Microstructures and Properties of Bainitic Nodular Cast Iron Treated by Controlled Cooling and Austempering Treatment

2010 ◽  
Vol 152-153 ◽  
pp. 259-262
Author(s):  
Ke Gao Liu ◽  
Ai Min Xu ◽  
Dong Xiang ◽  
Bin Xu
Keyword(s):  
Mechanical Properties ◽  
Cast Iron ◽  
Elevated Temperatures ◽  
Nodular Cast Iron ◽  
Lower Bainite ◽  
Salt Bath ◽  
Controlled Cooling ◽  
Electric Oven ◽  
Upper Bainite ◽  
Nodular Graphite

The mixed structures of bainite matrix, austenite and nodular graphite were obtained in nodular cast iron treated by controlled cooling and austempering in electric oven instead of nitrate salt bath. The relations between bainitic morphology and mechanical properties were investigated. Experimental results show that, the nodular cast iron treated by controlled cooling in water bath and austempering has microstructures of upper bainite and austenite, the mechanical properties fluctuate greatly due to its relatively narrow temperature region in processing. The consistency of mechanical properties of lower bainite nodular cast iron is superior to upper bainite nodular cast iron. The comprehensive mechanical properties of lower bainite nodular cast iron are improved by tempering. However, the brittleness increases greatly when martensite appears in mixed structures, while good mechanical properties can still be obtained by tempering at elevated temperatures.

Microstructures and Mechanical Properties of Troostite Nodular Cast Iron by Heat Treatment

2011 ◽  
Vol 480-481 ◽  
pp. 207-210
Author(s):  
Ke Gao Liu ◽  
Ai Min Xu
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Tensile Strength ◽  
Cast Iron ◽  
Treatment Process ◽  
Interlamellar Spacing ◽  
Nodular Cast Iron ◽  
Isothermal Treatment ◽  
Heat Treatment Process ◽  
Controlled Cooling

A troostite nodular cast iron was obtained by a heat treatment process of controlled cooling, reheating-up and isothermal treatment. Experimental results show that the troostite substrate demonstrates an interlamellar spacing below 100 nm. The supercooling condition in this specific heat treatment process is key to the formation of troostite. The mechanical properties are excellent, with tensile strength of 905.5~1029.5 MPa, hardness of 30.8~32.8 HRC, and elongation of 3.1~4.0 %.

scholarly journals Continuous Cooling Transformation (CCT) Diagrams Of Carbidic Nodular Cast Iron

2015 ◽  
Vol 60 (2) ◽  
pp. 705-710 ◽  
Author(s):  
G. Gumienny ◽  
T. Giętka
Keyword(s):  
Cast Iron ◽  
Chemical Composition ◽  
Nodular Cast Iron ◽  
Lower Bainite ◽  
Continuous Cooling Transformation ◽  
Continuous Cooling ◽  
Upper Bainite ◽  
Transformation Diagrams ◽  
Cct Diagrams ◽  
Kinetics Of

Abstract This work presents continuous cooling transformation diagrams for different kinds of carbidic nodular cast iron. We investigated the cast iron, chemical composition of which in nodular cast iron allows the obtainment of a metal matrix which consists of: pearlite, upper bainite and its mixture with lower bainite, ausferrite and martensite when the casts were cooled in the mold. The influence of the rate of cooling on the obtained microstructure and hardness of the casts was shown. The work describes the influence of the alloy additives on the curves of austenite decomposition in the carbidic nodular cast iron. Diagrams were plotted which enable an understanding of the kinetics of the transformations of austenite in carbidic nodular cast iron. The diagrams also indicate the possibility of obtaining pearlite, bainite, martensite and ausferrite with the established chemical composition and the wall thickness of the cast.

scholarly journals RESEARCH OF THE INFLUENCE OF SLOW-DOWN COOLING SPEED IN THE INTERVAL OF EUTEKTIC TRANSFORMATION ON THE STRUCTURE AND MECHANICAL PROPERTIES OF CAST IRON CASTINGS

2020 ◽  
pp. 51-55
Author(s):  
N. I. Gabelchenko ◽  
N. A. Kidalov ◽  
A. A. Belov ◽  
M. D. Bezmogorychnyy ◽  
A. I. Gabelchenko
Keyword(s):  
Mechanical Properties ◽  
Cast Iron ◽  
Cooling Rate ◽  
Quality Index ◽  
Fuel Oil ◽  
Controlled Cooling ◽  
Slowing Down ◽  
Eutectic Transformation ◽  
Iron Castings ◽  
Cooling Speed

The work is devoted to the study of the effect of slowing down the cooling rate in the interval of eutectic transformation on the structure and mechanical properties of castings from gray doeutectic iron. To slow down the cooling rate in the interval of eutectic transformation, an exothermic carbon-containing additive, fuel oil M-100, was used. It is shown that the use of controlled cooling can significantly increase the quality index of cast iron without introducing additional alloying elements into the composition of cast iron.

