Papers by Keyword: Decarburization

Abstract: The effect of austenitizing temperature on the quenching microstructure and properties of 51CrV4 steel was studied. The results show that with the increase of austenitizing temperature, the austenite grains grow gradually. After quenching, the hardness increased first and then decreased, and the strength increased first and then decreased after tempering at 460°C. When the austenitizing temperature was 880°C, the austenite grains were fine and uniform, about 16μm, the martensite structure was dense, the strength and hardness reached maximum. When the austenitizing temperature was 910°C, the decarburization phenomenon was obvious, and the strength, hardness and plasticity of the test steel decreased obviously. When the austenitizing temperature exceeded 910°C, the austenite grains grow sharply and some grains were abnormally coarse. The austenite grain size reached 20μm and the microstructure was coarser at austenitizing temperature of 950°C. Therefore, in order to ensure uniform grain size and no decarburization under the premise of complete austenitization, the best austenitizing temperature of 51CrV4 steel for good properties is 880°C.

Abstract: The paper deals with the influence of thermal load on functionality of the Toolox 33 hot work tool steel equivalent to the materials of W.Nr. 1.2311, 1.2312, 1.2738 and P20 in order to assess its suitability as a material for glass manufacture preform. Using light and electron microscopy it was shown that the steel was highly unfitting for this application where the steel comes into contact with the hot glass. Regarding the evaluation of the microstructure, it was shown that intense decarburization reflecting on the fracture behaviour of the surface layer during the thermal load has occurred. This fact was confirmed by a static tensile test and hardness measurements. Moreover, the thick layer of flakes has formed on the surface.

Abstract: The use crowd of escalators involves a wide range of people. Therefore, the safety research of escalator is concerned and should be pay more attention to continuously. In the present paper, the multiple material damage modes of escalator drive chain were analyzed. The material damage modes mainly contain the micro cracking, the wear damage and the decarburization defect. The tensile tests and friction&wear experiments were performed to investigate the influence of the material damage modes on the performance of the escalator drive chains in service. The tensile properties of the new drive chains without material damages were superior to those with decarburization defect and wear damage. The friction&wear experimental results indicated that the decarburization defects reduced the wear resistance of the escalator drive chain. The research results implied that the strict quality control and improved maintenance of the escalator drive chain was meaningful for the escalator using security.

Abstract: Electrospark deposition (ESD) was employed to clad WC-10%Co hard alloy on steel 1035 and the tribological properties of the coatings obtained were examined. The influence of the duration and frequency of discharges, the nature of the environment, and the carbon concentration in the electrode materials on the decarburization of tungsten carbide was studied. It is shown that the degree of tungsten carbide degradation can be reduced by decreasing the discharge frequency and increasing the concentration of carbon in the WC-Co electrode materials and also that the WC decarburization reaction is reversible on annealing.

Abstract: The consequences of surface finish and decarburization on the fatigue performance of cast and forged steel components in the railway industry is substantial, and means that fatigue cracking is an ongoing issue across the industry. Examples of loading spectra for coupler forces and track loads are presented, along with data from past investigations showing the severe penalty in terms of fatigue life caused by inadequate surface finish at critical locations of components under fatigue loads. Managers in railway industry need to understand the technical case for increased manufacturing requirements, as costs from operational losses may well have made the economic case for increased requirements more compelling. Various options for improving the surface finish at critical locations that are prone to fatigue are available, and should be explored to reduce the vulnerability of these components to failure via fatigue cracking.

