Welding and Metal Working Flashcards

What does SMAW stand for, and what is the common name for this welding process?

Answer: Shielded Metal Arc Welding; commonly called 'stick' welding

SMAW (Shielded Metal Arc Welding) uses a consumable flux-coated electrode ('stick') to create an arc. The flux coating creates a shielding gas and slag to protect the weld pool from atmospheric contamination.

What is the purpose of a welding preheat when welding medium to high carbon steel?

Answer: To reduce the cooling rate, preventing hydrogen cracking and hardening of the heat-affected zone

Preheat slows the cooling rate of the weld and heat-affected zone (HAZ), reducing thermal shock, preventing hydrogen cracking (delayed cracking), and minimizing hardening in higher-carbon steels.

In MIG (GMAW) welding, what is the purpose of the shielding gas?

Answer: To protect the molten weld pool from atmospheric oxygen, nitrogen, and hydrogen contamination

Shielding gas (typically CO2, Argon/CO2 mixtures, or pure Argon for aluminum) blankets the weld pool, preventing atmospheric gases from contaminating the weld. Contamination causes porosity, cracking, and poor weld quality.

What type of welding defect is caused by insufficient fusion between the weld metal and base metal?

Answer: Lack of fusion (incomplete fusion)

Lack of fusion (LOF) occurs when the weld metal and base metal (or weld passes) fail to fuse together. Causes include too low heat input, incorrect electrode angle, or contaminated surfaces. It creates a significant structural weakness.

What is the Rockwell hardness test measuring when it assigns an HRC value?

Answer: The resistance of a material to permanent indentation using a diamond cone (Brinell scale C)

Rockwell C (HRC) hardness uses a diamond cone (Brale) indenter under 150 kgf total load. It measures indentation depth — shallower depth = higher hardness number. Used for hardened steels (typically HRC 20-70).

What does 'heat-affected zone' (HAZ) refer to in welding?

Answer: The area of base metal adjacent to the weld that has been altered by welding heat without melting

The HAZ is the region of base metal next to the weld that was heated enough to alter its microstructure and mechanical properties but not enough to melt. It can become hardened, softened, or embrittled depending on the material.

What is the primary purpose of TIG (GTAW) welding and when is it preferred over MIG?

Answer: Precise, high-quality welds on thin materials and exotic alloys; preferred when weld quality requirements are highest

TIG/GTAW uses a non-consumable tungsten electrode and inert gas shielding. It offers precise heat control and produces clean, high-quality welds. Preferred for stainless steel, aluminum, titanium, thin materials, and precision applications.

When reading a weld symbol, what does the number to the LEFT of the weld symbol indicate?

Answer: The length of the weld

In AWS weld symbols, the number to the LEFT of the symbol indicates weld size (for fillet welds, the leg size; for groove welds, the depth of preparation). The number to the RIGHT indicates weld length.

What is porosity in a weld, and what commonly causes it?

Answer: Gas pockets trapped in the solidified weld metal; caused by contamination (moisture, rust, oil) or shielding gas loss

Porosity is gas (typically hydrogen or CO) trapped in the weld as bubbles when the weld solidifies. Causes include moisture on base metal or electrode, inadequate shielding, contamination, or excessive welding speed.

What is the purpose of annealing a metal?

Answer: To soften the metal, relieve internal stresses, and improve ductility by heating and slow cooling

Annealing involves heating metal to a specific temperature and cooling it slowly (in the furnace or in still air). This relieves residual stresses, softens the metal for machining or forming, and restores ductility.

In sheet metal work, what does a 'bend allowance' refer to?

Answer: The extra length of material needed to form a bend without distorting the flat pattern dimensions

Bend allowance (BA) is the arc length of material consumed in forming the bend. When calculating the flat blank size from a bent part, the bend allowance is added for each bend to account for the material that forms the curved zone.

What does 'undercut' describe as a welding defect?

Answer: A groove melted into the base metal along the weld toe that is not filled by weld metal

Undercut is a groove or channel melted into the base metal at the weld toe that remains unfilled. It reduces the effective cross-section of the base metal and creates a stress concentration point. Caused by excessive current, speed, or wrong angle.

What is the purpose of quench and temper heat treatment for steel?

Answer: Quenching creates a hard but brittle martensite structure; tempering reduces brittleness while retaining useful hardness

Quenching (rapid cooling from austenitizing temperature) creates martensite, which is very hard but brittle. Tempering (reheating to a lower temperature) converts some martensite to tempered martensite, reducing brittleness and improving toughness.

What type of cut does an oxy-fuel cutting torch make, and why can't it cut stainless steel the same way?

Answer: It burns (oxidizes) the iron; stainless steel's chromium oxide layer inhibits the oxidation reaction

Oxy-fuel cutting burns iron in a pure oxygen stream — the cutting oxygen reacts with the iron to form iron oxide. Stainless steel's chromium oxide protective layer (Cr2O3) prevents the iron from oxidizing, blocking the cut reaction.

What does the electrode designation E7018 mean in SMAW (stick) welding?

Answer: E = electrode, 70 = 70,000 psi tensile strength, 1 = all positions, 8 = low hydrogen with iron powder coating

AWS electrode classification: E = electrode, first two digits (70) = minimum tensile strength in ksi (70,000 psi), third digit (1) = positions (all positions), last digit (8) = coating type and current (low-hydrogen, iron powder, AC/DC).

What is the purpose of flux in brazing and soldering operations?

Answer: To prevent oxidation of the base metal surfaces during heating, allowing the filler metal to flow freely

Flux chemically cleans and protects metal surfaces from oxidation during heating. It promotes wetting — allowing the filler metal to flow into the joint by capillary action. Without flux, oxidation prevents proper bonding.

In machining, what does the cutting speed (surface feet per minute, SFM) of a lathe operation affect?

Answer: Tool life, surface finish quality, and productivity — it must be matched to the material being cut

Cutting speed (SFM or m/min) is the velocity of the workpiece surface past the cutting tool. Too slow wastes time; too fast generates excess heat, causing rapid tool wear and poor surface finish. Optimal speed depends on material, tool material, and depth of cut.

What is the difference between 'distortion' and 'warping' in welding, and what is a primary preventive technique?

Answer: Both refer to dimensional change from welding heat; prevented by clamping, tack welding, and balanced welding sequences

Both distortion and warping describe dimensional changes caused by non-uniform thermal expansion and contraction during welding. Prevention: minimize heat input, use clamps/fixtures, pre-set the joint, backstep weld, or balance welds around the neutral axis.

What does the term 'work hardening' (strain hardening) mean in metalworking?

Answer: Metal becomes harder and stronger but less ductile when cold-worked (bent, rolled, or formed at room temperature)

Work hardening (strain hardening) occurs when metal is plastically deformed at room temperature. Dislocations multiply and impede further movement, increasing hardness and strength but reducing ductility. Annealing can reverse it.

When performing an arc weld on cast iron, what special precautions are typically required?

Answer: Preheat to 400-700°F, use nickel-based electrodes, weld in short beads, and slow cool to prevent cracking

Cast iron is brittle and prone to cracking from welding heat. Preheat reduces thermal gradients, nickel electrodes deposit a weld that matches cast iron's low ductility, short beads limit heat buildup, and slow cooling prevents cracking.