Producing a Tough, High Strength Cast Steel Free of Temper Embrittlement

1979 ◽  
Vol 101 (1) ◽  
pp. 98-103
Author(s):  
S. Floreen
Keyword(s):  
Cast Steel ◽  
Temper Embrittlement ◽  
High Strength ◽  
Auger Spectroscopy ◽  
Coarse Grained ◽  
Transgranular Fracture ◽  
Tempering Temperature ◽  
Good Tolerance ◽  
Fine Grained ◽  
Martensite Packet

Temper embrittlement of a cast 3Ni-3Cr steel was produced by small amounts of either P or Mn in samples tempered at 650°C and air cooled. Auger spectroscopy examinations showed P embrittlement was produced by cosegregation of P, Ni, and Cr. Embrittlement by Mn appeared to be caused by Mn and S segregation. In coarse grained materials fractures were intergranular. In fine grained material, both intergranular and brittle transgranular fractures were observed, and Auger mapping showed impurity enrichment on transgranular fracture surfaces. Segregation and fracture on martensite packet boundaries is suggested as the origin of the transgranular fracture. Changing the tempering temperature and adding a half percent Mo solved the embrittlement problem. Water quenching was not required. A 150 mm thick casting of the new composition showed good tolerance for P and Mn, a yield strength of 500 MPa, and good toughness down to −80°C.

Microstructural Refinement in a Commercial Aluminum Alloy Processed by ECAP Using a Die Channel Angle of 110 Degrees

2015 ◽  
Vol 1114 ◽  
pp. 3-8
Author(s):  
Nicolae Şerban ◽  
Doina Răducanu ◽  
Nicolae Ghiban ◽  
Vasile Dănuţ Cojocaru
Keyword(s):  
Grain Refinement ◽  
Cross Section ◽  
High Strength ◽  
Secondary Phase ◽  
Coarse Grained ◽  
Metallographic Analysis ◽  
Second Phase ◽  
Channel Angle ◽  
Ambient Temperatures ◽  
Fine Grained

The properties of ultra-fine grained materials are superior to those of corresponding conventional coarse grained materials, being significantly improved as a result of grain refinement. Equal channel angular pressing (ECAP) is an efficient method for modifying the microstructure by refining grain size via severe plastic deformation (SPD) in producing ultra-fine grained materials (UFG) and nanomaterials (NM). The grain sizes produced by ECAP processing are typically in the submicrometer range and this leads to high strength at ambient temperatures. ECAP is performed by pressing test samples through a die containing two channels, equal in cross-section and intersecting at a certain angle. The billet experiences simple shear deformation at the intersection, without any precipitous change in the cross-section area because the die prevents lateral expansion and therefore the billet can be pressed more than once and it can be rotated around its pressing axis during subsequent passes. After ECAP significant grain refinement occurs together with dislocation strengthening, resulting in a considerable enhancement in the strength of the alloys. A commercial AlMgSi alloy (AA6063) was investigated in this study. The specimens were processed for a number of passes up to nine, using a die channel angle of 110°, applying the ECAP route BC. After ECAP, samples were cut from each specimen and prepared for metallographic analysis. The microstructure of the ECAP-ed and as-received material was investigated using optical (OLYMPUS – BX60M) and SEM microscopy (TESCAN VEGA II – XMU). It was determined that for the as-received material the microstructure shows a rough appearance, with large grains of dendritic or seaweed aspect and with a secondary phase at grain boundaries (continuous casting structure). For the ECAP processed samples, the microstructure shows a finished aspect, with refined, elongated grains, also with crumbled and uniformly distributed second phase particles after a typical ECAP texture.

Hybrid Design Concept Using High-Strength Cast Steel Inserts for Tubular Joints of Offshore Structures

1998 ◽  
Vol 120 (1) ◽  
pp. 10-19 ◽  
Author(s):  
C. M. Sonsino ◽  
R. Umbach
Keyword(s):  
Fatigue Life ◽  
Crack Initiation ◽  
Large Scale ◽  
Fatigue Behavior ◽  
Cast Steel ◽  
High Strength ◽  
Offshore Structures ◽  
Fine Grained ◽  
Tubular Joints ◽  
Medium Strength