Abstract: The SAE1070 steel grade, used especially in the automotive industry, has strict specifications and some of them are limits to oxidation and decarburization, which implies carbon loss through a variety of diffusion mechanisms. Temperature, atmospheric oxygen potential, carbon chemical potential gradient and time of high temperature exposure are some of parameters, that influence the extent of decarburization. Oxidation influences decarburization losses, in the metal/oxide interface, and as a result of this interface moves into the sample. During the reheating of billets for hot rolling, measures to contain oxidation to the minimum becomes a priority. In this work, the extent of oxidation and decarburization has been studied in the laboratory under industrial conditions as industrial scale experiments are expensive and not very practical. Mathematical modeling based on the results of laboratory experiments becomes attractive as this can be applied to industrial conditions. Isothermal tests for the evaluation of oxidation and decarburization were conducted in an electric furnace in the temperature range 600°C - 1100°C and time ranging from 2 hours to 48 hours. Decarburization and oxidation were measured by techniques such as weight change ue to removal of scale, micro-hardness testing and optical microscopy. Based on the methodology ,an algorithm has been developed for assessment of oxidation and decarburization occurring in the industrial reheating of billets With minor adjustments, it is shown that, the model can be satisfactorily applied with reasonable accuracy. Keywords: Decarburization, Oxidation , Steel billets , Modeling

Abstract: The fastening is an important part for fastening when laying the rails, which requires sufficient fastening pressure, strength, and durability. This article focuses on the fatigue fracture of the spring clip of a fastening and gets a result that the fracture accounts for alternating twist-bend load by examining macro-fracture. The crack origin is on the surface of the clip where significant decarburization and corrosion exists and its extension makes the clip break by examining metallographic structure and testing micro-hardness. The solution is to improve the heat treatment method and the surface quality avoiding corrosion.

Abstract: The mechanical properties and decarburization layer depths after heat treatment have been investigated for the experimental steels，which were melted by means of 10Kg vacuum induction furnace in the laboratory . It has been confirmed that additions of silicon and vanadium can improve strength of the steels and, the tensile strength of the steels increases with silicon content from 1.4% up to 2.0%. The reduction of carbon content and the addition of carbide forming elements decrease the decarburization sensitivity of the steels tested. The tensile strengths of the steels with carbon less than 0.5% are between 1016.88 to 1674.64 MPa, and the impact energy between 15.50 to 34.50 J, which are compared with the tensile strength of 1160.89MPa, the impact energy of 19.00 J for 55SiCrV. The steels with optimized compositions, which consists of 0.4~0.5% C, 1.6~2.0% Si, 0.8% Cr, 0.2% V, have a satisfactory property with high strength, high toughness and good anti-decarburization.

Abstract: Through the metallurgical testing on a lot of samples from different parts of the heated slab and the finished product in heavy rail manufacturing process, analysis on the surface decarburization characteristics of U71Mn and U75V is carried out. Through analyzing the main affecting factors on the decarburization depth of heavy rail in the heating and rolling process, some effective means to reduce the product surface decarburization are put forward. The results show: (1) The surface decarburization depth distribution of heavy rail slab heated in the regenerative furnace is seriously imbalanced, and the fluctuation ranges between 30% -40%.(2) Under the same production conditions, decarburization of U75V is serious, and the average depth of U75V is more than 11% higher than the U71Mn. (3) The rolling process in the production of heavy rail has a great influence on the distribution of the surface decarburization depth. (4) Because the deformation rate of rectangle slab in the rolling process everywhere is different, in order to reduce the decarburization depth of finished product, it is useful to select the narrow surface of slab to generate the head of heavy rail, as well as to change the structure of the slab cross-section from right-angle to arc.

Abstract: Ferrite growth behavior in Fe-C-Mn alloys has been studied using controlled decarburization experiments. Two types of kinetic transition are considered. A first transition is proposed which involves a change from ParaEquibrium (PE) contact conditions at short times to Local-Equilibrium with Negligible Partitioning at longer times (LENP). This transition is attributed to the gradual build up of an alloying element spike due to the diffusion of Mn across the interface. The cross-interface mobility of Mn is estimated based on the experimental results. In some alloys, we observe a transition to extended PE states at high temperatures. A simple model which quantitatively describes the experimental observations over a range of composition and temperature is proposed. A key feature of this model is the introduction of an alloying element capacity of the moving ferrite/austenite interface, X*. The introduction of this quantity is purely guided by the experimental data and, at present, there is no physically based method for calculating it.