Steel 5KhNM Research Articles

Improving the technology of chemical-thermal treatment of tool steels

The paper presents data on the study of the intensification of chemical-thermal treatment processes. Diffusion saturation of the surface of steels and alloys is most often carried out under high-temperature isothermal or isothermal-step exposure with complete recrystallization of steel into an austenitic state. This leads to overheating — the structure and mechanical properties, in addition to hardness and wear resistance, deteriorate. the main regularities and mechanisms of boration of ferritoperlite steels are investigated and described. It is shown that cyclic heating and cooling significantly accelerate the kinetics of the CTO process of iron-carbon alloys. It was found that thermal cycling during boration leads to an increase in the layer thickness up to 80% on carbon steels, with an increase in the degree of alloying, the effect decreases from 70% (cast steel 5KHNM) to 20% (steel X12M). With an increase in the carbon content in steel, the depth of the borated layer decreases both after isothermal high-temperature boration and after thermocyclic boration.

Structure and Properties of Bimetallic Tools from Steels 5KhNM/R6M5

The parameters of the process of production of flawless bimetallic billets from powder steel R6M5 (the external layer) and 5KhNM (the core) are assessed by mathematical simulation. The bimetal has mechanical properties comparable to those of cast and deformed high-speed steel, a more homogeneous structure, and a much lower cost.

Investigation of the variation in the size of samples made of 5СNM steel under thermal diffusion saturation with powder mixtures containing boron and copper

The change in the dimensions of parts after diffusion saturation of alloyed steel 5KhNM with boron and copper is investigated. Diffusion layers obtained on samples with different compositions of the saturating mixture are described. It is shown that when carrying out experiments on saturation of samples in a medium of powders with boron and copper, diffusion layers with an acicular structure with a thickness of 220...330 μm are obtained, and the increase in the observed size was from 44 to 135 μm, depending on the composition of the powder mixture. The properties of diffusion layers have been studied, including the distribution of microhardness and chemical elements at different distances from the surface.

Acoustic control of the residual stresses in steel 5KhNM samples

Heat treatment (HT) is one of the main and most important stages of the technological cycle of manufacturing metal products. Residual stresses (RS) arising in metals upon their heat treatment significantly affect the service life of the products. The goal of the study is developing a technique for non-destructive acoustic testing of the residual stresses in steel samples. The method is based on the phenomenon of acoustoelasticity, i.e., the dependence of the acoustic characteristics on the parameters of the environment under study. The fields of residual stresses in rectangular samples made of die steel 5KhNM were formed using various HT modes, including cooling both in traditional media (water, oil, air) and using a water-air mixture (WAM). Control of the ratio of water-air parameters as well as the direction of the WAM flow provided the desired cooling rate and locality of the process. It is shown that the level of residual stresses decreases with the distance from the cooling plane, the microstructure and elastic characteristics of the material also change. The effect of cooling on the formation of temperature fields and the value of residual stresses was analyzed using computer simulation (CAE ANSYS program). The values of the characteristics of 5KhNM steel formed a set of input parameters in simulation. The simulation results proved the experimental data. Acoustic measurements carried out on the measuring and computing complex «ASTRON», provided determination of the velocities of elastic (longitudinal and transverse) waves and the elastic moduli of the material under study. The RS values obtained by the acoustic method were compared with the data obtained by the X-ray method. It is shown that the differences between the values measured by acoustic and X-ray methods do not exceed 10%. The results can be used in a production environment when measuring the residual stresses by the acoustic method in large-sized dies made of 5KhNM steel.

Application of chips of steel 5KhNM in electroslag surfacing of dies in current-conducting mold

Application of chips of steel 5KhNM in electroslag surfacing of dies in current-conducting mold

Применение стружки из стали 5ХНМ при электрошлаковой наплавке штампов в токоподводящем кристаллизаторе

Применение стружки из стали 5ХНМ при электрошлаковой наплавке штампов в токоподводящем кристаллизаторе

Structure and Properties of Electro-Explosive TiC–Ni–Mo Coatings of Die Steel after Electron-Beam Treatment

In this paper, we studied the phase and elemental composition of the surface layer of die steel 5KhNM subjected to electro-explosive sputtering deposited composite TiC–Ni–Mo coating and subsequent pulsed irradiation with a high-intensity submillisecond electron beam. The modes of electron-beam processing providing the formation of a dense, with a mirror gloss, surface layer with a submicrocrystalline structure based on titanium carbide and intermetallic compounds based on Mo, Ni, and Ti are determined. The electron-beam processing of an electro-explosive coating in the melting mode is shown to lead to the formation of a structurally uniform and concentration-uniform surface layer. TiC–Ni–Mo coatings have a 1.26 times higher wear resistance compared to die steel 5KhNM used as a substrate. The microhardness of the formed coatings is 450–2400 HV, the nanohardness is 25.5 GPa, and the modulus of elasticity is E = 398 GPa.

