Influence Of Steel Composition Research Articles

Theoretical study on influence of steel composition on solidification behaviour in ingot casting of low alloy steels at similar casting conditions

The effect of chemical composition of four different steel grades on solidification of 4 MT ingot at similar casting conditions has been examined using finite element model. As a consequence of change in grade dependent thermophysical properties, variations were obtained in velocity of the solidifying metal, which varied with carbon content, temperature distribution, mushy zone formation, porosity and piping. Microsegregation, which is measured by local solidification time, increased with increasing carbon content due to variation in solidus and liquidus. Alloy steels were found more prone to formation of shrinkage and central porosity compared to carbon steels. It is observed that solidification behaviour could not be related to specific thermophysical property, and combination of thermophysical properties and the alloy solidification characteristics affect the same. Improvement in alloy steel ingot quality was achieved through variation in hot top design. This study shows that steel ingot quality and yield is affected by subtle changes in composition.

The role of the spinel phases on the rust activity in corroded steels

Carbon, CS, and weathering steels, WS, were totally immersed in a NaCl containing solution. The influence of steel composition and the presence/absence of air flux into the solution on the physical properties of spinel and other iron phases were investigated. Large amounts of defective magnetite were formed only on CS, whereas little amounts of small grain-sized defective maghemite were detected only on WS. The chemical composition of the steels greatly affects the type of spinel phase being formed and their relative abundance. A non-aerated environment favored the formation of magnetite in CS. The protective ability of the rust was unfavored in the presence of large amounts of spinels.

Influence of steel composition and pre-treatment conditions on morphology and microstructure of TiO 2 mesoporous layers produced by dip coating on steel substrates

Mesoporous titania films were prepared by template-assisted dip coating on AISI 430, 304 and 316Ti steel substrates that underwent different pre-treatment, namely grinding, grinding–calcination and grinding–etching. The influence of steel grade and pre-treatment conditions on the film morphology and microstructure was studied, and reasons for film degradation were elucidated. Among tested steels, 430 interfered with the coating process the most yielding films of poor integrity and with a strongly distorted pore structure. Steels 304 and 316Ti showed better resistance to the precursor solution, resulting in less fractured films and defined pore morphology. Grinding and subsequent calcination proved to be the best choice among tested pre-treatment methods which reflected in improved film quality. The results show that only a proper combination of steel grade and substrate pre-treatment affords high-quality titania coatings with defined porosity.

Influence of steel composition on strain induced corrosion cracking and other types of corrosion

PurposeTo make clear that C‐steel can differ very much in corrosion resistance under practical conditions only because of differences in chemical composition of the steels.Design/methodology/approachIn the electricity generating industry, “mild” (i.e. “plain carbon”) and low‐alloyed steels are used in huge quantities, for instance, in boilers, steam generators, heat recovery boilers and waste incineration boilers. The resistance to strain induced corrosion cracking (SICC) was determined by measuring the “repassivation” behaviour of the steels at freshly ground surfaces with an electrochemical technique. The corrosion current measured with time was used to calculate the cracking rates of a compact tension specimen.FindingsA correlation was found between chemical composition, corrosion resistance to SICC and experiences under practical conditions. The results of early‐published papers on boiler corrosion (testing in FeCl2 solutions), erosion corrosion (testing in wet steam at 20 bar), nitrate stress corrosion cracking (testing in NH4NO3 solutions) and SICC together with those originating from in‐service failures, were compiled into a reference database. This paper is a compilation of this work too.Originality/valueThe database and formulas presented make clear there is often a direct correlation between chemical composition of ordinary C‐steel and mentioned types of corrosion failures. The paper is of importance to designers, failure analysts and researchers.

Relation between formability and precipitates in Ti‐IF enamelling steels

The influence of steel composition and processing conditions on the nature of precipitates in Ti interstitial free (IF) steels for enamelling were investigated in detail. Steels designed for enamelling applications require a higher amount of precipitates than conventional deep drawing IF steels, e.g. for automotive applications. Formable IF grades for enamelling applications have high Ti, S and C contents and the properties have hitherto not been investigated in detail. This work focused on the correlation between precipitate nature, texture development and deep drawability. It was found that a low reheating temperature, a high coiling temperature and a C/S ratio in the range of 0.4–0.5, favoured the beneficial precipitation of Ti4C2S2. Furthermore, it is shown that for a steel with a given C/S ratio, a high Ti4C2S2/Ti4S5‐ratio resulted in improved deep drawability. The deep drawability decreases with increasing C/S ratio. This is due to the decrease in γ‐fibre intensity, caused by an increased amount of TiC‐precipitates.

