scholarly journals Minimisation of Heating Time for Full Hardening in Hot Stamping Using Direct Resistance Heating

2020 ◽  
Vol 4 (3) ◽  
pp. 80
Author(s):  
Tomoyoshi Maeno ◽  
Ken-ichiro Mori ◽  
Masato Sakagami ◽  
Yoshitaka Nakao ◽  
Ali Talebi-Anaraki
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Standard Deviation ◽  
Steel Sheet ◽  
Hot Stamping ◽  
Heating Time ◽  
Resistance Heating ◽  
Initial Microstructure ◽  
Fine Grain

To obtain enough hardness of the die-quenched products after hot stamping using direct resistance heating, the effects of the electrifying condition and initial microstructure of the quenchable steel sheet on hardness were examined in a hot bending experiment. The steel sheet was heated up to 900 °C in 3 to 10 s. The required heating time was shortened by normalising heat treatment due to the fine grain size of the sheet. The standard deviation of the hardness of the sheet heated to 900 °C in 3.2 s without temperature holding at the austenitising temperature was 12 HV, whereas the deviation reduced to 5 HV for temperature holding at the austenitising temperature of 3 s.

The Method of Eliminating Banded Structure and the Effects of Banded Structure on the Transverse Properties in 20G Steel

2013 ◽  
Vol 347-350 ◽  
pp. 1171-1175 ◽  
Author(s):  
Bin Wang ◽  
Hong Mei Hu ◽  
Cui Zhou
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Stress Concentration ◽  
Base Metal ◽  
Metallic Inclusion ◽  
Banded Structure ◽  
Grain Sizes ◽  
Fine Grain ◽  
Treatment Processes ◽  
Metallic Inclusions

The transverse properties were inferior to the longitudinal properties for the existence of banded structure in 20G steel. In order to eliminate the banded structure and improve the transverse performance of 20G steel, different heat treatment processes were adopted. The results showed that conventional normalizing could reduce the banded structure and refine the grain sizes. When 20G was heated with 10°C/min heating rated and then held at 920°C for 2h, the banded structure in the steel was almost eliminated and the microstructure was homogeneous with fine grain size, the strength increased by 14%. The non-metallic inclusion and carbide in the microstructure leaded to stress concentration and separation with the base metal. To some extent, heat treatment can improve the distribution and form of non-metallic inclusions.

Improvement of Strength and Ductility by Combining Static Recrystallization and Unique Heat Treatment in Co-20Cr-15W-10Ni Alloy for Stent Application

2021 ◽  
Vol 1016 ◽  
pp. 1503-1509
Author(s):  
Kosuke Ueki ◽  
Soh Yanagihara ◽  
Kyosuke Ueda ◽  
Masaaki Nakai ◽  
Takayoshi Nakano ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Static Recrystallization ◽  
High Strength ◽  
Small Variation ◽  
Grain Structure ◽  
Fine Grain ◽  
High Temperature Short Time ◽  
Average Grain Size ◽  
Strength And Ductility

The Co-20Cr-15W-10Ni (CCWN, mass%) alloy has excellent corrosion resistance and strength-ductility balance and is applied in almost all balloon-expandable stent platforms. To further reduce the invasiveness of stent placement, it is necessary to reduce the diameter of the stent. That is, both high strength and high ductility should be achieved while maintaining a low yield stress. In our previous studies, it was discovered that low-temperature heat-treatment (LTHT) at 873 K improves the elongation of the CCWN alloy. In this study, we focused on the grain refinement by swaging and static recrystallization to improve the strength of the alloy. The as-swaged alloy was recrystallized at 1373–1473 K for 100–300 s, followed by LTHT. A fine grain structure with an average grain size of 3–17 μm was obtained by static recrystallization. The η-phase (M12X-M6X type precipitates, M: metallic elements, X: C and/or N) formed during the recrystallization at 1373–1448 K. The alloys recrystallized at 1448 and 1473 K had a homogeneous structure with a small variation in the grain size. On the other hand, the alloys recrystallized at 1373 and 1423 K had an inhomogeneous structure in which fine and coarse grains were mixed. Both the strength and ductility of the CCWN alloy were improved by combining high-temperature short-time recrystallization and LTHT.

