Medium Alloy Steels Research Articles

Effect of liquid-nitrogen treatment on the properties of a steel 9KhS tool

In this connection, we investigated the effect of the holding time of specimens formed from medium-alloy tool steel 9KhS in liquid nitrogen; the amount of residual austenite in this steel after quenching from the optimal temperature of 850-870°C is negligible, and does not exceed 12%. The hardness, resilience, bending strength, and residual stresses were determined in accordance with Davidenkov's method during the gradual one-sided pickling of specimens in an electrolyte (45% H2SO 4 + 45% H3PO ~ + 10% H20) at 80°C.

Special features of delayed fracture of welded joints in high strength, medium alloy steels

Special features of delayed fracture of welded joints in high strength, medium alloy steels

Examination of the cold cracking resistance of welded joints in high strength, medium alloy steels by the implant method

Examination of the cold cracking resistance of welded joints in high strength, medium alloy steels by the implant method

Production of high-strength parts for constructional applications from multicomponent iron-base charges

Calculation of the activity of carbon in multicomponent compositions enables a suitable choice to be made of compositions of alloyed charges made up of individual powdered elements (the base material being an iron powder), from which materials can be obtained with strength properties approaching those of rolled medium-alloy steels. The strength of such composites is determined by structure-formation processes, particularly those taking place in contact zones. The main role in these processes is played by the mobility of carbon.

Effect of multilayer welding on the structure of the heat-affected zone in medium-alloy steels

1. After thermal cycling to simulate multilayer welding, the structure of medium-alloy bainitic steels (14Kh2N3MA) does not differ from that of samples subjected to a single-layer welding cycle. After the thermal cycle simulating multilayer welding one observes only an increase in the etchability of austenite grain boundaries in reagents containing picric acid. A high concentration of phosphorus is observed in austenite grain boundaries. 2. The lower resistance of the samples to cold cracking in the heat-affected zone of multilayer weld seams can be explained by the lower cohesive strength of existing austenite grain boundaries due to segregation of phosphorus in the boundaries. 3. To reduce the susceptibility of medium-alloy steels to cold cracking we recommend the optimal procedure for multilayer welding.

Sound radiation of heated metal cylinder under impulsive loading

In experimental work reported in this paper, the sound radiation of heated metal (medium alloy steel) cylinder subjected to longitudinal impact load has been studied in some detail. The data show that the attenuation rate and spectra of sound radiation from metal cylinder at elevated temperature (100°–250°C) are different from one at normal temperature (20°C). The attenuation rate first decreases with increasing temperature, has a minimum value of about 160°C and increases rapidly on the high temperature side (180°–250°C). The experimental data also showed that increased temperature caused a shift in the spectra. Effects of various parameters on sound radiation of metal cylinder are discussed.

Physicomechanical and damping properties of high-strength medium alloy steel

1. In type 34KhN3MF constructional steel, uniform distribution of structural defects due to double hardening and subsequent dispersion hardening, particularly as a result of type Me3C special carbides precipitated from the martensite during tempering, provides a quite high combination of damping capacity, strength, ductility, and impact strength. 2. It is desirable to increase the damping capacity of steels of this type by intensifying the mechanism of magnetomechanical hysteresis, which occurs most fully when the matrix of the steel is ferrite, particularly with high-temperature tempering. At the same time, carbide phase inclusions have the most suitable compact form for the combination of mechanical and damping properties. 3. The defectiveness of the α-phases and the austenite content have a substantial influence on the damping properties of the steel. The following correlations were established. The lower the defectiveness of the steel, the higher the characteristics Q D −1 (low amplitude), tanα, and Q M −1 , and the lower the paramagnetic austenite content, the higher the value of Q M −1 .

Effect of carbon on resistance to fracture of structural steel

1. Changing the carbon content within broad limits has practically no effect on the resistance to fracture of medium-alloy structural steel with the same strength (σb) after quenching and tempering. 2. The essential factor is the method of obtaining the strength level. At the same strength, the steel with a structure of low-temper martensite has higher resistance to fracture than the steel with high-temper martensite.

Kinetics of crack growth in maraging and medium-alloy steels during low-cycle impact fatigue tests

1. The duration of the period of crack nucleation in steels N18K9M5T and 30KhN2MFA varies little with the magnitude of cyclic stresses. 2. A period of slow crack growth is observed in steels 30KhN2MFA and N18K9M5T at σmax=165 kgf/mm2 and is characterized by fatigue microbands in the fracture-ductile in the maraging steel, brittle in the medium-carbon steel. With increasing crack length (period of accelerated crack growth) the area occupied by microbands in the fracture decreases and the percentage of dimpled fracture increases. 3. At high cyclic stresses (σmax=260 and 360 kgf/mm2) the period of slow crack growth is absent in steels 30KhN2MFA and N18K9M5T. 4. The rate of crack growth determined by the difference of electrical potentials is in satisfactory agreement with the width of fatigue microbands, particularly in the period of slow crack growth. In the period of accelerated crack growth it is somewhat higher than the width of microbands. 5. The high regularity of fatigue microbands in the fractures of steel N18K9M5T indicates greater evenness of the properties determining the resistance to fracture at high cyclic impact loads than for steel 30KhN·2MFA.

