Bearing Steel 100Cr6 Research Articles

Detection of tool breakage during hard turning through acoustic emission at low removal rates

The paper deals with a new method for the detection and prediction of the catastrophic tool failure (CTF) of ceramic inserts through an acoustic emission (AE) technique and associated chip formation analysis during the hard turning of bearing steel 100Cr6. The capability of different AE sensors with respect to the different processes in the cutting zone during hard turning is discussed as an initial study. Then a new concept of process monitoring is suggested based on the application of two sensors and rationing of chosen parameters such as AErms, AEstrength and AEabsolute energy. The specific character of the formed chip is associated with raw AE signals. Conventional data processing of AE signals does not enable the different phases of tool wear to be clearly recognised or the prediction of CTF, while the new suggested concept does. This concept is based on the rationing of AE features recorded in different frequency ranges in connection with the different processes in the cutting zone during chip separation.

Analysis of Selected Properties of Cutting Ceramics at Machining Process of Bearing Steel 100Cr6

Cutting tool durability is very important cutting tool property. Especially for cutting ceramic is necessary to define durability dependence on available set of cutting speeds and to determine lifetime of tools made of cutting ceramic. Durability of cutting tools is defined in standard ISO 3685. In standard ISO 3685 is defined T-vc dependence for different cutting materials and standard included process evaluation of tool durability for cutting materials made of high speed steel, sintered carbide and cutting ceramic. Specification cutting tools durability made of cutting ceramic in machining process of steel 100Cr6 is very important for economics of small and medium-sized enterprises, because cutting tool durability is factor that significantly affects the budget of these enterprises. This problematic is determined for small and medium-sized manufacturers of bearings, because steel 100Cr6 is most commonly used for production of bearing rings 100 mm in diameter. This material is usable for actuator (actuators and reduction gears) too. Description of cutting ceramic durability could mean for bearings manufacturer determination of optimal cutting parameter with maximum possible use of tool lifetime. Standard ISO 3685 contains instructions how to create T-vc dependence for cutting tools made of cutting ceramic. In this standard are only instructions how to create T-vc dependence according to Taylor. The article compares T-vc dependencies for various cutting ceramics (Al2O3, Al2O3+ZrO2, Al2O3+TiCN) with T-vc dependence defined in standard ISO 3685, because this standard describes T-vc dependence for all entered cutting materials together.

Magnetic Evaluation of Residual Stresses and Structure Transformations Induced in Soft Steel after Turning

This paper deals with the stress and temperature induced microstructure transformations in a soft bearing steel 100Cr6 after turning operation. Investigation is carried out through a technique based on Barkhausen e ect. Evaluation of surface integrity via structure transformations, X-ray di raction as well as microhardness inspection is carried out as well. Surface integrity is investigated with the respect to the variable tool wears and consequent mechanical and thermal loads applied on the inspected surfaces. Di erent surface microstructures caused by the mechanical and associated thermal aspects of the surface formation are discussed and correlated with the parameters obtained from the measured Barkhausen emissions.

Machining Performance of CBN Cutting Tools for Hard Turning of 100Cr6 Bearing Steel

This article presents the examination of cutting performance of a low CBN content cutting tool in the case of hard turning of 100Cr6 hardened bearing steel. One of the indicators of cutting performance is the wear rate, which can be calculated as a ratio of a measurable geometric parameter of a wear form and some technological parameters (cutting time, cutting length or removed material volume). The wear of CBN cutting tools is characterized by the extent of flank wear hence the wear rates related to cutting time and removed material volume are calculated based on the measured flank wear during the cutting experiments. The alteration of wear rates as a function of flank wear and cutting speed was examined.

