Carbon Equivalent Values Research Articles

Mechanical Properties of Thin Wall Ductile Iron-Influence of Carbon Equivalent and Graphite Distribution

This work focuses on the study of the mechanical properties and microstructure of plates of thin wall ductile iron, cast in sand moulds of vertical and horizontal configuration. All tests were carried out on ferritised samples. Melts of carbon equivalent values ranging from 4.06 to 4.85 were used to cast plates of thickness ranging from 1.5 to 4 mm. The results show that irons having carbon equivalent values greater than 4.6 exhibit a marked tendency to develop exploded graphite shapes and agglomeration of graphite nodules. As a result, these irons show scattered values of mechanical properties. As irons are produced with carbon equivalent values below 4.6 %, the mechanical properties improve, reaching levels that satisfy the requirements of standards developed for ferritised ductile irons sand cast in Y-blocks.

The Influence of Microstructural Features and Mechanical Properties on the Cold Formability of Ferritic Steel Sheets

In the present study, the formability of cold rolled and annealed steel sheets having carbon equivalent values in the range of 0.028 to 0.098 wt% were investigated. The steel sheet having the lowest carbon equivalent was a titanium-stabilized interstitial free steel, which established the highest strain hardening exponent, anisotropy coefficient and higher Forming Limit Diagram (FLD). Since plain strain intercept (FLD 0 ) is the most critical strain limit on the FLD, the empirical equations were derived between FLD 0 and microstructural features and mechanical properties. As a microstructural feature grain size and as a mechanical property anisotropy coefficient gave the most reliable correlations.

Effect of N-containing additive gases on global warming gas emission during remote plasma cleaning process of silicon nitride PECVD chamber using C4F8/O2/Ar chemistry

In this study, remote plasma cleaning process was investigated in a silicon nitride plasma enhanced chemical vapor deposition chamber using C4F8/O2/Ar and C4F8/O2/Ar+additive gas. The remote plasma source used in the present experiments showed the capability of nearly complete destruction, destruction removal efficiency ≅100%, of C4F8 gas with or without the additive N2, N2O and NO gases. The cleaning rate of the silicon nitride layers is increased 32–40% by adding N2, N2O and NO gases to the optimized C4F8/O2 cleaning chemistry. This is presumably due to the effective reaction of NO radicals formed in the remote plasma with N on the silicon nitride surface, followed by the effective fluorination of Si atoms. As a result, the million metric tons of carbon equivalent values could be effectively reduced due to the decreased emission of CF4 as well as the increased cleaning rate of the silicon nitride layers, comparable to those of NF3/Ar remote plasma cleaning. For the effective reduction of global warming effects, the experimental results indicate a possibility of using the alternative gas such as C4F8 with the N-containing additive gases for the environmentally benign remote plasma cleaning process.

A study on inhomogeneous distribution of temper graphite particles in strip-cast Fe-C-Si alloys

This study examined the relationship between solidification structure and graphitization characteristics of white cast iron strips produced by strip casting. Experimental results showed that there was an unusual distribution of temper graphite particles along the through-thickness direction of the graphitized strips in comparison with gravity-cast chill plate. In particular, the graphite-free zones appeared in the vicinity of the strip surface after the completion of graphitization, especially in the strip with low carbon and silicon content. There were abnormally straight interfaces between matrix and eutectic cementite with a strong preferred [001]c growth direction caused by the effect of directional solidification found in the near-surface regions of the strips. The interfaces did not form a site for the graphite to nucleate and gave rise to the graphite-free zones close to the strip surface. An increase in carbon and silicon content could significantly increase the number of temper graphite particles and shorten the time for the completion of graphitization, but an inhomogeneous distribution feature of graphite particles was still observed in strips with a higher carbon equivalent value (CE). Furthermore, variations in carbon and silicon content resulted in transitions in carbide morphology and composition, which had a tremendous effect on the graphitization characteristics of the cast iron strips.

Hybrid control of graphite cast iron structure by partial melt treatment process

The Modified Inmould Process, which forms a cast iron-graphite hybrid alloy with a spheroidal/flake graphite structure (SG/FG), has been developed by the author.1-3 Though this process can easily control the transitional structure of SG/FG, there are some mild restrictions caused by rapid collision during the mixing of molten metals in the mould on pouring. In this study, a new experimental process was designed to solve this difficulty. The plate-like mould cavity was separated into a reaction chamber (RC) and a product cavity by a thin dam. An alloy of FeSiMg for spheroidization of base molten metal was prepared in the reaction chamber. Molten metal was poured up from the bottom of the product cavity and a part of it flowed over the dam into the reaction chamber. After being spheroidized in the reaction chamber, spheroidal graphite (SG) iron melt flowed backward into the product cavity. The density of SG molten iron with a higher carbon equivalent value is generally lower than that of flake graphite (FG) molten metal. Thus SG molten metal moved into the upper end of the product cavity by replacement of the base metal, while the base metal remained stationary at the lower end of the cavity. As a result of the phenomena of flow, movement and replacement between mutual melts, a SG/FG transitional layer structure was formed, downward, throughout the cast product.

Effect of carbon equivalent and spheroidizer addition on the morphology of strip cast white cast iron plate

A fine and laminate solidification structure is a feature of cast iron strips produced by using strip casting. To determine the influence of the carbon equivalent value (CE) and spheroidizer addition containing magnesium on the eutectic cementite and graphite particles, samples with different carbon contents, silicon contents and different amounts of spheroidizer addition were prepared in this study. The experimental results show that the solidification structure is dendritic in the near-surface region with an equiaxed cell shape in the centre region. The area fraction of eutectic cementite increases with an increasing CE value in hypoeutectic specimens and the cementite morphology changes with a change in carbon and silicon content. The graphite nodule count and area fraction remain low until the CE value reaches 4.0. When the CE value exceeds 4.0, the graphite nodule count and area fraction significantly increase with an increasing CE value. Mg-containing spheroidizer can dramatically improve the graphite nodularity and increase the nodule count. In addition, some inclusion particles exist at the centres of spheroidized graphite nodules. These particles mainly contain Mg, S, Ca, La, Ce and Si.

