scholarly journals Effect of Relative Humidity on Mechanical Degradation of Medium Mn Steels

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1304 ◽  
Author(s):  
Qingyang Liu ◽  
Juanping Xu ◽  
Liancheng Shen ◽  
Qingjun Zhou ◽  
Yanjing Su ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Relative Humidity ◽  
Hydrogen Embrittlement ◽  
Hydrogen Concentration ◽  
High Strength Steels ◽  
Threshold Value ◽  
Tensile Tests ◽  
Constant Load ◽  
Mechanical Degradation ◽  
Delayed Cracking

Medium Mn steels have been considered as the next-generation materials for use in the automotive industry due to their excellent strength and ductility balance. To reduce the total weight and improve the safety of vehicles, medium Mn steels look forward to a highly promising future. However, hydrogen-induced delayed cracking is a concern for the use of high strength steels. This work is focused on the service characteristics of two kinds of medium Mn steels under different relative humidity conditions (40%, 60%, 80% and 100%). Under normal relative humidity (about 40%) at 25 °C, the hydrogen concentration in steel is 0.4 ppm. When exposed to higher relative humidity, the hydrogen concentration in steel increases slowly and reaches a stable value, about 0.8 ppm. In slow strain rate tensile tests under different relative humidity conditions, the tensile strength changed, the hydrogen concentration increased and the elongation decreased as well, thereby increasing the hydrogen embrittlement sensitivity. In other words, the smaller the tensile rate applied, the greater the hydrogen embrittlement sensitivity. In constant load tests under different relative humidity conditions, the threshold value of the delayed cracking of M7B (‘M’ referring to Mn, ‘7’ meaning the content of Mn, ‘B’ denoting batch annealing) steel maintains a steady value of 0.82 σb (tensile strength). The threshold value of the delayed cracking of M10B significantly changed along with relative humidity. When relative humidity increased from 60% to 80%, the threshold dropped sharply from 0.63 σb to 0.52 σb. We define 80% relative humidity as the ‘threshold humidity’ for M10B.

Microstructural Evolution and Tensile Strength of Laser-Welded Butt Joints of Ultra-High Strength Steels: Low and High Alloy Steels

2021 ◽  
Vol 883 ◽  
pp. 250-257
Author(s):  
Mikko Hietala ◽  
Atef Hamada ◽  
Markku Keskitalo ◽  
Matias Jaskari ◽  
Jani Kumpula ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Fusion Zone ◽  
Microstructural Evolution ◽  
Laser Energy ◽  
High Strength Steels ◽  
High Strength ◽  
Tensile Tests ◽  
Butt Joints ◽  
Dissimilar Joints ◽  
Ultra High Strength Steels

The present study is focused on joining two ultra-high strength steels plates of 3 mm thickness using laser-welding. Abrasion resistant steel with martensitic structure, tensile strength (Rm) ≥ 2 GPa, and cold-deformed austenitic stainless steel, Rm 1.3 GPa, were used for the dissimilar butt joints. Two different laser energy inputs, 160 and 320 J/mm, were presented during welding. The weld morphology and microstructural evolution of the fusion zone were recorded using optical microscopy and electron back scattering diffraction (EBSD), respectively. The mechanical properties of the dissimilar joints were evaluated by hardness measurements and tensile tests. It was found that fusion zone has undergone a change in morphology and microstructure during welding depending upon the energy input. Analysis of the microstructural evolution in the fusion zone by EBSD examination showed that the presence of a mixture of small austenite grains in a matrix of martensite. The changes in hardness profiles and tensile strength under the experimental parameters were further reported.

scholarly journals Comparison of Constant Load, SSRT and CSRT Methods for Hydrogen Embrittlement Evaluation Using Round Bar Specimens of High Strength Steels

2014 ◽  
Vol 100 (10) ◽  
pp. 1298-1305 ◽  
Author(s):  
Tetsushi Chida ◽  
Yukito Hagihara ◽  
Eiji Akiyama ◽  
Kengo Iwanaga ◽  
Shusaku Takagi ◽  
...  
Keyword(s):  
Hydrogen Embrittlement ◽  
High Strength Steels ◽  
High Strength ◽  
Constant Load ◽  
Round Bar

Studies of SCC and Hydrogen Embrittlement of High Strength Alloys Using Fracture Mechanics Methods

