Fracture Toughness and Crack Path Deviations in Laser Welded Joints

2004 ◽  
Author(s):  
Bostjan Bezensek ◽  
John W. Hancock
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Yield Strength ◽  
Weld Metal ◽  
Welded Joints ◽  
Crack Path ◽  
Fracture Behaviour ◽  
Misleading Information ◽  
Strength Gradient ◽  
Cleavage Failure

The resistance of laser welded joints to cleavage failure has been examined using fatigue cracked fracture toughness specimens and Charpy tests. The apparent toughness of a range of weld microstructures was determined, the lowest being for a crack located in the weld metal. Sharp cracks deviate into the microstructure with the lowest apparent toughness adjacent to the tip and propagate down the toughness gradient. Charpy tests differ in that the crack consistently propagates into the softer material, and extends down the yield strength gradient adjacent to the tip. Charpy tests can thus give misleading information about the fracture behaviour of mismatched weldments, as crack path deviations may mask a potentially dangerously low toughness weld metal. Recommendations are given on supplementing Charpy weld characterisation with the fracture mechanics tests to ensure conservatism in mismatched weldments.

Fracture Toughness of Pressure Boundary Steels With Higher Yield Strength

2010 ◽  
Author(s):  
Karan K. Gupta ◽  
Christopher L. Hoffmann ◽  
Andrew M. Hamilton ◽  
Frank DeLose
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Yield Strength ◽  
Weld Metal ◽  
Heat Affected Zone ◽  
Pressure Vessel ◽  
Plate Material ◽  
Steam Generators ◽  
Data Points ◽  
Minimum Yield

ASME Section III Appendix G provides a fracture mechanics methodology for evaluating the fracture resistance of pressure vessel materials based on comparing the applied stress intensity from service induced loadings on the assumed flaw to a material fracture toughness (KIR) curve. The applicable fracture toughness curve described in Appendix G is defined as a lower bound curve for static, dynamic, and crack arrest fracture toughness tests for a database that includes a number of pressure vessel materials having specified minimum yield strengths of 50 ksi or less. For materials which have specified minimum room temperature yield strength greater than 50.0 ksi but not exceeding 90.0 ksi, the same fracture toughness curve may be used provided fracture mechanics data points are obtained on at least three heats of the material on a sufficient number of specimens to cover the temperature range of interest, including the weld metal and heat affected zone, and provided that the data points are equal to or above that of the fracture toughness curve of Appendix G of the ASME Code (Fig. G-2210-1). At present, the pressure boundary components of steam generators and pressurizers typically use SA-508 Grade 3 Class 2 forgings and SA-533 Type B Class 2 plate material with minimum yield strength of 65 ksi and 70 ksi respectively. The fracture toughness for these materials is not readily available. This technical paper is compilation of fracture toughness of forging and plate material, weld metal, and heat affected zone of such higher strength forgings and plate materials. The paper includes toughness data of weld metal and heat affected zone resulting from high heat input process and includes the toughness test data with long term postweld heat treatment. All dynamic fracture toughness values for the ASME forgings with a minimum yield strength of 65 ksi and plate material with a minimum yield strength of 70 ksi, heat affected zone, and weld metals exceed the ASME specified minimum KIR given in Article G-2000 of the ASME Boiler and Pressure Vessel Code. This data concludes that the ASME specified minimum reference KIR curve can be used conservatively for the forging and plate materials with minimum yield strength of 65 ksi and 70 ksi that are currently specified for construction of steam generators and other Section III, Class 1 components.

Technical Basis for Expansion of ASME BPVC Section XI, KIC Curve Applicability

2019 ◽  
Author(s):  
Hongqing Xu ◽  
Nathan Palm ◽  
Anees Udyawar
Keyword(s):  
Fracture Toughness ◽  
Lower Bound ◽  
Fracture Mechanics ◽  
Yield Strength ◽  
Room Temperature ◽  
Ferritic Steels ◽  
Initiation Toughness ◽  
Room Temperature Yield Strength ◽  
Class 1 ◽  
Technical Basis

