Effect of Microstructural Evolution on Mechanical Properties of 55NiCrMoV7 Steel

2011 ◽  
Vol 287-290 ◽  
pp. 848-852
Author(s):  
Meng Ting Fan ◽  
Ming Yue Sun ◽  
Dian Zhong Li
Keyword(s):  
Mechanical Properties ◽  
Treatment Process ◽  
High Strength ◽  
Lower Bainite ◽  
Tempered Martensite ◽  
Tempering Temperature ◽  
Cooling Rates ◽  
Upper Bainite ◽  
Evolution Of Microstructure ◽  
Better Than

55NiCrMoV7 steel is extensively used as mould steel. However, how to obtain a product combined with both high strength and good toughness is still a problem in the heat treatment process. In current study, a series of 55NiCrMoV7 steel specimens were quenched with different cooling rates to obtain martensite, lower bainite and upper bainite, then tempered at 600°C, 620°C and 650°C, respectively. The micrographs show the evolution of microstructure with the variation of cooling rates and tempering temperature. Mechanical properties test has revealed that, 1) at the same tempering temperature, the tempered martensite has the highest strength and hardness, while the tempered lower bainite has the best impact toughness; 2) at the same ratio of yield strength to tensile strength (YS/TS), the ductility and toughness of martensite are better than that of bainite. Furthermore, fractographs of impact specimens show the ductile and brittle fracture behavior for martensite and upper bainite respectively.

Investigation of Microstructure and Mechanical Properties of Ultra High Strength Bainitic Steel

2013 ◽  
Vol 313-314 ◽  
pp. 77-81
Author(s):  
M.H. Sheikh Ansari ◽  
M. Aghaie-Khafri
Keyword(s):  
Mechanical Properties ◽  
Alloy Steel ◽  
High Strength ◽  
Lower Bainite ◽  
Good Combination ◽  
Bainitic Steel ◽  
Low Alloy Steel ◽  
Tempered Martensite ◽  
Medium Carbon ◽  
Bainitic Steels

In this study, medium carbon low alloy steel was used to obtain bainitic structures. The lower bainite and tempered martensite-lower bainite structures were achieved by isothermal austempering and up quenching treatment, respectively. Based on the results obtained these structures showed a very good combination of strength and toughness. Furthermore, it has been shown that austenitization time and temperature, as well as austempering time and temperature play a major role in achieving ultra-high strength bainitic steels.

The Effect of Quenching Media on the Microstructure and Mechanical Properties of SA508-3 Steel

2011 ◽  
Vol 311-313 ◽  
pp. 974-977 ◽  
Author(s):  
Lu Han Hao ◽  
Ming Yue Sun ◽  
Dian Zhong Li
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
Lower Bainite ◽  
Granular Bainite ◽  
Tempered Martensite ◽  
Quenching Media ◽  
Microstructure And Mechanical Properties ◽  
Allotriomorphic Ferrite ◽  
Upper Bainite

Three different quenching media (water, oil and air) were used to compare the effect of cooling rate on the microstructure and mechanical properties of SA508-3 steel. The result has demonstrated that the microstructure for water-quenched specimen is the mixture of martensite and lower bainite, for oil-quenched specimen is the mixture of upper bainite，lower bainite and a little martensite, while for air-cooled specimen is mostly granular bainite. The product of water and oil Q&T was tempered martensite with qualified mechanical properties. The air-cooled granular bainite was translated to massive and allotriomorphic ferrite during tempering, which had poor mechanical properties. To avoid the formation of granular bainite, it is necessary to increase the cooling rate to above 5°C/s.