On the Spheroidized Carbide Dissolution and Elemental Partitioning in High Carbon Bearing Steel 100Cr6

We report on the characterization of high carbon bearing steel 100Cr6 using electron microscopy and atom probe tomography in combination with multi-component diffusion simulations. Scanning electron micrographs show that around 14 vol pct spheroidized carbides are formed during soft annealing and only 3 vol pct remain after dissolution into the austenitic matrix through austenitization at 1123 K (850 °C) for 300 seconds. The spheroidized particles are identified as (Fe, Cr)3C by transmission electron microscopy. Atom probe analysis reveals the redistribution and partitioning of the elements involved, i.e., C, Si, Mn, Cr, Fe, in both, the spheroidized carbides and the bainitic matrix in the sample isothermally heat-treated at 773 K (500 °C) after austenitization. Homogeneous distribution of C and a Cr gradient were detected within the spheroidized carbides. Due to its limited diffusivity in (Fe, Cr)3C, Cr exhibits a maximum concentration at the surface of spheroidized carbides (16 at. pct) and decreases gradually from the surface towards the core down to about 2 at. pct. The atom probe results also indicate that the partially dissolved spheroidized carbides during austenitization may serve as nucleation sites for intermediate temperature cementite within bainite, which results in a relatively softer surface and harder core in spheroidized particles. This microstructure may contribute to the good wear resistance and fatigue properties of the steel. Good agreement between DICTRA simulations and experimental composition profiles is obtained by an increase of mobility of the substitutional elements in cementite by a factor of five, compared to the mobility in the database MOBFE2.

Atomic-scale investigation of ε and θ precipitates in bainite in 100Cr6 bearing steel by atom probe tomography and ab initio calculations

Carbide precipitation during upper and lower bainite formation in high-carbon bearing steel 100Cr6 is characterized using transmission electron microscopy and atom probe tomography. The results reveal that both ε and θ carbides precipitate in lower bainite isothermally held at 260°C and only θ precipitates form in upper bainite isothermally held at 500°C. ε and θ precipitate under paraequilibrium condition at 260°C in lower bainite and θ precipitates under negligible partitioning local equilibrium condition in upper bainite at 500°C. In order to theoretically study ε and θ precipitation and the ε→θ transition in bainite, thermodynamic calculations have been carried out using ab initio techniques. We find that ε and θ carbides in ferrite have almost identical thermodynamic stability, and hence have similar formation probability. In austenite, however, cementite formation is clearly preferred: it is favored by 5kJmol−1 at room temperature and still by 4kJmol−1 at 500°C. Hence, the thermodynamic predictions agree well with the atom probe tomography results.

Wear Rate of CBN Cutting Tool in Hard Turning of 100Cr6 Bearing Steel

The examination of wear and tool life of CBN cutting tools which are used for hard turning is a emphasized research theme, since the significant proportion of cost of machining associated with cutting tool. In this article we examined the wear of low CBN content cutting tool in case of hard turning of 100Cr6 bearing steel (HRC=62±2). The experiments were carried out with constant depth of cut and feed rate at three different cutting speeds. The flank wear of CBN inserts were measured after predetermined number of passes. The measured flank wear values were described as a function of cutting time and the calculated wear rate as a function of flank wear.The average wear rate were shown at three different cutting speeds.

Study of Elastic Deformations in Hard Turning

This paper deals with study of elastic deformations after hard turning of bearing steel 100Cr6. It is well known that elastic deformation could strongly affect precision of produced parts. This aspect takes a significant role during hard turning due to poor plasticity of machined material. This study presents information about elastic deformation when turning steel of different hardness and their relations to the cutting conditions. Result of this study indicates that elastic deformations are more pronounced during turning steels of high hardness and strongly depend on cutting conditions.

TRIP型マルテンサイト鋼板の伸びフランジ性に及ぼす合金元素添加の影響

The effects of Cr, Mo and Ni additions on the microstructure and stretch-flangeability of 0.2%C-1.5%Si-1.5%Mn-0.05%Nb, in mass%,TRIP-aided martensitic sheet steel produced by isothermal transformation process at a temperature below martensite-finish temperatures were investigated to develop the 3rd-generation sheet steel for automobile requiring high hardenability. When 0.5% or 1.0% Cr was added to the base steel, the combination of tensile strength of 1.5 GPa and hole-expanding ratio of 40% was attained. On the other hand, the Cr-Mo or Cr-Mo-Ni addition hardly influenced the stretch-flangeability and stretch-formability, although it increased the yield and tensile strengths, comparing to the base steel. The good balance of Cr-bearing steel was mainly caused by suitable combination of (1) volume fraction and (2) interparticle path of finely dispersed martensite-austenite complex phase (M-A phase), which suppressed a void initiation at the matrix/M-A phase interface on hole-punching and void coalescence or crack extension on hole-expanding.

