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Abstract

The paper presents properties of HS6-5-2 high speed steel subjected to deep cryogenic treatment (DCT) and subsequent tempering at different temperatures. DCT process of HS6-5-2 steel leads to shifting of maximum hardness peak to the lower temperature and the reduction of the obtained maximum hardness by about 1 HRC. These changes in hardness may be due to the shifting of the stage of nucleation and growth of carbide phases to lower temperatures or the changes taking place in the matrix, connected with the additional transformation of the martensite proceeding during the isothermal martensitic transformation occurring at cryogenic temperatures and more extensively occurring precipitation processes, lowering the content of the carbon in the martensite, determining thereby its lower hardness.
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Authors and Affiliations

A. Ciski
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Abstract

This article presents the results of investigations of the effect of heat treatment temperature on the content of the carbide phase of HS3-1-2

and HS6-5-2 low-alloy high-speed steel. Analysis of the phase composition of carbides is carried out using the diffraction method. It is

determined that with increasing austenitising temperature, the intensification of dissolution of M6C carbide increases. As a result, an

increase in the grain size of the austenite and the amount of retained austenite causes a significant reduction in the hardness of hardened

steel HS3-1-2 to be observed. The results of diffraction investigations showed that M7C3 carbides containing mainly Cr and Fe carbides

and M6C carbides containing mainly Mo and W carbides are dissolved during austenitisation. During austenitisation of HS3-1-2 steel, the

silicon is transferred from the matrix to carbides, thus replacing carbide-forming elements. An increase in a degree of tempering leads to

intensification of carbide separation and this process reduce the grindability of tested steels.

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Authors and Affiliations

R. Kluz
J. Jaworski
T. Trzepieciński
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Abstract

The paper presents the possibility of the usage of the concfocal microscope for define the type of tribological wear present during the technical dry friction on the testing machine of the pin-on-disc T-01M. The pin was a remelted high-speed steel and the disc was made from sintered carbides. The surface layer of the high-speed steel was remelted with the electric arc with different parameters. The intensity of the electric arc current was changed, the scanning speed and the single, overlapping remeltings were used. On the basis of the 3D, 2D view of the surface friction of the pin (made from the remelted high-speed steel), disc (made from the sintered carbides) and the surface roughness profile run along the marked line, the presence of the abrasive wear can be defined with the description of the elementary wear processes due to the abrasive and/or adhesive wear.

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Authors and Affiliations

A. Dziedzic
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Abstract

The rolls for the hot rolling finishing stands are cast centrifugally as two or three-layer rolls. The working layer is called a shell. The material of the shell is selected according to the position of the respective roll in the final finishing stand of the rolling mill. Typically, a combination of rolls made of a high-chromium cast iron + indefinite cast iron or high-speed steel + indefinite cast iron is commonly used. Great attention has been paid to indefinite cast iron in recent years and this material received a number of modifications that led to the increase of material properties up to 20% in comparison to the ordinary indefinite cast iron. But the goals of the new generation of material for hot rollers were chosen higher: increasing of production about 30% and more. This material has specific physical properties, heat treatment requirements as well as rolling mill requirements as is stated in the paper. It is expected that introduction of this material will reduce the difference between wear of the front and finishing stands, which can extend rolling campaigns and have a positive effect on the reduction rolls exchanges, the grinding of the rolls and the reduction of downtime.

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Authors and Affiliations

T. Válek
Z. Kuboň
J. Kosňovská
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Abstract

The microstructure evolution of boron-bearing high speed steel roll materials after casting and tempering was investigated. The results indicate that as-cast boron-bearing high speed steel consists of martensitic matrix, retained austenite and different borocarbides. The as-cast alloy has a hardness above 64 HRC, and the borocarbides distribute along the grain boundaries. After RE-Mg-Ti compound modification treatment, obvious necking and broken network appear in the grain boundaries. The hardness of boron-bearing high speed steel roll materials reduces gradually with the increase of tempering temperature. Under the same conditions, the toughness of the modified roll material is higher than that of the unmodified roll material. Wear tests show that the wear resistance of boron-bearing high-speed steel modified by RE-Mg-Ti compound modification treatment is better.
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Authors and Affiliations

Cheng Xiaole
1
Hou Jianqiang
2
Fu Hanguang
1

  1. School of Mechanical and Electrical Engineering, Xi’an Polytechnic University, Xi’an 710048, Shaanxi province, P. R. China
  2. MCC Jingcheng Engineering Technology Co., Ltd., Beijing 100176, P.R. China
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Abstract

The effect of laser processing on the structure, microstructure and hardness of high-speed steel produced by powder metallurgy was investigated. The samples were surfaces remelted with impulse CO2 laser radiation under different operation conditions. In the remelted layer, the presence of full remelting, partial remelting and heat affected zones was detected. As a result of concentrated laser beam treatment, microstructures characteristic of the rapid crystallization process were observed. The microstructure in the full remelting zone was characterized by a fine microdendritic structure with the average distance between the secondary axes of dendrites below 1 µm and the dissolution of primary carbides. Retained austenite was found in the remelted samples, the amounts of which depended on the treatment parameters and grew with an increase in the speed of the laser beam movement. There was no unequivocal effect of the distance of the irradiated surface from the focus of the beam focusing system on the content of retained austenite. Due to the presence of retained austenite in the remelted part, the hardness decreased by about 23% compared to the hardness of the material before the treatment. On the other hand, laser processing leads to strong refinement of the microstructure and eliminates the residual porosity of powder steels, which can increase the toughness and cutting performance of steel. The research also showed the possibility of shaping the geometry of the remelting zone by the appropriate selection of machining parameters

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Authors and Affiliations

J. Iwaszko
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Abstract

This work is an experimental study of thermo-mechanical surface hardening of mild steel with trace elements like titanium in negligible concentrations. This is somewhat an advanced technique used to harden steel surface which can be hardened in many typical ways. The concept is combining the thermal as well as mechanical technique to attain better results. It is quite obvious that mechanical refers to the compressive loading during machining and thermal refers to producing heat on the surface of work piece. The ideal conditions are when the heat produced is enough to achieve austenite and then subsequent quick cooling helps in the formation of martensite, which is metallurgically the most highly strong phase of steel, in terms of hardness. The coolant used preferably is the emulsified oil which flows on the surface during machining with variable rate of flow as the optimum effect is. This process hardens the surface of steel and increases its resistance against wear and abrasion. Preference is to achieve surface hardening using the conventional equipment so that operational cost is kept low and better results are attained. This technique has been quite successful in the laboratory. It can be termed as friction hardening. Some improvements in the process scheme and working environment can be made to get better results.
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Bibliography

[1] Muñoz, J.A., Avalos, M., Schell, N., Brokmeier, H.G. & Bolmaro, R.E. (2021). Comparison of a low carbon steel processed by Cold Rolling ( CR ) and Asymmetrical Rolling (ASR): Heterogeneity in strain path, texture, microstructure and mechanical properties. Journal of Manufacturing Processes. 64(February), 557-575. DOI: 10.1016/J.JMAPRO.2021.02.017.
[2] Hotz, H. & Kirsch, B. (2020). Influence of tool properties on thermomechanical load and surface morphology when cryogenically turning metastable austenitic steel AISI 347. Journal of Manufacturing Processes. 52(August 2020), 120-31. https://doi.org/10.1016/j.jmapro.2020.01.043.
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Authors and Affiliations

Ali R. Sheikh
1
ORCID: ORCID

  1. AGH University of Science and Technology, Poland

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