Procedures For SMAW on Grey Cast Iron Flashcards
What should you use to preheat grey cast iron? What can be used to tell when you’ve reached your desired preheat?
A large propane burner-style torch, called a “tiger torch” take your time for an even preheat.
A hand held infrared temperature sensor, temperature crayons such as “tempilstik°” mark the workpiece with the crayon rated at the temperature you need and the mark will melt when it reaches the desired temperature.
Wha can be used for Insulating grey cast iron for post heating
Kaowool and vermiculite are the most effective but other commonly used are dry sand, lime, absorbent clay (floor dry) and fire brick
The best electrode to use for grey cast iron is?
Nickel alloys. A 36% nickel iron alloy contracts much less than cast iron and carbon steel electrodes. Which means theres less shrinkage so less of a chance of cracks developing
What is buttering?
In a large weld joint on grey cast iron you can reduce the cost by limiting the amount of nickel filler metal you use. “Buttering” means surfacing the weld joint with a nickel alloy, then completing the weld with a less-expensive filler metal. The layer of nickel filler metal is compatible with cast iron base metal and provides a base for a secondary filler metal. The secondary filler metal can be a lower nickel alloy or low-carbon steel electrode
A way to stop a crack you’re welding to spread
Drill a stop hole 1/8in in diameter just beyond where the crack ends an alternative is to run a small weld bead at 90° across the end of the crack
What temperature should you preheat small casting to? And large castings?
260C (500F)
520C (950F)
Procedures for cold welding
Use minimum current and small diameter electrodes
Deposit the weld bead in short lengths (about 50mm [2in.] or less). Separate the deposits by using a skip or back-step sequence. Peen immediately afterwards.
What must the thickness be a low carbon steel patch if used on grey cast iron?
60% of the thickness of the cast iron
Repair time for cold welding
25mm (1in.) Long weld beads at a time. Do not do the next one until you can put your hand on the first weld and feel no discomfort
Electrodes used for cast iron
RCI- welding rods intended for oxyacetylene welding
ECI- coated electrodes with a cast iron core
ESt- coated electrode with a stainless steel core. Deposit is hard and not machinable
ENI- coated electrode with a nickel alloy core. Deposit is machinable when using a 99% nickel electrode
What are the electrode sizes and current settings used
Most widely used 3.3mm (1/8in.), although most electrodes are available in sizes ranging from 2.5mm (3/32in.) to 3.2mm (1/8 in.)
Current settings are generally low, from 70 to 90 A. Both AC and DC can be used. AC is preferred, because it gives a smoother operation at lower current values and produces a less-penetrating
