High Speed Steel Taps Research Articles

Effect of cryogenic and electrolytic passivation treatment on wear resistance of M2 high-speed steel

Through cryogenic treatment and electrolytic passivation treatment of M2 high-speed steel (HSS), the effect of electrolytic passivation process parameters on the life of M2 HSS taps and the combined effect of cryogenic treatment and electrolytic passivation treatment on the wear resistance of the M2 HSS were investigated by using a scanning electron microscope (SEM) and energy-dispersive spectrometer (EDS). The results show that the life of M2 HSS tap after electrolytic passivation treatment increases most significantly under the theoretical edge radius; the functional relationship between the charge consumption (y) and the tap edge radius (x) is as follows: y = 8.135x − 48.842. The wear resistance of the sample after cryogenic and electrolytic passivation treatment is the highest, which is 1.52 times higher than those of the traditional heat treatment sample. This is due to the increase of the number of carbides on the surface of the specimens after cryogenic treatment; the distribution and size of carbides are relatively uniform; the average size of carbides is reduced by 60.4%. There is a carbon layer on the surface of the sample after passivation, which can effectively improve the wear condition. The size and number of carbides in the surface layer of the sample remain unchanged after passivation treatment, indicating that cryogenic treatment plays a key role in the performance of the material.

PVD coatings for thread tapping of austempered ductile iron

Austempered ductile iron (ADI) has a high potential to substitute alloy steels in power-train applications. However, the machinability of ADI is difficult and tool life is shortened by the appearance of severe adhesive and abrasive wear on tool cutting edge. In this regard, the deposition of a suitable coating could reduce these phenomena. Previous works have investigated the behavior of coated tools on turning or drilling of ADI, but a knowledge gap exists regarding the tapping operation. In this study, the performance of six PVD coatings for the tapping of ADI-900 was investigated. The tools were coated using Cathodic Arc deposition and were analyzed in two sets of experiments. In the first set, four commercial coatings commonly used in cast iron machining were compared: a monolithic AlTiN, a nanostructured AlCrSiN, and two configurations of AlTiSiN (a multilayer and a gradient). Before film deposition, the high speed steel (HSS) substrate surface was micro-blasted. Cutting performance was evaluated by a combined analysis of tool wear, cutting torque data, and SEM-investigations of the tap surface. The best results were yielded by the gradient AlTiSiN (AlTiSiN-G) but coating delamination was also noticeable in the rake face. The application of a drag grinding pre-treatment led to an improvement of the coating adhesion and to a reduction of wear and torque values. In the second set of experiments, AlTiSiN-G was compared to a double layer TiAlCN-DLC coating and to AlTiSiN-18. The results confirmed that the use of HSS taps coated with AlTiSiN-G is a feasible solution for tapping of ADI-900.

The Influence of Tool Geometric Parameters on the Reliability of Deep Cryogenic High Speed Steel Taps

The selection of geometric parameters of cryogenic tap has a direct effect on the reliability of tools and the precision of processed workpiece. Based on nonsubstitute Type-I Censoring Life Tests, a mathematical model in dynamic reliability of cryogenic tap is built, and the change of its reliability is explored. Combined with cutting tool life expansion equation, the effects of geometric parameters on wear life are presented. The results show that of the geometric parameters, rake angle taps in its effect on reliability with the increase in machining time and impact loading action, thus the quality of rake angle should be controlled directly or indirectly so as to reduce its influence on reliability of cutting tool, which can ultimately improve the reliability of cutting tool and the precision of processed workpiece. Meanwhile, the proposed method provides a theoretical basis for improvements of the reliability of tool system.

