Question 1

Oxy-Acetylene Flames — Identify the Flame When Acetylene Flow Exceeds Oxygen If the torch is adjusted to deliver more acetylene and less oxygen than a neutral setting, what type of flame results?

Accepted Answer

Introduction / Context: Flame settings in oxy-acetylene welding are categorized as neutral, oxidising, and carburising (reducing). Understanding how gas ratios affect flame structure and metallurgical effects is critical to avoid embrittlement, excessive oxidation, or porosity. Given Data / Assumptions: Torch uses acetylene (fuel) and oxygen (oxidizer). Adjustment moves to higher acetylene and lower oxygen compared to neutral. Observation includes longer feather on the inner cone characteristic of a reducing flame. Concept / Approach: A carburising flame has excess acetylene. It shows a pronounced acetylene feather beyond the inner cone and introduces a reducing atmosphere that can carburize or deoxidize the work. This is useful for specific applications (e.g., some alloy brazings), but harmful for others due to carbon pickup or sooty deposits. Step-by-Step Solution: Compare gas ratios: acetylene up, oxygen down → rich fuel mixture.Identify visual cue: larger feather on the inner cone → carburising flame.Select the term “carburising”. Verification / Alternative check: Flame charts confirm three regimes; carburising occurs on the fuel-rich side of neutrality. Why Other Options Are Wrong: Neutral has balanced gas flow.Oxidising has excess oxygen, not acetylene.Other terms listed are not standard oxy-acetylene flame classifications. Common Pitfalls: Using a carburising flame on steels can cause sooty welds and carbon enrichment; adjust to neutral unless a procedure requires otherwise. Final Answer: carburising

Question 2

Moulding Equipment — Purpose of a Stripper-Plate Machine In foundry practice, what is the primary function of a stripper-plate machine with respect to pattern withdrawal from the mould?

Accepted Answer

Introduction / Context: Accurate pattern withdrawal is essential to preserve mould integrity. Mechanised systems such as stripper-plate machines improve repeatability and reduce damage compared to manual draw, especially for complex patterns or high-volume production. Given Data / Assumptions: A stripper-plate machine is available in a green sand moulding line. The goal is to release the pattern cleanly without enlarging or tearing the cavity. Pattern may have modest draft but requires controlled, uniform withdrawal. Concept / Approach: A stripper-plate (or draw) mechanism applies uniform, guided motion to separate the mould from the pattern. The plate supports sand surfaces around the pattern during withdrawal, preventing rapping damage and maintaining dimensions. This is especially useful for patterns with minimal draft or fine features. Step-by-Step Solution: Recognize that the machine’s function is pattern removal.The stripper plate lifts the mould or lowers the pattern in a controlled path.Therefore, its primary purpose is to draw the pattern from the mould reliably. Verification / Alternative check: Foundry equipment catalogs describe stripper-plate machines as pattern-drawing devices that reduce cavity damage and cycle time. Why Other Options Are Wrong: Core setting, tempering, and chaplet placement are separate operations with different tools/fixtures. Common Pitfalls: Insufficient draft remains problematic; even with a stripper plate, appropriate draft and surface finish are necessary. Final Answer: Yes

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