2005 ◽  
Vol 482 ◽  
pp. 11-16 ◽  
Author(s):  
Wolfgang Dietzel ◽  
Michael Pfuff ◽  
Guido G. Juilfs
Keyword(s):  
Plastic Deformation ◽  
Fracture Mechanics ◽  
Hydrogen Embrittlement ◽  
Hydrogen Diffusion ◽  
High Strength Steels ◽  
High Strength ◽  
Constant Load ◽  
Rate Of Change ◽  
Extension Rate ◽  
Hydrogen Atoms

Fracture mechanics based test and evaluation techniques are used to gain insight into the phenomenon of stress corrosion cracking (SCC) and to develop guidance for avoiding or controlling SCC. Complementary to well known constant load and constant deflection test methods experiments that are based on rising load or rising displacement situations and are specified in the new ISO standard 7539 – Part 9 may be applied to achieve these goals. These are particularly suitable to study cases of SCC and hydrogen embrittlement of high strength steels, aluminium and titanium alloys and to characterise the susceptibility of these materials to environmentally assisted cracking. In addition, the data generated in such R-curve tests can be used to model the degradation of the material caused by the uptake of atomic hydrogen from the environment. This is shown for the case of a high strength structural steel (FeE 690T) where in fracture mechanics SCC tests on pre-cracked C(T) specimens a correlation between the rate of change in plastic deformation and the crack extension rate due to hydrogen embrittlement was established. The influence of plastic strain on the hydrogen diffusion was additionally studied by electrochemical permeation experiments. By modelling this diffusion based on the assumption that trapping of the hydrogen atoms takes place at trap sites which are generated by the plastic deformation, a good agreement was achieved between experimentally obtained data and model predictions.

Study on Susceptibility of Hydrogen Embrittlement in a Tool Steel

2007 ◽  
Vol 561-565 ◽  
pp. 103-106 ◽  
Author(s):  
X.T. Wang ◽  
Tadeusz Siwecki
Keyword(s):  
Heat Treatment ◽  
Mechanical Property ◽  
Tensile Strength ◽  
Hydrogen Embrittlement ◽  
Strain Rate ◽  
Tool Steel ◽  
Hydrogen Content ◽  
Tensile Tests ◽  
Hydrogen Level ◽  
Low Strain Rate

Susceptibility of hydrogen embrittlement of a super grade AISI 420 tool steel was studied. Tensile samples were cathodically charged to different hydrogen level. Hydrogen induced mechanical property degradation was measured by tensile tests at a low strain rate. Fractography of broken surfaces was observed using SEM. Relationship between hydrogen content and tensile strength and elongation were studied. Critical hydrogen contents were obtained for different heat treatment states. It was found that for annealed materials could stand for a 3.5ppm hydrogen for keeping 80% of original ductility, and the effect of hydrogen on strength was unobvious. However, for material quenched and tempered at 250°C, only 0.3ppm hydrogen could lead the ductility drop to 80% of original. The material quenched and tempered at 500°C was more sensitive on hydrogen, less than 1ppm hydrogen could lead the strength drop to 80% of original.

Tensile Strength of Fibers Extracted from the Leaves of the angustifolia Haw Agave in Function of their Length

2009 ◽  
Vol 15 ◽  
pp. 103-108 ◽  
Author(s):  
Luis Silva-Santos ◽  
Luis Héctor Hernández-Gómez ◽  
M. Caballero-Caballero ◽  
I. López-Hernández
Keyword(s):  
Tensile Strength ◽  
Relative Humidity ◽  
Ultimate Tensile Strength ◽  
Viscoelastic Behavior ◽  
Tensile Tests ◽  
Ultimate Strain ◽  
Constant Length ◽  
Test Speed ◽  
Test Conditions

This paper presents the results of the tensile strength evaluation of the fibers of the leaves of the agave species angustifolia Haw. The purpose of the study was to determine the mechanical behavior of the fibers under the following test conditions: (1) in fibers of the agave leave as a whole; (2) in three different longitudinal sections of the fiber: base, center and tip; (3) with a variable length and a constant test speed and (4) with a constant length and a variable test speed. The experiment began with the classification of the agave leaves by level; later the fibers were extracted through the process of retting; next the fibers were stabilized at a temperature of 20 ºc ± 2 ºc and at a relative humidity of 65 %; then the tensile tests were carried out. Finally, the Ultimate Tensile Strength (UTS), the Modulus of Elasticity (ME) and the Ultimate Strain (%) were evaluated. The results show that the fibers exhibit viscoelastic behavior and their characteristics are within the range of other similar vegetal fibers, which are currently being used by industry in the manufacture of new composites.