The Effect of Electrolytic Strengthening Treatment on Tap’s Service Life

In this study High-speed steel taps are taken as the research object. Electrolysis technology was used to deal with the taps in various count time (7s 14s 21s 28s 35s) and then obtain the corresponding radii of the cutting edge (11.38μm 15.05μm 20.35μm 23.00μm 25.55μm). The experimental results exhibit quantitatively the effect of tool radius on the performance of tapping. A radius on the cutting edge prevents fast and unpredictable wear. Moreover, the existence of an optimum value of the radius has been revealed experimentally. Tapping test is used to prove the optimal cutting edge radius is 15.05μm and the taps life increase about 2.5 times than usual taps. It can provide an important theoretical basis for the modifications of the cutting edge radius and give a method to improve tap life.

Design of Electrolytic Strengthening Machine for Cutting Edge of Cutter

Many studies have proved the service life of cutter can be prolonged by electrolytic strengthening. Based on the theory of electrolytic strengthening technology, this paper introduced and developed prototype equipment for strengthening cutting edge of rotary cutter and put forward a calculation method of total electric quantity consumption during the electrolysis suitable for microcontroller. The M8 high-speed steel tap is taken as a strengthening example. After finished the strengthening process that it clearly see the results of the surface of tap was obviously polished by observing the micrograph. This equipment improves the reliability of electrolytic strengthening and the cost is relatively cheap.

Adapted DLC coatings for increasing tapping performance in TiAl6V4

AbstractThis paper reports on a new DLC‐coated high speed steel tool for tapping into TiAl6V4. In analogy tests on a high‐temperature tribometer, a comparative analysis was carried out on coating systems containing carbon, nitrides and oxides with respect to their suitability for tapping into TiAl6V4. This comparative analysis revealed that DLC coatings were characterized by extremely low friction coefficients, low levels of wear and low material adhesion. Cutting tests using high speed steel taps coated with the DLC coating system CROMTIVIc2 confirm the outstanding tribological properties of this coating system. Compared to conventional TiCN‐coated taps, the new DLC‐coated tool expands the current application field to include higher cutting speeds and longer tool life. It therefore provides the opportunity for significantly increasing productivity when tapping into TiAl6V4.

Effects of the sub-zero treatment condition on microstructure, mechanical behavior and wear resistance of W9Mo3Cr4V high speed steel

The sub-zero treatment can improve mechanical properties and wear resistance of many metallic materials and the improvement is largely affected by the sub-zero treatment condition. In this study, samples of W9Mo3Cr4V (W9) high speed steel (HSS) were treated at various sub-zero temperatures before and after tempering, respectively. The main objective of this work is to investigate the effect of the sub-zero treatment condition on mechanical properties and wear resistance of the W9 HSS and correlate it to variations in microstructure. Microstructures of the treated samples were characterized with electron microscopy (SEM and TEM), and corresponding properties, including hardness, impact toughness and wear resistance, were evaluated. It was demonstrated that the mechanical properties of the cryogenically treated samples were superior to those of conventionally treated ones. The cryogenically treated samples with subsequent tempering performed better than cryogenically treated samples that experienced prior tempering. The lower temperatures for sub-zero treatment were more effective in improving the mechanical properties. The life of W9 HSS taps in cutting 30CrMnTi steel was assessed, which showed a trend similar to that observed during wear testing. Efforts are made to clarify possible mechanisms responsible for the improvements.

Research on Cutting Performance of HSS Taps by Electric Enhanced

After tool edges sharpen, there are a variety of micro-defects in the area of edge, which will accelerate tool wear and shorten tool life. In order to increase tool life and production efficiency, the area of edge strengthen was needed. In this paper, the electrolysis technology was used to enhance the cutting edge of high-speed steel(HSS) tap, the rounding of the edge region of the forming edge and surface morphology of cutting edge were investigated. And the tapping tests were carried on the Ti6Al4V. The results showed that electrolysis enhanced technology can eliminate the defects, invert a circular edge and improve the tool edge strength. The original tap was worn rapidly in the early stages of wear and the cutting force was changed big variation. The results showed that tap strengthened can reduce tool wear and improve tool life.

