Resistant Cast Iron Research Articles

Static cracking resistance of cast irons. I. Nodular cast irons

Static cracking resistance of cast irons. I. Nodular cast irons

Static cracking resistance of cast iron

Static cracking resistance of cast iron

Special features of the method of determining static cracking resistance of cast irons

Special features of the method of determining static cracking resistance of cast irons

Strength and wear resistance of cast iron for the bushings in diesel cylinders

1. Complex economic alloying and modification, and optimization of the chemical composition and structure of gray cast iron is an effective means of improving the mechanical properties and wear resistance of cylinder bushings fabricated from this metal. 2. With the optimal total content of carbon, silicon, and alloying elements (Cr, Ni, Mo, V, Cu) and parameters of the macro- and microstructure of the metallic base and graphite (P, Pt, Pdl, 0–1.4, Gl, Graz45-Graz90, G4–G6), the modified cast SChKhNMD has sufficiently high strength properties (σb = 750–950 N/mm2, σ−1 = 140–150 N/mm2, and wear resistance (I=65–75 mg/100 h, PS=17.5–20.5 N/mm2).

Processes occurring during the tempering of wear-resistant cast irons

1. Carbon exerts a greater influence than manganese on the temper resistance of cast irons with 30% Cr. 2. The critical tempering temperature of wear-resistant cast irons depends on the carbon content and is independent of the manganese content. 3. According to diagrams that we have constructued, it is possible to determine the hardness of cast iron as a function of its carbon and manganese content and the tempering temperature; this makes it possible to assign heat-treatment regimes on a rational basis.

Effects of the thermal cycle on the resistance of cast irons to the formation of cracks in welding without preheat

Effects of the thermal cycle on the resistance of cast irons to the formation of cracks in welding without preheat

Microstructure of low-alloy cast iron with spheroidal graphite and high crack resistance

1. The results of investigations of the resistance of cast irons with different structures and shapes of graphite inclusions to brittle failure suggest the absence of correlation between KIc and δ, and the presence of a weak correlation between σu and σo.2. The critical embrittlement temperature can be estimated qualitatively from the results of tests on the resilience of specimens with an acute notch (Charpy-type). 2. Two-stage annealing at 920°C and 720°C with subsequent heating to Ac2, holding for 15...30 min, and cooling in air to 600...500°C, and thereafter in water or oil makes it possible to fix ductile austenite, which is stable to the normal temperature, along the ferrite-grain boundaries; in this case, redistribution of Mn, Ni, Cr, Mo, Cu, Al, and Si occurs between the α- and γ-solid solutions, and the fracture toughness KIc is increased as compared with the KIc of cast iron with an initial ferritic structure. 3. An increase of up to a total of 2.0...3.5% in the extent to which ferritic cast iron with spheroidal graphite is alloyed with Ni, Cu, Cr, Mn, Mo, and Al contributes to an increase in the amount and stability of austenite, even during slow cooling in air. 4. The investigations that we conducted to determine the feasibility of increasing the resistance to brittle failure, which were conducted on compact specimens for eccentric tensioning and which were computed by methods used for steel components, make it possible to expand the range of application of low-alloy cast iron with spheroidal graphite.

The effect of the metal base on the wear resistance of chromium cast iron

1. Dependence of abrasive and impact-abrasive wear resistance of cast iron on the microhardness of the base is linear. 2. With any carbon content cast iron with martensitic structure of the metal base has maximal abrasive and impact-abrasive wear resistance. 3. With the aid of the plotted diagrams we can select the optimal carbon content ensuring the required level of abrasive and impact-abrasive wear resistance.

Cyclic crack resistance of cast irons with nodular graphite

1. Full fatigue failure curves of irons with nodular graphite are presented and the correlation relationships between the parameters characterizing the growth rate of fatigue cracks in the medium-amplitude portion of the curve are established. 2. The dominant mechanism of fatigue failure for all of the investigated types of irons is transgranular cleavage. 3. Fatigue failure was accompanied by decohesion of the graphite nodules and the matrix. The fatigue crack path passed through the base matrix and the nodules remained intact. It was established that the graphite nodules, exerting a local retarding influence on fatigue crack development, promote local curvatures of the front and microspreading of the fatigue crack. 4. In the second part of the linear and the start of the third portions of the kinetic fatigue failure curve the formation of regular blocks of fatigue striations is characteristic. A good correlation was noted between the fatigue crack growth macrorate and the spacing of individual striations on the linear portion of the curve and also between the macrorate and the width of the blocks of striations at the end of the linear and the start of the third portion of the curve.

Improving the service properties of cast iron glass molds

A significant improvement in the outputand the quality of products made in the modern technological equipment of the glass plants can be achieved by improving the working properties of glass molds. In this case, the constructional material of the glass molds has a great significance. In spite of the positive results obtained while manufacturing the individual components of the glass molds from stainless steels, and nickel- or copper-base alloys, cast iron continues to be the main constructional material [I]. Therefore, efforts are constantly being made to improve its properties [2]. Solving this problem at the Konstantinovsk plant 'Avtosteklo' is complicated because of the rigid working conditions of the glass molds and the technological difficulties encountered during the production of castings. The temperature of the alkalescent (weakly alkaline) glass mass fed to the mold is 1480~ and the duration of its contact with the working surface of the mold reaches 30 sec per pressin~ cycle. Alloying gray iron with chromium and nickel improves the working porperties of the glass molds, but, in this case, the results obtained have not been stable. In a majority of cases (90%) the main reason for the glass molds to go out of order was crack formation on the working surface. This has a negative effect on the quality of the articles produced. Therefore, the work on improving the properties of the glass molds was aimed at increasing the crack resistance of cast iron. This problem was solved by converting graphite from a flaky shape to a more compact one. However, the choice of a cast iron having optimum properties and capable of imparting maximum crack resistance is not possible without knowing the reasons for failure and investigating the fracture mechanism of the glass molds. The data available in the literature [3] show the fracture mechanism of the individual components of the glass molds. We have continued the investigation in this direction. During the production of illumination-engineering hoods (domes), we obtained and tested cast iron molds (matrices) of the following composition (weight content, %) having different forms of graphite under the conditions existing at the 'Avtosteklo' plant: 3.6-3.8 carbon, 1.48-3.8 silicon, 0.3-0.45 manganese, 0.05-0.08 sulfur, and 0.08-0.1 phosphorous. The structure of the metallic matrix was transformed from ferritic PO(Fe) up to ferrito-pearliti c

