Joining a Mild Steel Shank to a High-Speed Steel Drill — Select the Proper Resistance Welding Process In tool manufacture, what resistance welding method is commonly used to join a mild steel shank to a high-speed steel (HSS) drill body?

Introduction / Context:Composite drills often consist of a high-speed steel (HSS) cutting portion joined to a tough mild steel shank to save cost and tailor properties. Selecting the appropriate resistance welding process ensures a sound joint with minimal defects and good alignment for subsequent grinding.

Given Data / Assumptions:

• Dissimilar steels: HSS (high alloy) and mild steel.
• Axial bar-to-bar joining geometry (coaxial rods).
• Need for high-quality bond along the full cross-section with minimal inclusions.

Concept / Approach:Flash butt welding uses controlled arcing (flashing) at abutting faces to uniformly heat and expel surface oxides. Once adequate plasticity and cleanliness are achieved, a strong upset force forges the joint. This method is well-suited to axial bar joints, managing differences in composition and thermal properties between HSS and mild steel.

Step-by-Step Solution:Prepare bars with square faces and alignment.Flash: bring ends together under low force to create arcing, heating, and expelling oxides.Upset: apply high axial force to forge the joint and consolidate the interface.Cool under control to reduce residual stress and preserve HSS properties.

Verification / Alternative check:Industrial practice routinely uses flash butt welding for drills, reamers, and similar tools with dissimilar shanks.

Why Other Options Are Wrong:Spot/seam welding suit sheet products, not coaxial bars.Upset butt welding lacks the flashing stage, making oxide removal less effective for HSS-MS combinations.Projection welding is for localized nuggets under raised features, not full-section bar joints.

Common Pitfalls:Overheating can degrade HSS temper; precise control of flashing and cooling is essential.

Final Answer:flash butt welding