08kp Steel Research Articles

Development of fatigue test technology of sheet automobile materials

Ensuring the operability of the cars’ parts and components is one of the most topical problems in the modern automotive industry. Most of the car parts are under cyclic loads leading to materials’ destruction. Therefore, one of the important factors affecting the performance of products is the fatigue strength of the material. In this paper, the existing methods of fatigue tests are analyzed, their advantages and disadvantages are presented. The methodology of fatigue tests of sheet automobile materials was developed. The main idea of this methodology is that it enables to study the fatigue of sheet automobile materials based on single-plane pure bending. This scheme is very close to the conditions of the actual load of car body structural elements. The results of the study of fatigue strength obtained using this methodology allow studying the kinetics of the failure process, fixing the beginning of macrofailure, crack growth rate and, as a consequence, maintainability of the structure. Comparative tests enable to determine the material that best meets the operating requirements and provides the reduction of the failure rate of the car metal structures. In this paper, important characteristics of fatigue strength were obtained for a number of automobile structural steels 08kp and 20kp: service life to complete failure, fatigue limit, period to fatigue crack nucleation and rate of further propagation and, as a consequence, maintainability of the structure. So, for example, the number of cycles for 08kp steel to complete failure (262,000 cycles) and the period to fatigue crack nucleation (82,000 cycles) is greater, and the rate of further growth (5.38.10-5 mm/cycle) is lower than for 20kp steel (174,000, 68,000 cycles and 8.86.10-5 mm/cycle, correspondingly). Although these parameters were obtained at higher stress (265 MPa) for 08kp steel against only 235 MPa for 20kp steel. This explains the operating advantage of 08kp steel against 20kp steel in the process of car design. The obtained data enable to prevent failure of structural elements and parts under cyclic loads at the stage of car maintenance, and as a consequence, to increase the car operation safety, and to reduce the cost of repair

Cold Rolling of Steel Strips with Metal-Working Coolants

The efficiency of cold rolling of steel strip in the main depends on the quality of technological lubricant and its cost. In this regard, it is important to develop new compositions of effective metalworking coolants that are low cost and provide maximum reduction in the friction coefficient. We developed and tested the new compositions of metalworking coolants on the basis of vegetable oil and chicken fat. The metalworking coolants were tested in Donbas State Engineering Academy (DSEA) on a laboratory rolling mill, 100 × 100, in cold rolling of 08Kp steel. The efficiency of the coolants was determined by the stretch ratio λ and the friction coefficient μ in the deformation zone, which was found by the forward slip method. We found the metalworking coolant with 100% concentration of boric acid esters of mono- and diglycerides is the most effective in the rolling of thin steel strips. Thus, the new metalworking coolants (MWC) on the basis of boric acid esters of mono- and diglycerides, synthesized on the basis of sunflower oil, can be recommended for use in the rolling of structural steels on account of its availability, high efficiency and low cost.

Synthesis and barrier properties of a film polymer nanocomposite based on polystyrene and cadmium sulfide nanoparticles

A film polymer nanocomposite with nanoparticles of a chalcogenide semiconductor, CdS, in a polystyrene matrix was prepared on the surface of 08kp steel. The barrier properties of the synthesized two-layer film nanomaterial in a 3 wt % aqueous NaCl solution were evaluated by measuring the electrode potential of coated and uncoated specimens and were compared with those of polymer films without nanofiller and with Fe3O4 nanoparticles. Introduction of hydrophobic CdS nanoparticles into the polymer matrix leads to significant enhancement (by ∼20%, as compared to Fe3O4) of the barrier properties of the polymer nanocomposite.

