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No. 4/2020
4-20 okladka www.jpg

Contents


Marian NIESLER
Janusz STECKO

Łukasiewicz Research Network – Institute for Ferrous Metallurgy

Sławomir STELMACH

Institute for Chemical Processing of Coal

USE OF CONIFEROUS WOOD BIOCHAR AS A SUBSTITUTE FUEL IN AN IRON ORE SINTERING PROCESS

The article presents the results of tests carried out at Łukasiewicz – IMŻ, in cooperation with the Institute for Chemical Processing of Coal, on the use of biochar from coniferous wood as a substitute fuel in the iron ore sintering process. It was found that, considering productivity, fuel consumption and properties of the obtained sinter, the content of the tested biochar should not exceed 10 wt% in total fuel. When using the tested biochar, the content of FeO in the sinter decreased. The sinter was characterised by better ISO T strength than when using only coke breeze. At the same time, the grindability of the ISO A sinter decreased with the increase in the content of the biochar in the total fuel. The use of the tested biochar can have a very positive effect on both the sinter strength and its reducing properties.

Keywords: biochar, biomass, coke breeze, iron ore sintering


Marek BURDEK
Jarosław MARCISZ
Jerzy STĘPIEŃ

Łukasiewicz Research Network – Institute for Ferrous Metallurgy

PRODUCTION TECHNOLOGY AND MECHANICAL PROPERTIES OF A NEW GRADE OF STEEL FOR FORGINGS WITH INCREASED STRENGTH AND IMPACT STRENGTH

The study involved the development of the basics of production technology and the testing of the mechanical properties of a new grade of steel for forgings with increased strength and impact strength, intended for special products. The scope of the tests included a proposal for a new steel composition along with the production of ingots and its further processing into forgings in industrial conditions, using an input with various dimensions of the cross-section, proposed as a result of numerical calculations, including the performance of heat treatment in two variants. As a result of tests and analyses, it was found that the proposed technology enables the production of semi-finished products with the assumed level of strength and impact strength.

Keywords: low-alloy steel, hot forging, forging, strength, impact strength


Hanna PURZYŃSKA

Łukasiewicz Research Network – Institute for Ferrous Metallurgy

Grzegorz GOLAŃSKI

Department of Materials Engineering, Częstochowa

Michał KWIECIEŃ
Dariusz PARYŻ

Power Research & Testing Company ENERGOPOMIAR, Gliwice

IMPACT OF USE ON RELEASE PROCESSES IN AUSTENITIC STEEL TP347HFG

The article presents an analysis of precipitation processes in heat-resistant TP347HFG steel after 41,000 h of operation at 585°C. Microstructure investigation showed that the use of the tested steel resulted mainly in the precipitation processes occurring at grain boundaries. Identification of the precipitates showed the presence of M23C6 carbides and σ phase particles along boundaries. Single M23C6 carbide particles were revealed also at twin boundaries. Inside austenite grains, apart from large, primary precipitates, finely-dispersed secondary NbX particles (X = C,N) were also observed.

Keywords: steels for the power industry, TP347HFG, microstructure, precipitation processes, mechanical properties, service life


Tymoteusz JUNG
Milena KIERAT

Łukasiewicz Research Network – Institute for Ferrous Metallurgy

INFLUENCE OF ALLOYING ELEMENTS ON THE MICROSTRUCTURE OF NEW COBALT MATRIX SUPERALLOYS REINFORCED WITH PHASE – L12

The article presents selected results of research on the primary structure of a new generation of cobalt-based Co-20Ni-10Al-5Mo-2Nb superalloys. Research on this group of materials was started in 2006 by J. Sato. These materials are anticipated to be able to replace nickel-based superalloys in the future due to their superior elevated temperature properties compared to the nickel-based superalloys. Today, γ’ nickel-based superalloys are still unrivalled in aerospace applications, however, cobalt-based superalloys are a response to their existing limitations, which do not allow the current pace of aircraft engine development to be maintained.

Keywords: Co20Ni10Al5Mo2Nb, casting, primary microstructure, segregation, dendrites


Adam ZIELIŃSKI

Łukasiewicz Research Network – Institute for Ferrous Metallurgy

IMPACT OF LONG-TERM AGEING ON SIGMA PHASE PRECIPITATION PROCESS IN STEELS WITH AUSTENITIC MATRIX

Super 304H, HR3C and Sanicro 25 grade austenitic matrix steels are used in the construction of pressure components of boilers with supercritical operating parameters. The article presents the results of microstructure examination in delivery condition and after ageing for up to 50,000 hours at 700°C. The microstructure examination was performed using scanning and transmission electron microscopy. The precipitates were identified using transmission electron microscopy. In particular, the study analysed the sigma phase precipitation process and its dynamics depending on the ageing time. It has been shown that the intermetallic sigma phase plays a significant role in the loss of durability of the tested steel. It is related to its significant increase due to the influence of high temperature, and its coagulation and coalescence dynamics strongly depend on the ageing/operating temperature level. The qualitative and quantitative identification of the intermetallic sigma phase precipitation process described in the study is important in the analysis of the loss of durability of the tested steels under creep conditions.

Keywords: Super 304H, HR3C, Sanicro 25, microstructure, sigma phase, ageing, loss of durability

2021-03-30


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