Effect of Austenization Temperature on the Martensitic Transformation in a Low-Alloy Ultra-High-Strength Steel

2011 ◽  
Vol 66-68 ◽  
pp. 1797-1801
Author(s):  
Zhi Xia Qiao ◽  
Dan Tian Zhang ◽  
Yong Chang Liu ◽  
Ze Sheng Yan
Keyword(s):  
Martensitic Transformation ◽  
High Strength Steel ◽  
Heating Temperature ◽  
Lath Martensite ◽  
High Strength ◽  
Treatment Temperature ◽  
Austenite Grain ◽  
Ultra High Strength Steel ◽  
Austenite Grains ◽  
Vanadium Carbides

The effect of austenization treatment temperature on the martensitic transformation in the 30CrNi3MoV ultra-high-strength steel was investigated by means of dilatometric measurements and microstructural observations. The results showed that the coarsening temperature of austenite grains in the 30CrNi3MoV steel is raised to about 1000°C due to the inhibition to the migration of austenite grain boundaries, not only by the fine and disperse vanadium carbides, but also by the solute atoms adsorbed near the boundaries. The martensite obtained in 30CrNi3MoV samples with different austenization temperatures varied in the structural constituent, as well as in the size. The martensite microstructures obtained in the samples austenized at relatively low temperatures were composed of both lath martensite and acicular martensite and they are small in size. Yet the microstructures in the 30CrNi3MoV samples with relatively high austenization temperatures were occupied mostly by coarse lath martensite. For the 30CrNi3MoV steel, the austenization heating temperature should be kept below 1000°C in order to achieve the optimum mechanical property.

Effect of Austenization Holding Time on the Martensitic Transformation in 30CrNi3MoV Ultra-High-Strength Steel

2011 ◽  
Vol 228-229 ◽  
pp. 1107-1111
Author(s):  
Zhi Xia Qiao ◽  
Dan Tian Zhang ◽  
Yong Chang Liu ◽  
Ze Sheng Yan
Keyword(s):  
Martensitic Transformation ◽  
High Strength Steel ◽  
High Strength ◽  
Holding Time ◽  
Critical Parameters ◽  
Treatment Technology ◽  
Heat Treated ◽  
Ultra High Strength Steel ◽  
Austenite Grains ◽  
Dislocation Defects

Any heat treatment technology must begin with the process of austenization, during which the holding time at austenite region is one of the critical parameters. The effect of austenization treatment holding time on the martensitic transformation in the 30CrNi3MoV ultra-high-strength steel was investigated by means of dilatometric measurements and microstructural observations. The results showed that extending the holding time at 900 oC won’t cause obvious coarsening of austenite grains due to the dragging effect of vanadium solute atoms adsorbed at austenite grain boundaries. Martensite microstructures obtained in the 30CrNi3MoV samples that were heat treated with different holding time varied a little. The austenization holding time has obvious influence on the Ms of the 30CrNi3MoV steel, because it simultaneously affect the size of prior austenite grains and the configuration of dislocation defects.

Martensitic Transformation in a Low-Alloy Ultra-High-Strength Steel

2011 ◽  
Vol 295-297 ◽  
pp. 1470-1473 ◽  
Author(s):  
Zhi Xia Qiao ◽  
Dan Tian Zhang ◽  
Yong Chang Liu ◽  
Ze Sheng Yan
Keyword(s):  
Martensitic Transformation ◽  
High Strength Steel ◽  
Lath Martensite ◽  
High Strength ◽  
Transformation Rate ◽  
Low Carbon ◽  
High Carbon ◽  
Process Characteristics ◽  
Ultra High Strength Steel ◽  
Carbon Martensite

Martensitic transformation is the most important phase transformation strengthening the 30CrNi3MoV ultra-high-strength steel during heat treatment process. Characteristics of the martensitic transformation in the 30CrNi3MoV steel were investigated by means of dilatometric measurements and microstructural observations. The results showed that the starting and finishing martensitic transformation temperatures of the 30CrNi3MoV explored steel are 317°C and 167°C respectively, which are hardly influenced by the cooling rate from austenite region. Such a wide temperature range of martensitic transformation in the 30CrNi3MoV steel results into the diversity of martensite microstructures. The microstructures in all the quenched 30CrNi3MoV samples are composed of mixture of lath and acicular martensite, corresponding to low-carbon and high-carbon martensite respectively. The transformation rate of acicular martensite is much slower than that of lath martensite, which can be attributed to the stabilization of the rest high-carbon austenite after the formation of lath martensite.