Microstructure and Mechanical Properties of the Heat Treated Hy-TUF Steel

2020 ◽  
Vol 989 ◽  
pp. 324-328
Author(s):  
Mikhail V. Maisuradze ◽  
Maksim A. Ryzhkov
Keyword(s):  
Mechanical Properties ◽  
Impact Strength ◽  
High Strength ◽  
Lower Bainite ◽  
Microstructure And Mechanical Properties ◽  
Heat Treated ◽  
Upper Bainite ◽  
Quenching And Tempering ◽  
Conventional Oil

A study of the high-strength HY-TUF steel applied for the manufacturing of heavy loaded parts was carried out. The mechanical properties of the austempered HY-TUF steel were compared to the characteristics obtained after the conventional oil quenching and tempering. The upper bainite with low impact strength was formed during the austempering at 400 °C and higher. Conventional oil quenching and tempering at temperature 400...500 °С also led to the embrittlement of the steel under consideration. The best combination of toughness and strength of the HY-TUF steel was achieved after the austempering at the temperature of lower bainite formation.

A Comparison of Tensile Strength and Impact Energy of Austempered versus Step Quenched 4340 Ultra High Strength Steel

2013 ◽  
Vol 553 ◽  
pp. 41-45
Author(s):  
Seyed Majid Safi ◽  
Seyed Yousef Ahmadi Brooghani ◽  
Hossein Amirabadi ◽  
Khalil Khalili ◽  
Mohamad Kazem Besharati Givi
Keyword(s):  
Tensile Strength ◽  
Impact Energy ◽  
High Strength ◽  
Lower Bainite ◽  
Mixed Structure ◽  
Tempered Martensite ◽  
4340 Steel ◽  
Upper Bainite ◽  
Identical Test ◽  
Austempering Temperature

This study was conducted to determine if austempered 4340 steel had different mechanical properties compared to step quenched 4340 steel. Tensile strength and impact energy was determined at room temperature under identical test conditions. The specimens were cut from a bar with 25 mm diameter and austenitized at 800°C for 60 min and followed by quenching at 430°C for the high austempering temperature to achieve the upper bainite morphology and at 360°C for the lower austempering temperature to achieve the lower bainite morphology. In the case of step quenched, the specimens were first austempered at 430°C and then austempered at 360°C to achieve the mixed structure of upper bainite and lower bainite morphology. The another set of specimens for step quenching, after austenitization were quenched to below Ms (martensite start temperature), followed by heating at 400°C to achieve the mixed structure of tempered martensite and lower bainite and 500°C to achieve the mixed structure of tempered martensite and upper bainite. It is also shown that the best combination of strength and ductility can be achieved by the mixed structure of tempered martensite and lower bainite that has been suggested in this investigation.

The development of a588 modified laterite steel using thermomechanical and low-temperature tempering process for weather resistant steel

Teknik ◽  
2021 ◽  
Vol 42 (2) ◽  
pp. 149-159
Author(s):  
Miftakhur Rohmah ◽  
Dedi Irawan ◽  
Dedi P. Utama ◽  
Toni B. Romijarso
Keyword(s):  
Mechanical Properties ◽  
Corrosion Resistance ◽  
Cooling Rate ◽  
Nickel Content ◽  
High Strength ◽  
Water Medium ◽  
Tempered Martensite ◽  
Tempering Temperature ◽  
Thermomechanical Process ◽  
Tempering Process

Laterite Steel A-588 has the potential to be a high strength low alloy for Corten steel application. Laterite steel A-588 is developed through a thermomechanical process followed by a tempering process to obtain high strength and corrosion resistance. This study aims to determine the correlation between the addition of nickel content, the variation of the cooling rate during heat treatment to the mechanical properties, and the corrosion resistance of A-588 laterite steel. The Cu, Cr, Ni, P, and Si elements significantly impact microstructure transformation. Laterite Steel A-588 with nickel and thermo-mechanical process variation has been focused on in this research. Laterite steel with 0,42%, 1%, 2%, and 3% nickel varied was homogenized, hot rolled, and heat treated with three cooling variations by water, oil, and air. They are processed with 150 C tempering. Low tempering temperature caused fine carbide precipitation and phase transition of martensite to bainite. This resulted in bainite as the final microstructure, lath tempered martensite, carbide, and ferrite. 3% Ni with a fast cooling rate increased the tempered martensite and bainite phase formation. It allowed the strength and hardness to increase relatively, followed by decreased elongation and corrosion resistance caused by the galvanic reaction. Most optimal of mechanical properties determined at a sample with 2% nickel in a water medium (strength 1203 MPa, elongation 10%, hardness 404 BHN, corrosion rate 1,306 mpy).

