• Journal of the Korean Society for Precision Engineering
• /
• v.13 no.7
• /
• pp.36-44
• /
• 1996

Drilling tests were carried out austempered ductile cast iron(ADI) to clarify the factors influencing the drilling characteristics of ADI material. The machinability of material was evaluated using high speed steel drill and cobalt contained drill of 6mm diameter. The spheroidal graphite cast iron materials were austemized at 900 .deg. C for 1 hour and then wear was kept at 375 .deg. C for 2 hours. Austempered ductile cast iron contains a great deal of retained austenite which contribustes to an improvement of impact strength. In this paper, machinability of ADI was invastigated by drilling experimentation. The results obtained are as follows:a) Flank wear incresses logarithmically with the increases of cutting time and proportionally with the increases of cutting force. b) Drilling hole number of about 2 times can be educed more step feed than ordinary feed due to the high hardness of ADI material and hardness increasing ascribed to the martensite of retained austenite.

• Tribology and Lubricants
• /
• v.33 no.3
• /
• pp.98-105
• /
• 2017

A pin-on-disk test is performed to measure the wear volume of a ductile cast iron (DCI) roll when it wears down using a high carbon steel and two alloy steels at different sliding velocities between the roll and the material (steel). Normal pressure is set as constant and test temperatures are 400, 500 and $600^{\circ}C$. In addition, thermal softening behavior of the DCI roll is examined using a high-temperature micro-hardness tester and the surface hardness variation of the DCI roll is expressed in terms of temperature and heating time. Based on experimental data, a wear coefficient used in Archard's wear model for each material is obtained. The wear volume is clearly observed when the test temperature is $400^{\circ}C$ and sliding velocity varies. However, it is not measured at temperatures of $500^{\circ}C$ and $600^{\circ}C$ even with variations in sliding velocity. From the optical photographs of the pin and disk, the abrasive wear is observed at $400^{\circ}C$ clearly, but no at $500^{\circ}C$ and $600^{\circ}C$. At higher temperatures, the pin surface is not smooth and has many tiny caves distributed on it. It is found that wear volume is dependent on the carbon contents rather than alloy contents. Results also reveal that the variations of wear coefficients are almost linearly proportional to the carbon contents of the material.

• Journal of Korea Foundry Society
• /
• v.25 no.1
• /
• pp.40-50
• /
• 2005

A series of heavy section ductile cast iron ingots with the cube length of 250mm were systematically investigated as functions of casting parameters of sand casting. Abnormal graphite formation was specially observed with the variation of Si content and Bi or Sb addition. Effects of chilling during casting and adaptation of riserless system were also examined, and proved to be effective for the prevention of both shrinkage and abnormal graphite such as chunky one. The formation of chunky graphite was effectively prevented by low Si content despite the promotion of pearlite matrix structure. The ferritic matrix was encouraged to form by high Si content and chunky graphite formation was effectively suppressed by the addition of Bi and Sb. Bi addition, however, was not good enough to control the microstructure owing to the sensitive cooling rate dependent inoculation behavior and relative low ability of nodulization. Sb addition, on the other hand, was proved to be effective for the microstructural control and enhancement of various mechanical properties such as strength, elongation, and impact energy. It may be suggested that optimized casting parameters should be applied to produce heavy section ductile cast iron with reliability.

• Journal of the Korean Society for Heat Treatment
• /
• v.1 no.1
• /
• pp.13-23
• /
• 1988

The hardenability of alloyed ductile cast irons was studied for 54 different alloy compositions obtained from eight commercial and laboratory foundries. The alloying elements investigated for their effects on hardenability were Si(2.0 to 3.0%), Mn(0.0 to 0.8%), Mo(0.0 to 0.6%), Cu(0.0 to 1.5%), and Ni(0.0 to 1.5%). Two hardenability criteria, a first-pearlite hardenability criterion and a half-hard hardenability criterion, were used to determine hardenability of ductile irons. Prediction models for each hardenability criterion were developed by multiple regression analysis and were well agreed with previous experimental results. Molybdenum was the most potent hardenability promoting element followed by manganese, copper and nickel ; silicon had little effect on hardenability and reduced the hardenability as silicon content increased. When alloying elements were presented in combination, strong synergistic effects on the hardenability were observed especially between molybdenum, copper and nickel. The hardenability of ductile iron was strongly influenced by austenitizing temperature. Increasing austenitizing temperature up to $955^{\circ}C$, hardenability increased gradually but decreasing rate and then decreased as temperature increased above $955^{\circ}C$. Unless reducing segregation by very long-time annealing treatment, the hardenability of ductile iron was not significantly influenced by segregation of alloying elements.

