Reactive diffusion in cutting high-alloy steel by means of a hard-alloy tool

Diffusional processes in the cutting of high-alloy steel by means of a hard-alloy tool are considered. At the front surface of the tool, a carbide coating may be formed on cutting, on the basis of carbide-forming elements in the steel and carbon diffusing from the hard alloy. Reactive diffusion without the formation of visible intermediate layers is assumed to affect tool wear.     

Predicting the limiting state of a multiblade hard-alloy tool

The limiting state of a composite multiblade tool with hard-alloy cutting plates may be predicted by measuring thermoelectric signals in the machining region.     

The cutting tool stresses in finish turning of hardened steel with mixed ceramic tool

Precision hard machining is an interesting topic in manufacturing die and mold, automobile parts, and scientific research. While the hard machining has benefit advantages such as short cutting cycle time, process flexibility, and low surface roughness, there are several disadvantages such as high tooling cost, need of rigid machine tool, high cutting stresses, and residual stresses. Especially, tool stresses should be understood and dealt with to achieve successful performance of finish hard turning with ceramic cutting tool. So, the influence of cutting parameters on cutting stresses during dry finish turning of hardened (52 HRC) AISI H13 hot work steel with ceramic tool is investigated in this paper. For this aim, a series finish turning tests were performed, and the cutting forces were measured in tests. After literature procedure about finite element model (FEM), FEM is established to predict cutting stresses in finish turning of hardened AISI H13 steel with Ceramic 650 grade insert. As shown, effect of the cutting parameters on cutting tool stresses in finish turning of AISI H13 steel is obtained. The suggested results are helpful for optimizing the cutting parameters and decreasing the tool failure in finish turning applications of hardened steel.     

Tool vibration in internal turning of hardened steel using cBN tool

The machining of hardened materials with hardness over 45 HRC has been an alternative to grinding since the 1970s, with the commercial availability of cubic boron nitride (cBN) and ceramic tools. However, the low toughness of these types of tool materials makes them very sensitive to damages caused by vibrations, which are critical for operations like internal turning, where the tool resembles a cantilever beam and therefore is susceptible to large deflections. This work aims to contribute to the study of tool performance in internal turning of long holes in hardened AISI 4340 steel in finishing conditions. Different machining conditions, two different tool holders (steel and carbide), and several tool overhangs were tested. The surface finish, acceleration (vibration) signals, and tool wear of cBN inserts were evaluated. The results show that vibration and the material of the tool holder may play a secondary role in the surface finish for stable turning, but the use of carbide tool holders makes the process stable for longer tool overhangs. Moreover, when the cutting becomes unstable, surface roughness is increased severely.     

The performance of TiN-coated high speed steel tool inserts in turning

While it is well known that thin, hard coatings can reduce tool wear and improve tool life and productivity, there is still little consensus over the degree of advantage coated tools have over their uncoated counterparts. This paper compares the behaviour of titanium nitride- (TiN-) coated and uncoated high speed steel (HSS) tool inserts during turning. Wear maps describing the crater wear characteristics of these tools are used to show that the extent of tool wear reduction due to the coatings depends strongly on the cutting speed and feed rate. The maps also demonstrate that the benefits of TiN coatings on HSS tools may be easily realized over a wide range of machining conditions.     

An investigation of tool wear in high-speed turning of AISI 4340 steel

A commercially available insert has been used to turn an AISI 4340 steel at speeds placed between 325 and 1000 m/min. The flank wear was measured in connection to cutting time. This is to determine the tool life defined as the usable time that has elapsed before the flank wear has reached the criterion value.It is shown that an increase in cutting speed causes a higher decrease of the time of the second gradual stage of the wear process. This is due to the thin coat layer which is rapidly peeled off when high-speed turning.The investigation included the realization of a wear model in relation to time and to cutting speed. An empirical model has also been developed for tool life determination in connection with cutting speed.On the basis of the results obtained it is possible to set optimal cutting speed to achieve the maximum tool life.     

淬火钢件的车削刀具与切削参数选择

着重说明了车削淬火钢件时,如何通过合理地选用刀具材料、刀具几何参数及切削用量达到理想的切削效果,并提出车削淬火钢件时应注意的若干问题.     

Feasibility of mild hard turning of stainless steel using coated carbide tool

Hard turning has been explored as an alternative to the traditional processing technique used to manufacture parts made of hardened steels. However, advanced cutting tool materials for hard turning applications are relatively expensive. The continuous developments in carbide tool material and its coating technology have offered inexpensive cutting tool alternatives for a mild range of hard turning operations. Commercially available TiAlN-coated carbide tool is utilized in this study to perform hard turning of stainless steel within the mild range (47–48 HRC) at various cutting parameters, i.e., cutting speed and feed. Empirical models to measure its performance by quantifying the effect of the cutting parameters to the tool’s service lifetime and the machined workpiece’s surface roughness are developed. The coated carbide tool performed hard turning with fair tool life and fine surface finish, especially at low cutting parameters as shown by the models’ solutions for the optimized input selection.     