Microstructure and Tensile Properties of Hot Worked High Nb Containing TiAl Alloy on Industrial Scale

2005 ◽  
Vol 475-479 ◽  
pp. 785-788
Author(s):  
Jun Pin Lin ◽  
Xiang Jun Xu ◽  
Jian Feng Gao ◽  
Yan Li Wang ◽  
Zhi Lin ◽  
...  
Keyword(s):  
Grain Size ◽  
Tensile Properties ◽  
High Temperatures ◽  
Tial Alloy ◽  
Hot Working ◽  
Industrial Scale ◽  
Initial Microstructure ◽  
Similar Composition ◽  
Fine Grain ◽  
Good Workability

. A hot working and its effect on the microstructure and tensile properties of Ti-45Al-9 (Nb, W, B, Y) alloy ingot on industrial scale were investigated. The results showed that the alloy has good workability in anα+γphase region. An ingot on industrial scale was successfully extruded followed by multi-step canned forging. The initial microstructure of the alloy is fine full lamellar (FL) microstructure. After hot working a sound pancake exhibiting a fine grain duplex (DP) microstructure with grain size about 20μm was obtained. The as-forged alloy has more balanced tensile properties than the small heats with similar composition and microstructure at both room and high temperatures.

Hot Stamping and Press Quenching of Ultrahigh Strength Steel Sheet Using Resistance Heating

2007 ◽  
Vol 344 ◽  
pp. 309-316 ◽  
Author(s):  
Seijiro Maki ◽  
Atsushi Hamamoto ◽  
Shouichi Saito ◽  
Kenichiro Mori
Keyword(s):  
Steel Sheet ◽  
Heating Temperature ◽  
Hot Stamping ◽  
High Strength ◽  
Resistance Heating ◽  
Input Energy ◽  
Ultrahigh Strength ◽  
Ultrahigh Strength Steel ◽  
Ac Power ◽  
Hardness Property

The feasibility of hot stamping and press quenching of ultrahigh strength steel sheet using resistance heating was investigated by demonstrating experiments. In the experiments, a rectangular blank of high strength steel sheet, SPFC980Y, 1.2mm thick, 20mm wide and 130mm long was used and it was resistance-heated with a pair of parallel electrodes placed 120mm away from each other, using an AC power supply with a function of input energy control. The relationship between input energy and heating temperature was examined and then hot stamping and press quenching performances were examined. The press quenching was also experimented in hot hat-shaped bending, and the influences of the heating temperature on spring-back and hardness property were investigated. The results of the experiments revealed that hot stamping and press quenching using resistance heating are highly feasible.

TEXTURE DEVELOPMENT AND DRAWABILITY OF FRICTIONALLY ROLLED AA 5052 AL ALLOY SHEET

2008 ◽  
Vol 22 (31n32) ◽  
pp. 5931-5936 ◽  
Author(s):  
INSOO KIM ◽  
SAIDMUROD AKRAMOV ◽  
HAE BONG JEONG ◽  
TAE KYOUNG NO
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Texture Component ◽  
Alloy Sheet ◽  
Al Alloy ◽  
X Ray ◽  
Fine Grain ◽  
Tensile Tester ◽  
Heat Treated ◽  
R Value

The microstructure, pole figure and r -value of the frictionally rolled and subsequently heat treated AA 5052 Al sheets were investigated by optical microscopy, x-ray diffractometer and tensile tester, respectively. Frictionally rolled AA 5052 Al specimens showed a fine grain size. After subsequently heat treated specimens, the ND//<111> texture component was increased. The r -values of the frictionally rolled and subsequently heat treated Al alloy sheets were about two times higher than those of the original Al sheets. These could be related to the formation of ND//<111> texture components through frictional rolling in and subsequent heat treatment of AA 5052 Al sheet.

Optimization of the Post Heat Treatment of Additively Manufactured IN718

2021 ◽  
Author(s):  
Alber Sadek
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
High Performance ◽  
High Strength ◽  
Fatigue Properties ◽  
Primary Carbide ◽  
Soaking Time ◽  
Fine Grain ◽  
Annealing Cycle ◽  
Treatment Procedures

Abstract IN718 has good fabricability, high strength at elevated temperature, and corrosion resistance, and it is widely deployed in many aerospace and other high-performance applications. With the molten pool rapid solidification during laser powder bed fusion (L-PBF), the resulting microstructure is anisotropic and inhibits macro-segregation. The as-built condition usually exhibits lower mechanical properties. Four different heat treatment procedures were designed and tested to study the effect of different heat treatment parameters on the type of precipitates and grain size. The investigated heat treatment procedures showed the formation of equiaxed grain size and a significant amount of γ' and γ" particles at the grain boundary in addition to primary carbide types (MC). Three types of microstructure characteristics and grain size were achieved. Coarse grain size suitable for creep application was achieved by increasing the soaking time at the aging cycle. The formation of serrated grain boundaries suitable for good fatigue and creep properties was achieved by decreasing the stress relief cycle's soaking time and temperature. Fine-grain size, which is preferable for fatigue properties, was achieved by decreasing the soaking time at the solution annealing cycle.

