scholarly journals The Effects of Phosphorus Segregation at Grain Boundaries and Boron Addition on the Impact Toughness of Medium Carbon Tempered Martensite Steels with 150 kgf/mm2 Strength Level

1991 ◽  
Vol 77 (12) ◽  
pp. 2155-2162 ◽  
Author(s):  
Tsuyoshi INOUE ◽  
Yoshio NAMBA
Keyword(s):  
Impact Toughness ◽  
Grain Boundaries ◽  
Strength Level ◽  
Boron Addition ◽  
Tempered Martensite ◽  
Phosphorus Segregation ◽  
Medium Carbon ◽  
The Impact

scholarly journals Influence of Vanadium on the Microstructure and Mechanical Properties of Medium-Carbon Steels for Wheels

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 978 ◽  
Author(s):  
Pengfei Wang ◽  
Zhaodong Li ◽  
Guobiao Lin ◽  
Shitong Zhou ◽  
Caifu Yang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Impact Toughness ◽  
Grain Refinement ◽  
Carbon Steels ◽  
Precipitation Strengthening ◽  
Austenite Grain Size ◽  
Medium Carbon ◽  
Microstructure And Mechanical Properties ◽  
Medium Carbon Steels ◽  
The Impact

Steels used for high-speed train wheels require a combination of high strength, toughness, and wear resistance. In 0.54% C-0.9% Si wheel steel, the addition of 0.075 or 0.12 wt % V can refine grains and increase the ferrite content and toughness, although the influence on the microstructure and toughness is complex and poorly understood. We investigated the effect of 0.03, 0.12, and 0.23 wt % V on the microstructure and mechanical properties of medium-carbon steels (0.54% C-0.9% Si) for train wheels. As the V content increased, the precipitation strengthening increased, whereas the grain refinement initially increased, and then it remained unchanged. The increase in strength and hardness was mainly due to V(C,N) precipitation strengthening. Increasing the V content to 0.12 wt % refined the austenite grain size and pearlite block size, and increased the density of high-angle ferrite boundaries and ferrite volume fraction. The grain refinement improved the impact toughness. However, the impact toughness then reduced as the V content was increased to 0.23 wt %, because grain refinement did not further increase, whereas precipitation strengthening and ferrite hardening occurred.

EFFECT OF BORON ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF HOT-ROLLED Nb-ADDED HSLA H-SECTION STEEL

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1885-1890 ◽  
Author(s):  
ZUOCHENG WANG ◽  
GUOTAO CUI ◽  
TAO SUN ◽  
WEIMIN GUO ◽  
XIULING ZHAO ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Impact Toughness ◽  
Charpy Impact ◽  
High Strength ◽  
Charpy Impact Test ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Boron Addition ◽  
Low Temperature Impact Toughness ◽  
The Impact

In our research, boron was added into the Nb -added high strength low alloy (HSLA) H -section steels. The contents of boron added were 4ppm, 8ppm and 11ppm, respectively. The mechanical properties of H -section steels with/without boron were examined by using uniaxial tensile test and Charpy impact test ( V -notch). The morphologies of the microstructure and the fracture surfaces of the impact specimens were observed by metalloscope, stereomicroscope and electron probe. The experimental results indicate that boron gives a significant increase in impact toughness, especially in low temperature impact toughness, though it leads to an unremarkable increase in strength and plasticity. For instance, the absorbed energy at -40°C reaches up to 126J from 15J by 8ppm boron addition, and the ductile-brittle transition temperature declines by 20°C. It is shown that boron has a beneficial effect on grain refinement. The fracture mechanism is transited from cleavage fracture to dimple fracture due to boron addition.