Influence of Ca-Ba and Sr Base Inoculants on Metallurgical and Mechanical Properties of Grey and Ductile Cast Irons

2018 ◽  
Author(s):  
Dhruv Patel ◽  
Devendra Parmar ◽  
Siddharthsinh Jadeja
Keyword(s):  
Mechanical Properties ◽  
Cast Iron ◽  
Uniform Distribution ◽  
Ductile Cast Iron ◽  
Grain Structure ◽  
Spheroidal Graphite ◽  
Primary Carbide ◽  
Cast Irons ◽  
Melt Temperature ◽  
Nodular Graphite

Microstructural adaptation of cast iron alloys by inoculation is a well-known practice to swell their mechanical properties. In foundries, several inoculants have been used to refine grain structure, and to obtain uniform distribution of graphite flakes. Inoculation is one of the most critical steps in cast iron production. The effectiveness of inoculants depends on melt temperature, method of addition, type of inoculants, and holding time. In this paper, the effect of Ca-based, Ba-based, Ca-Ba based and Sr-based inoculants on microstructure and tensile properties of grey cast iron IS-210 and spheroidal graphite iron IS-1862 is reported. Results showed both Ca and Ba based inoculants were effective in obtaining uniform distribution of flaky and nodular graphite in IS-210, and IS-1862 cast irons, respectively. But in a case of Sr-based inoculant were highly effective for increase the nodularity of SG cast iron as well as succeed supreme yield strength for both grey and ductile cast iron. The amounts of ferrite in the as-cast matrix are excess with controlled granulometry for elimination of primary carbide in Sr-based inoculant.

Microstructural Evolution of Compacted Graphite Iron under Thermo-Mechanical Fatigue Conditions

2011 ◽  
Vol 409 ◽  
pp. 757-762 ◽  
Author(s):  
S. Ghodrat ◽  
M. Janssen ◽  
Roumen H. Petrov ◽  
Leo Kestens ◽  
Jilt Sietsma
Keyword(s):  
Mechanical Properties ◽  
Cast Iron ◽  
Elevated Temperatures ◽  
Easy Access ◽  
Compacted Graphite Iron ◽  
Microstructural Changes ◽  
Oxide Layers ◽  
Cooling Cycle ◽  
Compacted Graphite ◽  
Mechanical Fatigue

Cast iron components in combustion engines, such as cylinder blocks and heads, are exposed for long periods of time to elevated temperatures and subjected to large numbers of heating and cooling cycles. In complex components, these cycles can lead to localized cracking due to stresses that develop as a result of thermal gradients and thermal mismatch. This phenomenon is known as Thermo-Mechanical Fatigue (TMF). Compacted Graphite Iron (CGI) provides a suitable combination of thermal and mechanical properties to satisfy the performance of engine components. However, TMF conditions cause microstructural changes, accompanied by the formation of oxides at and close to the surface, which together lead to a growth in size of the cast iron. These microstructural changes affect the mechanical properties and accordingly the thermo-mechanical fatigue properties. The aim of this research is to provide insight into the microstructure evolution of CGI, with its complex morphology, under TMF conditions. For this, optical and scanning electron microscopy observations are made after cyclic exposure to air at high temperature, both without and with mechanical loading. It was found that the oxide layers, which develop at elevated temperatures, crack during the cooling cycle of TMF. The cracking results from tensile stresses developing during the cooling cycle. Therefore, paths for easy access of oxygen into the material are formed. Fatigue cracks that develop also show oxidation at their flanks. In order to quantify the oxide layers surrounding the graphite particles, Energy Dispersive X-Ray Analysis (SEM-EDX) and Electron Probe Micro Analysis (EPMA) are used.

