Oxy-Acetylene Welding — Predominant Flame Type Which type of oxy-acetylene flame is used for most general welding operations to obtain neutral chemistry in the weld pool?

Introduction / Context:
Flame chemistry in oxy-acetylene welding governs oxidation or carburisation tendencies at the weld. Selecting the correct flame ensures proper metallurgical quality and mechanical performance of the joint.

Given Data / Assumptions:

• Process: oxy-acetylene gas welding.
• Goal: general-purpose welding with minimal alteration of base-metal composition.
• Base metals include common steels and non-ferrous alloys.

Concept / Approach:
A neutral flame has a balanced oxygen-to-acetylene ratio, producing neither oxidising nor carburising conditions. It provides a stable temperature and clean reducing zone that protects the molten pool without introducing excessive oxygen or carbon, making it the most widely used flame for general welding.

Step-by-Step Solution:
Identify objective: neutral weld chemistry.Select neutral flame (no excess O2 or C) for most jobs.Reserve oxidising flame for specific materials (e.g., some brasses) and carburising flame for certain alloy or hardfacing cases.Therefore, the predominant general-use choice is neutral flame.

Verification / Alternative check:
Welding handbooks recommend neutral flame for mild steel welding to avoid porosity and unwanted oxides/carbides.

Why Other Options Are Wrong:
Oxidising flame can cause oxide inclusions and brittleness in steels.Carburising flame can enrich carbon, leading to brittle welds in steels.“All of these” is incorrect because one flame type is predominant for general use.

Common Pitfalls:
Confusing neutral inner-cone appearance with carburising feather; proper flame adjustment is essential.

Final Answer:
neutral flame