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RESEARCH OF HEAVY CASTING METALLURGICAL DEFECTS
Čech, Jan ; Elbel, Tomáš (referee) ; Jelínek, Petr (referee) ; Šenberger, Jaroslav (advisor)
A massive castings defects are examined in this doctoral thesis, specialise in steels passing through peritectic transformation. There are typical types of defects at massive steel castings, as contrasted to „ordinary“ internal and surface ones. For massive steel castings are typical defects under feeders like conchoidal fractures, segregations, microporesities, reoxidation products. Combination of Al and Zr is an ordinary final deoxidation of EOP and LF steel for castings in ŽĎAS a.s. foundry. The aim of Al + Zr combination was to both deep deoxidation by Al (decrease of bubbles risk) and denitrification by Zr (decrease of conchoidal fractures). This theses refute premission mentioned above and verified persisting risk of defects under massive feeders, even though Al + Zr deoxidation is used. A final deoxidation by increased amount of Al was examinated, in combination with other deoxidation agents. Castings had 11 [cm] maximal modulus, and occurence of conchoidal fracture, reoxidation products and primary austenite grain size was evaluated. A selected optimal final deoxidations (Al, Al+Ti, Al+Zr) as a result from experiment described above, were evaluated on castings with 15 [cm] maximal modulus. The result of experiment is, that is not possible to repeatedly produce massive steel casting using EOP metallurgical equipment without defects under feeders, despite of deoxidation and pouring temperature optimalization. The defect indications look like conchoidal fracture, but there are microporesity and impurities instead. Finally, castings with maximal modulus 15 [cm] were produced using so called secondary metallurgy (LF, VD). Secondary metallurgy allowed to both significant decrease of sulfur and degassing of melted metal. Only this metallurgical procedure guarantees production of heavy steel castings without typical defects under massive feeders
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Manufacture of heavy steel castings
Klváček, Jan ; Pernica, Vítězslav (referee) ; Záděra, Antonín (advisor)
The aim of this bachelor thesis is perform a search on the topic of heavy castings of the steel. Production of heavy castings is a special part in manufacturing steel castings. Their properties are extremely influenced by a long time, which results in the creation of many metallurgical casting defects. Heavy castings are produced in small series or just a piece production. There-fore not possible remove defects during the manufacturing process. For the production of heavy castings are required specific requirements for this reason.
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Optimization of heavy steel castings manufacture
Procházka, Zdeněk ; Čech, Jan (referee) ; Šenberger, Jaroslav (advisor)
The Master’s thesis was conducted under the project FR-TI1/070 “Optimalization of heavy steel casting manufacture” in cooperation with ŽĎAS a. s. foundry. It evaluates rate of conchoidal fracture in samples extracted from experimental castings. The testing bar for the static tensile test were extracted from thermal axis of casting. The research part describes ways of deoxidating the liquid metal and usage of separate deoxidating chemical parts, followed by summary of research knowledge on conchoidal fractures. In the practical part, the process of sample evaluation is described. The conchoidal fracture, the surface of which was evaluated on the fracture surfaces, influences mechanical qualities of cast steel. Simultaneously, impacts of metallurgical factors on rate of conchoidal fracture were examined
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RESEARCH OF HEAVY CASTING METALLURGICAL DEFECTS
Čech, Jan ; Elbel, Tomáš (referee) ; Jelínek, Petr (referee) ; Šenberger, Jaroslav (advisor)
A massive castings defects are examined in this doctoral thesis, specialise in steels passing through peritectic transformation. There are typical types of defects at massive steel castings, as contrasted to „ordinary“ internal and surface ones. For massive steel castings are typical defects under feeders like conchoidal fractures, segregations, microporesities, reoxidation products. Combination of Al and Zr is an ordinary final deoxidation of EOP and LF steel for castings in ŽĎAS a.s. foundry. The aim of Al + Zr combination was to both deep deoxidation by Al (decrease of bubbles risk) and denitrification by Zr (decrease of conchoidal fractures). This theses refute premission mentioned above and verified persisting risk of defects under massive feeders, even though Al + Zr deoxidation is used. A