Study of Laser Welding and Heat Treatments Done in Different High Strength Steels: 4340, 300M, Maraging 300

2013 ◽  
Author(s):  
Andréia de Souza Martins Cardoso ◽  
Antonio Jorge Abdalla ◽  
Milton Sergio Fernandes de Lima ◽  
Felipe Martins Bonjorni ◽  
Miguel Justino Ribeiro Barboza ◽  
...  
Keyword(s):  
Laser Welding ◽  
High Strength Steels ◽  
High Strength ◽  
Heat Treatments

scholarly journals Laser Welding Dissimilar High-Strength Steel Alloys with Complex Geometries

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 792 ◽  
Author(s):  
Panos Efthymiadis ◽  
Khalid Nor
Keyword(s):  
Carbon Steel ◽  
Laser Welding ◽  
Cross Sections ◽  
High Carbon Steel ◽  
High Strength Steels ◽  
High Strength ◽  
Low Carbon ◽  
High Carbon ◽  
Material Chemistry ◽  
Metallurgical Defects

Laser welding of dissimilar high-strength steels was performed in this study for two different geometries, flat and circular samples with material thicknesses of 5 and 8 mm. The material combinations were a low carbon to a medium or high carbon steel. Three different welding systems were employed: a Nd:YAG, a CO2 and a fiber laser. The process stability was evaluated for all the experiments. The resulting full penetration welds were inspected for their surface quality at the top and bottom of the specimens. Cross sections were taken to investigate the resulting microstructures and the metallurgical defects of the welds, such as cracks and pores. Significant hardening occurred in the weld region and the highest hardness values occurred in the Heat Affected Zone (HAZ) of the high carbon steel. The occurrence of weld defects depends strongly on the component geometry. The resulting microstructures within the weld were also predicted using neural network-simulated Continuous Cooling Transformation (CCT) diagrams and predicted the occurrence of a mixture of microstructures, such as bainite, martensite and pearlite, depending on the material chemistry. The thermal fields were measured with thermocouples and revealed the strong influence of component geometry on the cooling rate which in term defines the microstructures forming in the weld and the occurring hardness.

The Effect of Simulated Repair Heat Treatments on the Physical Properties of High Strength Steels

1991 ◽  
Author(s):  
Robin Stevenson ◽  
Earl G. Brewer ◽  
Kraig Malstrom ◽  
H. Daniel Pursel
Keyword(s):  
Physical Properties ◽  
High Strength Steels ◽  
High Strength ◽  
Heat Treatments

Noise Reduction During Acoustic Monitoring of Laser Welding of High-Strength Steels

2009 ◽  
Author(s):  
Wei Huang ◽  
Radovan Kovacevic
Keyword(s):  
Laser Welding ◽  
Noise Reduction ◽  
Acoustic Signal ◽  
Welding Process ◽  
High Strength Steels ◽  
High Strength ◽  
Weld Penetration ◽  
Acoustic Signatures ◽  
Reduction Methods ◽  
Laser Welding Process

During the laser welding process of high-strength steels, different defects, such as a partial weld penetration, spatters, and blow-through holes could be present. In order to detect the presence of defects and achieve a quality control, acoustic monitoring based on microphones is applied to the welding process. As an effective sensor to monitor the laser welding process, however, the microphone is greatly limited by intensive noise existing in the complex industrial environment. In this paper, in order to acquire a clean acoustic signal from the laser welding process, two noise reduction methods are proposed: one is the spectral subtraction method based on one microphone and the other one is the beamforming based on a microphone array. By applying these two noise reduction methods, the quality of the acoustic signal is enhanced, and the acoustic signatures are extracted both in the time domain and frequency domain. The analysis results show that the extracted acoustic signatures can well indicate the different weld penetration states and they can also be used to study the internal mechanisms of the laser-material interaction.

Real-Time Monitoring of the Weld Penetration State in Laser Welding of High-Strength Steels by Airborne Acoustic Signal

2009 ◽  
Author(s):  
Wei Huang ◽  
Shanglu Yang ◽  
Dechao Lin ◽  
Radovan Kovacevic
Keyword(s):  
Laser Welding ◽  
Real Time ◽  
Optical Sensors ◽  
Weight Ratio ◽  
Welding Process ◽  
High Strength Steels ◽  
High Strength ◽  
Acoustic Signals ◽  
Real Time Monitoring ◽  
Laser Welding Process

Nowadays high-strength steels have great applications in different industries due to their good combination of formability, weldability, and high strength-to-weight ratio. To guarantee a high quality without the presence of defects such as partial penetration (PP) in the laser welding of high-strength steels, it is very important to on-line monitor the whole welding process. While optical sensors are widely applied to monitor the laser welding process, we are proposing to use a microphone to acquire the airborne acoustic signals produced during laser welding of high-strength steel DP980. In order to extract valuable information from a very noisy signal acquired in a harsh environment such as industrial welding, spectral subtraction (SS), a noise reduction method is used to process the acquired airborne sound signals. Furthermore, by applying the power spectrum density (PSD) estimation method, the frequency characteristics of the acoustic signals are analyzed as well. The results indicate that the welds in full penetration (FP) and PP produce different signatures of acoustic signals that are characterized with different sound pressure levels and frequency distributions ranging from 500 Hz to 1500 Hz. Based on these differences, two algorithms are developed to distinguish the FP from PP during the laser welding process. A real-time monitoring system is implemented by a LabVIEW-based graphic program developed in this research. A feedback control system that could guarantee the FP will be developed in the near future.

Microstructural Contributions to Stress Corrosion Cracking in High Strength Steels

1982 ◽  
Vol 40 ◽  
pp. 462-463
Author(s):  
R. Padmanabhan ◽  
W. E. Wood
Keyword(s):  
Heat Treatment ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
High Strength Steels ◽  
High Strength ◽  
Heat Treatments ◽  
Corrosion Cracking ◽  
Treatment Conditions ◽  
300M Steel ◽  
Conventional Heat Treatment

The effects of microstructural variables upon stress corrosion cracking resistance of 300M steel in 3.5% NaCl solution have been studied. Table 1 lists KIscc values for three heat treatment conditions. The martensite substructure was predominantly twinned plates for conventional heat treatment and dislocated laths for both high temperature and step heat treatments. A typical twinned region observed in the conventional heat treatment is shown in Fig. 1. Such twinned regions were less frequent in the other heat treatments. Both cementite and epsilon carbide were seen in all cases, as illustrated in Figs. 2 and 3 for conventional heat treatment. Epsilon carbide was usually observed within large grain boundary nucleated laths (autotempered martensite), with definite habit planes and growth directions. The formation of such laths have been discussed previously. Retained austenite, mostly in the form of interlath films, was observed in all cases with increased amounts present in coarser grained structures (Fig. 4).

Laser welding of ultra high strength steels

2003 ◽  
Vol 100 (10) ◽  
pp. 1015-1022
Author(s):  
G. Restrepo Garcés ◽  
P. Verrier ◽  
O. Glaise ◽  
S. Boidin
Keyword(s):  
Laser Welding ◽  
High Strength Steels ◽  
High Strength ◽  
Ultra High Strength Steels
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