Pearlite

About: Pearlite is a research topic. Over the lifetime, 6028 publications have been published within this topic receiving 65695 citations.

Study of the high strength and low yield ratio cold forging steel

Abstract: High strength and low yield ratio cold forging steel was studied by a thermomechanical simulator, a laboratory hot rolling mill and a multistage cold former. The results have shown that multiphase microstructure containing polygonal ferrite, dispersed pearlite, granular bainite and retained austenite was obtained by thermomechanical processing (TMP). The cold forging steel can be directly used to fabricate bolts from hot rolled bar due to its low yield ratio, and the mechanical properties of the finished bolts can meet the standard of class 8.8 bolts without heat treatment. This is because that the hot rolled bars after TMP possess multiphase microstructure, which contributes to an increase the mechanical properties, and the TRIP effect improves strength and ductility of the bolt.

Comparative Investigation of Phase Transformation Behavior as a Function of Annealing Temperature and Cooling Rate of Two Medium-Mn Steels

Abstract: Transformation-induced plasticity (TRIP)-assisted medium-Mn steels with a ferritic matrix containing considerable amounts of retained austenite are a promising candidate to fulfill the requirements for the third-generation of advanced high-strength steels (AHSS), which is currently under development. The influence of the intercritical annealing temperature and cooling rate on the final microstructure of a 0.1C3.5Mn and 0.1C5Mn steel, respectively, was elaborately investigated. Dilatometric experiments were carried out and additionally supported by microstructural observations. During soaking in the two-phase ferrite–austenite region and subsequent slow cooling the C and Mn concentration in the austenite increased and resulted in its chemical stabilization. The variation of the annealing temperature and cooling rate altered the amounts of ferrite, retained austenite, bainite, pearlite, and martensite in the final microstructure. Furthermore, two thermodynamical models for the prediction of the maximum retained austenite content and the optimal annealing temperature have been thoroughly evaluated in this work. It can be stated that the experimental data revealed a shift of the maximum retained austenite to higher annealing temperatures compared to the model calculations. As diffusional transformations were not considered in the applied models, slow cooling rates led to pronounced deviations between calculation and experiment, thereby showing the need for model adaptions.

Origin and mechanism of torsion fracture in cold-drawn pearlitic steel wires

Abstract: The structural and mechanical factors that control the torsion fracture behavior of cold-drawn eutectoid steel wires are examined. Two types of the fracture are identified; namely, flat- and cleavage-type. Torsion cracks are found to initiate in ferrite and propagate along the ferrite/cementite interface. The shear stress distribution within the wires is affected not only by the applied torque, but also by the residual stress. The maximum shear stress occurs halfway from center to the surface, where the cracks initiated. The growth of torsion cracks is sensitive to the orientation of cementite lamellas in pearlite grains. The influence of thermal history on the occurrence of cleavage fracture is ascertained, with the assistance of atom probe. It shows that the cleavage fracture results from a decrease in dislocation mobility, caused by thermally activated diffusion of carbon atoms into ferrite.

Heat insulating mortar powder and its prepn process

Abstract: The heat insulating mortar powder contains cementing material, foamed modified polystyrene grain, modified expanded pearlite, cementing material modifier and fiber. The foamed modified polystyrene grain contains foamed polystyrene grain, foamed polystyrene modifier and flyash; the modified expanded pearlite contains expanded pearlite, expanded pearlite modifier and sodium hydroxide; and the cementing material modifier contains polymer adhesive, air entraining and water reducing agent and flyash activator. The preparation process includes preparing foamed modified polystyrene grain, preparing modified expanded pearlite, preparing cementing material modifier, and mixing all the materials in certain proportion. The present invention has the advantages of small heat conducting coefficient, high compression strength, good construction performance, high adhering strength, etc.