Improvement on Mechanical Properties of Cu-Containing Low Alloy Steel of Long Part Forging for Offshore Applications by Manufacturing Process

2017 ◽  
Author(s):  
Yuta Honma ◽  
Gen Sasaki ◽  
Kunihiko Hashi
Keyword(s):  
Mechanical Properties ◽  
Alloy Steel ◽  
Charpy Impact ◽  
Low Alloy Steel ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Weight Test ◽  
Effective Grain Size ◽  
Drop Weight Test ◽  
Crack Tip Opening

Effects by intercritical quenching, which is quenching from dual-phase of ferrite (α) and austenite (γ) region from 953 to 1068 K, on mechanical properties and microstructures of Cu-containing low alloy steel based on ASTM A707 5L grade (hereafter called A707 modified steel) were investigated using 50 kg test ingots. The mechanical properties of the A707 modified steel, i.e. strength at room temperature and fracture toughness at low temperature, were significantly improved by intercritical quenching. This is probably because its effective grain size decreased by intercritical quenching. Then, the optimum temperature of intercritical quenching for A707 modified steel was 1068 K near the AC3 point. Based on the experimental results of the test ingot, we applied intercritical quenching to a trial full-size forging production of about 20,000 mm in length, and researched the tensile, Charpy impact, crack tip opening displacement (CTOD) and drop weight test (DWT) properties across whole length of the trial production. It was found that the trial production has good mechanical properties across whole length. From the present work, an appropriate intercritical quenching is considered to apply for improvement method of the mechanical properties in A707 modified steel forgings.

Effects of Crack Starter Bead Preparation in Drop-Weight Test on Nil-Ductility Transition Temperature

1999 ◽  
Vol 121 (2) ◽  
pp. 196-202
Author(s):  
M. Higuchi ◽  
T. Yamauchi ◽  
Y. Tanaka ◽  
K. Iida
Keyword(s):  
Alloy Steel ◽  
Test Results ◽  
Base Metals ◽  
Low Alloy Steel ◽  
High Toughness ◽  
Drop Weight ◽  
Steel Base ◽  
Weight Test ◽  
Drop Weight Test ◽  
Bead Height

The procedure for making crack starter weld deposit on drop-weight test (DWT) specimens was altered from two passes to one pass in about 1990. The effects of some parameters of crack starter weld process on drop-weight test results were studied. Results of this study indicated that length of overlap of the second pass and height of crack starter beads were most effective on nil-ductility temperature (TNDT). When overlap length and bead height of two-pass deposit were small enough, TNDT obtained by two-pass deposit became lower than one-pass TNDT, the discrepancy being by as much as 25°C. TNDT values for 24 Japanese steels were determined using two different DWT methods, one-pass deposit and two-pass deposit having small overlap length and bead height. The difference of TNDT depending on DWT method could be seen only for high-toughness low-alloy steel base metals. For other materials (i.e., low-to-medium-toughness low-alloy steel base metals, weld metals, and high-toughness carbon steels), TNDTS by two-pass and one-pass deposits were essentially the same. For lower-toughness steels, TNDT was frequently lower than the temperature of vTcv − 33°C), and thus, the reference nil-ductility temperature RTNDT was determined from Charpy impact test results. These results can be taken as a way of interpreting the past toughness evaluations made for operating plants using the two-pass TNDT.

scholarly journals Effect of Intercritical Quenching Temperature of Cu-Containing Low Alloy Steel of Long Part Forging for Offshore Applications

2019 ◽  
Vol 9 (8) ◽  
pp. 1705 ◽  
Author(s):  
Yuta Honma ◽  
Gen Sasaki ◽  
Kunihiko Hashi
Keyword(s):  
Mechanical Properties ◽  
Alloy Steel ◽  
Offshore Structures ◽  
Area Ratio ◽  
Treatment Temperature ◽  
Reverse Transformation ◽  
Low Alloy Steel ◽  
Transformation Behavior ◽  
Crack Tip Opening Displacement ◽  
Α Phase