Abstract When the Appendix G methodology, fracture toughness criteria for protection against failure, was first adopted by ASME Section III in 1972, it included a lower-bound Kir curve for ferritic steels with specified minimum room-temperature yield strength up to 50 ksi. In 1977, Section III Appendix G added a requirement to obtain fracture-toughness data for at least three heats (base metal, weld metal, and heat-affected zone) if the KIR curve is used for ferritic steels with specified minimum room-temperature yield strength between 50 and 90 ksi. The three-heat data requirement has not changed when the lower bound curve was adopted by Section XI, or when the lower-bound crack initiation toughness curve was changed from the dynamic Kir curve to the static KIc curve during the 2000s. Based on the accumulation of fracture-mechanics data of ferritic steels with specified minimum yield strength between 50 ksi and 90 ksi and their use for Class 1 pressure vessel production, Section XI recently expanded the applicability of the KIc curve to SA-508 Grade 2 Class 2, SA-508 Grade 3 Class 2, SA-533 Type A Class 2, and SA-533 Type B Class 2 whose specified minimum room-temperature yield strength is 65 ksi or 70 ksi. This paper describes the technical basis including the fracture-mechanics data to support the expansion of the applicability of the KIc curve by ASME Section XI.

scholarly journals Fracture and fracture toughness of nanopolycrystalline metals produced by severe plastic deformation

2015 ◽  
Vol 373 (2038) ◽  
pp. 20140366 ◽  
Author(s):  
A. Hohenwarter ◽  
R. Pippan
Keyword(s):  
Fracture Toughness ◽  
Plastic Deformation ◽  
Fracture Mechanics ◽  
Severe Plastic Deformation ◽  
Fracture Behaviour ◽  
Basic Research ◽  
Point Of View ◽  
Metallic Materials ◽  
Grain Sizes ◽  
Ultrafine Grained

The knowledge of the fracture of bulk metallic materials developed in the last 50 years is mostly based on materials having grain sizes, d , in the range of some micrometres up to several hundred micrometres regarding the possibilities of classical metallurgical methods. Nowadays, novel techniques provide access to much smaller grain sizes, where severe plastic deformation (SPD) is one of the most significant techniques. This opens the door to extend basic research in fracture mechanics to the nanocrystalline (NC) grain size regime. From the technological point of view, there is also the necessity to evaluate standard fracture mechanics data of these new materials, such as the fracture toughness, in order to allow their implementation in engineering applications. Here, an overview of recent results on the fracture behaviour of several different ultrafine-grained ( d <1 μm) and NC ( d <100 nm) metals and alloys covering examples of body- and face-centred cubic structures produced by SPD will be given.

Fracture Performance Evaluation of Laser Beam Welded Joints Based on the Weibull Stress Criterion

2009 ◽  
Author(s):  
Yasuhito Takashima ◽  
Mitsuru Ohata ◽  
Fumiyoshi Minami
Keyword(s):  
Fracture Toughness ◽  
Brittle Fracture ◽  
Laser Beam ◽  
Weld Metal ◽  
Welded Joints ◽  
Shielding Effect ◽  
Stress Criterion ◽  
Fracture Performance ◽  
Weibull Stress ◽  
Fracture Toughness Specimen

This paper examines the fracture performance of laser beam welded joints of a high strength steel with a notch in the weld metal (WM). The standard fracture toughness specimen (3-point bend specimen, 3PB) and tension panel (edge through-thickness crack panel, ETCP) are tested at a low temperature in the brittle fracture range. The focus lies on the difference between near crack-tip plastic constraints for the standard fracture toughness specimen and the tension, and on the very narrow and highly hardened WM shielding high strain in the weld metal from external loading. The ETCP has presented a higher critical CTOD at brittle fracture initiation than the 3PB specimen. The fracture performance of ECTP is predicted from CTOD fracture toughness test results by means of the Weibull stress criterion with the consideration of the shielding effect of the weld metal. The results show an advantage of the Weibull stress criterion for the fracture transferability analysis of toughness results. Furthermore, the influence of very narrow and highly hardened weld metal of laser beam welded joints on the toughness requirement has been analyzed by means of the Weibull stress criterion. The effect of the distinctive strength mismatch of laser beam welded joints on required CTOD fracture toughness of laser beam welded joints in 3PB necessary to meet design requirement of joint performance is discussed taking into account the shielding effect on crack opening behavior and toughness collection due to constraint loss between ETCP and 3PB specimen. The required CTOD in 3PB is a little bit lower than arc welded joints. Therefore, it should be noticed that the very narrow and highly hardened WM does not necessarily lead to poor fracture performance of the welded joints.

