Rate Controlling Steps of SCC of High Strength Steels

CORROSION ◽  
1979 ◽  
Vol 35 (9) ◽  
pp. 397-402 ◽  
Author(s):  
B. STELLWAG ◽  
H. KAESCHE
Keyword(s):  
Stress Intensity ◽  
Crack Growth ◽  
Room Temperature ◽  
High Strength Steels ◽  
High Strength ◽  
Intensity Curve ◽  
Plateau Region ◽  
The Common ◽  
Cracking Process ◽  
Emission Studies

Abstract Stress corrosion crack velocities have been measured for a high strength steel in 0.5N NaCI solution at room temperature without potentiostatic control. Changing the strength level of the steel alters the shape of the SCC velocity vs stress intensity curve distinctly. With increasing strength, the common plateau region (so called stage II) disappears, and SCC velocity becomes exponentially dependent on stress intensity. Additional experiments (acoustic emission studies, crack growth incubation measurements, load change tests, fractography) confirm the current understanding, that absorbed hydrogen is the damaging species. The results can be well interpreted by assuming that lattice decohesion of the metallic bonds by absorbed hydrogen is a fundamental feature of the cracking process. Conclusions can be drawn as to the rate controlling steps of crack growth.

Development of Low Carbon Microalloyed Ultra High Strength Steels

2005 ◽  
Vol 500-501 ◽  
pp. 551-558 ◽  
Author(s):  
A. Ghosh ◽  
Brajendra Mishra ◽  
Subrata Chatterjee
Keyword(s):  
Room Temperature ◽  
High Strength Steels ◽  
High Strength ◽  
Low Carbon ◽  
Hsla Steels ◽  
Finish Rolling ◽  
Ultra High Strength Steels ◽  
Rolling Temperatures ◽  
Carbon Microalloyed ◽  
Carbon Concentrations

In the present study HSLA steels of varying carbon concentrations, alloyed with Mn, Ni, Cr, Mo, Cu and micro-alloyed with Nb and Ti were subjected to different finish rolling temperatures from 850oC to 750oC in steps of 50oC. The microstructure of the steel predominantly shows martensite. Fine twins, strain induced precipitates in the martensite lath along with e-Cu precipitates are observed in the microstructure. With an increase in carbon content the strength value increases from 1200MPa UTS to 1700MPa UTS with a negligible reduction in elongation. Impact toughness values of 20-26 joules at room temperature and −40oC were obtained in sub-size samples.

Fatigue Crack Propagation Limit Curves for S690QL and S960M High Strength Steels and their Welded Joints

2018 ◽  
Vol 1146 ◽  
pp. 44-56 ◽  
Author(s):  
János Lukács ◽  
Ádám Dobosy ◽  
Marcell Gáspár
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Welded Joints ◽  
High Strength Steels ◽  
High Strength ◽  
Base Materials ◽  
Propagation Limit

The objective of the paper is to present the newest results of our complex research work. In order to determination and comparison of the fatigue resistance, fatigue crack growth tests were performed on different grades of S690QL quenched and tempered, and S960TM thermomechanically rolled high strength steels.15 mmand30 mmthick base materials were used for our investigations. Welded joints were made from these base materials, using gas metal arc welding with matching, overmatching, and undermatching filler metals. In the paper, the performance of the welding experiments will be presented, especially with the difficulties of the filler material selection; along with the results of the fatigue crack growth examinations executed on the base materials and its welded joints. Statistical aspects were applied both for the presenting of the possible locations of the cracks in the base materials and the welded joints and for the processing of the measured data. Furthermore, the results will be compared with each other, and the possibility of derivation of fatigue crack propagation limit curves will be referred.

Fatigue Crack Propagation Limit Curves for High Strength Steels and their Application for Engineering Critical Assessment Calculations

2014 ◽  
Vol 891-892 ◽  
pp. 563-568 ◽  
Author(s):  
János Lukács ◽  
Marcell Gaspar
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Welded Joints ◽  
Research Work ◽  
High Strength Steels ◽  
High Strength ◽  
Critical Assessment ◽  
Propagation Limit

There are different prescriptions containing fatigue crack propagation limit curves and rules for the prediction of the crack growth. The research work aimed (i) to determine fatigue crack propagation limit curves for high strength steels and their welded joints, based on the Paris-Erdogan law; (ii) to use the determined limit curves for engineering critical assessment (ECA) calculations. Experiments were performed on different high strength steels and their welded joints; and the propagating cracks in the specimens represent the different possible locations of the real cracks in the structural elements. Fatigue crack growth tests were executed byΔK-decreasing and constant load amplitude methods. The evaluation process consists of six steps, and by means of the selected values a statistical method can be proposed for determination of the limit curves. Engineering critical assessment calculations were performed on a welded structural element having crack like defects.

Observations on the Stress Corrosion Crack Propagation Characteristics of High Strength Steels

CORROSION ◽  
1971 ◽  
Vol 27 (11) ◽  
pp. 471-477 ◽  
Author(s):  
C. S. CARTER
Keyword(s):  
Stress Intensity ◽  
Stress Corrosion ◽  
Stress Corrosion Crack ◽  
Crack Velocity ◽  
High Strength Steels ◽  
High Strength ◽  
Testing Procedure ◽  
Crack Morphology ◽  
Wide Range ◽  
The Relationship

Abstract The relationship between stress corrosion crack velocity and crack-tip stress intensity is discussed. In most high strength steels, there is a wide range of stress intensity over which crack velocity is essentially constant. Methods of estimating this velocity are described. Values for a variety of high strength steels are presented and the effects of metallurgical variables are indicated. Implications with regard to testing procedure, crack morphology, and service performance are outlined.

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