Improvement on Impact Toughness of Cold Formed S420 Steel by Direct Quenching

2021 ◽  
Vol 1016 ◽  
pp. 648-653
Author(s):  
Antti Kaijalainen ◽  
Juho Mourujärvi ◽  
Juha Tulonen ◽  
Petteri Steen ◽  
Jukka I. Kömi
Keyword(s):  
Grain Size ◽  
Tensile Strength ◽  
Impact Toughness ◽  
Yield Strength ◽  
Uniform Elongation ◽  
Cold Deformation ◽  
Strength Level ◽  
Cold Forming ◽  
Direct Quenching ◽  
The Impact

The aim of this work is to study the effect cold forming rate (CFR) on the mechanical properties and microstructure of a conventional TMCP and a direct-quenched steel in 420 MPa strength level. The microstructure was characterized using FESEM-EBSD. Tensile properties and Charpy-V impact toughness were determined. As the CFR increased, the yield and tensile strength raised quite linearly with both steels. Yield strength values increased from 450 MPa (as-rolled material) to 700 MPa (25 % CFR). However, tensile strength increased less compared to yield strength. Uniform elongation decreased linearly till about 10 % CFR and total elongation till about 15 – 20 % CFR. The impact values decreased quite linearly in -40 °C and -60 °C test temperature when the cold forming rate increased. In longitudinal direction (L-T) the impact values were at high level at -40 °C and -60 °C with both steels with all CFR. In transverse direction (T-L) the impact results were lower. Impact energies were enhanced by direct quenching compared to conventional steel in every CFR stage. EBSD results showed no major difference between steels in the grain sizes in generally. However, cold forming decreased the grain size and increased low-angle grain boundaries in correlation with increasing CFR. Small size of the coarsest grains (d90%) usually indicate better toughness, however in this case the impact values were decreased even with smaller grain size as cold deformation occurs. On the other hand, the strength level increased with forming rate. Therefore, a brief discussion of the microstructural features controlling the impact toughness is given.

Impact Toughness of Grade 92 Steel Aging at 700°C

2017 ◽  
Author(s):  
Gu Baolan ◽  
Xu Tong
Keyword(s):  
Impact Toughness ◽  
Grain Boundaries ◽  
Aging Time ◽  
Impact Energy ◽  
Laves Phase ◽  
Time Increase ◽  
Phase Coarsening ◽  
Grade 92 Steel ◽  
The Impact ◽  
Variation Trends

The evolution of microstructures and the variation of impact toughness of Grade 92 steel aged 200,500, 800, 1000 hours at 700 °C were studied in this paper. The results show that the impact energy of Grade 92 steel was reduced significantly with the aging time increase. After 200 h aging, the value of impact energy decreased about 10%; then the impact energy variation trends to be stable with 500 h aging. When the aging time increase to 800 h, the impacts energy decreased about 26% compared with the original sample; and then the variation trends stable with 1000 h aging. The precipitation and growth of M23C6 Phases at the prior austenite grain boundaries and martensitie lath boundaries during aging are major reasons of the impact energy decrease. 200 h aging, M23C6 carbides precipitate at the grain boundaries. Laves phase was discovered after 500 h aging, then the M23C6 and Laves phase coarsening with the aging time. This made the impact toughness degradation more.

scholarly journals Influence of Austempering of As-Cast Medium Carbon High-Silicon Steel on Wear Resistance

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7518
Author(s):  
Marko Sedlaček ◽  
Grega Klančnik ◽  
Aleš Nagode ◽  
Jaka Burja
Keyword(s):  
Wear Resistance ◽  
Low Temperature ◽  
Impact Toughness ◽  
Isothermal Holding ◽  
Rock Breaking ◽  
Silicon Steel ◽  
Tempered Martensite ◽  
Medium Carbon ◽  
High Silicon Steel ◽  
High Silicon

The aim of this study was to evaluate the effect of austempering compared to quenching and low-temperature tempering on wear resistance of an as-cast medium carbon high-silicon steel intended for rock breaking. Austempering was done by isothermal holding at 270, 300 and 350 °C in molten salt baths, while quenching was done in water. The austempering treatments resulted in microstructural combinations of bainite and martensite. The isothermal holding at 270 °C resulted in bainite and self-tempered martensite, while isothermal holdings at 300 and 350 °C resulted in bainite and untempered martensite. The two quench and temper treatments resulted in tempered martensite. In general austempering resulted in lower hardness values when compared to quenching and tempering but higher impact toughness. The wear resistance was best for quenching and low temperature tempering, followed by austempering at 270 °C, but at slightly lower hardness and 25% higher impact toughness. The other two austempering treatments resulted in worse wear resistance.