NIMROD 617KS

Alloy Digest ◽  
2002 ◽  
Vol 51 (5) ◽  
Keyword(s):  
Fracture Toughness ◽  
High Temperature ◽  
Weld Metal ◽  
Tensile Properties ◽  
Base Metal ◽  
Heat Treating ◽  
Nominal Composition

Abstract Nimrod 617KS is an Inconel-type consumable with a nominal composition of nickel, 24% Cr,12% Co, and 9% Mo and is used to join UNS N06617 and Nicrofer 6023 to themselves. The alloy is designed for high-temperature service and is often used as the weld metal in dissimilar cases to ensure the weld is as strong as the base metal. This datasheet provides information on composition, hardness, and tensile properties as well as fracture toughness. It also includes information on heat treating and joining. Filing Code: Ni-583. Producer or source: Metrode Products Ltd.

VALLOUREC VM 85 13Cr

Alloy Digest ◽  
2016 ◽  
Vol 65 (4) ◽  
Keyword(s):  
Fracture Toughness ◽  
Corrosion Resistance ◽  
Carbon Steel ◽  
Yield Strength ◽  
Physical Properties ◽  
Tensile Properties ◽  
Alloy Carbon ◽  
Sour Service ◽  
Minimum Yield

Abstract Vallourec VM 85 13Cr (minimum yield strength 85 ksi, or 586 MPa) is a low alloy carbon steel for use in oil country tubular goods as a material suitable for sour service. This datasheet provides information on composition, physical properties, hardness, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as forming. Filing Code: CS-198. Producer or source: Vallourec USA Corporation.

VALLOUREC VM 90 13CR

Alloy Digest ◽  
2016 ◽  
Vol 65 (3) ◽  
Keyword(s):  
Fracture Toughness ◽  
Corrosion Resistance ◽  
Carbon Steel ◽  
Yield Strength ◽  
Physical Properties ◽  
Tensile Properties ◽  
Alloy Carbon ◽  
Sour Service ◽  
Minimum Yield

Abstract Vallourec VM 90 13CR (minimum yield strength 90 ksi, or 620 MPa) is a low alloy carbon steel for use in oil country tubular goods as a material suitable for sour service. This datasheet provides information on composition, physical properties, hardness, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as forming. Filing Code: CS-197. Producer or source: Vallourec USA Corporation.

N-A-XTRA M800

Alloy Digest ◽  
2016 ◽  
Vol 65 (11) ◽  
Keyword(s):  
Fracture Toughness ◽  
Yield Strength ◽  
Structural Steel ◽  
Tensile Properties ◽  
Impact Energy ◽  
Heat Treating ◽  
Service Temperature ◽  
Minimum Yield ◽  
Minimum Impact

Abstract N-A-XTRA M800 is a quenched and tempered structural steel produced as heavy plates. N-A-XTRA steel can be supplied in six different grades with a minimum yield strength of 550, 620, 700 and 800 MPa (79.8, 89.9, 101.5 and 116.0 ksi). Some grades are delivered with different toughness properties. This last quality is for low service temperature with minimum impact energy at -40 deg C (-40 deg F) for grade N-A-XTRA M in a thickness range from 3 to 120 mm (0.118 to 4.724 in.). This datasheet provides information on composition and tensile properties as well as fracture toughness. It also includes information on forming, heat treating, and joining. Filing Code: SA-771. Producer or source: ThyssenKrupp Steel Europe AG.

RUUKKI RAEX 300

Alloy Digest ◽  
2012 ◽  
Vol 61 (2) ◽  
Keyword(s):  
Fracture Toughness ◽  
Wear Resistance ◽  
Shear Strength ◽  
Impact Toughness ◽  
Yield Strength ◽  
Physical Properties ◽  
Tensile Properties ◽  
High Strength ◽  
Structural Components ◽  
Wear Resistant

Abstract RUUKKI RAEX 300 (typical yield strength 900 MPa) is part of the Raex family of high-strength and wear-resistant steels with favorable hardness and impact toughness to extend life and decrease wear in structural components. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and shear strength as well as fracture toughness. It also includes information on wear resistance as well as forming, machining, and joining. Filing Code: SA-643. Producer or source: Rautaruukki Corporation.

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