A North American Medical Manufacturer Solves Material Pickup, Die Galling, and Premature Die Failure with High-Purity ESR Tool Steel

Executive Summary

A North American medical device manufacturer was experiencing recurring material pickup, die galling, workpiece scratching, and premature die damage during the precision cold extrusion of stainless steel medical components.

Conventional countermeasures—including cavity polishing and lubricant optimization—provided only temporary improvement. The underlying problem was not simply surface friction. Under the extremely high pressures generated during cold extrusion, workpiece material was penetrating microscopic defects within the tool steel and becoming mechanically anchored to the die surface.

KUTU analyzed the failure mechanism and recommended replacing the conventional air-melt tool steel with a high-density, high-purity ESR (Electroslag Remelting) tool steel featuring a cleaner microstructure, refined carbide distribution, and improved internal uniformity.

The result was a fundamental change in die behavior: by reducing the microscopic sites where workpiece material could mechanically interlock with the die, the solution addressed the source of material pickup rather than repeatedly treating its symptoms.

1. Customer Background: Precision Medical Components Under Extreme Pressure

The customer was a North American medical manufacturing company supplying precision components for the medical and surgical equipment industry.

Its production line included precision cold extrusion of stainless steel components, including applications involving 316L stainless steel.

Unlike conventional machining, cold extrusion forces the workpiece through a precisely engineered die cavity under extremely high compressive loads.

This process provides significant advantages:

• Excellent dimensional consistency
• High material utilization
• Improved mechanical properties
• Reduced secondary machining
• High production efficiency

However, these advantages come with one major challenge:

The die material must withstand extreme pressure while maintaining an exceptionally stable cavity surface.

Even microscopic imperfections inside the die can become significant failure sites after repeated extrusion cycles.

2. The Problem: Material Pickup Was Damaging Both Dies and Parts

The manufacturer began experiencing a recurring pattern of production problems.

The main symptoms included:

• Material pickup on the die cavity
• Micro-galling
• Scratches on finished components
• Increasing friction during extrusion
• Localized cavity damage
• Premature die cracking or chipping
• Increasing scrap rates
• Unexpected production interruptions

Initially, the problem appeared to be a typical lubrication or surface-finishing issue.

The production team therefore attempted several conventional countermeasures.

First Attempt: Improve Cavity Polishing

The die cavity was polished more carefully in an effort to eliminate microscopic surface irregularities.

The logic was straightforward:

Smoother surface → lower friction → less material pickup.

However, the improvement was temporary.

After continued production, material pickup returned.

Second Attempt: Optimize Lubrication

The manufacturer also adjusted the lubricant and application conditions.

This reduced friction to some extent, but it did not eliminate the problem.

The same pattern eventually returned:

Material pickup → surface damage → workpiece scratching → die maintenance → production interruption.

At this point, KUTU began investigating the problem from a metallurgical perspective.

3. Root Cause Analysis: The Hidden Problem Was Micro-Infiltration

The critical finding was that the problem was not limited to the visible surface of the die.

Under extreme cold extrusion pressure, the workpiece material can interact with microscopic defects within the tool steel.

This phenomenon can be described as micro-infiltration or material penetration into microscopic voids and weak structural regions.

For high-pressure cold extrusion, this distinction is critical.

A die may appear perfectly polished under conventional inspection while still containing microscopic structural discontinuities beneath or near the working surface.

4. How Does Micro-Infiltration Cause Die Galling?

Consider what happens during repeated extrusion cycles.

Step 1 — Extreme Pressure

Precision cold extrusion can generate extremely high localized stresses, potentially exceeding 1,500 MPa depending on the material, geometry, reduction ratio, and process conditions.

The ductile workpiece material is forced against the die cavity under severe compressive loading.

Step 2 — Material Enters Microscopic Defects

If the tool steel contains microscopic porosity, inclusions, carbide-related voids, or other local discontinuities, the workpiece material can penetrate or mechanically engage with these regions.

The important point is that this interaction can occur below the scale of ordinary visual surface inspection.