Adhesion and barrier properties of polymeric nanocomposite films

Polymeric nanocomposite films with superparamagnetic Fe3O4 nanoparticles in polystyrene or poly(methyl methacrylate) matrices on the surface of 08kp steel were prepared. The adhesion of the synthesized two-layer film nanomaterials and their barrier properties in 3 wt % aqueous NaCl solution were studied in comparison with the unfilled polymer films. Adequate mathematical description of the influence of the nanoparticle concentration (0–10%) on the adhesion of the polymeric nanocomposites was made. The barrier properties of the polymeric nanocomposite films were evaluated by measuring the electrode potentials of the uncoated and coated specimens. Based on the experimental data obtained, the following nanocomposite was suggested as material for film deposition: poly(methyl methacrylate) + 5.6 wt % Fe3O4 with the nanoparticle size of approximately 10 nm. Films of this material ensure high adhesion (100%) and sufficiently good (86%) barrier properties.

Determination of the size of the fatigue prefracture zone by the method of phase-shifting interferometry

We consider a new method for determining the size of the fatigue prefracture zone (a new structural-mechanical parameter d* of constructional materials) by the method of phase-shifting interferometry, based on the results of a comparative analysis of the surface profile of metallic specimens in the neighborhood of a constructional stress concentrator prior to and after a certain quantity of loading cycles. To obtain interferograms in laser light, we applied a Twyman–Green interferometer. Using these results, we determined the 3-D distribution of plastic strains near the concentrator vertex, which enabled us to establish that d* = 256–268 μm for low-carbon 08kp steel at a load ratio R = 0.1. The obtained value of this parameter is in good agreement with data obtained by other methods.

Corrosion-protecting properties of products of pyridine quaternization with chloromethylated benzyltoluenes

Substituted N-benzylpyridinium chlorides were prepared by pyridine quaternization with chloromethylated mono-, di-, and tribenzyltoluenes. The inhibiting effect of the products on corrosion of 08kp steel in 20% solutions of HCl at 60°C and of H2SO4 at 80°C was studied.

Methods for the construction of the diagrams of fatigue crack-growth rate of materials

We study different parameters used for the construction of the diagrams of fatigue crack-growth rate of materials in the force, deformation, and energy approaches and tested for 08kp low-strength steel and 60 high-strength steel. The applicability of the dependences known from the literature for the evaluation of the crack-tip opening displacement and local strain energy at the crack tip is analyzed. It is shown that the range of local strains Δe* and the total range of dissipation of local energy in a loading cycle ΔW t * specify the fatigue crack-growth rate in the material and that the da / dN−Δe* and da / dN−ΔW t * diagrams are more sensitive to the structural and mechanical characteristics of the materials than the ordinary da / dN−ΔK diagrams.

Investigation of the Possibility of Using Additional Parameters in Pulsed Magnetic Testing of Rolled Steel Sheets in a Manufacturing Technological Flow

The laws of distribution of the normal, radial, and azimuthal components of the remanent magnetization field strength and the length of magnetized section for two-sided local pulsed magnetization of rolled steel sheets of 08kp steel annealed at various temperatures are investigated. It is shown that the maxima of these components and the length of the positive part of the normal component can be used for testing the quality of annealing of the above mentioned steel. The effect of displacement of a sheet on the testing results is estimated in determining the arithmetical and geometrical means of the parameters measured. The use of multiple correlation analysis significantly increases the correlation coefficients.

Enhancement of the durability of structural steels and their welded joints by plastic deformation

The fatigue and corrosion-fatigue resistance of low-alloy steels increases as degree of plastic prestraining increases to 29%. The resistance of the 08kp steel prestrained and hardened by surface plastic deformation and its welded joints to fatigue and corrosion-fatigue fracture is higher than for the 08GSYuT alloyed steel. The procedures of pneumatic shot blasting and shot blasting prove to be efficient methods for increasing the cyclic and low-cycle durability of welded joints both in air and corrosive media. The corrosive medium considerably decreases the low-cycle durability of welded joints of sheet steels. The effect of the medium is more pronounced for alloyed steels and becomes weaker as the amplitude of strains increases.

