Energy-saving technology for the preliminary heat treatment of large forgings

Bashnin, Yu. A.; Mernik, É. B.

doi:10.1007/bf00700364

Cited by 3 publications

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“…The dark network is accompanied by a reduction of fatigue strength by 40-75%, and threshold strength. The dark network adversely influences the properties of nitrocarburized parts; consequently, it should be avoided [20]. The microstructure of a nitrocarburized layer after quenching and low tempering consists of tempered martensite, carbonitrides in an outer part of the layer and retained austenite (Fig.…”

Section: Resultsmentioning

confidence: 99%

Ensuring the Quality of Self-Tapping Screws by Replacing the Thermochemical Treatment Line

Molochkova

Zvyagina

Abarovich

2022

MSF

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The paper compares the technical characteristics of two thermochemical treatment (TCT) lines for self-tapping screws at OJSC MMK-Metiz. Quenching on TCT line 1 is carried out in the furnace by AUTOMATION SERVICE, while quenching on TCT line 2 is carried out in the furnace by KOHNLE. The authors described quenching and tempering schedules in these two furnaces, studied the microstructure of screws at all process stages, determined technical parameters and properties of finished products after thermochemical treatment. The research showed that the best performance had TCT 2 by KOHNLE. The metallographic analysis indicated more stable parameters of the layer thickness after nitrocarburizing, core and surface hardness, which was in full compliance with regulatory documents. By introducing a better structure of a new TCT line by KOHNLE, a TCT process period became shorter, and a range of self-tapping screws might be extended entailing a higher output of finished products.

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Section: Resultsmentioning

confidence: 99%

Ensuring the Quality of Self-Tapping Screws by Replacing the Thermochemical Treatment Line

Molochkova

Zvyagina

Abarovich

2022

MSF

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“…The difference in the purposes of the preforms, the wide range of the steels used, and the various methods of their melting complicate the choice of the optimum variant of antiflake heat treatment by the enterprise. This explains the existence of various regimes of such heat treatment, which are often based only on the practical experience of the enterprise and thus are far from being optimum, which is explainable by inadequate development of the theory of antiflake heat treatment and the use of out-of-date equipment [42]. The widely used technology of antiflake heat treatment of large forgings is characterized by a long duration (up to 15 -16 days, i.e., 380 h), which decreases the efficiency of thermic furnaces and increases the consumption of fuel [43].…”

Section: Mechanism Of Flake Formation Role Of Hydrogen Redistributiomentioning

confidence: 96%

“…This explains the existence of various regimes of such heat treatment, which are often based only on the practical experience of the enterprise and thus are far from being optimum, which is explainable by inadequate development of the theory of antiflake heat treatment and the use of out-of-date equipment [42]. The widely used technology of antiflake heat treatment of large forgings is characterized by a long duration (up to 15 -16 days, i.e., 380 h), which decreases the efficiency of thermic furnaces and increases the consumption of fuel [43]. Generalization of experience in antiflake heat treatment of large forgings in Russia allows us to consider critically the regimes used and outline ways for their optimization and standardization.…”

Section: Mechanism Of Flake Formation Role Of Hydrogen Redistributiomentioning

confidence: 96%

“…This provides fuller decomposition of austenite and accelerates diffusion emission of hydrogen from the forging into the atmosphere, because the periodically formed austenite "jacket" acts as a diffusion pump. As a result, the total duration of the AFHT is decreased by 16 -18%, i.e., by 4 days [43].…”

Section: Mechanism Of Flake Formation Role Of Hydrogen Redistributiomentioning

confidence: 98%

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Hydrogen and flakes in steel