Investigation of the Austenite Grain Growth in HY-TUF Steel

2020 ◽  
Vol 299 ◽  
pp. 482-486
Author(s):  
Mikhail V. Maisuradze ◽  
Maksim A. Ryzhkov
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Heating Temperature ◽  
High Strength ◽  
Silicon Steel ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Austenite Grains ◽  
Austenite Grain Growth ◽  
Intensive Growth

The high strength silicon steel HY-TUF, applied for manufacturing of the heavy loaded aerospace and engineering parts, was investigated. The effect of the heating temperature in the range 900...1000 °C on the austenite grain size was studied. The steel under consideration had a significant scatter of the austenite grain size. The most intensive growth of the austenite grains was observed in the temperature range 975...1000 °C.

In situ observation on microstructure evolution of 22MnB5 in hot stamping process

2019 ◽  
Vol 116 (2) ◽  
pp. 209
Author(s):  
Ling Kong ◽  
Yan Peng
Keyword(s):  
Martensitic Transformation ◽  
Grain Boundary ◽  
Cooling Rate ◽  
Microstructure Evolution ◽  
Hot Stamping ◽  
High Strength ◽  
Continuous Cooling ◽  
Austenite Grain ◽  
Austenite Grains ◽  
Austenite Grain Boundary

High temperature confocal laser scanning microscopy (CLSM) was used to investigate the microstructure evolution of high-strength boron steel 22MnB5 during hot stamping. The experimental results show that it is complete austenitized at temperatures about 810 °C during the heating process. Most of the initial austenite grain size is small and locally coarse. At 920 °C to 1000 °C, the phenomenon of B remelted and solidified was observed which played a very good pinning role at the austenite grain boundary, preventing coarsening of austenite grains. The segregation of B and the addition of Mn result in a significant reduction in both the minimum boron reverse melt content and the final solidification temperature. In the continuous cooling stage, martensitic transformation occurs at the cooling rate of 60 °C/s, and the martensite start point is 400 °C and martensite finish point is 280 °C. A large number of bursts are concentrated from 380 °C to 330 °C. There are two main forms of martensitic transformation: first, martensite begins to appear at the coarse austenite grain boundary, and grows transgranularly. Second, the new martensite laths starts from the previously formed laths and grows at a certain angle into the austenite grains. The main factor in the increase of martensite in continuous cooling is the formation of variable temperature martensite rather than the growth of martensite laths. At the cooling rate of 20 °C/s, the bainite and ferrite transformation appeared and the conversion temperature of bainite was about 600 °C. The cooling speed has a great influence on the performance of the 22MnB5 hot stamping component. The room temperature microhardness at cooling rates of 5 °C/s, 20 °C/s, and 60 °C/s was 194 HV, 243 HV, and 430 HV, respectively. Therefore, ensuring sufficient cooling rate is a key condition for obtaining ultra-high strength hot stamping components.

The Effect of Heating Process on Strength and the Original Austenite Grain Size of Hot Forming Parts

2014 ◽  
Vol 1063 ◽  
pp. 28-31
Author(s):  
Kuan Hui Hu ◽  
Xiang Dong Liu ◽  
Guan Wen Feng ◽  
Rong Dong Han
Keyword(s):  
Grain Size ◽  
Heating Temperature ◽  
Hot Stamping ◽  
Lath Martensite ◽  
Testing Machine ◽  
Heating Process ◽  
Austenite Grain Size ◽  
Heat Temperature ◽  
Austenite Grain ◽  
Austenite Grains

