Naslov
The Effect of Controlled Atmosphere on Decarburization of 42CrMo4 Steel Pipes During Heat Treatment

Autori
Gojić, Mirko ; Črnko, Josip ; Kosec, Ladislav

Vrsta, podvrsta i kategorija rada
Radovi u zbornicima skupova, cjeloviti rad (in extenso), znanstveni

Izvornik
Proceedings of the 8th Seminar of the International Federation for Heat Treatment and Surface Engineering IFHTSE 2001 / Liščić Božidar - Zagreb : Craoatian Society for Heat Treatment and Surface Engineering, 2001, 79-86

Skup
8th Seminar of the International Federation for Heat Treatment and Surface Engineering IFHTSE 2001

Mjesto i datum
Cavtat, Hrvatska; Dubrovnik, Hrvatska, 12.09.2001. - 14.09.2001

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Steel; pipes; atmosphere; annealing; oxidation; decarburization; microstructure; mechanical properties

Sažetak
In this work the effect of the protective atmosphere on the oxidation and/or decarburization during annealing of pipes in the industrial and laboratory conditions was studied. The cold-rolled pipes (outside diameter of 130 mm and wall thickness of 6.5 mm ) made from 42CrMo4 steel were annealed at 920oC and 700oC in the industrial furnace RoDr type 3300/4200 equipped with the device for production of controlled atmosphere (CO, CO2, H2 and N2) GW type 200.Also pieces of pipes (length of 300 mm) were annealed at the same temperature in a laboratory furnace without the protective atmosphere. Mechanical and microstructural testing of pipes were carried out. The nomogram of uncompleted combustion of the natural gas and air at l=0.54-0.75 for the industrial furnace was given. By normalizing annealing of cold-rolled pipes at 920oC in the controlled containing 5.2 vol. % CO2-12 vol. % CO-11.5 vol. % H2-71.3 vol. % N2 mixture a bright pipe surfaces with a small depth of decarburization were obtained. During annealing of pipes at 700oC in the controlled atmosphere containing 10.2 vol. % CO2-2.3 vol. % CO-2.4 vol. % H2-81.5vol. % N2 the decarburization and/or oxidation of pipes were not observed. However, during annealing of pipes at 920oC and 700oC without controlled atmosphere an important depth of decarburization (above 0.1 mm) was observed. The obtained results were confirmed by metallographic analysis. The difference between mechanical properties of pipes at the same annealing temperature in the industrial and laboratory furnace was explained on the basis of the different cooling rates from the annealing temperature.

Izvorni jezik
Engleski

Znanstvena područja
Metalurgija

POVEZANOST RADA