L10/11 Joining Flashcards
What are the 3 distinct zones for a typical welded joint?
- Loose metal - metal to be joined Heat affected zone (HAZ)
- within the base metal but has different microstructures. These differences are dependent on heating/coolingrate prior heat treatmeants and cold working Fusion zone
- region that has melted during welding can consist of resolidified base metal in autogenous welding or weld metal if filler was used. Essentially a cast structure with coarse grain formation due to slow coolings
What are the 6 types of weld defects? Describe each.
Prorosity
- caused by trapped gases, chemical reactions, or weld contamination Incomplete fusion
- production of poor weld beads and bridging Inclusions
- compounds such as oxides and fluxes trapped in the weld pore Cracks
- Occur in different locations and directions in the weld zone Residual stresses
- Due to non uniform heating and cooling of part creating warpage and distortion Weld profile
- These include, underfill, cracks, inclusions, overlap, undercutting, porosity, and incomplete profile
What is the process of brazing? and the melting temperature?
- A filler metal is placed between the faying surfaces of the base metal and the temperature is raised to melt the filler but not the workplace. The molten metal fills the gap through capillary action.
- Melting Temp > 723K
Important: Alan mentioned that expensive tools like carbide are usually brazed onto a cheaper material such as the lathe tool pieces
Complications due to the HAZ, warpage, and residual stresses are reduced by? What is fluxes impact on brazing?
- Lower temperatures Fluxes must be used to prevent oxidation and improve melting characteristics of the molten filler metal
4 common methods to brazing?
- Torch brazing
- Furnace brazing
- Induction brazing
- Braze Welding
What is soldering and the melting temperature?
- Very similar to brazing but at a lower temperature
* Melting temp
When should soldering not be used? Applications? What are popular methods?
- Generally not used for high temperature applications or structural applications due to low melting point and low strength
- Very popular in electronics and plumbing
- Torch and iron soldering methods are very popular for low quantity applications. Reflow soldering is used in large scale electronic manufacturing
Should fluxes be used in soldering?
Fluxes must be used and most soldering wire is flux covered
What are the 6 typesof structural adhesive bonding?
- Epoxy-based
- Acrylic
- Anaerobic
- Cyanoacrylate
- Urethanes
- Silicones
Benefits and limitations of adhesives?
Benefits
- Able to distribute loads, bond dissimilar materials, no distortion, can join porous or fragile materials
- Lightweight, strong Limitations
- Low temp, low peel strength, reliability, dependent on surface prep
Advantages of Threaded Fasteners and Rivets
- Non permanent joining method
- ease of manufacture and assembly
- ease of maintenance and repair
- Moveable joints
Screws and bolts are among the most common for threaded fasteners. What are 3 ways to secure them?
- Nuts
- Threaded Holes
- Self Tapping
In high vibration situations, various lock washers and nuts may be employed to prevent loosening
Rivets are the most common semi permanent method of joining. True or false, they may be solid, hollow, and depending on the type can be installed from one side only.
True
Solid rivets must be “blank” to be installed
“Upset” at room temperature or high temperatures
What is Metal Stitching?
- Another fastening method similar to ordinary stapling of paper
- Suitable for thin materials
What is Seaming?
- Seaming is the folding of two pieces together to lock them
What is Crimping? Applications?
- Crimping is a method of joining without fasteners using beads and dimples
- Caps of cans and electrical connections
Design Considerations for welded joints?
- Proper weld locations
- Proper fit of joint
- Inconsistent section thickness
Design considerations for brazing?
- Surface area
- Fatigue Loading
- Sufficient bonding