• Journal of Korea Foundry Society
• /
• v.40 no.3
• /
• pp.76-84
• /
• 2020

The effects of Alloying Element and Heat Treatment on the mechanical properties of ductile cast iron poured into shell stack molds were investigated. The strength and hardness were increased and the elongation was decreased roughly with the increased amounts of tin and copper added, respectively. Those were greatly increased with the increased amount of tin added and the elongation was roughly decreased with it. In the simultaneous addition of copper and tin, the strength and hardness of the tin increased, but the elongation rate decreased. Those were greatly increased and this was decreased with normalizing. In the case of specimens with smaller section sizes during austempering processing, the strength and hardness were higher than those with larger sections, but the elongation rate was lower.

• Journal of Korea Foundry Society
• /
• v.15 no.2
• /
• pp.146-155
• /
• 1995

This study was performed to investigate the effect of austempering temperature on the mechanical properties and fracture characteristics of the ductile cast iron with Cu, Mo and Cu, Mo, Ni. The results obtained from this study are summarized as follows; Microstructures of Cu-Mo and Cu-Mo-Ni ductile cast iron by austempering were obtained low bainite with some martensite at $250^{\circ}C$, mixture structure of upper and low bainite obtained at $300^{\circ}C$ and upper bainite obtained at $350^{\circ}C$. Tensile, impact and fracture toughness properties were remarkably controlled by retained austenite. With increasing austempering temperature, tensile and yield strength, hardness decreased, while the elongation and impact absorption energy, fracture toughness increased. With adding Ni, tensile and yield strength increased and elongation, facture toughness and impact absorption energy decreased. Retained austenite increased with increasing austempering temperature and the fracture surface were shown mixture structure of fibrous and dimple.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.7 no.6
• /
• pp.90-96
• /
• 1998

The ductile cast iron is austempered at 300, 350 and 40$0^{\circ}C$ temperature in order to investigate the basic factors for monitoring drill wear in automatic production process, and cutting force and AE RMS signals are measured with changing cutting condition for ADI(Austempered Ductile Cast Iron) with different mechanical properties. The signals of cutting force were influenced by cutting speed and feedrate greatly. On the other hand AE RMS signals are influenced by cutting speed where as it is not related with feedrate. As the depth of drilling increases, cutting force shows a slow increase and the value of AE RMS increases until the range of h/d=4. But over the range it increases greatly due to an amount of chip discharge and friction with inner wall of drilling hole, etc. As the drill diameter increases at a constant depth of drilling. Cutting force increases linearly, but the level of AE RMS does not increases linearly due to circumferential velocity and great influence of h/d.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.11 no.6
• /
• pp.935-944
• /
• 1987

The surface rolling, one of the plastic working processes, provides good surface roughness with the reduction of diameter and the increase of surface hardness. In this study three Nachi 6000ZZ bearing were used for surface rolling on ductile cast iron. The results obtained are as follows; (1) The good surface roughness can be obtained with roller surface radius of curvature of 24mm after the 2nd rolling. (2) The surface roughness of ductile cast iron was 0.48.mu.mRmax by the contact pressure of 140kgf/mm$^{2}$ and surface hardness was Hv 395 with roller surface radius of curvature of 24mm after the 2nd rolling. (3) The reduction of specimen diameter of ductile cast iron were -12.8.mu.m due to rolling. (4) Within the diameter variation of -11.mu.m, surface roughness and surface hardness were increased, but at the range of exceeding -14.mu.m of the diameter variation the surface roughness became worse and the surface roughness became worse and the surface hardness was increased. (5) Dynamic contact area was about 25% to 30% of static contact area. The calculated contact pressure showed a good agreement with the experimental contact pressure.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2002.05a
• /
• pp.96-102
• /
• 2002

This paper was studied on the wear-corrosion behavior of ductile cast iron in the acidic environment. In the dry atmosphere and variety of pH solution, wear-corrosion characteristics and friction coefficient of GCD 60 with various sliding speed and distance were investigated. And electrochemical polarization test of GCD 60 was examined in the environment of various pH value. The main results are as following : In the dry atmosphere, boundary friction appears below nearly 5 $kg_{f}$ of contact load, and it is considered that solid friction occurs over nearly 5 $kg_{f}$ of contact load. As pH value becomes low, wear-corrosion loss in the aqueous solution increases. As the corrosion environment is acidified, corrosion potential of GCD 60 becomes noble, polarization resistance becomes low, and corrosion current density increases.

• Journal of the Korean Society for Heat Treatment
• /
• v.15 no.6
• /
• pp.255-259
• /
• 2002

Effect of martensite on the mechanical properties of austempered ductile cast iron was investigated after obtained the martensite by subzero treatment. Retained austenite was transformed to martensite by subzero treatment, and with decreasing subzero treatment temperature, volume fraction of martensite was increased. With increasing of the volume fraction of martensite, tensile strength was increased and elongation was decreased, ratio of increasing of strength and decreasing of elongation was higher in case of specimens with lot's of Cu contents. With increasing of the volume fraction of martensite, hardness slowly increased until only about 5% and it rapidly increased in a straight proportion when it is above 5%, while impact value was rapidly decreased until about 7% but it had a little change when it is above 7%.