Optimization of Deep Cryogenic Treatment Process for 100Cr6 Bearing Steel Using the Grey-Taguchi Method

This article presents a method for optimizing the deep cryogenic treatment (DCT) process parameters for 100Cr6 bearing steel, based on the Taguchi method with Grey relational analysis. The DCT parameters considered for the optimization included the cooling rate, soaking temperature, soaking time, and tempering temperature, with the quality targets of dimensional stability, wear resistance, and hardness. As per the Grey-Taguchi technique, nine experimental trials based on the L9 (34) orthogonal array were conducted. The optimum parameters for 100Cr6 bearing steel were arrived at based on Grey relational analysis. Analysis of variance (ANOVA) was performed and soaking temperature was identified as the most influential factor in deep cryogenic treatment of 100Cr6 bearing steel. The improvement in dimensional stability, wear resistance, and hardness of the deep cryotreated samples under optimized treatment conditions was 13.77, 49.02, and 19.35%, respectively. A microstructural examination was carried out to identify the possible mechanism of cryogenic treatment in improving the properties of the 100Cr6 bearing steel. A confirmation test was subsequently conducted to validate the test results.

Cryogenic machining as an alternative turning process of normalized and hardened AISI 52100 bearing steel

Environmental and health friendly technologies with economic justification have nowadays an increasing importance in global industrial trends. Idea of global sustainable development dictates cleaner and less health hazardous machining processes. With these limitations in mind, the main issue is now to change the way mechanical components are being machined and move to alternative technologies that could moreover increase the machining performance. Cryogenic machining is one possibility to reach this goal. It consists of a system for cutting (turning, milling, etc.) assisted by liquid nitrogen, which enables a clean process with possible lower production costs and higher productivity. This article presents the results of turning hardened and normalized bearing steel AISI 52100 (DIN 100Cr6), comparing conventional flood and dry with cryogenic machining. Turning results show drastic improvements in tool lifetime (up to 370%) for cryogenic machining of normalized bearing steel 100Cr6 and reduction of thermal residual stress inducements in case of hardened bearing steel 100Cr6, while tool life is also extended.

MULTIPARAMETRIC ANALYSIS OF SURFACE INTEGRITY AFTER TURNING THROUGH BARKHAUSEN NOISE IN RELATION TO TOOL WEAR

This paper deals with application of micromagnetic inspection of surface integrity after turning bearing steel 100Cr6 in dependence on increasing tool wear. This paper indicates influence of tool wear on the selected parameters of Barkhausen noise (RMS value, peak position). The analysis also contains measurement of residual stresses carried out by mechanical method and also analysis of microstructure modifications. The results of experiments show that RMS values of Barkhausen noise decreases with the tool wear as a results of increasing compressive stresses formation in the near surface layers. Moreover the structure transformation occurs in these layers for higher values of flank wear VB.

Comparison of different approaches to verify creep behaviour of 100Cr6 steel

Heating before hardening or case hardening plays an important role in the heat treatment of steel. Due to the presence of high temperatures, creep can arise even at moderate stresses and can cause distortion. This contribution focuses on the modelling of creep behaviour using different model approaches. We present an approach for the verification of different creep laws and the determination of material parameters using uniaxial experimental data. Regarding parameter identification, an optimisation scheme has been developed in order to find the best approximation for the material behaviour. This procedure is applied to the investigation of creep of the austenitic phase of the bearing steel 100Cr6 (SAE 52100).