scholarly journals Effect of Cooling Rate on The Microstructure And Cryogenic Impact Toughness of HAZ in 9% Ni Steel

2021 ◽  
Vol 59 (11) ◽  
pp. 781-795
Author(s):  
Hae Won Eom ◽  
Joo Yeon Won ◽  
Sang Yong Shin
Keyword(s):  
Grain Size ◽  
Impact Toughness ◽  
Grain Boundaries ◽  
Cooling Rate ◽  
Volume Fraction ◽  
Lath Martensite ◽  
Coarse Grained ◽  
High Angle ◽  
Tempered Martensite ◽  
Effective Grain Size

The effects of cooling rate on the microstructure and cryogenic impact toughness of coarse-grained heat-affected zone (CGHAZ) and inter-critically reheated coarse-grained HAZ (IC CGHAZ) in 9% Ni steel were investigated. CGHAZ and IC CGHAZ specimens were prepared from 9% Ni steel by controlling the cooling rate of the simulated welding process. The microstructure of the CGHAZ specimens consisted of autotempered martensite and lath martensite. As the cooling rate increased, the volume fraction of the autotempered martensite and the effective grain size decreased. A large amount of fine carbides was distributed inside the auto-tempered martensite, the dislocation density was low, and high angle grain boundaries were not observed. The microstructure of the IC CGHAZ specimens consisted of tempered martensite and lath martensite. As the cooling rate increased, the volume fraction of the tempered martensite and effective grain size decreased. Finer carbides were distributed inside the tempered martensite than in the auto-tempered martensite, the dislocation density was low, and high angle grain boundaries were not observed. Cryogenic fracture revealed that ductile fracture occurred in the auto-tempered martensite and tempered martensite, and brittle fracture occurred in the lath martensite. The crack propagation path was zig-zag in the high angle grain boundaries of the lath martensite. The volume fraction of auto-tempered martensite and tempered martensite and the effective grain size in the HAZ specimens had a significant effect on cryogenic impact toughness. In the IC CGHAZ specimens, cryogenic impact toughness decreased and then became constant as the cooling rate increased, due to a decrease in the volume fraction of the tempered martensite and effective grain size.

scholarly journals Toughness Property Control by Nb and Mo Additions in High-Strength Quenched and Tempered Boron Steels

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 95
Author(s):  
Irati Zurutuza ◽  
Nerea Isasti ◽  
Eric Detemple ◽  
Volker Schwinn ◽  
Hardy Mohrbacher ◽  
...  
Keyword(s):  
Solid Solution ◽  
Transition Temperature ◽  
High Strength ◽  
Unit Size ◽  
Tempered Martensite ◽  
Size Refinement ◽  
Direct Quenching ◽  
Property Control ◽  
The Impact ◽  
Impact Transition Temperature

The synergetic effect on hardenability by combining boron with other microalloying elements (such as Nb, Mo and Nb + Mo) is widely known for high-strength medium carbon steels produced by direct quenching and subsequent tempering treatment. The improvement of mechanical properties could be reached through optimization of different mechanisms, such as solid solution hardening, unit size refinement, strain hardening, fine precipitation hardening and the effect of carbon in solid solution. The current study proposes a procedure for evaluating the contribution of different microstructural aspects on Charpy impact toughness. First, the effect that austenite conditioning has on low-temperature transformation unit sizes and microstructural homogeneity was analysed for the different microalloying element combinations. A detailed crystallographic characterization of the tempered martensite was carried out using electron backscattered diffraction (EBSD) in order to quantify the effect of unit size refinement and dislocation density. The impact of heterogeneity and presence of carbides was also evaluated. The existing equations for impact transition temperature (ITT50%) predictions were extended from ferrite-pearlite and bainitic microstructures to tempered martensite microstructures. The results show that microstructural refinement is most beneficial to strength and toughness while unit size heterogeneity has a particularly negative effect on ductile-to-brittle transition behaviour. By properly balancing alloy concept and processing, steel having a yield strength above 900 MPa and low impact transition temperature could be obtained by direct quenching and tempering.

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