Step 3 — Mechanical Interlocking

The infiltrated workpiece material becomes mechanically anchored inside microscopic irregularities.

As the extrusion cycle continues, the interface experiences:

• High pressure
• Sliding friction
• Repeated loading
• Localized shear stress

The embedded material can eventually become unstable.

Step 4 — Material Shears Off

During subsequent cycles, the trapped workpiece material may shear away from the die surface.

Part of it remains attached to the cavity.

This creates the beginning of material pickup and micro-galling.

Step 5 — Die Surface Becomes Increasingly Damaged

The accumulated material changes the geometry and surface condition of the cavity.

The resulting failure chain becomes:

Microstructural defect

↓

Material infiltration

↓

Mechanical interlocking

↓

Material pickup

↓

Increased friction

↓

Workpiece scratching

↓

Localized stress concentration

↓

Die chipping or cracking

This explained why polishing and lubricant adjustments alone could not permanently solve the problem.

They were treating the surface symptoms, while the underlying weakness was associated with the internal cleanliness and structural uniformity of the tool steel.

5. KUTU’s Technical Solution: Upgrade the Die Steel

KUTU’s recommendation was not simply to make the cavity smoother.

Instead, we changed the foundation of the tooling system:

From Conventional Air-Melt Tool Steel to High-Purity ESR Tool Steel

The new die material was selected based on its ability to withstand extreme pressure while minimizing microscopic structural defects.

The key requirement was:

High density + high cleanliness + uniform microstructure + sufficient toughness.

6. Why ESR Tool Steel Was the Right Choice

Electroslag Remelting (ESR) is a secondary refining process used to improve the cleanliness and internal quality of tool steel.

For demanding tooling applications, the advantages of ESR processing include:

Reduced Non-Metallic Inclusions

Cleaner steel reduces potential internal stress concentration sites and crack initiation points.

Improved Microstructural Uniformity

A more uniform structure provides more consistent mechanical behavior throughout the die.

Refined Carbide Distribution

Better-controlled carbide morphology can reduce large carbide-related weak regions that may contribute to premature failure.

Higher Structural Integrity

For high-pressure applications, internal quality is just as important as surface hardness.

This was the key principle behind KUTU’s recommendation.

7. Why Polishing Alone Could Not Solve the Problem

One of the most important lessons from this project was that surface quality and internal steel quality are not interchangeable.

A die can have an excellent polished finish and still contain microscopic structural weaknesses.

Polishing primarily modifies the surface.

It cannot fundamentally eliminate:

• Internal porosity
• Non-metallic inclusions
• Carbide segregation
• Internal structural discontinuities

Likewise, a coating may improve surface wear resistance, but it cannot automatically eliminate defects beneath the coating or prevent material from interacting with an unsuitable substrate.

For extreme cold extrusion, the substrate itself must provide sufficient structural integrity.

8. Production Results

After implementing the upgraded tool steel solution and validating the tooling under production conditions, the manufacturer achieved a substantial improvement in die stability.

The most important result was the suppression of the original failure mechanism:

Material infiltration and recurring galling were effectively eliminated under the evaluated production conditions.

The improvement translated into several practical benefits.

Reduced Material Pickup

The die cavity remained significantly more stable during production, reducing the need for frequent removal of accumulated workpiece material.

Improved Surface Quality

With less material pickup and galling, the risk of scratching the extruded medical components was substantially reduced.

Longer Die Service Life

The improved internal quality and resistance to localized damage allowed the die to remain in service for significantly more production cycles.

Reduced Unplanned Downtime

Fewer die interventions meant fewer unexpected production interruptions.

Lower Scrap Risk

More stable tooling reduced the risk of components being rejected because of cavity-induced surface defects.

9. The Economic Impact Goes Beyond Die Life

For a medical component manufacturer, the cost of a failed extrusion die is not limited to the price of the replacement die.

A premature die failure can trigger a much larger chain of costs:

Die failure

→ Production stoppage

→ Tool replacement

→ Setup and alignment

→ Trial production

→ Scrap during restart

→ Delivery delays

→ Additional inspection

→ Increased manufacturing cost

Therefore, extending die life can create value in several areas simultaneously.

