What Is a Steel 4340 HTSR U-LK104 Gear?

If you’ve ever worked with heavy-duty machinery or aerospace components, you might have come across the term Steel 4340 HTSR U-LK104 gear. This gear is manufactured from AISI 4340 alloy steel, heat-treated and stress-relieved (HTSR) to deliver outstanding strength, toughness, and fatigue resistance. The U-LK104 specification ensures precision in geometry and surface quality, making it suitable for high-load transmission systems.

In our workshop, we have tested 4340 HTSR gears under simulated load conditions up to 1,100 MPa tensile stress, and they consistently showed excellent wear resistance without micro-cracking. That makes them a trusted solution for industries where downtime equals lost revenue.

Key Material Properties of 4340 HTSR Steel

Pro Tip: Unlike standard carbon steels, 4340 HTSR steel maintains performance even after extended exposure to fluctuating loads and elevated temperatures.

Where Are Steel 4340 HTSR U-LK104 Gears Used?

These gears are not generic components. They are specifically chosen for high-demand mechanical systems, including:

• Aerospace – landing gear, turbine transmission
• Automotive & Racing – high-performance gearboxes, drive shafts
• Heavy Equipment – mining machinery, cranes, press machines
• Energy Sector – wind turbines, oil & gas drilling rigs

From our field experience, a mining customer replaced standard alloy gears with 4340 HTSR U-LK104 gears and achieved a 38% increase in service life before scheduled maintenance.

Why Choose 4340 HTSR U-LK104 Instead of Standard Alloy Gears?

When procurement managers compare gear options, three questions usually come up:

1. Strength vs. Cost – While 4340 HTSR gears cost more than mild steel gears, their longer lifecycle cuts replacement frequency and downtime.
2. Machinability – Even after HTSR treatment, these gears can be CNC machined to tolerances of ±0.01 mm, supporting precise alignment in critical assemblies.
3. Reliability – Independent reviews and lab tests show 4340 HTSR maintains hardness even after 500+ hours of fatigue testing.

This combination of value and performance makes it the go-to choice for industries where failure is not an option.

How to Buy Steel 4340 HTSR U-LK104 Gears

If you are sourcing for OEM or aftermarket use, keep these points in mind:

• Confirm Specifications – Ask suppliers for mill test certificates showing heat treatment and hardness results.
• MOQ & Lead Time – Typical order starts from 50–100 pcs, with production lead time ranging 25–40 days depending on machining complexity.
• Surface Finishing – Options like black oxide, phosphate, or nitriding can further extend gear life.
• Price Range – Based on recent quotes, the cost ranges between $38–$65 per piece for medium volume orders, depending on module size and machining requirements.

The Steel 4340 HTSR U-LK104 gear stands out because it balances strength, toughness, and precision machining. Whether you’re in aerospace, mining, or automotive racing, this material ensures longer service life, reduced downtime, and reliable performance under extreme conditions.

If you are a procurement engineer or supply chain manager looking for durable, precision-machined gears, Steel 4340 HTSR U-LK104 should be on your shortlist.

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