Ductile-to-Brittle Transition Behavior of High-Nitrogen 18Cr-10Mn-0.35N Austenitic Steels Containing Ni and Cu

2010 ◽  
Vol 654-656 ◽  
pp. 158-161 ◽  
Author(s):  
Byoung Chul Hwang ◽  
Tae Ho Lee ◽  
Seong Jun Park ◽  
Chang Seok Oh ◽  
Sung Joon Kim
Keyword(s):  
Charpy Impact ◽  
Charpy Impact Test ◽  
Austenitic Steels ◽  
Favorable Effect ◽  
High Nitrogen ◽  
Delta Ferrite ◽  
Brittle Transition ◽  
Transition Behavior ◽  
Ductile To Brittle Transition ◽  
Crystallographic Planes

Ductile-to-brittle transition behavior of high-nitrogen 18Cr-10Mn-0.35N austenitic steels containing Ni and Cu was investigated by means of Charpy impact test and fractographic analysis. The commonly observed fracture mode of the specimens tested at -196 oC was transgranular cleavage-like brittle with flat facets occurring along {111} crystallographic planes, thereby leading to the occurrence of ductile-to-brittle transition. For all the steels investigated in the present study, the ductile-to-brittle transition temperature (DBTT) measured from Charpy impact tests was much higher by 90 to 135 oC than that predicted by empirical equation strongly depending on N content. The combined addition of Ni and Cu enabled the 18Cr-10Mn-0.35N steels to have the lowest DBTT, which could be explained by relatively high austenite stability and favorable effect of Cu as well as the absence of delta-ferrite.

scholarly journals Identification of ductile to brittle transition temperature by using plane strain specimen in tensile test and correlation with instrumented Charpy impact test: experimental and numerical study

2018 ◽  
Vol 19 (1) ◽  
pp. 107 ◽  
Author(s):  
Frank Tioguem ◽  
Matthieu Maziere ◽  
Franck Tankoua ◽  
André Galtier ◽  
Anne-Françoise Gourgues-Lorenzon
Keyword(s):  
Transition Temperature ◽  
Plane Strain ◽  
Numerical Study ◽  
Charpy Impact ◽  
Tensile Tests ◽  
Charpy Impact Test ◽  
Fracture Mechanisms ◽  
Brittle Transition ◽  
Brittle Transition Temperature ◽  
Ductile To Brittle Transition

This study addresses the correlation between the ductile-to-brittle transition temperature ranges of high strength 4140 steel obtained respectively from tensile tests under plane strain (PS) conditions and from conventional Charpy impact tests. Specimens were taken respectively at 25 mm (P) and at 55 mm (M) from skin of a cylindrical 90-mm-radius hot rolled bar water quenched from 875 °C, tempered at 600 °C and air cooled. P and M samples respectively showed a fully martensitic and a martensite-bainite microstructure. Fracture surface observations showed good agreement for physical fracture mechanisms (cleavage facet size, mixed ductile + brittle fracture in the transition region, ductile fracture at higher temperatures) between PS and Charpy, in particular sensitivity of upper bainite to cleavage fracture that reduces fracture energy in the lower self-energy on Charpy tests.

Middle Shelf During Ductile to Brittle Transition on Ferrite + Pearlite Structure Steel Sheet

2018 ◽  
Vol 941 ◽  
pp. 453-457
Author(s):  
Hiroyuki Kawata ◽  
Osamu Umezawa
Keyword(s):  
Fracture Surface ◽  
Steel Sheet ◽  
Charpy Impact ◽  
High Strength ◽  
Charpy Impact Test ◽  
Propagation Path ◽  
Transition Curve ◽  
Brittle Transition ◽  
Ductile To Brittle Transition ◽  
Step Transition

