Papers by Keyword: Cast Steel

Abstract: Three prototype metallurgical rolls were produced on the basis of G200CrNiMo4-3-3 material. The method applied for the microstructure forming was different for each roll: the roll marked WOT – as cast state (without a modification and heat treatment); the metallurgical roll marked WMT – during its casting the FeCaSi deoxidizing was applied and then modification by a complex inoculant and argoning; the metallurgical roll marked WNT – subjected to a heat treatment (incomplete normalizing).The mentioned above differences in the technology of making rolls caused changes in their microstructure.The cementite eutectic and pearlitic matrix occurred in each roll. The main differences in the microstructure of cast steel rolls concerned a morphology of precipitates of hypereutectoid cementite. In the WOT roll cementite was mainly in the Widmannstӓtten system. Precipitates of hypereutectoid cementite in the WMT roll occurred along grain boundaries of primary austenite. A large fraction of spheroidal hypereutectoid cementite, precipitated in the whole volume of the primary austenite grain, appeared in the WNT roll. The microstructure influenced the rolls hardness and was equal 260 ÷ 350 HBW.Tribological investigations indicated decreasing the abrasive wear resistance with increasing the hypereutectoid cementite fraction within the primary austenite grains.

Abstract: It is a common understanding that hot forging will improve the properties of a steel part in relation to when the same part is made by casting solely. A study has been performed where two crank pin disks of a particular steel alloy, one hot forged and the other cast, both in quenched and annealed condition, have been tested using a new innovative “eye”-specimen bending test. The used test procedure is described, and it is shown that the forged and the cast material will collapse and beak down in very different way in this test.

Abstract: The subject of investigations constituted the G200CrNiMo4-3-3 cast steel applied for metallurgical rolls. This is the material, which microstructure can be modified by the heat treatment. The presented hereby work concerns the initial state (as cast condition) of the investigated cast steel. This cast steel constitutes the initial material for the heat treatment. The morphology of carbide precipitates, including the cementite precipitated on grain boundaries of the primary austenite, hypereutectoid cementite precipitated in the Widmannstӓtten system and lederburitic cementite, were characterised in the study. The results of investigations of mechanical and fractographic properties of the G200CrNiMo4-3-3 cast steel, were also presented. Among others, the values of fracture work in the impact test, fracture toughness (K_Ic) and wear resistance were given. The crack pathway together with the hypereutectoid cementite fraction role in its development, was presented. The obtained investigation results, presented in the hereby paper, will constitute the comparison base for the assessment of the heat treatment influence on the microstructure and properties of the tested G200CrNiMo4-3-3 cast steel.

Abstract: The surface composite layer Ni/ZrO₂ on the ZG45 cast steel surface was fabricated through vacuum infiltration casting method. This paper researched on the Ni/ZrO₂ composite infiltrated layer morphology, hardness and the friction property under fry friction. The results show that the added of the ZrO₂ ceramic particles increase the composite infiltrated layer hardness and the wear resistance. The 15% ZrO₂ composite infiltrated layer wear resistance is better than the 10% ZrO₂ composite infiltrated layer. Different ZrO₂ contents have same change trend. The friction coefficient decreases with the temperature increasing. The 10% ZrO₂ friction coefficient changes obviously with the temperature increasing. The 15% ZrO₂ friction coefficient changes evener than the 10% ZrO₂ but the protection of friction and wear is more obvious.

Abstract: This paper presents results of experimental research and numerical calculations for thermal fatigue of G-X12CrMoVNbN9-1 martensitic cast steel. The tests were performed using hydraulic testing machine equipped with the heating chamber. The experimental research included static tests under mechanical load conditions at four temperature levels (20°C, 400°C, 550°C, 600°C) aimed at determining material characteristics needed for the numerical model. Main cyclic tests were carried out under thermal load conditions. The parameter, which was maintained at unchanged level during tests was the specimen strain ε = const = 0. The specimen temperature was changed. The numerical calculations for the same temperature change program were performed with the use of ABAQUS software. Experimentally and numerically determined stress value versus test time were compared.

Abstract: The surface composite layer Ni/ZrO₂ on the ZG45 cast steel surface was fabricated through vacuum infiltration casting method. This paper researched on the Ni/ZrO₂ composite infiltrated layer morphology, hardness and the friction property under fry friction. The results show that the main phase structure of the layer is ZrO₂, Cr₂B, NiB and FeNi. The macrohardness of the layer is HRC60~64. The micohardness presents gradient change. The maximum hardness appears at subsuface. The 10% ZrO₂ composite infiltrated layer wear resistance increases 10 times and 15% ZrO₂ composite infiltrated layer increases 22.6 times than ZG45 under the 100N load. The 10% ZrO₂ composite infiltrated layer wear resistance increases 8.5 times and 15% ZrO₂ composite infiltrated layer increases 21.9 times under 250N load. The wear resistance has greatly improved.

Abstract: A study of rare earth effects on inclusion modality of 8Cr4MoV cold work roll steels was carried out in the laboratory, the steels smelting by a 50kg vacuum induction furnace, atmospheric casting, processing sample after annealing, then inspecting the steels’microstructure, inclusion modality and composition; The results showed that the steels’ microstructure fine, micro-hardness increased with increasing rare earth content, while the average size of inclusions decreased significantly, also the morphology and composition of inclusions significantly changed from the angular black manganese sulfide to the ball white sulfur oxides of rare earth, and thus played roles of deoxidation, desulfurization, purification and deterioration of liquid steel , it will help improving the fatigue performance of the work roll.

Abstract: The microstructure of 40CrNi2Mo steel matrix strengthened with wear resistance alloy is observed by the optical scope, SEM with EDS and FESEM. Analysis emphasis is lied on the distribution regulation of nanosized WC particulates in the microstructure of the steel matrix. Experimental results show that the method of adding wear resistance alloy in steel matrix can avoid gravity segregation phenomenon effectively and guarantee a uniform distribution of WC in steel matrix. nanosized WC particulates distributing evenly in steel matrix improve the wear resistance, and make microstructure of the steel matrix more uniform, finer and denser proved by its high-expansion micrograph.

Abstract: The effect of different tungsten-bearing materials addition in a surface preform, such as Ni-base WC particles, ferrotungsten powders and casting WC particles, on the reinforcement phases at the surface compound layer with a carbon steel substrate is investigated under the condition of vacuum expandable pattern casting V-EPC. The microstructures and reinforcement phases are characterized by optical microscopy, SEM and EDS. Experimental results show that it is impossible to synthesize the independent WC particles in each condition. The tungsten-containing materials are all inclined to decompose during steel infiltration and the released tungsten elements tend to combine with carbon to form fish born-like or strip-like WC or W₂C carbides and dissolve in other type of carbides and matrix.

Abstract: using finite element method to study the stress variation of cylindrical specimen during the cooling process of quenching, through the establishment of the computer models of mechanical property and thermal property, and using computer to perform the numerical simulation of temperature environment and structure in the process of quenching, simplify the operation process on one hand, and facilitate the analyses of complicated nonlinear problems on the other hand. The outcome according to the stress variation of the outside surface of cylinder indicates that during the process of quenching, the cooling speed of the inner surface of cylinder is much slower than that of the outer surface, leading to the reverse between the center stress and the outer surface stress of hollow cylinder, which finally turns into internal stress distribution of structural stress type.