scholarly journals The Effect of Preheating Current on the Melting Behavior of Bolt Projection Welding of Al-Si Coated Hot-Stamped Boron Steel

2021 ◽  
Vol 59 (12) ◽  
pp. 893-903
Author(s):  
Jae-Hun Kim ◽  
Hyun-Uk Jun ◽  
Joo-Yong Cheon ◽  
Jae-won Kim ◽  
Jae-deuk Kim ◽  
...  
Keyword(s):  
Heat Generation ◽  
Coating Layer ◽  
Early Stage ◽  
Melting Behavior ◽  
Weld Interface ◽  
Outer Edge ◽  
Boron Steel ◽  
Projection Welding ◽  
Large Heat ◽  
Stable Growth

This study evaluated the effect of preheating on early stage melting behavior of a Al-Si coated hot stamped boron steel bolt during projection welding. A large amount of heat was generated in the early stage of projection welding. Because of the large heat generation, a rapid collapse of the projection occurred and a molten coating layer remained on the interface of the welded part. This caused welding defects such as expulsion and porosity. However, preheating helped remove the molten Al-Si coating layer by pushing it out toward the outer edge of the molten pool. This suggests that preheating can effectively minimize or remove the molten coating layer within the weld. Preheating also prevented the rapid collapse of the projection by partially melting the projection, and thus improving the contact area. These phenomena can prevent the concentration of current density at the weld interface and hence decrease heat generation. Finally, the preheating current improved nugget quality by promoting the stable growth of the melted metal and by preventing expulsion and porosity.

scholarly journals TEM Microstructural Evolution and Formation Mechanism of Reaction Layer for 22MnB5 Steel Hot-Dipped in Al–10% Si

Coatings ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 467 ◽  
Author(s):  
Dongik Shin ◽  
Jeong-Yong Lee ◽  
Hoejun Heo ◽  
Chung-Yun Kang
Keyword(s):  
Formation Mechanism ◽  
Microstructural Evolution ◽  
Reaction Layer ◽  
Coating Layer ◽  
Vertical Section ◽  
Diffusion Reaction ◽  
Boron Steel ◽  
Formation Mechanisms ◽  
22Mnb5 Steel ◽  
Mechanism Of Reaction

Microstructural evolution and formation mechanism of reaction layer for 22MnB5 steel hot-dipped in Al–10Si (in wt %) alloy was investigated. The microstructural identification of the reaction layer was characterized via transmission electron microscopy and electron backscatter diffraction. In addition, the formation mechanisms of the phases were discussed with vertical section (isopleth) of the (Al–Si–Fe) ternary system. The solidified Al–Si coating layer consisted of three phases of Al, Si, and τ5 (Al8Fe2Si). The reaction layer on the Al–Si coating layer side is a fine τ5 phase (Al8Fe2Si) of 5 μm thickness. The layer on the steel side consisted of an η phase (Fe2Al5) of thickness of 500 nm or less. τ1 (Al2Fe3Si3, triclinic) phase of 200-nm-thickness was formed in the η phase, and κ phase (Fe3AlC) of 40–50 nm thickness was formed between η phase and steel. The τ5 phase was formed by isothermal solidification at 690 °C in the liquid Al–10 wt % Si when 3.73–29.0 wt % of Fe was dissolved from the boron steel into the Al–Si liquid bath. It was considered that the η phase was formed by the diffusion reaction of Al, Si, and Fe between τ5 and ferrite steel. κ (Fe3AlC) phase was formed by the reaction of the carbon, which is barely employed in η and τ phases, and diffused Al.

Investigation on Friction Coefficient Considering Al-Si Coating Layer Fracture of Boron Sheets in Hot and Cold Deep Drawing

2020 ◽  
Vol 846 ◽  
pp. 117-121
Author(s):  
Min Sik Lee ◽  
Jun Park ◽  
J.S.Suresh Babu ◽  
Chung Gil Kang
Keyword(s):  
Friction Coefficient ◽  
Deep Drawing ◽  
Deformation Behavior ◽  
Coating Layer ◽  
Surface Condition ◽  
Forming Limit ◽  
Boron Steel ◽  
Drawing Process ◽  
Forming Process ◽  
Deep Drawing Process

In this paper, hot and cold deep drawing processes are determined with direct deep drawing process and indirect deep drawing process. To predict the friction coefficient, the finite-element method, which can predict deformation behavior until the fracture of a blank sheet, was proposed using the forming limit diagram (FLD) curve. The effect of fracturing of the coating layer on the friction coefficient during the hot and cold deep drawing processes was investigated. The deformation behavior of the coating layer of the boron steel sheet that affects the friction coefficient in the hot and cold deep drawing processes was also proposed. A forming method that can control the surface condition of the formed product is further proposed by explaining the fracture of the coating due to the forming process.

scholarly journals Corrosion Behaviors of the Eutectic Structure in Zn-Al-Mg Alloy Coated Steel in Chloride Containing Aqueous Environment

2020 ◽  
Vol 58 (9) ◽  
pp. 610-616
Author(s):  
Jae-Won Lee ◽  
Se-Young Oh ◽  
Bora Park ◽  
Min-Suk Oh ◽  
Sung Jin Kim
Keyword(s):  
Coating Layer ◽  
Early Stage ◽  
Galvanic Corrosion ◽  
Salt Spray ◽  
Eutectic Structure ◽  
Mg Alloy ◽  
Aqueous Environment ◽  
Corrosion Mechanism ◽  
Coated Steel ◽  
Corrosion Behaviors

