Odlewnie Polskie (Poland)

The subject of this study is to show that the parameters of the melting process of high chromium cast iron affect the cost of casting and the properties of the cast iron. The analysis of the quality of the casting and its price was conducted in terms of the metal charge of high chromium cast iron. As is well known, in order to obtain the correct structure of the casting, and thus good strength properties, it is necessary to use clean batch components free of undesirable impurities. Unfortunately, the quality of the metal charge is proportional to its price. Thus, the use of expensive batch components offers the possibility of obtaining healthy and meeting the strength properties of castings. However, there is a flaw in this approach. And it is from the point of view of economics that production plants are forced to look for savings. Expensive feedstock materials are replaced by cheaper counterparts giving the possibility of obtaining castings with similar properties often, however, at the cost of increased inferior quality. It seems that a way out of this situation is to introduce a modification procedure into the alloyed iron manufacturing technology. The selected modifiers should affect the fragmentation of the structure of the primary austenite. At this point, it can be hypothesized that this will result in the elimination of hot cracking in high chromium cast iron. The industrial research carried out at the "Swidnica" Foundry Ltd. made it possible to show by means of the Althoff-Radtke method that by using the modification of the liquid metal of the so-called "inferior and cheaper" composition of the metal charge, a reduction in the occurrence of hot cracks and shrinkage cavities can be achieved. In addition, iron-niobium modification not only reduced the formation of casting defects in castings, but also slightly improved the impact strength of high-chromium cast iron. The work was written as part of an implementation PhD.

Chromium cast irons have gained a well-settled position among wear-resistant materials where a low manufacturing cost is one of the key factors. The wear properties of these alloys are commonly improved by the addition of carbide-forming inoculating elements such as Ti, V, B, etc., allowing the formation of underlays for the precipitation of both M7C3 carbides and austenite. On the other hand, Sr may work as a surface-active element that adsorbs on the surface of the growing crystal, inhibiting its growth. This mechanism may support the M7C3 nucleation process. The experiment was conducted on near-eutectic chromium cast irons with 20% of Cr and 2.5–3% of C. Different amounts of strontium were used as the microstructure modifier. The improvement of carbides’ stereological parameters and collocation resulted in the improvement in functional properties—wear resistance and impact strength without a significant increase in hardness as well as a decrease in carbide phase. Two types of wear studies with a modified pin-on-disc method and tests in reciprocating motion of samples in the metal-mineral system were performed. The results showed that addition modification with Sr can increase the impact strength of the alloy. EDS analysis of the samples provided results similar to hypoeutectic Al-Si alloys modified with strontium.

Abstract Tests were carried out on samples of low-alloy ductile iron with additions of Ni, Cu and Mo, subjected to austempering heat treatment. The samples were austenitized at 850, 900 and 950 °C, and then austempered at T = 210, 240, 270, 300 and 330 °C. The ausferritizing treatment was carried out in a salt bath for the time τ = 2 - 8 hours. Additionally, tests and studies covered samples subjected to the ausferritizing treatment at 270 °C with the time of holding castings in a bath from 2 to 24 hours. Evaluation covered the results of the ADI microstructure examinations and hardness measurements. The ADI matrix morphology was identified counting the average number of ausferrite plates and measuring their width and spacing. The regression equations HB = f (τ, T) and τ = f (HB, T) were derived to establish the, so-called, “process window”, allowing obtaining a priori the required microstructure of ADI and, consequently, the required mechanical properties, mainly hardness, shaping the functional properties of castings, abrasion wear resistance – in particular.

The results of studies on the use of magnesium alloy in modern Tundish + Cored Wire injection method for production of vermicular graphite cast irons were described. The injection of Mg Cored Wire length is a treatment method which can be used to process iron melted in an electric induction furnace. This paper describes the results of using a high-magnesium ferrosilicon alloy in cored wire for the production of vermicular graphite cast irons at the; Tundish + Cored Wire to be injected methods (PE) for pearlitic-ferritic matrix GJV with about 25 %ferrite content. The results of calculations and experiments have indicated the length of the Cored Wire to be injected basing on the initial sulfur content and weight of the treated melt. The paper presents a microstructure matrix and vermicular graphite in standard sample and different walled castings. The results of numerous trials have shown that the magnesium Tundish + PE Method process can produce high quality vermicular graphite irons under the specific industrial conditions of the above mentioned foundries.