Aluminum Weld HAZ Fundamentals
To appreciate the effect of arc welding on the heat-affected zone (HAZ) of various aluminum alloys, it is necessary to evaluate the various types of aluminum alloys, how they obtain their strength, and the potential for changes in strength after welding.
The Types of Aluminum Alloys
When we consider the seven aluminum alloy series used for wrought alloys (Table 1), we can see that the main alloying elements used for producing each series are immediately identifiable. Further examination of each of these elements' effects on aluminum is possible.
The principal effects of alloying elements in aluminum are as follows:
Pure Aluminum 1xxx. Although the 1xxx series alloys are almost pure aluminum, they do respond to strain hardening, especially if they contain appreciable amounts of impurities such as iron and silicon.
Understanding Stainless Steel Heat-Affected Zones
The structural changes that occur in the heat-affected zone (HAZ) of stainless steel weldments can potentially degrade strength, toughness, and corrosion resistance. Therefore, it is important to understand which grades of stainless steel are susceptible and the kinds of degradation that can occur. The potential problems associated with stainless steel HAZs include excessive grain growth, chromium carbide precipitation, precipitation of intermetallic compounds, and improper phase balance.
Stainless steels can be divided into families characterized by the crystal structure of predominant phase or phases that are present in the microstructure. The nature of the HAZ and the possible problems that can occur in the HAZ often depend on the stainless steel family.
C. Meadows and J. D. Fritz
Power Supply Designed for Small-Scale Resistance Spot Welding
Resistance spot welding (RSW) is one of the welding processes that involves the joining of two or more metal parts together in a localized area by applying heat and pressure (Ref. 2). For applications such as medical devices and electronic components, the welded parts are thinner and smaller compared to common RSW applications. Therefore, the authors refer to this process as "Small Scale" RSW (SSRSW) (Refs. 1, 5).
Studies of the SSRSW have shown that 20% of the welding quality issues are welding schedule or power supply related (Refs. 35). Therefore, the study of different weld schedules and control schemes will contribute to weld quality improvement.
L. J. Brown and J. Lin
Exploring Temper Bead Welding
For many years, metallurgists have recognized that welding can have both positive and negative effects on the properties of the base metals being joined, as well as on previously deposited weld metal. Historically, one way of ameliorating some of the deleterious effects was postweld heat treatment of welds. Postweld heat treatment was sometimes known as stress relieving because it lowered residual stress in welds from yield-point order of magnitude to about one-third of yield. For high-carbon steels or low-alloy steels, postweld heat treatment also tempered hard microstructures containing martensite, improving resistance to cracking by improving the toughness of the weld metal or heat-affected zone (HAZ).
W. J. Sperko
Hobart Marks 75 Years of Welder Education
Troy, Ohioans, and visitors nationwide convened May 14 to celebrate the 75th anniversary of the founding of what has evolved into the Hobart Institute of Welding Technology (HIWT) (see lead photo), and the rededication of the Unity of Man fountain (Fig. 1) gracing the main entrance to the facility.
With such an impressive legacy to celebrate, HIWT Chairman and President André A. Odermatt joined with numerous local and national dignitaries, including HIWT past president and current AWS Executive Director Ray Shook, for the event ‹ Fig. 2.
Presentation of the AWS Plaque
Shook said it was his privilege to have worked for Hobart Brothers for 23 years and to serve as the school's president for two years. Shook noted, "The rededication of the Unity of Man fountain is the ideal venue to highlight the unity that exists between HIWT and AWS. The cornerstone of this unity," Shook added, "is the AWS Certified Welding Inspector (CWI) program."
H. M. Woodward
Standardization in Welding
If you look for a definition of standardization in a dictionary from early in the 20th century, you would not find one. At most, you will find "standard" defined as "principle used as a rule." The concept of standard, as we understand it now, appeared around 1920 with the definition "formula defining a type of thing, a product, a technical process in order to simplify and rationalize its production." As for "standardization," it was more recently defined as "a set of technical rules resulting from an agreement between producers and users, and leading to specify, unify, and simplify for a better output in all fields of human activity."
This definition of standardization is already 20 years old and does not correspond with today's reality.
J. -P. Gourmelon
WELDING RESEARCH SUPPLEMENT
*Reliable Calculations of Heat and Fluid Flow during Conduction Mode Laser Welding Through Optimization of Uncertain Parameters (.pdf)
Thermal simulations that induced coarse-grain conditions in the HAZ aided a study on postweld heat treatment schedules for high-strength steel pipe
J. E. Ramirez et al.
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WELDING JOURNAL - July 2005, Volume 84, Number 7