The effect of tempering temperature on the coercive force of high-carbon steels measured at room temperature and a temperature above the curie point of cementite

The role of cementite in the formation of the H _c of carbon steels after quenching and tempering is determined based on analysis of dependences of the coercive force of У9A steel in the measurement temperature range from the temperature of liquid nitrogen to the cementite Curie point. It is shown that the key contribution to the formation of the maximum in the H _c (T _temp) dependence measured at room temperature is due to the magnetic hardness of cementite, whose maximum lies at T _temp = 500°C. The coercive force measured at 250°C is mainly related to the interaction of the domain walls of the ferrite matrix with nonferromagnetic inclusions of cementite, the maximum of which is at T _temp = 400°C, thus causing a shift of the maximum in the H _c (T _temp) dependence measured at the temperature above the cementite Curie point toward lower tempering temperatures.     

The effect of the plastic tension of steels on the dependences of the coercive force on elastic compressive stresses

The effect of compressive stresses σ^? on the coercive force H _c of annealed isotropic low-carbon steels, which were preliminarily subjected to plastic tension ? _pl ⁺ of different values, has been studied. It was shown that the shape of hysteresis loops H _c (σ^?) and their changes with increasing ? _pl ⁺ are related to induced residual compressive and tensile stresses, which result from plastic tension, and also to the occurrence of plastic compressive deformations ? _pl ^? because of the Bauschinger effect. The causes of the openness of the first cycle of the H _c (σ^?) dependence and also for the occurrence of maximum of the H _c (σ^?) function in the ascending branch of this cycle are considered. A procedure for determining the residual tensile stresses, which result from the preliminary plastic tension, has been suggested and achieved experimentally. It was shown that the magnetoelastic change of magnetization, which is observed in the plastic compression, can serve as an indicator of these deformations σ _pl ^? .     

Correlation of the impact elasticity of cast steels with their coercive force

The character of the correlation of the impact elasticity of cast and subsequently normalized and thermostrengthened steels 08XΓΦЛ and 08XΓTЛ with their coercive force is studied. Such a correlation in the form of a curve characterized by a maximum is observed for both low-carbon and low-alloyed hot-rolled steels.     

Magnetic properties of cementite and the coercive force of a Fe-5 at % C alloy after hardening and tempering

The role of cementite in the mechanisms of formation of H _c for specimens of a model high-carbon Fe-5 at % C alloy after hardening and tempering is determined from the analysis of the temperature dependences of the coercive force measured in the range from the temperature of liquid nitrogen to the Curie point for cementite. This analysis is based on the different characters of the temperature dependences of the contributions to H _c due to cementite as weakly magnetic inclusions at which the matrix’s domain walls are decelerated and cementite as a hard magnetic phase. It is shown that the magnetic hardness of cementite makes the main contribution to the formation of the coercive force in the region of medium and high tempering temperatures.     

The influence of biaxial elastic deformation on the coercive force and local remanent magnetization of construction steels

The influence of biaxial elastic tension-compression and tension-tension deformation on the coercive force and remanent magnetization of Cτ3 steel and 09Γ2C pipe steel cross-shaped specimens is studied. It is shown that coercive force grows monotonically with increasing load in the direction of compression under elastic tension-compression deformation and almost does not change under elastic tension-tension deformation. The local remanent magnetization decreases for all the considered types of biaxial elastic deformation. The possibility of using these methods for the evaluation of the stressed state of complexly deformed carbon steel products is discussed.     

Measuring coercive force in local domains of a sample

A method has been proposed for determining the coercive force in local domains of bulk samples magnetized normally to the surface. The method is based on local measurement of the normal magnetic-field component at the sample surface, in the gap between the sample and the pole of a magnetizing device. The coercive force is determined by the magnetic field for which local magnetization in the measured domain becomes zero. Conditions for the correctness of coercive-force measurements have been established.     

A simple instrument for the measurement of maximum occlusal force in human dentition

A simple instrument for the measurement of maximum occlusal force has been developed and the results of an initial clinical trial have been reported. The maximum occlusal force in subjects with dentures was significantly lower than in a group of young male subjects with natural dentition. In the young males the bite force between the molars and premolars was significantly greater than between the incisors. The maximum bite force was not dependent on position for subjects with dentures.     

On new possibilities for making local measurements of the coercive force of ferromagnetic objects

The possibility of reducing the influence of both the gap in a transducer-object combined circuit and the shape of tested objects on the results of local measurements of their coercive force is investigated. It is shown that additional measurements of the maximum magnetic flux in the circuit and the tangential component of the magnetic field on the surface of the tested area of the object, which is retained after the magnetizing current is turned off, allow a substantial decrease in the corresponding errors.     

Using a corrected least-squares procedure and accounting for structural parameters when analyzing the correlation between the impact strength of low-alloyed steels and their coercive force

The use of a corrected least-squares procedure that takes the error of impact-strength estimation into account, as well as several structure parameters, such as the equiaxial grain size number, Widmanstätten ferrite grain size number, and bainite percentage, allowed us to substantially improve the constraint equations between the impact strength and coercive force for a group of specimens. These specimens were sampled from no. 60 flange beams made of 09Г2 steel and exhibited no preliminary correlation between these parameters.     

