Fracture Mechanisms in Steel Castings

The investigations were inspired with the problem of cracking of steel castings during the production process. A single mechanism of decohesion - the intergranular one - occurs in the case of hot cracking, while a variety of structural factors is decisive for hot cracking initiation, depending on chemical composition of the cast steel. The low-carbon and low-alloyed steel castings crack due to the presence of the type II sulphides, the cause of cracking of the high-carbon tool cast steels is the net of secondary cementite and/or ledeburite precipitated along the boundaries of solidified grains. Also the brittle phosphor and carbide eutectics precipitated in the final stage solidification are responsible for cracking of castings made of Hadfield steel. The examination of mechanical properties at 1050°C revealed low or very low strength of high-carbon cast steels

Bimetalni lim St3S+Cu

The paper presents a theoretical analysis of the asymmetrical process of rolling bimetal plates composed of the base St3S layer and a Cu cladding layer. Investigation carried out aimed at determining the curvature of bimetal band depending on the value of roll peripheral speed asymmetry factor av. Computer simulations were performed on three different layer thickness ratios, HS/HH. Numerical studies were based on computer simulations carried out using the Forge 2D software. For computations, this program uses the finite-element method. The asymmetry of the process resulted from a non-uniform distribution of rolling reduction into the bimetal band layers, which caused the band to bend at the rolling mill exit. To counteract this behaviour, an asymmetry of working roll peripheral speeds was introduced.Članak daje teorijsku analizu učinka odnosa debljine sloja bimetalnih limova sastavljenih od osnovnog sloja St3S i sloja presvučenog bakrom. Provedena istraživanja su imala za cilj odrediti zakrivljenost bimetalne trake ovisno o vrijednosti faktora asimetrije av periferne brzine. Izvedene su kompjuterske simulacije tri sloja s različitim omjerima HS/HH debljine. Numeričke studije su se zasnivale na kompjuterskim simulacijama provedenim pomoću softvera Forge 2D. Za izračune, ovaj se program služi metodom konačnih elemenata. Asimetrija procesa rezultira od nejednolikog rasporeda redukcije u slojeve bimetalne trake koje uzrokuju savijanje trake na izlazu iz valjačkog stana. Kao protuteža takvom ponašanju uvedena je asimetrija perifernih brzina radnog valjka

Production of magnesium-aluminium bimetallic bars using the explosive cladding method

The paper presents the results of the preparation of semi-finished products in the form of magnesium-aluminium round bimetallic bars by the explosive cladding method. The system of samples consisted of an aluminium tube (1050 grade) and magnesium bar (grade AZ31) was prepared. The analysis of microstructure and mechanical tests of the joint quality was carried out. On the base of obtained results it was found that the explosive cladding parameters used to obtain the semi-finished bimetallic product characterized by a slight ovality and mechanical connection of the individual layers were correct

Technological Assessment of the Possibility of Making Light-section Castings of GX2CrNiMoN25-6-3 Cast Steel by the Centrifugal Casting Method

The paper presents the results of investigation into the technological possibility of making light-section castings of GX2CrNiMoN25-6-3 cast steel. For making castings with a wall thickness in the thinnest place as small as below 1 mm, the centrifugal casting technology was employed. The technology under consideration enables items with high surface quality to be obtained, while providing a reduced consumption of the charge materials and, as a result, a reduction in the costs of unit casting production

The Analysis of AISI A3 Type Ferritic-Austenitic Cast Steel Crystallization Mechanism

High-alloy corrosion-resistant ferritic-austenitic steels and cast steels are a group of high potential construction materials. This is evidenced by the development of new alloys both low alloys grades such as the ASTM 2101 series or high alloy like super or hyper duplex series 2507 or 2707 [1-5]. The potential of these materials is also presented by the increasing frequency of sintered components made both from duplex steel powders as well as mixtures of austenitic and ferritic steels [6, 7]. This article is a continuation of the problems presented in earlier works [5, 8, 9] and its inspiration were technological observed problems related to the production of duplex cast steel

The Role of Carbon in the Mechanism of Ferritic-Austenitic Cast Steel Solidification

The paper presents the results of research on the microstructure of GX2CrNiMoCuN25-6-3-3 and GX2CrNiMoCuN25-6-3 cast steels with a varying carbon content. The cause for undertaking the research were technological problems with hot cracking in bulk castings of duplex cast steel with a carbon content of approx. 0.06% and with 23% Cr, 8.5% Ni, 3% Mo and 2.4% Cu. The research has shown a significant effect of increased carbon content on the ferrite and austenite microstructure morphology, while exceeding the carbon content of 0.06% results in a change of the shape of primary grains from equiaxial to columnar

The Microstructure of Thin-walled GX2CrNiMoN25-6-3 Cast Steel Made by Centrifugal Casting

The paper presents the results of investigation into the technological possibility of making light-section castings of GX2CrNiMoN25-6-3 cast steel. Due the fact that the GX2CrNiMoN25-6-3 duplex cast steel has a complex microstructure authors of this paper took on its analysis. For making castings with a wall thickness in the thinnest place as small as below 1 mm, the centrifugal casting technology, as it was presented in the paper [1], is one of the most effective technology. In the paper was made the analysis of four different parameters of the casting process and different parameters of heat treatment

Technological Assessment of the Possibility of Making Light-section Castings of GX2CrNiMoN25-6-3 Cast Steel by the Centrifugal Casting Method

The paper presents the results of investigation into the technological possibility of making light-section castings of GX2CrNiMoN25-6-3 cast steel. For making castings with a wall thickness in the thinnest place as small as below 1 mm, the centrifugal casting technology was employed. The technology under consideration enables items with high surface quality to be obtained, while providing a reduced consumption of the charge materials and, as a result, a reduction in the costs of unit casting production

The Cracking Mechanism of Ferritic- Austenitic Cast Steel

In the high-alloy, ferritic - austenitic (duplex) stainless steels high tendency to cracking, mainly hot-is induced by micro segregation processes and change of crystallization mechanism in its final stage. The article is a continuation of the problems presented in earlier papers [1-4]. In the range of high temperature cracking appear one mechanism a decohesion - intergranular however, depending on the chemical composition of the steel, various structural factors decide of the occurrence of hot cracking. The low-carbon and low-alloy cast steel casting hot cracking cause are type II sulphide, in high carbon tool cast steel secondary cementite mesh and/or ledeburite segregated at the grain solidified grains boundaries, in the case of Hadfield steel phosphorus - carbide eutectic, which carrier is iron-manganese and low solubility of phosphorus in high manganese matrix. In duplex cast steel the additional factor increasing the risk of cracking it is very "rich" chemical composition and related with it processes of precipitation of many secondary phases

The Role of Carbon in the Mechanism of Ferritic-Austenitic Cast Steel Solidification

The paper presents the results of research on the microstructure of GX2CrNiMoCuN25-6-3-3 and GX2CrNiMoCuN25-6-3 cast steels with a varying carbon content. The cause for undertaking the research were technological problems with hot cracking in bulk castings of duplex cast steel with a carbon content of approx. 0.06% and with 23% Cr, 8.5% Ni, 3% Mo and 2.4% Cu. The research has shown a significant effect of increased carbon content on the ferrite and austenite microstructure morphology, while exceeding the carbon content of 0.06% results in a change of the shape of primary grains from equiaxial to columnar