Study on the Life of High Speed Steel Taps with Cryogenic Treatment

The influences of various processes of cryogenic treatment, optimization of parameters and prolongation the life of the high speed steel taps have been studied in the paper. Taking W9Mo3Cr4V for an example, the influences of temperature raising and decreasing rate, cryogenic treatment temperature and holding time, times for treatment, temper process and sequence of cryogenic treatment are discussed. Two kinds of cryogenic treatment process that one is before temper and the other is after it are put forward. Process flow is designed according to the process suitability and economy, the reported research results and existent problem. The results show that the life is prolonged after cryogenic treatment and the life is longer if the cryogenic treatment is carried out before tempering. To different material, the quantity of prolonging is different. To 30CrMnTi, 1.43 times of life of the tap is prolonged if the cryogenic treatment is arranged before tempering and only 61% is prolonged after tempering. To 1Cr18Ni9Ti, 1.08 times is prolonged before tempering and only 46% is prolonged after tempering. To 5CrMnMo, 1.65 times is prolonged before tempering and only 89% is prolonged after tempering. Research indicates that after cryogenic treatment, the harder the material is, the better the cutting is.

Tool Failure of Surface-treated High Speed Steel Tap

Tool Failure of Surface-treated High Speed Steel Tap

623 表面処理されたハイスタップの工具損傷(GS-13 加工・工具)

623 表面処理されたハイスタップの工具損傷(GS-13 加工・工具)

Electrolyic Strengthening Technology of Cutting Edge of High-speed Steel Taps

A method of electrolytic strengthening on the cutting edge of the cutter is studied to prolong the life of the cutter and to improve the cutting stability.The equipment and the manufacturing processes are developed for electrolytic strengthening on the cutting edge of the rotary cutter.High-speed steel tap is taken as an example, some process parameters of electrolytic strengthening on the cutting edge of the cutter, such as electrolyte, cathode materials, cutting speed and the electrolyte temperature as well as the relationship between the cutting edge strengthening capacity and the distance between anode and cathode, current density, polishing time and the voltage between anode and cathode, are studied.If electrolytic strengthening with optimized processes is used to polish taps, the orderly cutter edge of taps will have uniform strengthening degree of each tooth knife edge, the geometry of the cutter edge can meet the requirement of the cutter edge strength, and the surface roughness of the rake face of the taps can be reduced.When the above research results are applied to cutting 40Cr, ZG230～450 and 1Cr18Ni9Ti, the 40Cr, ZG230～450 taps life can be prolonged by 200%, but there is no obvious change in life of the stainless steel taps.The study indicates that the service life of high-speed steel taps can be prolonged by electrolytic strengthening, and the effect is related with the machined materials and the strengthening degree of the cutting edge.

Performance of high-speed steel taps at high cutting speed

The main goal of this paper is the evaluation of the performance of high-speed steel taps when machining grey cast iron at high cutting speeds. It is used for two types of high-speed steel, one with addition of vanadium (HSS-E) obtained by conventional method, classified as AISI M3 and other obtained by powder metallurgy (HSS-PM), classified as AISI M7. These two tool materials are used in two coated situation: with TiN and multilayer TiN-TiNAl. The tests were carried out at two different cutting speeds, 37.5 and 75 m/min. The tool life criteria were based on dimensional tolerances of the threads, on tool wear and also on catastrophic failure of the tool. Analysis in the Scanning Electron Microscope (SEM) and optical microscope were done to determine the type and mechanisms of wear. The results showed that the effect of the cutting speed depends on the coating. The best performance was achieved with the multilayer coating TiN-TiNAl.