In a joint project of a German working group supported by the ECSC and the Studiengesellschaft fu¨r Stahlanwendung e.V., the fatigue behavior of large-scale hybrid tubular joints with inserts manufactured from the high-strength cast steel GS-12 MnMo 7 4 welded into tubular members formed from the fine-grained steel StE 500 were compared to the behavior of large-scale welded tubular joints. The latter were made from medium-strength fine-grained steel StE 355 and high-strength StE 690. In addition, data from hybrid joints with cast steel inserts of medium-strength GS-8 Mn 7 welded into StE 355 tubulars is available for comparison. The tests were carried out under variable amplitude loading in artificial seawater. The results were evaluated for the failure criteria fatigue life to crack initiation (a = 1 mm) and through crack. With medium-strength (Rp0.2 > 355 N/mm2) hybrid tubulars, where by the use of cast steel inserts the welds were removed into areas of lower stress concentration, fatigue lives higher than a factor of 100 were achieved compared to the welded nodes, even those made from StE 690. However, by the use of high-strength (Rp0.2 > 500 N/mm2) cast steel inserts and tubular members of corresponding strength, the fatigue life to crack initiation was improved by a factor of two despite a thickness reduction compared to the medium-strength design. Post-weld treatments of the welded tubulars without cast steel inserts like shot-peening, TIG-dressing, or their combination resulted only in a slight increase of fatigue life. The results of this investigation do not only show how to improve the fatigue life by a new design using cast steel inserts, but indicate also how to revise design codes from the point of damage calculation (damage sum of 0.50 for welded nodes and 0.25 for cast steel inserts instead of the conventional value of 1.00), as well as consideration of fatigue life to initiation of a technically detectable crack with a defined depth e.g., a = 1 mm.

Effect of Tempering Temperature on Mechanical Properties of High Strength Wear Resistant Cast Steel

2013 ◽  
Vol 791-793 ◽  
pp. 440-443
Author(s):  
Hong Bo Li ◽  
Jing Wang ◽  
Han Chi Cheng ◽  
Chun Jie Li ◽  
Xing Jun Su
Keyword(s):  
Mechanical Properties ◽  
Impact Toughness ◽  
Cast Steel ◽  
High Strength ◽  
Fracture Morphology ◽  
Temperature Quenching ◽  
Tempering Temperature ◽  
Wear Resistant ◽  
Dimple Fracture ◽  
The Impact

This paper mainly studied the high temperature quenching oil quenching, tempering temperature on the influence of high strength steel mechanical properties of wear resistant. The results show that high strength and toughness wear-resistant cast steel with 880°C× 30min after oil quenching, the hardness of 38.6HRC steel, the impact toughness value reaches 40.18J/cm2. After 200°C, 400°C and 600°C tempering, with the increase of the tempering temperature, the hardness decreased linearly, as by 600°C tempering, the hardness has been reduced to 22.3HRC. Impact toughness with the tempering temperature, the overall upward trend, the impact toughness of some reduced at 400°C, the highest impact toughness value reaches 113.34J/cm2. From the fracture morphology can be seen, with the increase of tempering temperature, ductile fracture increased, by 600°C tempering is dimple fracture, obviously can not see the traces of brittle fracture.

The critical influence of La content on the microstructure-toughness relationship in the simulated coarse-grained heat-affected zone of high-strength low-alloy steels

2021 ◽  
Vol 118 (2) ◽  
pp. 212
Author(s):  
Yuxin Cao ◽  
Xiangliang Wan ◽  
Feng Zhou ◽  
Hangyu Dong ◽  
Kaiming Wu ◽  
...  
Keyword(s):  
Heat Affected Zone ◽  
Acicular Ferrite ◽  
High Strength ◽  
Coarse Grained ◽  
Low Alloy Steels ◽  
Fine Grained ◽  
Welding Thermal Cycle ◽  
Alloy Steels ◽  
High Fraction ◽  
The Impact

The present study was envisaged to investigate the role of La content on the particle, microstructure and toughness in the simulated coarse-grained heat-affected zone (CGHAZ) of high-strength low-alloy steels. Three steels with La content of 0.016 wt.%, 0.046 wt.% and 0.093 wt.% were prepared and simulated in a 100 kJ/cm heat input welding thermal cycle. Subsequently, the particle and microstructure of selected specimens were characterized and the impact absorb energy was measured at −20 °C. The results indicated that the La2O2S inclusions in 0.016 wt.%-La steel were gradually modified to LaS-LaP in 0.046 wt.%-La steel and to LaP in 0.093 wt.%-La steel. A higher fraction of acicular ferrite was obtained in the simulated CGHAZ of 0.016 wt.%-La steel, since the inclusion of La2O2S was more powerful to induce the formation of acicular ferrite. Furthermore, the fraction of M-A constituents in the simulated CGHAZ increased with increasing La content. The impact toughness in the simulated CGHAZ of 0.016 wt.%-La steel was the highest, owing to the high fraction of the fine-grained acicular ferrite and low fraction of M-A constituent.