Fatigue failure resistance of deformed structural steels

1. The mechanical properties of the examined steels in static and cyclic loading change under the effect of plastic deformation but no correlation has been found between these changes. 2. Preliminary hardening of the steels characterized by low capacity for strain hardening in static loading slightly increases their fatigue resistance in air (by less than 30%). 3. The corrosion fatigue resistance tends to vary after plastic deformation of the steels in relation to their strain capacity. After hardening (22–29%) the resistance to corrosion failure at 105 cycles increases in the 40Kh, 07GSYuFT, and 08GSYuT steels (parameter A decreases) and decreases for 08kp, 20Kh13, and 14Kh17N2 steels (the value of A increases or remains almost constant). 4. Irrespective of the treatment method and lower values of the yield and tensile strength, 08kp steel has a higher resistance to fatigue in air and in a corrosive medium than the 08GSYuT and 07GSYuFT alloy steels.

Effect of low temperature on the initiation and growth of fatigue cracks in 08kp steel with different grain size

Effect of low temperature on the initiation and growth of fatigue cracks in 08kp steel with different grain size

Effectiveness of inhibitors in the hydrogen impregnation of low-carbon steel being elastically deformed

This paper presents an increatigation of the effectiveness of inhibitors in cathodic polarization of metal being elastically deformed. Wire specimens of 08kp low-carbon steel annealed in vacuum were tested at 1123 degrees K for 2 h. Similar experiments were made in inhibited acid. PGU-1 inhibitor, influencing the hydrogen impregantion, increases the strength and plasticity of specimens. However, with an increase in load the effectiveness of the inhibitor decreases. Fractographic analysis of fractures of 08kp steel specimens after tensile testing revealed that the fracture of nonhydrogen-impregnated specimens in air had a ductile character.

Protective coatings that increase the durability of thin-sheet 08kp steel

Tests were made on 115 • 6 • 0.8 mm samples using the known method [ 1 ] at a temperature of 20~ in bending using a symmetric cycle with a frequency of 8 Hz, which is characteristic of the operating loads of agricultural machinery [2, 3]. The samples were successively ground with emery paper of different grain size. The final grinding was done longitudinally with 0 grain size paper. Then the samples were degreased with acetone. The tests were made using a base of 106 cycles in air and in a corrosive medium in the original condition and after preliminary corrosion in the open air for 12 months. Since a film of electrolyte containing SOland C1ions [4] is formed on the surface of metal parts under atmospheric conditions, a solution of 0.5 N Na2SO 4 + 0.05 N NaC1 with pH = 6.7 was selected for the tests.

Effect of strain frequency on development of corrosion-fatigue cracks in 08KP steel

Effect of strain frequency on development of corrosion-fatigue cracks in 08KP steel

Properties of laminated steel-silver composite materials

1. The tensile strength σv (130 kg mm2) and microhardness HV (350 kg/mm2) of 08kp steel-Ag multilayer composite materials (MCM) substantially exceed both σv and HV of alloy mixtures of the same composition (65 and 150 kg/mm2, respectively) and σv and HV of 08kp steel (90 and 180–200 kg/mm2, respectively). 2. The gain in strength Δσv due to the work-hardening induced by rolling with a reduction of 70% is 95 kg/mm2 for the MCM, compared with 40 and 10 kg/mm2 for the steel and silver, respectively. 3. The coercive force HC of the MCM (48 Oe) is many times that of alloy mixtures of the same composition (8 Oe) or of 08kp steel (1–2 Oe). 4. Reducing the layer thickness to less than 100 A transforms the composite into a powder type material with a flaky structure. During the rolling of such a material, the flakes slide over one another, and both the thickness of the material and its properties remain unchanged.

Investigation of the structure and properties of 08kp steel previously loaded in tension

Investigation of the structure and properties of 08kp steel previously loaded in tension

Effect of vacuum annealing conditions on certain physicochemical properties of 08kp steel

Effect of vacuum annealing conditions on certain physicochemical properties of 08kp steel

Electron microscope investigation of the microstructure of 08kp steel quenched from the rolling temperature

Electron microscope investigation of the microstructure of 08kp steel quenched from the rolling temperature