final deoxidation by increased amount of Al was examinated, in combination with other deoxidation agents. Castings had 11 [cm] maximal modulus, and occurence of conchoidal fracture, reoxidation products and primary austenite grain size was evaluated. A selected optimal final deoxidations (Al, Al+Ti, Al+Zr) as a result from experiment described above, were evaluated on castings with 15 [cm] maximal modulus. The result of experiment is, that is not possible to repeatedly produce massive steel casting using EOP metallurgical equipment without defects under feeders, despite of deoxidation and pouring temperature optimalization. The defect indications look like conchoidal fracture, but there are microporesity and impurities instead. Finally, castings with maximal modulus 15 [cm] were produced using so called secondary metallurgy (LF, VD). Secondary metallurgy allowed to both significant decrease of sulfur and degassing of melted metal. Only this metallurgical procedure guarantees production of heavy steel castings without typical defects under massive feeders
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Study of foundry defects in heavy castings
Čech, Jan ; Elbel, Tomáš (referee) ; Šenberger, Jaroslav (advisor)
A massive castings defects are examined in this doctoral thesis, specialise in steels passing through peritectic transformation. There are typical types of defects at massive steel castings, as contrasted to „ordinary“ internal and surface ones. For massive steel castings are typical defects under feeders like conchoidal fractures, segregations, microporesities, reoxidation products. Combination of Al and Zr is an ordinary final deoxidation of EOP and LF steel for castings in ŽĎAS a.s. foundry. The aim of Al + Zr combination was to both deep deoxidation by Al (decrease of bubbles risk) and denitrification by Zr (decrease of conchoidal fractures). This theses refute premission mentioned above and verified persisting risk of defects under massive feeders, even though Al + Zr deoxidation is used. A final deoxidation by increased amount of Al was examinated, in combination with other deoxidation agents. Castings had 11 [cm] maximal modulus, and occurence of conchoidal fracture, reoxidation products and primary austenite grain size was evaluated. A selected optimal final deoxidations (Al, Al+Ti, Al+Zr) as a result from experiment described above, were evaluated on castings with 15 [cm] maximal modulus. The result of experiment is, that is not possible to repeatedly produce massive steel casting using EOP metallurgical equipment without defects under feeders, despite of deoxidation and pouring temperature optimalization. The defect indications look like conchoidal fracture, but there are microporesity and impurities instead. Finally, castings with maximal modulus 15 [cm] were produced using so called secondary metallurgy (LF, VD). Secondary metallurgy allowed to both significant decrease of sulfur and degassing of melted metal. Only this metallurgical procedure guarantees production of heavy steel castings without typical defects under massive feeders
|
|
|
Optimization of heavy steel castings manufacture
Procházka, Zdeněk ; Čech, Jan (referee) ; Šenberger, Jaroslav (advisor)
The Master’s thesis was conducted under the project FR-TI1/070 “Optimalization of heavy steel casting manufacture” in cooperation with ŽĎAS a. s. foundry. It evaluates rate of conchoidal fracture in samples extracted from experimental castings. The testing bar for the static tensile test were extracted from thermal axis of casting. The research part describes ways of deoxidating the liquid metal and usage of separate deoxidating chemical parts, followed by summary of research knowledge on conchoidal fractures. In the practical part, the process of sample evaluation is described. The conchoidal fracture, the surface of which was evaluated on the fracture surfaces, influences mechanical qualities of cast steel. Simultaneously, impacts of metallurgical factors on rate of conchoidal fracture were examined
|
|
|
Manufacture of heavy steel castings
Klváček, Jan ; Pernica, Vítězslav (referee) ; Záděra, Antonín (advisor)
The aim of this bachelor thesis is perform a search on the topic of heavy castings of the steel. Production of heavy castings is a special part in manufacturing steel castings. Their properties are extremely influenced by a long time, which results in the creation of many metallurgical casting defects. Heavy castings are produced in small series or just a piece production. There-fore not possible remove defects during the manufacturing process. For the production of heavy castings are required specific requirements for this reason.
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