Harmonic Structure Design of Co-Cr-Mo Alloy with Outstanding Mechanical Properties

2014 ◽  
Vol 939 ◽  
pp. 60-67 ◽  
Author(s):  
Choncharoen Sawangrat ◽  
Osamu Yamaguchi ◽  
Sanjay Kumar Vajpai ◽  
Kei Ameyama
Keyword(s):  
Mechanical Properties ◽  
Mechanical Milling ◽  
Three Dimensional ◽  
High Strength ◽  
Surface Region ◽  
Structure Design ◽  
Coarse Grained ◽  
Harmonic Structure ◽  
Fine Grained ◽  
Plasma Sintering

Co-Cr-Mo alloy powders were subjected to controlled mechanical milling at room temperature under Ar atmosphere to fabricate bimodal microstructure in the MM powders, having nanosized grains in the surface region and micron-sized coarse grains in the center of the milled powders. Subsequently, the MM powder was compacted by spark-plasma sintering (SPS) process. The sintered compacts indicated two structure areas: (i) ultra-fine grained (UFG) regions, called shell, and (ii) the coarse grained regions called core. The shell and the core correspond to the surface and center of the MM powders, respectively. The shell regions established a continuous three dimensional network of high strength ultra-fine grained regions, which surrounded the discrete coarse grained ductile regions. Such a microstructure is referred as Harmonic Structure. The sintered Co-Cr-Mo alloy compacts exhibited outstanding mechanical properties. The yield strength increased from 605 to 635 MPa, and ultimate tensile strength increased from 1201 to 1283 MPa. Moreover, the elongation was maintained more or less same as that of coarse grained compacts. Therefore, the harmonic structure design leads to the new generation microstructure of Co-Cr-Mo alloy, which demonstrates outstanding mechanical properties, i.e. superior strength and excellent ductility as compared to conventional materials. Keywords: mechanical milling, Co-Cr-Mo alloys, mechanical properties, harmonic structure.

scholarly journals The Preparation Process, Microstructure and Properties of Cellular TiC–high Mn Steel-bonded Carbide

2020 ◽  
Author(s):  
Guoping Li ◽  
Haojun zhou ◽  
Hao Yang ◽  
Mingchu Huang ◽  
Yingbiao Peng ◽  
...  
Keyword(s):  
Cellular Structure ◽  
Rupture Strength ◽  
Weight Ratio ◽  
High Strength ◽  
Coarse Grained ◽  
Preparation Process ◽  
Hard Phase ◽  
Fine Grained ◽  
High Toughness ◽  
Mn Steel

TiC–high Mn steel-bonded carbide with a cellular structure was designed and fabricated by powder metallurgy techniques using coarse and fine TiC particles as the hard phase. This preparation process was carefully investigated and optimized. The microstructure of the TiC steel-bonded carbide was observed using a scanning electron microscope. Results showed that there are two types of microstructures in the TiC steel-bonded carbide: the coarse-grained TiC and fine-grained TiC. The transverse rupture strength and impact toughness of the alloy reach maximum values 2231 MPa and 12.87 J/cm2, respectively when the starting weight ratio of MP-A (containing coarse TiC particles) to MP-B (containing fine TiC particles) is 60:40. Hence, this study serves as a feasible example of how to prepare a high-strength and high-toughness TiC–high Mn steel-bonded carbide.

scholarly journals Increasing Fatigue Life of 09Mn2Si Steel by Helical Rolling: Theoretical–Experimental Study on Governing Role of Grain Boundaries

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4531
Author(s):  
Sergey Panin ◽  
Ilya Vlasov ◽  
Pavel Maksimov ◽  
Dmitry Moiseenko ◽  
Pavlo Maruschak ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Grain Boundaries ◽  
Elastic Energy ◽  
High Strength ◽  
Coarse Grained ◽  
Material Structure ◽  
Structure Transformation ◽  
Helical Rolling ◽  
Fine Grained ◽  
Fine Grained Structure

The structure and mechanical properties of the 09Mn2Si high-strength low-alloyed steel after the five-stage helical rolling (HR) were studied. It was revealed that the fine-grained structure had been formed in the surface layer ≈ 1 mm deep as a result of severe plastic strains. In the lower layers, the “lamellar” structure had been formed, which consisted of thin elongated ferrite grains oriented in the HR direction. It was shown that the five-stage HR resulted in the increase in the steel fatigue life by more than 3.5 times under cyclic tension. The highest values of the number of cycles before failure were obtained for the samples cut from the bar core. It was demonstrated that the degree of the elastic energy dissipation in the steel samples under loading directly depended on the area of the grain boundaries as well as on the grain shapes. The fine-grained structure possessed the maximum value of the average torsional energy among all the studied samples, which caused the local material structure transformation and the decrease in the elastic energy level. This improved the crack resistance under the cyclic mechanical loading. The effect of the accumulation of the rotational strain modes at the grain boundaries was discovered, which caused the local structure transformation at the boundary zones. In the fine-grained structure, the formation of grain conglomerates was observed, which increased the values of the specific modulus of the moment of force. This could be mutually compensated due to the small sizes of grains. At the same time, the coarse-grained structures were characterized by the presence of the small number of grains with a high level of the moments of forces at their boundaries. They could result in trans-crystalline cracking.