A theory for fatigue crack propagation

A new continuum mechanics model is developed for predicting fatigue crack propagation rates using a fracture mechanics approach. The model demonstrates the critical dependence of fatigue crack growth on the fatigue ductility exponent, the fatigue ductility coefficient, the elastic modulus and the fracture toughness; it is related to the stress intensity range, implying that fatigue crack growth is critically dependent upon the condition at the tip of the crack. Four materials are studied, namely a creep resistant stainless steels, FV535; a 2 1 2 per cent nickel-chromium-molybdenum direct hardening steel, 2S96D; a nickel base heat resisting alloy INCO 901; and a ferrous alloy containing titanium carbide in a medium alloy tool steel matrix, known as Ferrotic C. The developed model provides a means of predicting crack propagation rates based on mechanical properties, and the simplified model provides a fundamental basis for a more general form of the Paris relationship.

Transformation from austenite in alloy steels

This paper is concerned with the direct transformation of austenite at high temperatures to form ferrite and alloy carbide dispersions. The ferrite/austenite interfaces vary from high energy random boundaries to low energy planar boundaries which grow by step propagation, while the alloy carbide morphologies include a pearlitic form, fine fibers and fine banded arrays of particles. It is shown that these morphologies are closely related to the mode of growth of the ferritic matrix. The role of various alloying elements on the carbide dispersion is examined, and the effects of other metallurgical variables on the banded dispersions are discussed, including factors which influence the dispersion stability. The mechanical properties of directly transformed alloy steels are shown to depend largely on the ferrite grain size and the state of the carbide dispersion. Micro-alloyed steels subjected to controlled rolling provide an excellent example of the achievement of high strength and toughness levels by control of these variables. The paper finally attempts to show how such benefits can be achieved in low and medium alloy steels, and in particular where resistance to creep failure at elevated temperatures is an important property.

Relationship between the strength level and toughness for medium-alloy constructional steels

Relationship between the strength level and toughness for medium-alloy constructional steels

BRAKE DIE

Abstract BRAKE DIE is a medium-alloy tool steel heat treated at the mill by oil-quenching and tempering to develop the best combination of properties. It is used for all types of dies on hand-operated and mechanically operated press brakes for the forming and bending of sheets, strip and other flat-rolled metallic and nonmetallic materials. It also will give good service in any application requiring wear resistance, toughness, high mechanical properties and good machinability. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: TS-302. Producer or source: Bethlehem Steel Corporation.

Resistance to fracture of welded joints of medium-alloy steels

1. The region of plastic deformation during fracture increases with increasing coefficient n1. This refers to steels in which the initial section of plastic deformation described by the strengthening coefficient n1 on the strain diagram is fairly long. 2. The energy spent in fracture calculated by the method of thermoelectric pulses and serving as the characteristic of rapid crack growth in sheet materials is in most cases smaller than the energy determined by Drozdovskii's method. 3. The weakening of the welded joint as compared with the base metal differs in different stages of fracture, which must be taken into account in determining the permissible stress.

The interrelationship of the composition of medium alloy weldable steels with strength under diaxial tension

1. A method is proposed for testing in diaxial tension which makes it possible to record the total deformation of the material at the failure stress. 2. It was established that the increase in strength in diaxial tension of weldable medium alloy steels occurs up to the value of the tensile strength, which is 200 kg/mm2 at 0.38–0.40% C. this places in doubt the desirability of the present use of the method of welding high pressure vessels with the use of low carbon (C≤0.2%) low strength weld wires. 3. It was shown that the alloy system has an influence on the deformation capacity of the material in diaxial tension by changing the elements of the structure, in particular the size of the martensite grains and the homogeneity of the distribution of carbon in it. The character of the action of the primary alloying elements on the properties of weldable steels was studied. 4. It was established that with an increase in the alloying element content the coefficient of reduction of wall thickness (ψ) of the base and the weld metal in diaxial tension decreases. An acceptable value for the coefficient of reduction of wall thickness is obtained by limiting the total content of alloying elements to that necessary to obtain the required hardenability in the steel.

Effect of small palladium additions on the hydrogen permeability of medium-alloy steel

Effect of small palladium additions on the hydrogen permeability of medium-alloy steel

Increase in the strength of steel with strain aging of martensite

1. Strain aging of martensite in low-and medium-alloy steels with 0.09–0.35% C substantially increases the strength with a fully acceptable decrease of the ductility and toughness. 2. To obtain a good combination of mechanical properties with strain aging of martensite in lowalloy steels it is necessary to have the optimal carbon concentration (0.2–0.3%), to ensure sufficient and even deformation of the quenched steel through the section, which is achieved with over 5% reduction, and to use high-temperature thermomechanical treatment as the preliminary treatment.

Multistage heat treatment

Multistage heat treatments have been used to clarify transformation mechanisms and to provide a basis for reducing heat treating time in commercial practice and/or obtaining improved properties. The influence of stepped transformation on the kinetics of the bainite reaction is examined and the results suggest means for improving the hardenability of medium alloy steels. The application of double aging treatments to age hardening systems also is examined.

Composition effects in vacuum-quantometer analysis of medium-alloy steels

Composition effects in vacuum-quantometer analysis of medium-alloy steels

Mechanism of strain aging of martensite

1. Deformation (rolling) of quenched low-carbon medium-alloy steel improves the strength characteristics, with retention of good plasticity and ductility. 2. The properties of martensite after deformation depend on the extent of development of the strain aging process. 3. The development of the strain aging process during deformation of martensite and during subsequent heating depends on the rolling reduction, tempering before rolling, and the carbon content of the steel. 4. The best combination of mechanical properties for steels susceptible to irreversible temper brittleness is attained by deformation of martensite tempered at low temperature with 15–20% rolling reduction.