Voronenko

1997

Met Sci Heat Treat

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Flakes are special discontinuities in steel parts that have the form of silver-colored spots on fracture surfaces or thin hair-like cracks on a ground and etched template. They appear and grow after a considerable incubation period, often in the operation of the part, which makes them a dangerous defect. Depending on the dimensions, number, and position in the metal, flakes can decrease the toughness and ductility of steel to zero and reduce markedly the service life of steel parts and structures, causing unexpected and serious failures. The present review briefly generalizes recent works devoted to the formation of flakes in steel.Metallurgists encountered flakes as early as in the first world war in mechanical treatment of large preforms for gun barrels. Thousands of research papers and several monographs [1 -5 and other works] have been published by Russian specialists since that time but the problem has not ceased to be important. For a long time metallurgists could determine neither the mechanism nor the causes of the formation of flakes. Lengthy and intense discussions of the causes of their formation have shown that this phenomenon should be associated with the effect of hydrogen and internal stresses. States of hydrogen in steel.It has been established that hydrogen in steel can be present in various states, namely, atomic-protonic hydrogen dissolved in the crystal lattice ("free," diffusion mobile), atomic hydrogen bound to defects of the crystal structure (dislocations, vacancies, intergrain and interphase boundaries), molecular hydrogen bound with micro-and macrovoids, hydrogen bound chemically to hydrideforming metals (Ti, Nb, V, Zr, rare-earth metals), hydrogen bound chemically to nonmetals (C, O, S, N), for example in an oxidized state in the form of water vapor adsorbed in pores and hydroxyl groups incorporated in nonmetallic inclusions. There are data that hydrogen forms compounds of the solidsolution type with some alloying elements in steels and can be dissolved'in the carbide phase, i.e., can have the form of hydrocarbides [ 1, 2, 5 -7].It is assumed that the process of formation of flakes is caused only by the portion of hydrogen that can move over the volume of the metal, i.e., is in an atomic-protonic state. However, at present there are no reliable methods of fractional separation of different forms of hydrogen [ 1 ].The authors of [8,9] studied the forms of existence of hydrogen in metals of the Fe group by the method of degassing specimens in heating. The hydrogen content in the specimens Prometei Research Institute of Machine Materials, Nizhnii Novgorod, Russia. and the distribution over its various forms were determined by integrating the corresponding curves describing the dependence of the rate of emission of H 2 on the temperature. The specimens had various initial states (cast, forged, hydroextruded) and the corresponding amounts of structural defects. The thermokinetic heating curves of all the metals had two well-defined groups of peaks corresponding to tow-temperature (at 100-650...

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“…Наличие дефектов металлургического производства приводит к значительному снижению эксплуатационной стойкости подшипников, поскольку большинство дефектов является концентраторами напряжений и очагами зарождения трещин под действием знакопеременных нагрузок [1].…”

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Technology of calibrated wire production for bearing rolling elements manufacturing

Belash,

Kozyreva,

Belash

2023

Litʹë metall.

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The article considers technological schemes of cold‑formed wire production for bearing rolling elements production. Several technological schemes of wire production are considered. The paper presents a step‑by‑step development of drawing technology of alloyed (chromium) bearing steel grade. Problems arising at drawing of bearing steels are described. The reason of formation of “flaking” on the surface of rod is revealed. Ways of solving the problem of unsatisfactory drawing of wire from bearing steel grades are stated.Relevance and novelty of technical and technological solutions of the present work are caused by the absence of production of calibrated wire for manufacturing of rolling elements of bearings on the territory of the Republic of Belarus. The development of this type of production will allow to increase the production of high‑tech products with a deep degree of processing (calibrated wire) for the growth of profitability and efficiency indicators. Creation of production of calibrated wire for manufacturing of rolling elements of bearings will allow to reach new consumers of metal products with increase of added value of finished products.

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Energy-saving technology for the preliminary heat treatment of large forgings

Cited by 3 publications

References 0 publications

Ensuring the Quality of Self-Tapping Screws by Replacing the Thermochemical Treatment Line

Ensuring the Quality of Self-Tapping Screws by Replacing the Thermochemical Treatment Line

Hydrogen and flakes in steel

Technology of calibrated wire production for bearing rolling elements manufacturing

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