scholarly journals The Preparation Process, Microstructure and Properties of Cellular TiC-High Mn Steel-Bonded Carbide

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 757 ◽  
Author(s):  
Guoping Li ◽  
Haojun Zhou ◽  
Hao Yang ◽  
Mingchu Huang ◽  
Yingbiao Peng ◽  
...  
Keyword(s):  
Production Cost ◽  
Rupture Strength ◽  
Weight Ratio ◽  
High Strength ◽  
Coarse Grained ◽  
Preparation Process ◽  
Hard Phase ◽  
Fine Grained ◽  
High Toughness ◽  
Mn Steel

TiC-high Mn steel-bonded carbide with a cellular structure was designed and fabricated by powder metallurgy techniques using coarse and fine TiC particles as the hard phase. This preparation process of the alloy was designed carefully and optimized. The microstructure of the alloy was observed using a scanning electron microscope. The results show that there are two types of microstructures observed in this TiC steel-bonded carbide: the coarse-grained TiC structure and fine-grained TiC structure. The transverse rupture strength and impact toughness of the alloy reach maximum values 2231 MPa and 12.87 J/cm2, respectively, when the starting weight ratio of MP-A (containing coarse TiC particles) to MP-B (containing fine TiC particles) is 60:40. Hence, this study serves as a feasible and economical example to prepare a high-strength and high-toughness TiC-high Mn steel-bonded carbide with little production cost increase.

In Situ Neutron Diffraction Study on the Mechanical Behavior of an Ultra-Fine-Grained Steel

2006 ◽  
Vol 524-525 ◽  
pp. 639-644 ◽  
Author(s):  
Kai Xiang Tao ◽  
Hahn Choo ◽  
H. Li ◽  
Bjørn Clausen ◽  
Donald W. Brown ◽  
...  
Keyword(s):  
Grain Size ◽  
Neutron Diffraction ◽  
High Strength ◽  
Neutron Diffraction Study ◽  
Coarse Grained ◽  
Transformation Induced Plasticity ◽  
Fine Grained ◽  
High Elongation ◽  
In Situ Neutron Diffraction

The martensitic phase transformation in an ultra fine grained (UFG) TRIP (transformation induced plasticity) steel with combination of high strength and high elongation was investigated during room temperature tensile test using in situ neutron diffraction. Two types of specimens, namely coarse grained (grain size of about 50 μm) and ultra-fine-grained (grain size of about 350 nm) specimens were examined. The lattice strain evolution of the austenite and martensite phases was observed and the load partitioning between the phases was identified.

Interaction Study of Carbide Precipitation and Impurity Segregation under Temper Embrittlement Conditions in a Coarse-Grained Heat-Affected Zone in Q690 Steel

2014 ◽  
Vol 1015 ◽  
pp. 189-193 ◽  
Author(s):  
Zhen Shun Li ◽  
Sheng Li Li ◽  
Xiang Hai Zhang ◽  
Ji Zhi Liu
Keyword(s):  
Grain Boundaries ◽  
Heat Affected Zone ◽  
Temper Embrittlement ◽  
High Strength ◽  
Carbide Precipitation ◽  
Coarse Grained ◽  
Hydraulic Support ◽  
Phosphorus Segregation ◽  
Impurity Segregation ◽  
Mining Face

This work studied the interaction between carbide precipitation and impurity segregation under temper embrittlement (TE) conditions in a coarse-grained heat-affected zone (CGHAZ) in Q690 steel, a low-alloy high-strength structural steel used in the hydraulic support in the fully-mechanized mining face. From the perspective of carbide precipitation, through thermodynamics calculation and analysis, it was found that the existence of cementite at the grain boundaries was preceded by impurities segregation (primarily phosphorus). The precedent phosphorus segregation thus enhances the nucleation rate of cementite at the grain boundaries by lowering the ferrite/cementite interfacial energy. Both carbide precipitation and impurity segregation at the grain boundaries reached a maximum as a result of their mutual role in the temperature range of TE.

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