A New Modified Austempering to Increase Strength and Ductility Simultaneously for UHS Steels

2010 ◽  
Vol 297-301 ◽  
pp. 1109-1115 ◽  
Author(s):  
Seyed Majid Safi ◽  
M.K. Besharati Givi
Keyword(s):  
Heat Treatment ◽  
High Strength Steels ◽  
High Strength ◽  
Lower Bainite ◽  
Treatment Method ◽  
Mixed Structure ◽  
Tempered Martensite ◽  
Modified Method ◽  
Upper Bainite ◽  
Strength And Ductility

In this paper, a modified up-quenching heat treatment method to the ASSAB 705M steel (ultra high strength steel) is proposed. A low alloy steel (0.33%C), was used to study the effect of isothermal austempering, successive austempering and modified up-quenching austempering heat treatment on the mechanical properties. The specimens, were cut from a bar with 25mm diameter and after achieving the best temperature and time of austenitizing, austenitized at for 60 min and followed by quenching at for the high austempering temperature to achieve the upper bainite morphology and at for the lower austempering temperature to achieve the lower bainite morphology. In the case of successive austempering, the specimens were first austempered at for different periods (500 sec and 60 sec) and then austempered at for 1000 sec to achieve the mixed structure of upper bainite and lower bainite morphology. The specimens selected for up-quenching, after austenitization were quenched to below ( ) for 120 sec. followed by heating at to achieve the mixed structure of tempered martensite and lower bainite and to achieve the mixed structure of tempered martensite and upper bainite for 1000 sec. All of the processes were performed in the salt bath furnaces. Experimental results are presented and the advantages of the modified method are discussed. As well, it is shown that the best combination of strength and ductility can be achieved by the proposed heat treatment method. This modified method, can offer techniques that simultaneously improve not only strength 12 %( compare with results of strength after other heat treatment methods), but also ductility 38 %( compare with results of ductility after other heat treatment methods). While, conventional heat treatment of ultra high strength steels (UHSS) cannot always meet the strict engineering requirements for improved strength and ductility simultaneously. It has been shown that the mixed structure of tempered martensite and lower bainite that has been suggested in this investigation offers a good combination of strength and ductility. The technical reason for this superiority returns back to the fact that it has increased dislocation density. As a result of the increment of the dislocation density, in the morphology, the inter lath carbide (e.g. cementite) decreases, and the intra lath carbide increases. This modified austempering is applicable to all the ultra high strength steels, has noticeable economic advantages because it is simple. Use of this modified austempering for heavy parts, leads to the lightness of heavy parts and combination of the thermomechanical methods with this modified austempering can yield even much more improvements.

Effect of Tempering Process on Structure and Properties of Super Martensitic Stainless Steel

2012 ◽  
Vol 581-582 ◽  
pp. 1023-1026 ◽  
Author(s):  
Hu Dai Sun ◽  
Kun Yu Zhao ◽  
Jia Qun Rui ◽  
Wen Jiang ◽  
Xiao Chen Han ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Corrosion Resistance ◽  
Treatment Process ◽  
Martensitic Stainless Steel ◽  
Volume Fraction ◽  
Tempered Martensite ◽  
Super Martensitic Stainless Steel ◽  
Mechanical Properties And Corrosion ◽  
Better Than ◽  
Tempering Process

Two types of super martensitic stainless steels (Cr13 and Cr15) were designed. The effect of tempering process on their microstructure, mechanical properties and corrosion resistance was studied. The results showed that the main microstructure of tested steels was tempered martensite and a small number of reversed austenite when specimens were tempered in temperature range of 550-750°C. The variation of mechanical properties corresponded to the austenite volume fraction well. Both the two types of steels displayed a favorable comprehensive mechanical properties after tempering at 650°C, their product of strength and elongation reached to 18.44GPa•% and 18.44 GPa•% respectively. With the best heat treatment process,tempered at 650°C after quenching at 1050°C,the corrosion resistance of 2# steel is more better than 1# steel.

