The Impact of Selective Oxidation on the Phase Transformation in the Sub-Surface of Advanced High Strength Steels

2011 ◽  
Vol 82 (7) ◽  
pp. 839-846 ◽  
Author(s):  
M. Norden ◽  
G. Paul ◽  
M. Blumenau ◽  
T. Heller ◽  
K.-J. Peters
Keyword(s):  
Phase Transformation ◽  
Selective Oxidation ◽  
High Strength Steels ◽  
High Strength ◽  
Advanced High Strength Steels ◽  
The Impact

scholarly journals Pulse spray gas metal arc welding of advanced high strength S650MC automotive steel

10.30544/682 ◽  
2021 ◽  
Vol 27 (4) ◽  
pp. 505-517
Author(s):  
Ashok Kumar Srivastava ◽  
Pradip K Patra
Keyword(s):  
Weld Joint ◽  
Heat Input ◽  
Arc Welding ◽  
Gas Metal Arc Welding ◽  
High Strength Steels ◽  
High Strength ◽  
Filler Wire ◽  
Advanced High Strength Steels ◽  
Metal Arc Welding ◽  
The Impact

With an increasing demand for safer and greener vehicles, mild steel and high strength steel are being replaced by much stronger advanced high strength steels of thinner gauges. However, the welding process of advanced high strength steels is not developed at the same pace. The performance of these welded automotive structural components depends largely on the external and internal quality of weldment. Gas metal arc welding (GMAW) is one of the most common methods used in the automotive industry to join car body parts of dissimilar high strength steels. It is also recognized for its versatility and speed. In this work, after a review of GMAW process and issues in welding of advanced high strength steels, a welding experiment is carried out with varying heat input by using spray and pulse-spray transfer GMAW method with filler wires of three different strength levels. The experiment results, including macro-microstructure, mechanical properties, and microhardness of weld samples, are investigated in detail. Very good weldability of S650MC is demonstrated through the weld joint efficiency > 90%; no crack in bending of weld joints, or fracture of tensile test sample within weld joint or heat affected zone (HAZ), or softening of the HAZ. Pulse spray is superior because of thinner HAZ width and finer microstructure on account of lower heat input. The impact of filler wire strength on weldability is insignificant. However, high strength filler wire (ER100SG) may be chosen as per standard welding practice of matching strength.

Coupled Temperature-Microstructure Model for Predicting Temperature Distribution and Phase Transformation in Steel for Arbitrary Cooling Curves

2020 ◽  
Vol 13 (3) ◽  
Author(s):  
Sandip K. Saha ◽  
Akhilesh Kumar
Keyword(s):  
Heat Transfer ◽  
Phase Transformation ◽  
Steel Plate ◽  
Plate Thickness ◽  
High Strength Steels ◽  
High Strength ◽  
Rolling Speed ◽  
Transfer Model ◽  
Advanced High Strength Steels ◽  
Quenching Time

Abstract This study aims at developing a numerical model that can be employed for simulating the thermomechanical treatment to develop the advanced high strength steels. The developed numerical method is used to calculate the heat transfer coefficient of the quenching medium during the continuous cooling of the steel using the inverse heat transfer model for predefined cooling paths. Further, the phase transformation models are used to predict the final microstructure of the steel plate. The cooling rate, plate thickness, and rolling speed are varied to evaluate the temperature and microstructure distribution in the steel plate. It is found that on increasing the quenching time, the transformation fraction from austenite to ferrite and bainite phases increases and the corresponding martensite fraction decreases. The temperature variation in the plate is significant due to the change in plate thickness and rolling speed for a given quenching time. The present model will be useful for designing process parameters to obtain desired microstructures in third-generation advanced high strength steels.

Dependence of Impact Performance on Process Parameters and Weld Attributes for Spot Welded Advanced High Strength Steels

2004 ◽  
Author(s):  
Girish S. Karve ◽  
Hongyan Zhang
Keyword(s):  
Impact Strength ◽  
Process Parameters ◽  
Peak Load ◽  
High Strength Steels ◽  
High Strength ◽  
Welding Parameters ◽  
Impact Performance ◽  
Advanced High Strength Steels ◽  
The Impact ◽  
Spot Welded