Optimizing the carbon and manganese concentrations in wear-resistant chromium cast irons

1. The composition of cast iron intended for operation under abrasive wear conditions must be selected with at least two parameters kept in mind — the abrasive (microcutting, and impact — abrasive wear resistance. 2. The carbon and manganese concentrations have different effects on the abrasive and impact-abrasive wear resistance of cast iron. The abrasive wear resistance of cast iron rises with increasing amounts of carbon and drops with increasing amounts of manganese.

Chromosiliciding in molten salts to improve the cavitation resistance of cast iron

Chromosiliciding in molten salts is recommended for protecting cast iron and steel parts against cavitation erosion.

Mechanical characteristics of SCh15-32 cast iron in the plane stressed state

1. The ability of cast iron to resist changes in volume under conditions of first loading and steady elasticity with loading conditions −1≤α≤0.5 decreases sharply with increasing stress levels. Under conditions where the component of the compressive stress σ3 has a higher absolute value than the component of the tensile stress σ1 the resistance of cast iron to changes in volume increases sharply. With an increase of the stress level the value of\(K_{I\left| {\alpha = - 1.65} \right|} = f = (\sigma _1 )\) (during first loading) decreases somewhat. With increasing stress levels during steady elasticity the ability of cast iron to resist changes in volume\(K_{y\left| {\alpha = - 1.65} \right|} = f = (\sigma _1 )\) increases. 2. With increasing stress levels the ability of cast iron to resist shear strain changes less than the ability to resist changes in volume. Beginning at some stress level, the resistance to shear strain becomes more stable and during steady elasticity the variation of Gy with σ1 approaches the asymptotic, approximating a straight line parallel to the x axis σ1. 3. The obtained characteristics of the elastoplastic deformation, elasticity, resistance to changes in volume and shear strain and the relations governing their changes in relation to the stress level and loading conditions make it possible to determine the range of applications for cast iron in machine construction. By means of these characteristics it is also possible to explain several phenomena that occur in cast iron structures during operation.

Cavitation resistance of steel 110F6 in different structural conditions

1. Steel 110F6 subjected to isothermal hardening at 300° to obtain a structure of bainite+carbide with a hardness of HRC 38-50 is characterized by high cavitation resistance that exceeds the cavitation resistance of cast iron by a factor of 150–170. 2. The steel can be recommended for facing machine parts operating under severe cavitation conditions.

The resistance of cast iron brake drums to heat checks

The resistance of cast iron brake drums to heat checks

Effect of chromium and titanium on creep and relaxation of cast iron

1. Alloying of cast iron with chromium and nickel is inadvisable for parts needing high resistance to creep and relaxation at 400–500°. 2. For cast iron working at temperatures up to 330° the addition of chromium is desirable, since it stabilizes pearlite and hardens the cast iron. 3. At a concentration of ∼0.2%, titanium substantially increases the resistance of cast iron to creep and relaxation at all temperatures investigated (330, 400, 520°).

The wear resistance of cast irons

1. Cast iron 300Kh13G3M with a martensite matrix and M7C3 chromium carbides is more durable than Ni-Hard under abrasive wear conditions. 2. Obtaining a martensitic structure by adding manganese in an amount permitting quenching in air makes it possible to surmount the technological difficulties in casting and machining. 3. In its wear resistance, casting properties, and machinability, cast iron 300Kh13G3M is superior to Ni-Hard. In addition, it does not contain scarce nickel.

Increasing the oxidation resistance of cast iron dies for pressing headlight diffusers

Increasing the oxidation resistance of cast iron dies for pressing headlight diffusers

Effect of structure of the wear resistance of white cast iron

1. No direct relationship was found between the hardness and the wear resistance of white cast irons. 2. The wear resistance of cast iron increases with the hardness of the carbides. 3. The wear resistance of hypoeutectic chromium cast irons increases linearly with the quantity of carbides if the type of carbide does not change. An increase of the carbon concentration above the eutectic does not increase the wear resistance, since large brittle needles of hypereutectic carbides are formed. 4. The wear resistance decreases with increasing sizes of the carbides. 5. The wear resistance of white cast irons increases linearly with the hardness of the metallic base. The wear resistance is highest when the metallic base is martensitic. In some cases metastable austenite provides an equal wear resistance. Stable austenite reduces the wear resistance.

Thermodynamic and structural factors determining the wear resistance of aluminum cast irons

When the carbon content in aluminum cast iron containing about 2.5% Al is reduced (to about 2.5%),. carbon is concentrated near the dendritic branches where a specific variety of “pearlite” (containing a finely dispersed carbon-rich γ′-phase) is formed, the interdendritic regions remaining ferritic. Modifying cast irons of this kind with cerium leads not only to spherodization of graphite but also to the formation of γ′-phase dendrites with a corresponding reduction in the carbon content in the ferritic matrix surrounding γ′-phase dendrites and “pearlite.” This has a beneficial effect on the wear resistance of cast iron.