing from the front and rear surfaces also significantly increases the working capacity of a tool. To explain the identified results and patterns all three components of the cutting force have been monitored. The analysis of the recording results of cutting force components has shown that their magnitude and correlation significantly depends on the tool material used and material being processed. It has been determined that the role of coating in improving tool performance significantly depends on the operating conditions including the cutting depth. The coating, which showed itself as the most effective (among those considered) at the cutting depth of 0.5 mm, may not be effective at the cutting depth of 1.5 mm and yields to the coating that was second efficient or even third at the depth of 0.5 mm. The conducted experimental studies have allowed to identify the tool materials, whose wear resistance period is the most rational for the stainless steel 09X17H7Yu. These materials include both rational domestic and imported tool materials. Compared tool materials are significantly (two or more times) unequal by the period of their wear resistance. It has been found out that the recommended by the catalogs reference data on cutting mode parameters and an expected durability period for imported tool materials are not confirmed. It has been found out that the recommendations for the choice of domestic tool material and cutting mode parameters are either absent or outdated for this grade of stainless steel. Some technological methods of hardening domestic tool materials that allow to improve tool material performance as good as coating have been revealed. Having studied a number of tool materials, we have identified the most rational for the given operating conditions under finishing and rough machining. Their use allows to carry out machining without changing the cutting edge or plate for an hour or more, which makes them applicable to modern metal cutting high-performance equipment with numerical control and in the structure of automated complexes.