Structure and properties of TM processed HSLA steels

This paper deals with the influence of steel composition (with respect to the microalloying elements) and thermomechanical treatment on structure and mechanical behaviour of HSLA (High Strength Low Alloy) steels. Four different microalloyed steels have been TM rolled under variing conditions. The austenite structure prior to transformation could be revealed by means of a special etching technique. The precipitation behaviour has been studied by TEM, STEM and APFIM investigations. The results of mechanical testing can be explained in terms of structure (both austenite and transformed material), steel composition and TM treatment. It could be shown how precipitates in different steels influence the recrystallization behaviour of the austenite and how the austenite structure is related to the transformed structure. For example, fine strain-induced Nb carbonitrides prevent or reduce recristallization. Addition of Ti leads to relatively coarse complex carbonitrides. As a consequence, the content of solute Nb decreased and only few Nb carbonitrides precipitate during deformation. Hence the Ti-bearing steel shows a stronger tendency for recrystallization and the mechanical properties (especially the low-temperature ductility) deteriorate

Diffusion Chromising of Steel by CVD Using Chloride Compounds: 4 Influence of Steel Composition

The effects of carbon content and low titanium additions on the structure and thickness of chemical vapour deposited chromium coatings produced at 930°C have been studied. Diffusion of chromium in these steels has been examined by calculation of the average diffusion coefficients and determination of the concentration dependence of the interdiffusion coefficient by the Boltzmann- Matano method. The structure and thickness of the coating obtained depend largely on the amount of soluble carbon in the steel. The steels that contained 0.002–0.004% soluble carbon were most suitablefor chromising since only a very thin surface carbide layer was formed. Those steels which contained >0·05% soluble carbon at 930°C produced coatings containing dispersions of (Cr,Fe)23C6 carbide. Such coatings remain thinner and are no longer pure diffusion coatings.

Failure of Steel Couples Under Boundary Lubrication: Influence of Steel Composition, Microstructure, and Hardness

If oil-lubricated sliding or rolling couples are overloaded, separating oil films can be broken through so that the friction coefficient increases severely. Thereby an instantaneous failure of tribosystems can be caused. This type of failure was investigated by means of an Amsler-wear-test-machine with two contacting and rotating disks that were immersed into a tempered oil bath. The load was increased in steps until failure was indicated by an increase of the coefficient of friction. The results reveal a strong influence of the chemical composition and of the microstruture of the steels while hardness does not show an influence. Failure is restricted if protective reaction layers can form on the stressed surfaces. As most of the alloying elements reduce the formation of such layers failure load is lowered by them. Unalloyed ferrite is able to form thick reaction layers causing a high failure load. Less reactive components of the microstructure like cementite, martensite, and above all austenite decrease the failure load.

海水中における電気防食の難易に対する鋼組成の影響

海水中における電気防食の難易に対する鋼組成の影響

Discussions on “Influence of Steel Composition on Additive Performance”

Discussions on “Influence of Steel Composition on Additive Performance”

ステンレス鋼配管のすき間腐食に及ぼす鋼種およびガスケット材質の影響

The Influence of steel composition and insulating gasket materials on the crevice corrosion of stainless steel piping has been investigated through the loop test and the polarization measurements in 5% NaCl (pH=3.0) at 50°C.The result of the loop test showed that the crevice corrosion tendency was markedly varied with the composition of stainless steels and of gasket materials attaching to the steel. For the stainless steel composition, the tendency decreased in the order: SUS 24, SUS 28, SUS 33 and 18Cr-16Ni-5Mo. For the gasket material, it decreased in the order: chrysotile asbestos, blue asbestos, SBR and Teflon.The polarization measurements were also made on the stainless steel specimen (crevice-free) and that coupled with gasket materials (crevice-containing). The current density ratio-potential curves showed the same tendency obtained from the loop test. The larger the ratio in the potential range from passivation to pitting potential, the larger the crevice corrosion tendency of the couple of a stainless steel and a gasket material.The variation of the crevice corrosion tendency contributed by the gasket materials can be explained mainly on the swelling nature when immersed in the environmental solution, and on the adhesional wetting nature of the surface.