Potential savings include:

• Lower tooling consumption
• Lower scrap costs
• Fewer production interruptions
• Less operator intervention
• Reduced maintenance frequency
• More stable production planning

For high-volume medical manufacturing, even a relatively small reduction in scrap or downtime can have a significant annual financial impact.

10. Why This Case Matters for Medical Cold Extrusion

Medical components demand much tighter control than many conventional industrial products.

A tooling problem can affect more than productivity.

It can also influence:

• Surface quality
• Dimensional consistency
• Process stability
• Inspection workload
• Product rejection rates

This makes die material selection a strategic manufacturing decision rather than simply a purchasing decision.

The correct tool steel must be selected according to the actual failure mechanism.

If the failure is primarily wear, wear resistance may be the priority.

If the failure is impact fracture, toughness becomes critical.

But when extreme pressure causes material pickup and micro-galling, the internal cleanliness and structural integrity of the die steel become especially important.

11. KUTU’s Best-Practice Approach to High-Pressure Tooling

Based on this project, KUTU recommends evaluating high-pressure cold extrusion tooling through four levels.

1. Steel Cleanliness

Check:

• Non-metallic inclusions
• Internal defects
• Steelmaking route
• Material consistency

For critical tooling, consider ESR tool steel.

2. Microstructural Uniformity

Evaluate:

• Carbide size
• Carbide distribution
• Segregation
• Forging quality

A refined and uniform microstructure provides a stronger foundation for high-pressure applications.

3. Heat Treatment

Even premium ESR steel requires appropriate heat treatment.

Control:

• Preheating
• Austenitizing
• Quenching
• Tempering
• Final hardness

The objective is not simply maximum hardness.

The die needs the correct balance of:

Hardness + toughness + dimensional stability.

4. Working Surface and Process Conditions

Finally, optimize:

• Cavity finish
• Die geometry
• Lubrication
• Extrusion pressure
• Alignment
• Workpiece preparation

The best result comes from combining premium material quality with controlled processing.

12. Key Lesson: Fix the Root Cause, Not Just the Surface

This project demonstrated an important principle in precision tooling:

When material pickup repeatedly returns after polishing and lubrication adjustments, investigate the die steel itself.

If high-pressure forming is forcing workpiece material into microscopic structural defects, surface polishing can only provide temporary relief.

The more fundamental solution is to reduce the structural defects that allow mechanical interlocking to occur.

For demanding cold extrusion applications, high-purity, high-density ESR tool steel can provide a significantly stronger foundation for stable die performance.

Conclusion

The North American medical manufacturer’s die failure problem was not ultimately a simple polishing or lubrication issue.

The recurring combination of:

material pickup + micro-galling + workpiece scratching + premature die damage

was linked to the interaction between extreme extrusion pressure and the microscopic structural quality of the tool steel.

KUTU addressed the problem at its source by upgrading the tooling material to a high-purity ESR tool steel with improved internal cleanliness, density, and microstructural uniformity.

The result was a more stable die surface, reduced material pickup, improved production consistency, and a significant reduction in the risk of premature tooling failure.

For manufacturers working with high-pressure cold extrusion, stainless steel medical components, precision forming, and other demanding applications, the lesson is clear:

When the pressure is extreme, tool steel quality must be evaluated below the surface.

About KUTU MOLD STEEL

KUTU MOLD STEEL specializes in high-performance mold and tool steels for demanding industrial applications.

We support manufacturers with material selection for:

• Precision cold extrusion
• Medical component tooling
• Stamping dies
• Cold forging dies
• Hot work tooling
• Die casting molds
• High-wear precision tooling

When conventional tool steel reaches its performance limit, KUTU helps customers identify whether the real problem lies in material cleanliness, microstructure, heat treatment, tooling design, or operating conditions—and select a more suitable steel solution.

The right tool steel is not simply the hardest steel. It is the steel whose microstructure matches the actual failure mechanism.