Effects of Tempering Temperature on the Microstructure and Mechanical Properties of Low Alloy Ultra-High Strength 45CrNiSiMnMoVA Steel

2021 ◽  
Vol 1036 ◽  
pp. 11-19
Author(s):  
Hong Xia Bi ◽  
Ming Hua Tang ◽  
Zhi Lan Ren ◽  
Yong Zhou
Keyword(s):  
Mechanical Properties ◽  
Mechanical Property ◽  
Microstructure Evolution ◽  
Coupling Effect ◽  
Lath Martensite ◽  
High Strength ◽  
Lower Bainite ◽  
Tempering Temperature ◽  
Complex Phase ◽  
Precipitated Phases

The effects of different tempering temperatures on the microstructure evolution and mechanical properties of the new low-alloy ultra-high-strength 45CrNiSiMnMoVA steel after quenching were investigated by mechanical property tests, SEM and TEM. The results show that a complex phase organization consisting of martensite/ lower bainite of the tested steel after treated at 920°C×1h+(320~380)°C×4h was obtained, and the partition interface of the lath martensite bundle became blurred from clear with the increase of tempering temperature; In the proposed tempering temperature range, the toughness of the alloy has become better while maintain the strength without decreasing basically, and when the tempering temperature is 350°C, the alloy has the optimal comprehensive mechanical properties of strength, plasticity and toughness together. The analysis concluded that the strong toughening of the tested steel was mainly attributed to the coupling effect of the alloying elements in the steel and the composite toughening of the nano-precipitated phases, among other aspects.

Microstructure and Mechanical Properties of High Strength Alloyed Steel for Aerospace Application

2018 ◽  
Vol 284 ◽  
pp. 351-356 ◽  
Author(s):  
Mikhail V. Maisuradze ◽  
Maksim A. Ryzhkov
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
High Strength ◽  
Single Stage ◽  
The Novel ◽  
Tempering Temperature ◽  
Quenching And Partitioning ◽  
Aerospace Application ◽  
Cooling Conditions ◽  
Quenching And Tempering

The high strength aerospace steel alloyed with Cr, Mn, Si, Ni, W and Mo was studied. The austenite transformations under continuous cooling conditions were investigated using the dilatometer analysis at the cooling rates 0.1...30 °C/s. The mechanical properties of the studied steel were determined after the conventional quenching and tempering heat treatment. The dependences of the mechanical properties on the tempering temperature were obtained. The novel quenching and partitioning heat treatment was applied to the steel under consideration. The microstructure and the mechanical properties were studied after three different modes of the quenching and partitioning (QP) treatment: single-stage QP, two-stage QP and single-stage QP with subsequent tempering (QPT).

The Influence of Thermomechanical Controlled Processing on Bainite Formation in Low Carbon High Strength Steel

2014 ◽  
Vol 783-786 ◽  
pp. 21-26
Author(s):  
Xiao Jun Liang ◽  
Ming Jian Hua ◽  
Anthony J. DeArdo
Keyword(s):  
Mechanical Properties ◽  
High Strength Steel ◽  
High Strength ◽  
Manganese Steel ◽  
Low Carbon ◽  
High Manganese ◽  
Bainite Transformation ◽  
High Manganese Steel ◽  
Cooling Rates ◽  
Controlled Processing

Thermomechanical controlled processing is a very important way to control the microstructure and mechanical properties in low carbon, high strength steel. This is especially true in the case of bainite formation, where the complexity of the austenite-bainite transformation makes the control of the processing important. In this study, a low carbon, high manganese steel containing niobium was investigated to better understand the roles of austenite conditioning and cooling rates on the bainitic phase transformation. Specimens were compared with and without deformation, and followed by seven different cooling rates ranging between 0.5°C/s and 40°C/s. The CCT curves showed that the transformation behaviors and temperatures are very different. The different bainitic microstructures which varied with austenite deformation and cooling rates will be discussed.

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