Research on Vibration Tapping of Hardened Steel

As high-speed steel tap is incapable of small-hole tapping (M3) in hardened steel, vibration tapping is introduced in this paper to solve this problem. Theoretic analysis with fracture mechanics indicates that the impact effect of the tap on the workpiece results in extended micro cracks and a much lower tapping torque. And the torsional rigidity of the tap is enforced in vibration tapping as proved by dynamic analysis. The experimental results show that with well chosen amplitudes, tapping torque decreases as vibration frequency increases and increases with the increase of net cutting time ratio, with the latter being the more significant influencing factor. In vibration tapping of hardened steel, 24 threads can be machined with a single tap. Vibration tapping is then proved to be a practical solution to the problem of small-hole tapping in hardened steel.

Investigation of the torque characteristics in vibration tapping of hardened steel

Vibration tapping is presented in this paper to solve this problem, as high-speed steel tap is incapable of tapping small-hole (M3) in hardened steel (50HRC). Theoretical analysis with fracture mechanics indicates that the impact effect of the tap on the workpiece results in increased II-type stress intensity factor and extended micro cracks, leading to lower plastic deformation, reduced cutting forces and a much lower tapping torque, and the torsional rigidity of the tap is enhanced in vibration tapping as proved by dynamic analysis. The experimental results show that with well chosen amplitudes, tapping torque decreases as vibration frequency increases, and tapping torque increases as net cutting time ratio increases, where net cutting time ratio influences the tapping torque more significantly. Vibration tapping is then proved to be a practical solution to the problem of small-hole tapping in hardened steel.

Performance evaluation of ion-implanted cutting tools and dies

The relative performance of ion-implanted and unimplanted machine tool taps, inserts, and punch-die sets was compared using blind tests. Performance of the tools, defined as the number of parts machined to within specifications, was evaluated under actual and simulated production conditions; relative performance was obtained by dividing the average performance of implanted tools by the average performance of unimplanted tools. The tools were implanted with a combination of 80 keV N + and N + 2. Implanted high speed steel taps exhibited performance by factors 1.5 to more than 4 as compared to unimplanted taps. Implanted TiN-coated metal cutting carbide inserts exhibited performance from factors of 2–4, and the performance factors of nitrogen-implanted punch-die sets ranged from 2.0 to 2.6.

Fracture toughness, strain hardening and life of AISI M2 high speed steel taps

The fracture toughness and strain-hardening characteristics of AISI M2 high speed steel were measured after a variety of heat treatments. It was found that the fracture toughness is a sensitive function of heat treatment, depending on both the austenitizing and the tempering temperature. The fracture toughness exhibited an inverse correlation with hardness. The strain-hardening rate depended on heat treatment and plastic strain. At small plastic strains the strain-hardening rate follows the behaviour of the secondary-hardening reaction. The strain-hardening rate decreases with increasing plastic strain and approaches zero for specimens tempered at 560–580°C. Tapping experiments showed that it is advantageous to use a low austenitizing temperature and to temper below the secondary-hardening peak. A linear correlation exists between tap life and (K Ic / SHR) 2 HV where K Ic , SHR and HV are the fracture toughness, the initial strain-hardening rate and the Vickers hardness respectively. (K Ic / SHR) 2 HV is believed to correlate with the difficulty that a pre-existing crack has in propagating under tapping conditions.

The Influence of a Solid-Film Lubricant on the Action and Life of Metal Cutting Taps and Other Tools

Three modes of tap failure have been considered: too high a cutting force, jamming of the swarf in worn corners of the cutting edges, and loss of thread form. In tests in which a high speed steel tap cut a 1.5 percent Ni-Cr-Mo steel with neat mineral oil as the lubricant, chip thickness and tap wear increased with tap use until the jamming limit was reached. Coating the tool with an inorganically-bonded molybdenum disulphide film did not alter the failure mode but increased tap life by reducing the rate of progress to failure. Adding an EP agent to the oil completely changed the route to failure and increased tap life even more. The tool coating reduced tapping forces only initially. It was soon mainly swept away. Thereafter, however, the residue still had an influence on tap performance through its action in reducing pick-up on the tap rake faces. Supplementary tests contrast the behavior of the coating in tapping and turning operations.