The steels consisting of multi-phase structure show an advantage for their high strength and good formability. The ductile to brittle transition with decreasing temperature has been investigated by Charpy impact test with sub-size specimen for the ferrite + pearlite structure steel sheet. The transition curve of the absorbed energy showed a two-step transition behavior, and the “middle shelf” appeared clearly in the curve. The cleavage-like fracture with few dimples appeared on the fracture surface of the specimens at the middle shelf, and the plastic strain was detected just below the fracture surface. This result suggested that the fracture at the middle shelf propagates with the quasi-cleavage fracture accompanied with plastic deformation. Although the traces of fracture surface corresponded to (001), (011), and (112) bcc-iron planes, the (001) cleavage plane was not dominant for the fracture propagation path at the middle shelf.

scholarly journals Mechanical Properties and Impact Toughness of Molybdenum Alloyed Ductile Iron

2020 ◽  
Author(s):  
D. Franzen ◽  
B. Pustal ◽  
A. Bührig-Polaczek
Keyword(s):  
Mechanical Properties ◽  
Transition Temperature ◽  
Ductile Iron ◽  
Calculated Data ◽  
Charpy Impact ◽  
Charpy Impact Test ◽  
Brittle Transition ◽  
Brittle Transition Temperature ◽  
Ductile To Brittle Transition ◽  
High Silicon

Abstract Grades of high silicon ductile iron offer excellent combinations of static strength and ductility as well as good machinability due to their fully ferritic, solution strengthened matrix. As a result of elevated silicon contents, however, the ductile-to-brittle transition temperature in the Charpy impact test is significantly increased. Thus, minimum required Charpy impact energies cannot be met for many applications by using high silicon ductile iron. Therefore, alloys with lower strength and higher toughness properties are commonly used for many technical applications. The enormous lightweight construction potential of high silicon ductile iron can therefore not be fully exploited. The present investigation pursues the metallurgical approach of partially substituting silicon with molybdenum as an alternative strengthening element in order to improve the toughness properties while maintaining similar static mechanical properties. Molybdenum serves as a carbide-stabilising element in ductile iron, while simultaneously promoting ferrite formation and is therefore regarded to be suitable alloying element. In Charpy impact tests, the ductile-to-brittle transition temperature could be reduced by about 55 °C by reducing the silicon content to 2.95 wt% and adding 0.21 wt% molybdenum compared to a high silicon alloy. Additionally, it was possible to mathematically describe the transition behaviour of the studied alloys using nonlinear regression functions and to achieve a sufficient correlation of empirically determined and calculated data. This present metallurgical concept offers a promising metallurgical tool for further improving the toughness properties of alloyed ductile iron.

Anisotropy of Mechanical Properties of API-X70 Spiral Welded Pipe Steels

2013 ◽  
Vol 753 ◽  
pp. 538-541 ◽  
Author(s):  
Haytham M. Al Jabr ◽  
John G. Speer ◽  
David K. Matlock ◽  
Peng Zhang ◽  
Sang Hyun Cho
Keyword(s):  
Rolling Direction ◽  
Charpy Impact ◽  
Charpy Impact Test ◽  
Impact Testing ◽  
Granular Bainite ◽  
Secondary Phases ◽  
Pronounced Increase ◽  
Ductile To Brittle Transition ◽  
Welded Pipe ◽  
Anisotropy Of Mechanical Properties

The effects of microstructure and texture on the toughness anisotropy of two API-X70 pipeline steels were investigated. One steel contained no nickel (0Ni) and the other contained 0.3 wt pct nickel (0.3Ni). Charpy V-notch impact testing was conducted on plate samples for both steels in three directions: longitudinal (L), transverse (T), and diagonal (D) with respect to the rolling direction. The microstructures of both steels were mixed and consisted of acicular ferrite, granular bainite, and small amounts of polygonal ferrite, with martensite-austenite and retained austenite islands as secondary phases. The ductile to brittle transition temperatures (DBTT) for the Charpy impact test were higher in the D direction for both plates, with a pronounced increase in the 0Ni steel. The anisotropy in toughness was mainly attributed to the crystallographic texture.

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