To clearly understand the effect of the eutectic structure in the Zn-Al-Mg alloy coating on the corrosion behaviors in chloride containing aqueous environments, a bulk Zn-MgZn<sub>2</sub> sample was fabricated by diffusion bonding process, and a variety of experiments, such as electrochemical polarization and galvanic corrosion measurements, salt spray tests, and cyclic corrosion tests, were carried out. This study revealed that the corrosion potential values of MgZn<sub>2</sub> and Zn samples exposed to a 5 wt.% of NaCl solution were approximately -1.5 and -1 VSCE, respectively, and the MgZn<sub>2</sub> showed a higher corrosion current density than Zn at the early stage of corrosion. The continued dissolution of MgZn<sub>2</sub> phase from the eutectic structure in the coating layer provides not only sacrificial protection, but also environmental conditions for the co-formation of two types of corrosion products (simonkoleite (Zn<sub>5</sub>(OH)<sub>8</sub>Cl<sub>2</sub>·H<sub>2</sub>O) and hydrotalcite (ZnAl<sub>2</sub>(OH)<sub>6</sub>Cl<sub>2</sub>·H<sub>2</sub>O)) which have an inhibiting effect on the outer surface. The formation areas and kinetics of the two products on the coating surface were different, and they were greatly dependent upon the types of eutectic structures in the coating layer. Based on the results, a modified anti-corrosion mechanism of Zn-Al-Mg alloy coated steel sheet in chloride containing aqueous environment was proposed.

scholarly journals Effect of the Die Temperature and Blank Thickness on the Formability of a Laser-Welded Blank of a Boron Steel Sheet with Removing Al-Si Coating Layer

2014 ◽  
Vol 6 ◽  
pp. 925493 ◽  
Author(s):  
M. S. Lee ◽  
J. H. Moon ◽  
C. G. Kang
Keyword(s):  
Automobile Industry ◽  
Steel Sheet ◽  
Coating Layer ◽  
Hot Stamping ◽  
Thin Sheet ◽  
Welding Process ◽  
High Strength ◽  
Absorption Capacity ◽  
Boron Steel ◽  
Thick Sheet

Reducing carbon emissions has been a major focus in the automobile industry to address various environmental issues. In particular, studies on parts comprised of high strength sheets and light car bodies are ongoing. Accordingly, this study examined the use of boron steel, which is commonly used in high strength sheets. Boron steel is a type of sheet used for hot stamping parts. Although it has high strength, the elongation is inferior, which reduces its crash energy absorption capacity. To solve this problem, two sheets of different thickness were welded so the thin sheet would absorb crash energy and the thick sheet would work as a support. Boron steel, however, may show weakening at the welding spot due to the Al-Si coating layer used to prevent oxidation from occurring during the welding process. Therefore, a certain part of the coating layer of a double-thickness boron steel sheet that is welded in the hot stamping process is removed through laser ablation, and the formability of the hot-work was examined.

EFFECT OF COMBINATED APPLICATION OF PROBIOTIC AND ENTEROSORBENT ON THE DYNAMICS OF CORTISOL IN CHICKENS IN THE EARLY POSTEMBRIONIC PERIOD

2020 ◽  
Keyword(s):  
Marked Reduction ◽  
Marked Decrease ◽  
Early Stage ◽  
Relative Increase ◽  
Stress Factors ◽  
Control Group ◽  
Group A ◽  
Group 2 ◽  
Stable Growth ◽  
The Relationship

The research is devoted to the study of chickens’ cortisol dynamics at an early stage ofpost-embryonic development with the use of probiotics such as zoonorm, enterosorbent based on polymethylsilxane polyhydrate and their complex. To achieve the goal, 4 groups of analogue chickens were formed, 1 was a control group, 2 - received a probiotic in a mixture with feed at a dose of 0.2 g per head in morning feeding; 3 - 0.3% weight enterosorbent 2 hours after evening feeding; 4 - a combination of two preparations at the appropriate time. The introduction of drugs was carried out from 5- to 25-day age. All the indicators were analyzed in 5-, 15-, 25- and 35-day chicks. As a result of the research, chicks in all groups showed an increase in cortisol concentrations. In the control group a stable growth of the indicator was observed, which reached a maximum in 35 days, an increase in the concentration of the hormone by 41.6% was accompanied by an increase in glucose to 14.6 to 0.5 mmol/L, a decrease in cholesterol and triglycerides. In chicks 2 and 3 groups the highest value of cortisol is noted in 25 days, 4 - in 15 days. In 2 and 3 groups, with maximum cortisol levels, glucose concentrations were 14.64 and 14.91 mmol/L, with a marked decrease in triglycerides and cholesterol. In the 4th group of 15-day-old chicks, an 8.4% increase in cholesterol and triglycerides resulted in a 37.3 and 68.9% decrease in cholesterol and triglycerides. At the end of the experiment, the 4th group was found to reduce cortisol to 5.07 nmol/L, glucose to 12.32 to 0.13 mmol/L, and a relative increase in triglycerides. In conclusion, the relationship between synthesis of cortisol, cholesterol, triglycerides, glucose and their metabolism was confirmed. There has been a marked reduction in the influence of stress factors and increased resistance of chickens with the complex use of probiotic and enterosorbent.

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