HSLA-100 Steels: Influence of Aging Heat Treatment on Microstructure and Properties

The structural steels used in critical construction applications have traditionally been heat-treated low-alloy steels. These normalized and/or quenched and tempered steels derive strength from their carbon contents. Carbon is a very efficient and cost-effective element for increasing strength in ferrite-pearlite or tempered martensitic structures, but it is associated with poor notch toughness. Furthermore, it is well known that both the overall weldability and weldment toughness are inversely related to the carbon equivalent values, especially at high carbon contents. The stringent control needed for the welding of these traditional steels is one of the major causes of high fabrication costs. In order to reduce fabrication cost while simultaneously improving the quality of structural steels, a new family of high-strength low-alloy steels with copper additions (HSLA-100) has been developed. The alloy design philosophy of the new steels includes a reduction in the carbon content, which improves toughness and weldability.

超高強度ボルトの遅れ破壊に関する実験的研究 : その1 鋼種と形状の観点から

Accelerated delayed fracture tests were carried out on the subject of the ultra high strength bolts in number of 1480. Experimental parameters were 8 kinds of metal materials and 6 kinds of strength level as well as shape of thread. Each test bolt was inserted into the test cylinder and loaded. The cylinder was coated by epoxy resin to eliminate corrosion, further it has load cell function putting the wire strain gages on both sides. The loaded assemblies were exposed to alternate immersion cycle in sulfuric acid solution accomplished by subjecting the specimens to the solution for period of 10 minutes per hour, followed by drying in air for a period of 50 minutes. We got conclusions as follows, the development of cracks or failures of bolts were caused mainly by tempering temperature, which was able to be related to carbon equivalent value of bolts material. On the other hand, the effect of shape of thread and bolts strength level accordance with the quality of the material and tempering temperature, themselves were of secondary importance.

Manufacturing and fabrication of thermomechanically rolled heavy plates

The development of heavy plates for constructional steelwork, shipbuilding and line pipes is characterized by a reduction of the carbon equivalent values. At the same time the strength and toughness properties are improved. Significant progress has been made by application of modern TM-rolling processes including accelerated cooling. Process control has been optimized to produce a homogeneity comparable to normalized plates. Strength and hardness profiles demonstrate the actual homogeneity. The properties after cold forming and strain aging have been evaluated. The weldability, in particular welding without preheating, is shown as a function of the H 2 -content of the weld metal. Flame straightening of TM-rolled plates is possible and is demonstrated for different types of flame straightening procedures

Effect of carbon equivalent and inoculation on residual stresses in grey iron castings

It is virtually impossible to produce castings free from internal stresses using conventional methods of founding. Castings with appreciable stresses distort during storage, transportation, machining and service. Though composition and melt treatment are known to affect the magnitude of residual stress in castings, the data on the effect of carbon equivalent and inoculation on the magnitude of residual stress in castings are limited. In the present investigation, an attempt is made to study (i) the effect of carbon equivalent on residual stress in cast iron castings, and (ii) the effect of inoculants such as calcium silicide and ferrosilicon on residual stress in iron castings in the carbon equivalent range 3.0–4.0%. The results of the investigation indicate the following: (i) the residual strains decrease linearly with increase in carbon equivalent in the uninoculated and inoculated irons; (ii) the tensile residual stresses decrease linearly with increase in carbon equivalent value of the uninoculated, calcium silicide-inoculated and ferrosilicon-inoculated cast iron castings; (iii) the ratio of UTS to residual stress increased on inoculating the grid castings. This increase is higher for calcium silicide-inoculated grids than for ferrosilicon-inoculated grid castings. This implies that from the residual stress point of view, inoculation of the iron with calcium silicide is beneficial.

The Influence of Carbon Equivalent Value, Pouring Temperature and Cooling Rate on the Inverse Chill in Spheroidal Graphite Cast Iron

The Influence of Carbon Equivalent Value, Pouring Temperature and Cooling Rate on the Inverse Chill in Spheroidal Graphite Cast Iron

低Ni-Cr-Mo-V-B系高張力鋼の熱処理について

An 80kg/mm2 high tensile steel with a low carbon equivalent value and difficult to harden by quenching was tempered after water-quenching or transformed isothermally and the mechanical properties and the internal friction were measured. The internal friction at room temperature was calculated from the time during which the strain amplitude of the sample set free after being subjected to a transversal resonance vibration by the electromagnetic method decreased to 1/n of the initial value.The experimental results are as follows:(1) The sample quenched in water has a low strain amplitude-dependent internal friction and shows a low quenchability.(2) The strain amplitude-independent internal friction of the specimen quenched in water from 900.. decreases remarkably by tempering in the temperature range from 20.. to 200.., shows litte change in the range from 300.. to 500.., and increases in the range from 550.. to 700... These changes correspond to the changes in the Charpy impact value. The three stages in the variation of internal friction are interpreted respectively as due to the precipitation of carbides from martensite, the decomposition of martensite and the formation of carbides.(3) The transition temperature rise by tempering in the temperature range between 300.. and 500.., reaches a minimum after tempering at 700... The transition temperature is influenced by the form and distribution of carbides.(4) The sample transformed isothermally has a strain amplitude-dependent internal friction.