scholarly journals Alloy Optimization for Reducing Delayed Fracture Sensitivity of 2000 MPa Press Hardening Steel

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 853 ◽  
Author(s):  
Hardy Mohrbacher ◽  
Takehide Senuma
Keyword(s):  
Tensile Strength ◽  
Hydrogen Embrittlement ◽  
Alloying Elements ◽  
Steel Alloy ◽  
Delayed Fracture ◽  
Press Hardening ◽  
Automotive Body ◽  
Body Design ◽  
Delayed Cracking ◽  
Press Hardening Steel

Press hardening steel (PHS) is widely applied in current automotive body design. The trend of using PHS grades with strengths above 1500 MPa raises concerns about sensitivity to hydrogen embrittlement. This study investigates the hydrogen delayed fracture sensitivity of steel alloy 32MnB5 with a 2000 MPa tensile strength and that of several alloy variants involving molybdenum and niobium. It is shown that the delayed cracking resistance can be largely enhanced by using a combination of these alloying elements. The observed improvement appears to mainly originate from the obstruction of hydrogen-induced damage incubation mechanisms by the solutes as well as the precipitates of these alloying elements.

scholarly journals Comparison of Constant Load, SSRT and CSRT Methods for Hydrogen Embrittlement Evaluation Using Round Bar Specimens of High Strength Steels

2016 ◽  
Vol 56 (7) ◽  
pp. 1268-1275 ◽  
Author(s):  
Tetsushi Chida ◽  
Yukito Hagihara ◽  
Eiji Akiyama ◽  
Kengo Iwanaga ◽  
Shusaku Takagi ◽  
...  
Keyword(s):  
Hydrogen Embrittlement ◽  
High Strength Steels ◽  
High Strength ◽  
Constant Load ◽  
Round Bar

scholarly journals Determination of Critical Hydrogen Concentration and Its Effect on Mechanical Performance of 2200 MPa and 600 HBW Martensitic Ultra-High-Strength Steel

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 984
Author(s):  
Eric Fangnon ◽  
Yuriy Yagodzinskyy ◽  
Evgenii Malictki ◽  
Saara Mehtonen ◽  
Esa Virolainen ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Hydrogen Concentration ◽  
Mechanical Performance ◽  
Thermal Desorption Spectroscopy ◽  
Local Stress ◽  
High Strength ◽  
Constant Load ◽  
Strength Degradation ◽  
Load Test ◽  
Extension Rate

The influence of hydrogen on the mechanical performance of a hot-rolled martensitic steel was studied by means of constant extension rate test (CERT) and constant load test (CLT) followed with thermal desorption spectroscopy measurements. The steel shows a reduction in tensile strength up to 25% of ultimate tensile strength (UTS) at critical hydrogen concentrations determined to be about 1.1 wt.ppm and 50% of UTS at hydrogen concentrations of 2 wt.ppm. No further strength degradation was observed up to hydrogen concentrations of 4.8 wt.ppm. It was observed that the interplay between local hydrogen concentrations and local stress states, accompanied with the presence of total average hydrogen reducing the general plasticity of the specimen are responsible for the observed strength degradation of the steel at the critical concentrations of hydrogen. Under CLT, the steel does not show sensitivity to hydrogen at applied loads below 50% of UTS under continuous electrochemical hydrogen charging up to 85 h. Hydrogen enhanced creep rates during constant load increased linearly with increasing hydrogen concentration in the steel.

DOGAL 600 and 800 DP

Alloy Digest ◽  
2010 ◽  
Vol 59 (12) ◽  
Keyword(s):  
Tensile Strength ◽  
Physical Properties ◽  
Surface Treatment ◽  
Tensile Properties ◽  
High Strength Steels ◽  
High Strength

Abstract Dogal 600 and 800 DP are high-strength steels with a microstructure that contains ferrite, which is soft and formable, and martensite, which is hard and contributes to the strength of the steel. The designation relates to the lowest tensile strength. This datasheet provides information on composition, physical properties, hardness, and tensile properties. It also includes information on forming, joining, and surface treatment. Filing Code: CS-160. Producer or source: SSAB Swedish Steel Inc. and SSAB Swedish Steel.

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