Carbidic Bainitic and Ausferritic Ductile Cast Iron

2013 ◽  
Vol 58 (4) ◽  
pp. 1053-1058 ◽  
Author(s):  
G. Gumienny
Keyword(s):  
Cast Iron ◽  
Solid State ◽  
Thermal Effects ◽  
Metal Matrix ◽  
Lower Bainite ◽  
Ductile Cast Iron ◽  
Iron Metal ◽  
Derivative Analysis ◽  
Upper Bainite ◽  
Matrix Components

Abstract This article presents new kinds of carbidic ductile cast iron with different microstructures of the metal matrix. This cast iron was obtained using the Inmold method nodularisation which guarantees strong refining of graphite and the metal matrix components. A different microstructure of the metal matrix of the cast iron was obtained without any thermal treatment (unwrought) by a suitable composition of alloy additives. It was shown that by adding molybdenum, chromium, nickel and copper it is possible to obtain in the cast iron metal matrix consisting of upper bainite, its mixture with lower bainite or ausferrite in the casts with the wall thickness of 3/25 mm. The process of cast iron crystallization is presented and described with the help of the thermal and derivative analysis (TDA) curves. It also shows the thermal effects from transformation of austenite in solid state.

The Effect of Quenching Media on the Microstructure and Mechanical Properties of SA508-3 Steel

2011 ◽  
Vol 311-313 ◽  
pp. 974-977 ◽  
Author(s):  
Lu Han Hao ◽  
Ming Yue Sun ◽  
Dian Zhong Li
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
Lower Bainite ◽  
Granular Bainite ◽  
Tempered Martensite ◽  
Quenching Media ◽  
Microstructure And Mechanical Properties ◽  
Allotriomorphic Ferrite ◽  
Upper Bainite

Three different quenching media (water, oil and air) were used to compare the effect of cooling rate on the microstructure and mechanical properties of SA508-3 steel. The result has demonstrated that the microstructure for water-quenched specimen is the mixture of martensite and lower bainite, for oil-quenched specimen is the mixture of upper bainite，lower bainite and a little martensite, while for air-cooled specimen is mostly granular bainite. The product of water and oil Q&T was tempered martensite with qualified mechanical properties. The air-cooled granular bainite was translated to massive and allotriomorphic ferrite during tempering, which had poor mechanical properties. To avoid the formation of granular bainite, it is necessary to increase the cooling rate to above 5°C/s.

Property and Application of Austempered Ductile Cast Iron

2011 ◽  
Vol 328-330 ◽  
pp. 1297-1300
Author(s):  
Guang Si Luo
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Cast Iron ◽  
Treatment Process ◽  
Nodular Cast Iron ◽  
Ductile Cast Iron ◽  
Heat Treatment Process ◽  
Engineering Material ◽  
High Fatigue ◽  
Austempered Ductile Cast Iron

Austempered ductile cast iron is newly developed engineering material with a favorable combination of comprehensive mechanical properties. Its properties, such as good comprehensive mechanical properties, high fatigue strength, and good fiction and wear characteristics are included. The application of ADI at home and abroad was presented as well. In order to ensure and improve mechanical properties of ADI, it should ensure high rank nodularity in terms of nodular cast iron, improve graphite nodules, reduce segregation and properly cut down the content of silicon and manganese. While in terms of heat treatment, in order to achieve ideal austenite ferrites, stable and reliable heat treatment process as well as relevant equipment is required.

XRD Evidence for Phase Structures of Niobium Alloyed Austempered Ductile Iron

2012 ◽  
Vol 457-458 ◽  
pp. 431-434
Author(s):  
Bulan Abdullah ◽  
Siti Khadijah Alias ◽  
Ahmed Jaffar ◽  
Saad Nor Hayati ◽  
Mohd Faizul Idham ◽  
...  
Keyword(s):  
Ductile Iron ◽  
Phase Structure ◽  
Niobium Carbide ◽  
Lower Bainite ◽  
Salt Bath ◽  
X Ray Diffraction ◽  
X Ray ◽  
Phase Structures ◽  
Upper Bainite ◽  
Bath Furnace

This paper presents the changes on phase structures of niobium alloyed ductile iron after austempering process which started by austenitizing process at 900°C and held at 350°C for 1 hour, 2 hours and 3 hours in salt bath furnace. The phase structure were observed by light microscope, and then verified through X-Ray diffraction (XRD). The phase structure of as cast niobium alloyed ductile iron mainly consists of graphite nodules embedded in ferrite and pearlite phases with presence of niobium carbide. Austempering process resulted in the structure of graphite nodules embedded in ferrite platelets and bainitic structures. Increasing the austempering holding times had resulted in coarsening of the ferrite platelets structures and transformation from lower bainite to upper bainite structures.

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