Ways to Improve the Quality of Die Steel 5KhNM

There was performed an analysis of influence of the deoxidation technology, hydrogen content and high concentration of titanium in steel 5KhNM (Rus. “5XHM”) on quality of die blanks, evaluated based on the results of the ultrasonic test.The fractographic examinations of fractures and the X-ray microprobe analysis of chemical composition of non-metallic inclusions were conducted, the evaluation of macro- and micro-structure of a die blank with high titanium content was performed.It is demonstrated that defects of dies from steel 5KhNM (Rus. “5XHM”) are cracks from merged flakes and micro-flakes; in most cases large concentrations of sulphides appeared to be hydrogen collectors for formation of flakes and micro-flakes.

Study of force, strain, and energy criteria for the low-cycle strength of steel 5KhNM in the presence of stress concentrators

The stability of force, strain, and energy criteria for strength in zones of a structural concentrator in relation to the number of loadings, nominal stress intensity, and lowcycle strain curve kinetics is analyzed. It is shown that as a low-cycle failure criterion for a structural element it is desirable to use the local specific energy of elastoplastic deformation as the most stable physical parameter.

Effect of the parameters of dynamic loading on the ratio of static and dynamic hardness

On the basis of Prandtl's relation the effect of the magnitude of deformation and of the strain rate on the dynamic hardness was analyzed. A semiempirical equation was obtained which correlates static and dynamic hardness with a view to the parameters of static and impact loading of the indentor. The theoretical and experimental results of hardness measurements on specimens of steel 5KhNM in the range of static hardness 175–530 HB are compared.

Structure and properties of die steel 5KhNM produced from primal and ordinary metallurgical charge

1. Die steel 5KhNM melted from a primal charge (SI) has better strength and ductile characteristics than steel melted from an ordinary metallurgical charge (OMC). 2. Steel melted on the basis of SI has a lower content of constant (S, P) and residual (nonferrous metals) impurities (one half to one quarter), and also of nonmetallic inclusions than steel melted on the basis of OMC. 3. In the temperature range 300–500°C (the operating temperature range of die steel) steel melted on the basis of SI has much better wear resistance than steel melted on the basis of OMC.

Comparative evaluation of the crack resistance of tool steels

1. It is recommended to use as parameters for calculating crack resistance the nominal stress intensity factors: KJ, determined by the method of the J-integral, taking crack growth into account, and Kδ, calculated according to the critical crack opening δc using the theoretical values of the rotational factor. The use of Kδ is preferable because of the conservativeness of the evaluation in the range of operating temperatures of heavy-duty hot-forging dies. 2. In regard to crack resistance in the range of the operating temperatures of forging dies, steel 5KhNM is better than steel 4Kh5V2FS.

Operating stability and mechanical properties of type 5Kh2SF steels for hot-forming dies

In the molybdenum-free steels, post-temper hardness increases by HRC 3-4 as the vanadium content is increased from 0.16 to 0.90%, and it varies from HRC 37 to HRC 43 as a function of quenching temperature (Fig. la). A rather high temper stability is characteristic for the molybdenum-free steel 5Kh2SF from a commercial melt with 0.57% C. The lowest temper stability is observed in the case of steel 5KhNM.

Heat treatment of steel 5KhNM to improve the wear resistance of equipment for explosive forming

Heat treatment of steel 5KhNM to improve the wear resistance of equipment for explosive forming

Pore geometry of silicide layers on steel 5KhNM

1. Porous layers of different thickness are formed at the surface of specimens by siliciding steels with a vapor method. The pores are predominantly cone shaped. 2. The depth of pore occurrence in silicide layers on steel 5KhNM is greater than in layers on carbon steels, and this is evidently due to the stimulating effect of chromium on pore formation.

Properties of steel 5KhNM modified with nitrides

1. Steel 5KhNMAF has higher resistance to tempering up to 650° and retains higher strength at elevated temperatures (up to 600°) than standard steel 5KhNM. 2. Hot working dies of steel 5KhNMAF have a longer service life than dies of standard steel 5KhNM. 3. Hot working dies made of steel 5KhNMAF modified with the nitride-containing ZhVdN master alloy should be quenched from 950° and tempered at 500° for 2–3 h.

Effect of electroslag remelting on the properties of die steel 5KhNM

1. ESR makes steel 5KhNM-Sh more resistant to heat cracks. 2. The original fatigue strength of steel 5KhNM-Sh is about three times higher than that of steel 5KhNM, but the low-cycle fatigue strength is highest at a smaller number of thermal cycles. 3. Thermal cycling with a small number of thermal cycles increases the low-cycle fatigue strength and can be considered one method of strengthening steel. 4. There are almost no changes in the structure of the steel during thermal cycling.

Production of cyclinder sleeves of steel 5KhNM by means of electroslag casting

Electroslag casting makes it possible to obtain high-quality castings of steel 5KhNM in place of forgings. Melting can be conducted in a welded steel crystallizer that can be prepared without high material or labor costs.

Wear resistance of broaching bits in relation to boriding and heat treatment

The use of electrolytic boriding and heat treatment for broaching bits of steel 5KhNM makes it possible to increase the wear resistance 2–5 times.

Carbonitriding of forging tools of steel 5KhNM in the process by heating to quenching temperature

Carbonitriding of forging tools of steel 5KhNM in the process by heating to quenching temperature