The effect of cementite on the formation of the magnetic hysteresis properties of thermally treated carbon steels

The role of cementite in the mechanisms of formation of the coercive force of high-purity 60 and 13 model steels and 9A and 12A industrial steels after quenching and subsequent medium- and high-temperature tempering is determined from the analysis of the temperature dependences of the coercive force. It is shown that cementite as a hard-magnetic phase plays an important part in the formation of the dependence H _c (T _temp) measured at room temperature. The maximum contribution caused by the coercivity of cementite to H _c of the model steels is proportional to the volume content of cementite. In the industrial steels, an effect on the coercivity of cementite is produced by carbideforming unavoidable impurities.     

Regularities of the change in the coercive force under biaxial asymmetric deformation of steel 3

The change in the coercive force under biaxial asymmetric (tension and compression in mutually perpendicular directions) cyclic deformation of cross-shaped steel 3 specimens in the elastic region of deformations was studied. Specimens were deformed beforehand under biaxial asymmetric loading to various degrees of plastic deformation. It was demonstrated that the elastic-deformation dependences of the coercive force measured along the tension and compression directions are qualitatively similar to those under uniaxial tension or compression. It was also shown that, under cyclic elastic loading, these dependences are reversible for well-annealed steel and have a hysteresis that expands with increasing degree of plastic deformation for plastically deformed steel. The possible causes of the hysteresis in the dependence of the coercive force on the elastic cyclic deformations under biaxial loading are discussed. It was supposed that the hysteresis of the coercive force was caused by the appearance of free (not bound in carbide phases) carbon atoms playing the role of interstitial impurity atoms for the α-iron lattice in plastically deformed carbon steels. The possibility of estimating the stressed-strained state of steel under biaxial loading using a magnetic method was discussed.     

A permanent-magnet-based attached instrument used to inspect articles on the basis of their coercive force

An attached magnetic instrument that uses two permanent magnets to magnetize and demagnetize an article is considered. When one of the magnets is set at a fixed angle, the rotation angle of the other magnet is proportional to the coercive force of an article and is used as the tested parameter.     

Effect of the carbon content on the magnetic and electric properties of thermally treated carbon steels and the possibilities of testing the quality of tempering of articles produced from them via the eddy-current method

The magnetic and electric characteristics of 4.7-, 2.2-, and 1.5-mm-thick hardened and tempered carbon-steel specimens with a carbon content of 0.35–1.02% have been studied. The relations of these characteristics to the carbon content, structure, and hardness of the studied specimens are analyzed. The structural state, the thickness, and the acceptable limits of the carbon-content variation in carbon-steel articles, properties that allow the quality of medium-temperature tempering to be tested with the use of the eddy-current method, have been determined.     

On the influence of plastic deformations of low-carbon ferromagnetic steels on the changes in the shapes of their hysteresis loops and the field dependences of the differential permeability

It is shown that inflections in the hysteresis loops of Ст3 low-carbon steel after its plastic deformation are determined by the appearance of a magnetic state of the easy-plane type in a part of the grains. The residual compressive stresses were found at which the maximum possible number of jumps of 90° domain boundaries (DBs) are observed. An expression for the energy of a domain with a 90° DB was obtained. It depends only on the field, the residual stresses, and the angle between the field and the chosen easy axis (EA) of a grain that is located in the easy plane (EP). This made it possible to find the conditions for the onset of irreversible jumps of the 90° DBs to the EP and back. As a result of the proposed theoretical model, the values of the fields of the differential permeability μ _d (H) peaks were determined, which are observed in positive and negative magnetic fields on the descending hysteresis-loop back. The ratios of the magnitudes of these peak were also found.     

Coercive force of ferromagnetic steels under the biaxial symmetrical tension of a material

Patterns of coercive force variations of Ct.3 and X70 ferromagnetic steels under biaxial symmetrical tension within both elastic and plastic ranges of deformation were studied using X-shaped specimens. It was shown that the coercive force of isotropic polycrystalline materials increased during plastic deformation under biaxial symmetrical tension and was proportional to applied stresses (loads). Plastic deformation of materials with high initial coercive-force anisotropy along the principal directions (X70 steel) leads to an abrupt decrease in anisotropy and subsequent alternation of its sign. The patterns of a material’s coercive force behavior allow the coercive force to be used for estimating the stress-strain state (from both an increase in the coercive force and its variations during loading as compared to that of the initial material) of articles made from the studied steels under biaxial symmetrical tensile deformation.     

回火温度对35CrMo钢应力腐蚀性能的影响

研究了不同回火温度对35CrMo钢组织的影响,并在空气坏境、3.5%NaCl溶液和稀硫酸溶液中对35CrMo钢进行开缺口和未开缺口慢应变应力腐蚀试验。结果表明:在酸液中的35CrMo钢的力学性能下降最为剧烈;具有应力集中缺口的试样受腐蚀溶液影响大于未开缺口试样。淬火后在550℃回火40 min的试样在腐蚀介质中能承受的载荷相比其他工艺试样大,而在600℃回火的试样在腐蚀介质中持续的时间更长。