METHODOLOGY OF THE ASSESSMENT OF THE ABRASIVE TOOL’S ACTIVE SURFACE USING LASER SCATTEROMETRY

Diagnostics of abrasive tools requires the use of modern measurement techniques which allows for fast assessment of a surface in order to determine, for example, the degree of its wear or to detect various type of defects. A wide group of optical measurement methods used for this type of assessment are based on the phenomenon of light scattering. One such method based on imaging and analysis of light scattering from a surface is laser scatterometry. In this paper, by utilizing laser scatterometry supported by image analysis techniques, a proposal for a methodology of assessment of the degree to which smearing of the grinding wheel active surface (GWAS) occurs during the plunge grinding process, was presented and discussed. Select results of experimental investigations carried out on bearing steel 100Cr6 were also presented. The obtained results confirmed the efficacy of the above-mentioned techniques that could be an interesting alternative to other methods already used in such measurements.

Transmission Electron Microscopy Studies of X210CrW12 and 100CR6 Thixo-Cast Steels

Two kinds of deformed carbon steel were used as a feedstock for thixoforming: X210CrW12 tool steel cold worked, of composition 2,1 %C, 10,5 %Cr, 0,7 %W, 0,4 %Si (all in weight %), and bearing steel 100Cr6: (0,9% C, 1,4% Cr, 0,4% Mn, 0,3% Si, 0,2% Cu). The microstructures of X210CrW12 steel after thixoforming process at temperature of 1230°C, performed at 30 % of liquid show presence of globular grains (average size from 30 µm 50 µm) surrounded by the eutectic mixture. Measured chemical composition of the austenite in globules was: 2,5% C, 0,4% Si, 0,7% Mn, 12% Cr, 1,3% W, 0,1%V, 87% Fe and that of the eutectic mixture: 5%C, 0,4% Si, 0,6%, Mn, 1,1%, W, 17,5% Cr, 75,4% Fe in thixocast of X210CrW12 steel. Measured carbon content is too high, most probably due to contamination effect. TEM studies of this steel after thixoforming shows that the eutectic mixture consists of ferrite α-Fe and Cr7C3 carbides. Thixoforming of 100Cr6 bearing steel was conducted at temperature of 1420°C at about 25 % of liquid fraction. Thixocast microstructure consists of globular grains consisting of martensite needles and residual austenite (20 μm to 40 μm in size and average composition 0,9%C, 1,4 %Cr, 0,5%Mn, 0,3%Si). The chemical composition of the eutectic is following: 2,4% C, 2,6% Cr, 0,2%Si, 0,6%Mn.

An implicit algorithm to verify creep and TRIP behavior of steel using uniaxial experiments

AbstractCreep is a complex material feature occurring in mechanical structures under moderate stresses and relatively high temperatures. Transformation‐induced plasticity (TRIP) is a macroscopic phenomenon of steel behavior. If phase transformations occur under deviatoric stress, a permanent inelastic strain is obtained even if the yield stress is not reached. Thus, creep and TRIP do not have a yield stress like plasticity and visco‐plasticity. Sometimes, during heat treatment of steel, creep and TRIP appear together. In order to determine creep or TRIP behavior it is necessary to verify concrete material laws and to determine corresponding material parameters. For this reason, often uniaxial experiments with small probes are performed in special devices. It is the main purpose of this study, to develop a procedure for the verification of possible laws for creep and TRIP and for determining material parameters, using experimental data. Therefore, an implicit algorithm in two variants will be developed: strain‐driven and stress‐driven. These algorithms can also be applied to simulations of (spatially homogenous) uniaxial experiments. Based on these algorithms, an optimization scheme will be developed for finding material parameters which realize a best approximation. Finally, the developed procedure will be applied for the investigation of creep and TRIP during heating of the bearing steel 100Cr6 (SAE 52100).

