An Evaluation of the Microstructure of High-Aluminum Cast Iron in Terms of the Replacement of Aluminum Carbide with Titanium Carbide or Tungsten Carbide

One of the problems with recycling is that of widespread contaminated steel scrap with an unwanted aluminum addition. In this paper, we will present a specific solution to this problem. The implementation of high-aluminum cast iron production has been considered. This cast iron is a cheap material resistant to high temperatures; additionally, it has increased abrasion resistance. Despite the above-mentioned advantages, high-aluminum cast iron has not been widely used in the industry so far, due to the difficulties encountered during machining and the occurrence of the phenomenon of spontaneous disintegration. The paper presents a method for replacing aluminum carbide with titanium carbide or tungsten carbide. This research shows that the carbide replacement procedure is sufficient in stopping the phenomenon of self-disintegration of a casting made of high-aluminum cast iron. Moreover, a new material was obtained, i.e., high-aluminum cast iron with precipitates of hard tungsten carbide and flake graphite. When considering the abrasive resistance of this material, flake graphite can be treated as the natural lubricant phase and tungsten carbide precipitation, as the hardening phase.

Shaping the Microstructure of High-Aluminum Cast Iron in Terms of the Phenomenon of Spontaneous Decomposition Generated by the Presence of Aluminum Carbide

A suitable aluminum additive in cast iron makes it resistant to heat in a variety of environments and increases the abrasion resistance of the cast iron. It should be noted that high-aluminum cast iron has the potential to become an important eco-material. The basic elements from which it is made—iron, aluminum and a small amount of carbon—are inexpensive components. This material can be made from contaminated aluminum scrap, which is increasingly found in metallurgical scrap. The idea is to produce iron castings with the highest possible proportion of aluminum. Such castings are heat-resistant and have good abrasive properties. The only problem to be solved is to prevent the activation of the phenomenon of spontaneous decomposition. This phenomenon is related to the Al4C3 hygroscopic aluminum carbide present in the structure of cast iron. Previous attempts to determine the causes of spontaneous disintegration by various researchers do not describe them comprehensively. In this article, the mechanism of the spontaneous disintegration of high-aluminum cast iron castings is defined. The main factor is the large relative geometric dimensions of Al4C3 carbide. In addition, methods for counteracting the phenomenon of spontaneous decay are developed, which is the main goal of the research. It is found that a reduction in the size of the Al4C3 carbide or its removal lead to the disappearance of the self-disintegration effect of high-aluminum cast iron. For this purpose, an increased cooling rate of the casting is used, as well as the addition of elements (Ti, B and Bi) to cast iron, supported in some cases by heat treatment. The tests are conducted on the cast iron with the addition of 34–36% mass aluminum. The molten metal is superheated to 1540 °C and then the cast iron samples are cast at 1420 °C. A molding sand with bentonite is used to produce casting molds.

ATI X-751

ATI X-751 is a high-aluminum version of ATI X-750. It is a high-strength, precipitation hardenable, nickel-chromium alloy that employs nickel and titanium as the hardening elements. The alloy has good creep-rupture strength up to 815 °C (1500 °F), and excellent oxidation and corrosion resistance up to 980 °C (1800 °F). This datasheet provides information on composition, physical properties, and hardness. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Ni-776. Producer or source: ATI.

Evaluation of soil contamination by heavy metals at public cemeteries in the municipality of Lages, southern Brazil

ABSTRACT The burial of bodies is a potentially polluting activity. Taking this into consideration, the aim of the present study was to verify the compliance of two cemeteries with environmental legislation and to quantify the concentrations of heavy metals in soils affected by burial activities. Physicochemical characterization of the soil was performed by analyzing control samples from areas near the cemeteries. Concentrations of cadmium, lead, chromium, nickel, zinc and copper were determined using high-resolution continuum source atomic absorption spectrometry. The two cemeteries had unsatisfactory properties for the retention of metal cations, with clay percentages ranging from 15.40 to 41.40% and sand percentages ranging from 28.75 to 66.85%. The control samples presented low cation exchange capacity (12.27 to 22.73 cmolc/dm³) and high aluminum (Al3+) saturation (66.74 to 90.16%). Although neither of the two cemeteries had concentrations above the limits established for the metals analyzed by Resolution No. 420/2009 of the National Environment Council, the contaminants may be leaching to groundwater due to inadequate soil characteristics.

Precipitation Hardening of Triplex Steel by Using Nickel Aluminum Inter-Metallic Precipitates

This paper deals with three types of triplex steel, where containing 25 to 28 wt.% manganese, 0.8 to 0.89 wt.% Carbon, 9.9 to 11.11 wt.% Aluminum, and with different Nickel content. Two types contain Ni in range of 0.9 to 2 wt.% and third type doesn’t contain Ni. The precipitation of Nano-size kappa carbides is the most proper technique used for this objective. It is expected that inter-metallic strengthening mechanism should act more effective in promoting the strength of Triplex steel with ductility. From this point of view, this research was designed to study the effect of inter-metallic inductive alloying element as Nickel on promoting of the strength and ductility of the high aluminum containing high manganese steel. Optical microscope, scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to detect of inter-metallic precipitates through steel investigated ranged in Nickel from 0 to 2 wt.%. Mechanical and strain hardening properties were determined in the steel investigated after different regimes of heat treatment. It was found that Ni3Al inter-metallic compound provides the austenite matrix with good strength and ductility, depending on the ageing time. Further deterioration was obviously observed in the steel investigated as increasing the ageing time, attributing to coarse structure occurrence.

The Spontaneous Emulsification of Entrained Inclusions During Casting of High Aluminum Steels

Mold slag entrainment during the continuous casting process presents a late stage source of non-metallic inclusions (NMI) with a high likelihood of ending up in the final product. The reaction between the entrained slag phase and surrounding liquid steel in the continuous casting mold affects the inclusion morphology and properties. However, there is a lack of information on the kinetics of the NMI-steel reaction. A novel approach, utilizing controlled synthetic inclusion/metal samples, has been developed to study the reactions between free inclusion-slag droplets and steel. The technique combines High-Temperature Confocal Scanning Laser Microscopy (HT-CSLM), X-ray Computed Tomography (XCT) and advanced electron microscopy techniques offering rapid controlled heating performance and extensive characterization of the samples. This method offers the ability to observe the size, shape and composition of an unconstrained reacting inclusion and to investigate the interface between the materials with respect to reaction time. This study interrogates a low aluminum steel (0.04 wt pct) and a high aluminum steel (1 wt pct) in contact with an inclusion-slag phase with a starting composition aligned to a typical mold slag. It was found that the reaction between silica and aluminum across the interface of the two phases provided a driving force for spontaneous emulsification to occur. Products of such emulsification will have a significant effect on the inclusion size distribution and potentially the prevalence of inclusion retention in molten steels solidifying in the continuous caster (for example if emulsified buoyancy forces are reduced to near zero) and hence in the subsequent solid product.