In order to improve fuel economy and safety of vehicles, many advanced materials such as aluminum alloys and advanced high strength steels have been introduced in automobile body construction in recent years. A key to the adoption of such materials is their manufacturability, such as forming and welding. Resistance welding, as the major enabling technique, has been widely applied in joining these materials. Although there has been a large amount of research in characterizing static and fatigue strengths of Al or AHSS welds, their impact performance is largely unknown, even though it is extremely important for safety. In this paper, the impact strength of AHSS spot welded specimens is analyzed, as a function of welding process parameters and weldment geometry. Both energy and peak load during impacting, as well as failure mode were recorded. The geometric attributes of spot welds, such as indentation width, nugget width, indentation depth, etc. were measured before the specimens were destructively tested. Then these quantities were linked to the impact strength of the welds. Besides several advanced high strength steels, high strength, low alloy (HSLA) steels were also tested in the study for comparison. Models were developed to correlate impact strength with individual factors, both welding parameters and spot weld geometry variables. The effects of interactions between the factors were also investigated. The results showed that these parameters should be examined together in determining a weld’s impact performance.

Trimming of Advanced High Strength Steels

2005 ◽  
Author(s):  
Sergey F. Golovashchenko ◽  
Andrey M. Ilinich
Keyword(s):  
Carbon Steel ◽  
Low Carbon Steel ◽  
High Strength Steels ◽  
High Strength ◽  
Low Carbon ◽  
Advanced High Strength Steels ◽  
Stretch Flanging ◽  
Alternative Materials ◽  
The Impact ◽  
Current Standards

Modern product design and manufacturing often utilizes a wide variety of materials. Where once low carbon steel predominated, a variety of different materials such as aluminum alloys and advanced high-strength steels (AHSS) are now being utilized. Although such alternative materials may provide a variety of benefits in manufacturing and design, these same materials may present difficulties when subjected to manufacturing processes originally designed for low carbon steel. One such manufacturing area where difficulties may arise is in trimming operations. A defect that may arise directly in the trimming operation are burrs. Burrs decrease the quality and accuracy of stamped parts and cause splits in stretch flanging and hemming. Current standards limit the production of burrs through accurate alignment of the upper and lower edges of the trim knives. The clearance between the shearing edges should be less than 10% of the material thickness. For automotive exterior sheet, this requires a gap less than 0.06mm. Unfortunately, tolerances often exceed the capabilities of many trim dies resulting in the production of burrs. To satisfy the current standards of quality and to meet customer satisfaction, stamped parts frequently need an additional deburring operation, which is often accomplished as a metal-finish operation and conducted manually. The objective of the research described in this paper was to study the mechanisms of burr generation and the impact on AHSS formability in stretch flanging. Results on both the conventional trimming process and a recently developed robust trimming process, which has the potential to expand tolerances of trim die alignment, will be discussed.

Effect of Dew Point on the Selective Oxidation of Advanced High Strength Steels

2017 ◽  
Vol 891 ◽  
pp. 292-297 ◽  
Author(s):  
Magdalena Maderthaner ◽  
Alexander Jarosik ◽  
Gerhard Angeli ◽  
Roland Haubner
Keyword(s):  
Grain Boundaries ◽  
Selective Oxidation ◽  
Surface Segregation ◽  
High Strength Steels ◽  
High Strength ◽  
Dew Point ◽  
Annealing Atmosphere ◽  
Advanced High Strength Steels ◽  
Surface Oxides ◽  
Segregation Of Alloying Elements

The effect of the dew point (and therefore oxygen partial pressure) on the selective oxidation of Advanced High Strength Steels was investigated. Steels with different Si contents, 0.2 wt% Si, 0.8 wt% Si and 1.5 wt% Si were used. The steel samples were annealed at 840 °C for 60 s and various gas atmospheres prior to hot-dip galvanized at 460 °C. The dew point of the 5 % H2-N2 annealing atmosphere was lowered from-30 °C (equivalent to 380 ppm H2O) to-58 °C (equivalent to 14 ppm H2O) in order to investigate surface segregation of alloying elements Si, Mn and Cr. These conditions are reducing for Fe, but oxidizing the oxygen-affine elements. Oxide morphology changed from a complete covering surface at high dew point to separated oxide spots at grain boundaries at low dew point. At the low dew point Cr was not oxidized. Oxides with a low Mn/Si-ratio seems to be amorphous. The Si-oxides are especially located at grain boundaries, Mn-oxides tend to cover the surface. Oxides covering the steel surfaces are detrimental for subsequent procedures as hot dip galvanizing, painting and welding.

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