Effect of cooling parameters on the microstructure and properties of Mo-bearing and Cr-bearing steels

To develop low-cost low carbon bainitic steel, Mo-bearing and Cr-bearing steels were melted in a vacuum induction furnace and were researched by thermal simulation and hot rolling at the laboratory. As the cooling rate increases from 0.2 to 50°C/s, the transformation temperatures of two steels lie between 650 and 400°C, and the final microstructures of them change from quasi-polygonal ferrite and granular bainite to lath bainite. Compared with cooling in air or by interrupted cooling, Mo-bearing and Cr-bearing steel plates cooled by sprayed water boast higher strength and superior toughness, for large-size islands are responsible for the poor mechanical properties. Compared to Mo, Cr is effective to isolate the bainitic reaction in low carbon steel, and the bainitic microstructure can also be obtained in Cr-bearing steel cooled at a wide range of cooling rate.

Discriminating pores from inclusions in rolled steel by ultrasonic echo analysis

The quality of steel is degraded by inclusions and pores which form during production. When exposed to external stress, large inclusions initiate cracks that weaken the mechanical strength of steel components. In this study, an ultrasonic immersion pulse-echo setup, which is currently used for quality control, was employed for signal-based inclusion and pore discrimination. The results from the used wavelet and short-time Fourier transform methods were verified with optical microscopy and scanning electron microscopy. The ultrasonic method was tested on 22 rolled bearing steel 100Cr6 samples featuring a total of 24 inclusions and 16 pores. Based on the differences in the echo peak frequency, it was possible to discriminate all pores from inclusions with the wavelet transform method. Sulfide and oxide inclusions also featured differences within the 9–14 MHz frequency range. The developed ultrasonic method was found to be capable of discriminating inclusions from pores in rolled bearing steel 100Cr6.

Characteristics of 100Cr6 bearing steel after thixoforming process performed with prototype device

A device based on a high pressure die-casting(HPDC) machine was constructed, with a capacity to produce thixo-casts from steel. After inductive heating to the required semi-solid temperature range, the samples were transported in a protective argon atmosphere to a cylinder of modified HPDC and injected into a pre-heated die. Bearing steel 100Cr6 (after forging) was used as the feedstock material. The metallographic analysis of the steel showed a homogenous structure within a whole volume characterized by a grain size between 2 μm and 8 μm. Differential scanning calorimetry (DSC) analysis allowed to estimate the process temperature for thixoforming at 1 390 °C which was attributed to about 45% of a liquid phase. With such technological parameters after the semi-solid processing the microstructure consisted of globular grains of size from 15 μm to 40 μm. The microstructure of globules indicated predominant presence of martensite (about 76% volume fraction) with residual austenite between plates. X-ray analysis confirmed that the thixo-cast samples contain mainly martensite and residual austenite. The hardness of the initial forged sample was HRC 27 and after the thixoforming process it was HRC 60, which confirms the presence of martensite and carbides. The thixo-casts were subjected to low tempering, at temperature of 150 °C for a period of 2 h, in order to remove stresses created during the process of thixoforming and to increase plasticity. The hardness after tempering was HRC 62.3. Additionally, in order to identify phases present in the thixo-casts, transmission electron microscopy (TEM) was carried out.

Investigations on Semi-solid Joined Steel Components and their Bonding Quality

To characterise the bonding quality of semi-solid joined components, fundamental investigations were carried out by producing composite test specimens. By using steel as a semi-solid base matrix and different steel or copper alloys as inserted materials, an interesting field of material combinations was realised. Two different steel grades, the cold forming tool steel X210CrW12 and the bearing steel 100Cr6, were chosen as the material of the base matrix. Geometry variations were tested along with the variation of materials mentioned. The results supply information about the influence of the inserts shape on an early cooling of the base material during form filling or remelting of the insert caused by overheating. Qualitative and quantitative analyses of the mechanical characteristics of the bonding were carried out using mechanical tests. Metallographic analyses complete the description of the bonding mechanisms at the contact zone between the solidified matrix and the insert. The investigations on basic geometries show a good joining quality, which is mainly based on a strong force and form closure caused by contraction of the solidifying and cooling base matrix. In addition, material closure occurs in areas that are strongly heated during the joining process. These results provide key information for the design of prospective components of a new generation.