Extended Solubility and Stability in Vapor Quenched Ni3al-X Intermetallics.

1988 ◽  
Vol 133 ◽  
Author(s):  
Rong Wang
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Solid Solubility ◽  
Thick Disk ◽  
High Rate ◽  
Amorphous Phases ◽  
Fine Grain

ABSTRACTA series of fine-grain and amorphous Ni3Al-X alloys, where X is a solute of 1 to 45 at.% Hf, C or Hf+C in continuously graded compositions, was formed simultaneously into a 0.2 mm-thick disk by high-rate sputter co-deposition. The as-deposited Ni3Al-X alloys exhibited a disordered Ll2 structure and extended solid solubility limits beyond which amorphous phases were formed. Heat-treatment of the alloys at 900°C resulted in fine grain size of 0.5 to 1.5 μm. Ultra-fine dispersoids less than 500 Å in size were observed and they seemed resistant to coarsening.

Effect of Heat Treatment on the Isothermal Oxidation of Fe-33Ni-19Cr Alloy

2018 ◽  
Vol 280 ◽  
pp. 237-242 ◽  
Author(s):  
Noraziana Parimin ◽  
Z. Zulnuraini ◽  
S.A. Che Sakdun
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Minimum Weight ◽  
Isothermal Oxidation ◽  
Boundary Area ◽  
Heat Treated Sample ◽  
X Ray ◽  
Fine Grain ◽  
Heat Treated ◽  
Average Grain Size

This research investigates the effect of heat treatment on the isothermal oxidation behaviour of Fe-33Ni-19Cr alloy. The samples were undergone heat treatment at three different temperatures namely, 1000oC, 1100oC and 1200oC for 120 minutes of soaking time followed by water quench to differ the grain size of alloy. The heat-treated sample was ground by using SiC paper atP600 finished. The samples were weighed using analytical balance and the surface area was measured before oxidation test. The heat-treated Fe-33Ni-19Cr alloys were isothermally oxidized at 850oC for 150 hours. The characterization on oxidized samples were carried out using scanning electron microscope equipped with energy dispersive x-ray (SEM-EDX) and x-ray diffraction (XRD). The result shows that, the average grain size increases as the heat treatment temperature increased. Fine grain size develops higher grain boundary area which acts as an ion diffusion path across the metal-gas interface during oxide formation. HT1000 sample with fine grain structure shows minimum weight gain and low oxidation rate compared to HT1100 and HT1200 samples. Uniform oxide layerformed on surface of the fine grain size sample. Whereas spallation of oxide scales was identified on the coarse grain size sample. Phase analysis shows that the oxidized sample formed several oxide phase.

Effect of Phase Composition and Microstructure of Oxide Scale on the Corrosion Resistance of SS400 Hot Rolled Strip

2011 ◽  
Vol 399-401 ◽  
pp. 1951-1957
Author(s):  
Xian Liang Zhou ◽  
Min Zhu ◽  
Xiao Zhen Hua ◽  
Zhi Guo Ye ◽  
Xia Cui ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Corrosion Resistance ◽  
Oxide Scale ◽  
Electrochemical Impedance ◽  
Rolled Strip ◽  
Fine Grain ◽  
Treatment Processes ◽  
The Difference ◽  
Hot Rolled

Different phase compositions and microstructures of oxide scales were formed on the surface of SS400 hot rolled alloys by employing various heat treatment processes. Cyclic wet-dry immersion corrosion test, electrochemical impedance spectroscopy were used to investigate the corrosion resistance of strips with scales fabricated by different heat treatment processes. The results reveal that difference in the corrosion resistance of the various scales is due to the difference in the grain size of Fe3O4phase. Furthermore, the difference in the corrosion resistance of different oxide phases, exhibited by various scales, also render the strips to give various corrosion behaviors. It is surmised that the strip with oxide scale, which consist of a small mount of the outer layer Fe2O3phase distributed continuously and a large quantity of the inner layer Fe3O4phase with the fine grain size, and possess nice compactness, continuity, integrity in the morphology structure, has the best corrosion resistance.

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