202 Flashcards
How high can GTAW welding temperatures reach?
19427^C (35000^F)
What’s is shielding gases primary use?
To protect the weld from atmospheric contamination
What are the four types of GTAW welds?
Spot welding, hot wire GTAW, cold wire GTAW, high amperage GTAW
What is hot wire GTAW?
It’s a mechanized process which feeds wire directly into the puddle, resistance heating preheats the filler metal to a near molten using a separate AC power supply
What do hot wire and cold wire GTAW have in common?
They are both mechanized processes
What is a common use of high-amperage GTAW process?
It is often used to weld root passes in a carbon steel pipe
What gas is used with the GTAW process?
100% Argon
At what speed will fans or drafts blow the protective gas envelope away?
50 CFM (cubic feet per minute)
What are the 6 key items that the GTAW process requires?
Welding power source, welding torch assembly, work lead, non-consumable tungsten electrode, shielding gas, filler metal (if required)
Why must you have post purge settings with GTAW?
It protects the tungsten electrode from deterioration due to oxidation
What happens during the peak of a pulsed current?
It’s the period of time when penetration and metal flow occur
What is the average range for amount of pulses per minute?
2-10 pulses per minute
When using pulsed GTAW on stainless what is the depth to width ration of the weld?
2:1
When GTAW welding with out using a filler wire what is this called?
Autogenous welding
What are the power source options for GTAW?
Transformers, transformer/rectifier, generators, or inverter type welding machine
What metals are commonly welded with AC when GTAW welding?
Magnesium and aluminum
Define amperage
Measure if the number of electrons that flow past a given point in one second
Define voltage
Pressure needed to push the electrons through the conductor
What is the most common gas nozzle? Why?
Ceramic gas nozzles are the most common because they are the least costly
How are gas nozzles sized?
They are sized by 1/16”, a number 6 is 6/16”
What do gas lenses allow for?
Shielding gas to flow in a laminar fashion (arranged in thin layers)
Why is the chemical symbol for tungsten W?
Cause the German term for tungsten is wolfram
What direction should grinding marks run on a tungsten electrode?
Longitudinal
What kind of tungsten is used with aluminum?
Pure tungsten
What are the factors that influence choice of welding filler?
Required mechanical and physical properties, joint design, and required finish or appearance of the welded part
Why can’t you use a mild steel brush on aluminium?
Because it may deposit carbon into the weld area
What affect does the nickel added to stainless steel have on the weld puddle?
It becomes much more fluid
What kind of stainless steel is a 300 series?
Austenitic stainless steel
Why can titanium be used in tig versus other process?
Because titanium burns up if crossed through an open arc, it’s used to stabilize the weld puddle
What does appropriate stick out do for the GTAW process?
Maintains gas shield around the electrode and molten weld metal
Three ways to strike an arc in GTAW?
Touch start, high frequency start and lift start
Name 5 components of a GTAW cable and torch assembly?
Torch handle and head, gas control valves, cable covers, nozzles, collet and collet body, gas lens, and electrode
Name two safety devices on a water cooled torch?
A fuse link (if coolant is lost this cause the fuse to melt and stops the system) and coolant flow safety interlock system, this systems tells if there is water flowing through the torch
Why would there be a gas control on the torch?
If there are no solenoid valves used
When is GTAW preferred?
When the highest possible quality welds for the more critical weld applications
At what speed will a draft blow away the protective gas envelope?
50 surface feet per second
What does pulse current control?
It controls the high(peak) and low (background) currents
What is an advantage of pulsed GTAW?
Greater control of heat input
What is orbital GTAW?
It’s is a semi and fully automatic welding process in which a welding arc travels 360 degrees around a work price with interruption
What metals is DCEN generally used on?
Ferrous metals