In our previous study, intercritical quenching from the dual-phase region of ferrite and austenite regions, which is called lamellarizing (L) treatment, brought a clear improvement of balance between the strength and toughness of Cu-containing low alloy steel based on American Society for Testing and Materials (ASTM) A707 5L grade. Moreover, the results imply that the reverse transformation behavior during L treatment is very important in order to optimize the L treatment temperature. Hence, the purpose of this paper is to clarify the mechanism by which L treatment improves the mechanical properties in terms of reverse transformation behavior. Additionally, offshore structures require good weldability, because the structures generally have a lot of weld joints. Therefore, weldability was also investigated in this study. The investigation revealed that coarse Cu precipitates are observed in the not-transformed α phase, so the strength tendency in relation to the L treatment temperature is relevant to the area ratio of the not-transformed α phase and the transformed γ phase during L treatment. From the in situ electron back scatter diffraction (EBSD) results, it is believed to be possible to enhance the mechanical properties of Cu-containing low alloy steel by controlling the area ratio of the reverse-transformed gamma phase and selecting the appropriate L treatment temperature. Furthermore, the long part forging of Cu-containing low alloy steel has a good weldability, since the maximum hardness of the heat-affected zone (HAZ) is less than 300 HV, and the HAZ of steel has a good crack tip opening displacement (CTOD) property with less than 2.3 kJ/mm of heat input of GTAW.

The Significance of Low Toughness Areas in the Seam Weld of Linepipe

2004 ◽  
Author(s):  
Robert M. Andrews ◽  
Glyn C. Morgan ◽  
W. Jack Beattie
Keyword(s):  
Fracture Mechanics ◽  
Charpy Impact ◽  
Coarse Grained ◽  
Plastic Collapse ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Seam Weld ◽  
Weld Defect ◽  
T Stress ◽  
Crack Tip Opening

There are concerns that there may be areas of low toughness in the seam welds of submerged are welded linepipe. These areas are typically associated with the Coarse Grained Heat Affected Zone and manifest themselves through low values obtained in Charpy impact and crack tip opening displacement (CTOD) tests. Although it is possible to locate areas of low toughness in linepipe seam welds, it is not clear if these are structurally significant. If it can be shown that low toughness areas in the seam weld HAZ do not affect the fitness for service of the pipe as a structure, these could be accepted for use. Under funding from PRCI, a study has been carried out to investigate this problem quantitatively. Experience in the offshore structural field, where the similar problem of local brittle zones in weld HAZs has received considerable attention, was reviewed. A constraint based fracture mechanics analysis was developed using the T-stress approach. Cracked body finite element analyses were used to obtain the T-stress for a range of surface breaking and buried defects in typical linepipe geometries. The results from these models were used to develop a constraint modified Failure Assessment Diagram for a fracture analysis. Fracture analyses showed that the structural constraint is low and failure will occur by plastic collapse for practical seam weld defect sizes. This shows that even when the seam weld toughness is very low, the dominant failure mode for the structure will be plastic collapse. Hence the low toughness values obtained in fracture mechanics tests are not structurally significant for practical defect sizes likely to occur in linepipe.

Structural Integrity Evaluation of API 5L X65 Pipe Subjected to Pre-Strain up to Tensile Strain Using the API 579 Procedure

2007 ◽  
Vol 345-346 ◽  
pp. 1353-1356
Author(s):  
Jong Hyun Baek ◽  
Cheol Man Kim ◽  
Young Pyo Kim ◽  
Chang Sung Seok
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Tensile Test ◽  
Structural Integrity ◽  
Mechanical Damage ◽  
Charpy Impact ◽  
Charpy Impact Test ◽  
Ground Subsidence ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement

Mechanical properties of the pre-strained material are different with those of virgin material without pre-strain. Buried pipelines for natural gas transmission may be deformed by outside force such as ground subsidence, ground liquefaction, cold bending and mechanical damage. Plastic deformation affects the tensile properties and fracture toughness. The effects of prestrain on the mechanical properties of API 5L X65 pipe were diversely investigated through the tensile test, crack tip opening displacement test and Charpy impact test. Axial tensile pre-strain of 1.5, 5 and 10% was applied to plate-type tensile specimens cut from the pipe body prior to mechanical testing. Tensile test revealed that yield strength and tensile strength were increased with increasing tensile pre-strain. However, Fracture toughness for crack initiation decreased with increasing tensile pre-strain. Structural integrity evaluation of the API 5L X65 pipe with crack-like flaws was assessed by using the level 2 in the API 579 code.