精密干式硬态车削淬硬工具钢时表面粗糙度的参数优化

使用PCBN刀具对不同淬硬状态工具钢Cr12MoV进行了精密干式硬态车削试验,运用正交实验法分析了切削速度、试件硬度、刀具前角、切削深度4个因素间的交互作用,并得到了最优车削参数.试验表明:影响表面粗糙度最显著的因素是切削速度与淬火硬度,切削深度影响最小.     

Wear resistance of a coated hard-alloy tool in the machining of high-temperature chromium alloys

The influence of the hard-alloy substrate and the composite coatings of a tool on its wear resistance in the machining of high-temperature chromium alloys is investigated. The effectiveness of the coated hardalloy tool is determined by the properties of the hard alloy and the coatings. For hard alloys characterized by relatively low strength and crack resistance, the coatings prove ineffective, on account of the brittle failure of the substrate and the consequent destruction of the coating. On alloys with low thermal stability, the coatings are ineffective on account of weakening of the binder at the high temperatures associated with machining. It makes sense to use a hard alloy with mechanical properties such that the coating may operate effectively. Better properties are not needed.     

TiN涂层刀具切削高锰钢的磨损破损研究

研究奥氏体高锰钢切削过程中TiN涂层硬质合金刀具的磨损、破损机制,测量了切削温度并得出后刀面磨损量与 切削时间和切削速度的关系曲线,以及刀具前、后刀面显微磨损、破损形貌和化学变化。结果表明,TiN涂层硬质合金刀 具切削奥氏体高锰钢时耐磨性优于单一硬质合金刀具,且适于低速切削(小于30m/min)。     

An investigation of heat partition and tool wear in hard turning of H13 tool steel with CBN cutting tools

This paper presents results of an investigation into the tool life and the tool wear behaviour of low content CBN cutting tools used in hard turning of hardened H13 tool steel. The approach followed here required both experimental work and finite element thermal modelling. The experiments involved measuring the cutting forces, cutting temperatures, tool wear, and the contact area. Using the measured cutting forces and the contact area in the orthogonal cutting model, we calculated the heat flux on the tool and applied it in the FE thermal analysis. The temperatures history from the analysis was matched with the experimental data to estimate the fraction of heat entering the tool for both conventional and high speeds. The heat partition into the tool was estimated to be around 21–22% for conventional speeds, whereas for high-speed turning, it was around 14%. The tool wear, however, was found to be dominated by chipping for both cutting speeds and could be reduced considerably by reducing the amount of heat entering the tool.     

Online monitoring and measurements of tool wear for precision turning of stainless steel parts

Online monitoring and measurements of tool wear were carried out using cutting forces for precision turning of stainless steel parts. The best combination of features was selected from 14 features extracted from force signals by using a Sequential Forward Search algorithm. Back-propagation neural networks (BPNs) used two features for online classification. When the adaptive neuro-fuzzy inference system (ANFIS) was applied, seven features were needed for the classification. For online measurements, only one feature is needed for BPN. Three features are needed for ANFIS for online measurements. For online classification of turning tool conditions, a 2?×?20?×?1 BPN can achieve a success rate of higher than 86% while a 7?×?2 ANFIS can reach a success rate of higher than 96%. For online measurements of tool wear, the estimation error can be as low as 1.37% when a 1?×?20?×?1 BPN was used while the error can be as low as 0.56% using a 3?×?3 ANFIS. Therefore, the 3?×?3 ANFIS can be used first to predict the degradation of tool conditions during the turning process. It can also be used to measure the tool wear online so as to take feedback control action to enhance accuracy of the process. Once the detected tool wear is close to the worn-out threshold, the 7?×?2 ANFIS will be then applied to classify the tool conditions in order to stop the turning operation on time automatically so as to assure the quality of products and to avoid catastrophic failure.     

Some studies on hard turning of AISI 4340 steel using multilayer coated carbide tool

Hard turning with multilayer coated carbide tool has several benefits over grinding process such as, reduction of processing costs, increased productivities and improved material properties. The objective was to establish a correlation between cutting parameters such as cutting speed, feed rate and depth of cut with machining force, power, specific cutting force, tool wear and surface roughness on work piece. In the present study, performance of multilayer hard coatings (TiC/TiCN/Al₂O₃) on cemented carbide substrate using chemical vapor deposition (CVD) for machining of hardened AISI 4340 steel was evaluated. An attempt has been made to analyze the effects of process parameters on machinability aspects using Taguchi technique. Response surface plots are generated for the study of interaction effects of cutting conditions on machinability factors. The correlations were established by multiple linear regression models. The linear regression models were validated using confirmation tests. The analysis of the result revealed that, the optimal combination of low feed rate and low depth of cut with high cutting speed is beneficial for reducing machining force. Higher values of feed rates are necessary to minimize the specific cutting force. The machining power and cutting tool wear increases almost linearly with increase in cutting speed and feed rate. The combination of low feed rate and high cutting speed is necessary for minimizing the surface roughness. Abrasion was the principle wear mechanism observed at all the cutting conditions.