Strength, microstructure and austenitic grain size of a hot formed steel WHT1300HF after simulative hot stamping were studied by using universal testing machine for materials and optical microscopy. The results show that the yield strength of the hot stamping parts presented the tendency of earlier decrease and later increase with the extension of holding time, tensile strength was first reduced and then hold above 1400 MPa. In addition, the microstructure of the hot stamping parts was lath martensite, and martensite lath length and packet width increases with the heating temperature increased from 850 °C to 1050 °C. Especially, the effect of heat temperature on the original austenite grain size was more obvious, such as the austenite grains grew up quickly with the increase of heating temperature, and the original austenite grain diameter was 37.8 μm when the temperature reached 1050 °C.

Influence of Austenite Grain Size on Martensite Start Temperature of Nb-V-Ti Microalloyed Ultra-High Strength Steel

2016 ◽  
Vol 848 ◽  
pp. 624-632 ◽  
Author(s):  
Ji Dong ◽  
Chen Xi Liu ◽  
Yong Chang Liu ◽  
Chong Li ◽  
Qian Ying Guo ◽  
...  
Keyword(s):  
Grain Size ◽  
Dislocation Density ◽  
High Strength Steel ◽  
Volume Fraction ◽  
High Strength ◽  
Austenite Grain Size ◽  
Microstructure Observation ◽  
Austenite Grain ◽  
Ultra High Strength Steel ◽  
Start Temperature

In order to investigate the effect of austenite grain size on martensite start temperature of Nb-V-Ti micro-alloyed ultra-high strength steel, the phase transformation features of Nb-V-Ti micro-alloyed steel was investigated. It has been found that martensite start temperature increased with the increase of austenite grain size as a consequence of the increase of austenitizing temperature. Based on microstructure observation, two types of MX carbonitrides with different compositions and morphologies have been identified. With the increase of the austenite grain size, both the volume fraction of precipitates and the dislocation density decreased, which may be induced by the strengthening of the austenite matrix directly and increasing the resistance of austenite to plastic deformation. Hence, the increase of martensite start temperature could be attributed to a decrease in volume fraction of precipitates and dislocation density.

Effect of Pre-Heating Temperature on Microstructure and Properties of 22MnB5 Steel Hot Stamping

2014 ◽  
Vol 1063 ◽  
pp. 108-111
Author(s):  
Ping Li ◽  
Yu Sheng Liu ◽  
Tian Zong Gongzi ◽  
Ke Min Xue
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Martensitic Transformation ◽  
Heating Temperature ◽  
Hot Stamping ◽  
High Strength ◽  
High Tensile Strength ◽  
22Mnb5 Steel ◽  
Stamping Process ◽  
Ultra High Strength Steel

The hot stamping process of ultra high strength steel(UHSS) sheet is an innovative way to manufacture the components with a ultra high tensile strength. The sufficiency of martensitic transformation in formed component is affected by pre-heating temperature of blank directly. In this paper, experiments of heating UHSS blanks to 700°C, 800°C, 900°C and 1000°C were implemented to investigate the effect of pre-heating temperature on the formed component’s microstructure and mechanical properties. The results indicate that 900°C is the best pre-heating temperature for hot stamping process. The microstructure of formed component is all fine and uniform martensite. Meanwhile, tensile strength and vickers hardness raise up to 1580MPa and 450HV, respectively.

CRUCIBLE D6

Alloy Digest ◽  
1962 ◽  
Vol 11 (5) ◽  
Keyword(s):  
Fracture Toughness ◽  
Tensile Strength ◽  
Low Temperature ◽  
High Strength Steel ◽  
High Strength ◽  
Heat Treating ◽  
Steel Company ◽  
Temperature Performance ◽  
Ultra High Strength Steel ◽  
Crucible Steel

Abstract Crucible D6 is a low alloy ultra-high strength steel developed for aircraft-missile applications and primarily designed for use in the 260,000-290,000 psi tensile strength range. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness, creep, and fatigue. It also includes information on low temperature performance as well as forming, heat treating, machining, and joining. Filing Code: SA-129. Producer or source: Crucible Steel Company of America.

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