Estimation of CTOD in the Case of Very Thick Plates by Knowing CVN Value at a Given Temperature

2010 ◽  
Author(s):  
Sylvain Pillot ◽  
Ste´phanie Corre ◽  
Ce´dric Chauvy ◽  
Patrick Toussaint
Keyword(s):  
Mechanical Properties ◽  
Fracture Mechanics ◽  
Tensile Properties ◽  
Material Properties ◽  
Crack Tip ◽  
Heat Treatments ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Thick Plates ◽  
Crack Tip Opening

Material properties assessment at given temperature and thickness is of primary importance for steelmakers. Generally, a list of mechanical properties requirements, namely tensile, Charpy V-Notch (CVN), fracture mechanics, as well as chemical or heat treatments limits are furnished by customers. Subsequently, the best compromise has to be found by the steel producer in order to reach these requirements. Concerning tensile and CVN properties, experience is large and metallurgists are used to determine the best product optimizations so as to reach the requirements’ values. However, optimization is generally more complicated regarding fracture mechanics. Tools are therefore needed in order to evaluate these properties with reference to conventional (i.e. tensile and CVN) properties. The objective of the present paper is to present some rules that can be used to extrapolate Crack Tip Opening Displacement (CTOD) values from CVN and tensile properties. Recent example is given to illustrate this methodology. In addition, special attention will be paid to the comparison of estimated and measured CTOD values.

Influence of Heat Treatment on Crack Tip Opening Displacement and on Resistance of Crack Propagation of Alloyed Steel

2013 ◽  
Vol 592-593 ◽  
pp. 660-663
Author(s):  
Dragan Pustaić ◽  
Franjo Cajner
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Chemical Composition ◽  
Crack Tip ◽  
Spring Steel ◽  
Experimental Investigations ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Treatment Procedures ◽  
Crack Tip Opening

The aim of the performed investigations was to determine the influence of two different heat treatment procedures, i.e. hardening and tempering vs. austempering, on some mechanical properties, as well as the influence of these procedures on the magnitude of some fracture mechanics parameters for example, crack tip opening displacement (CTOD) and J-integral. The experimental investigations were performed on the specimens made of spring steel 65Si7 (chemical composition: 0.69% C, 1.56% Si and 0.90% Mn).

Experimental Study on Fracture Toughness of Q460C the High-Strength Construction Steel at Low Temperature

2011 ◽  
Vol 71-78 ◽  
pp. 890-897 ◽  
Author(s):  
Yuan Qing Wang ◽  
Yun Lin ◽  
Yan Nian Zhang ◽  
Yong Jiu Shi
Keyword(s):  
Low Temperature ◽  
High Strength ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Three Point Bending ◽  
Function Fitting ◽  
Ductile Brittle Transition Temperature ◽  
Boltzmann Function ◽  
Fracture Appearance ◽  
Crack Tip Opening

Three point bending tests were carried out on 14mm-thick Q460C the high-strength structural steel at low temperature, and scanning electronic microscope of the fracture appearance was analyzed. The results showed that the obvious feature of brittle mechanism was shown on the three point bending specimen fracture whose testing took place at -40°C. And the crack tip opening displacement value of Q460C steel, which was less than that of Q235 steel, Q345 steel and Q390 steel at low temperature, tended to decrease with respect to the temperature reduction. Moreover, a Boltzmann function fitting analysis was applied to the experimental data, and the ductile-brittle transition temperature and the changing regularity were obtained.

Effect of controlled rolling on the mechanical properties of low-alloy steel H-beams

1986 ◽  
Vol 28 (4) ◽  
pp. 248-251
Author(s):  
V. M. Farber ◽  
V. N. Davydov ◽  
V. V. Machikhin ◽  
V. F. Evdokimov ◽  
E. G. Zudov
Keyword(s):  
Mechanical Properties ◽  
Alloy Steel ◽  
Controlled Rolling ◽  
Low Alloy Steel
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