In metal processing and manufacturing, the service life and stability of shear blades are critical determinants of production efficiency and operating costs. Addressing the demanding requirements of shearing 6–8mm thick Q345 steel plates, Licheng Blade has developed high-performance shear blades using the novel cold-work die steel LD, following extensive research into end use and material innovation. End users demonstrate that these blades achieve a fourfold increase in service life compared to traditional cold-work die steels such as SKD11, hot-work die steels like H13, and W6Mo5Cr4V2 high-speed steel, thereby resolving longstanding challenges related to blade chipping, limited service life, and difficulties in regrinding.

1. Main Problems of Shear Blades Made of Traditional Materials
Traditional shearing blades have been tested with various die steels and high-speed steels, but practical production continues to reveal issues that negatively affect efficiency, precision, and cost.
Edge Design and Usage Limitations:
I.Wedge Angle vs. Strength: When it comes to knife cutting, like a pair of scissors, a smaller angle cuts more sharply but reduces strength and shortens life, while an excessive angle increases resistance. Blade angles generally range from 80° to 90°, with 90° typically chosen to maximize the number of available cutting edges.
II.Overlap Angle Range: The included angle between dual edges during transverse shearing is 0–10 degrees, while longitudinal slitter blades intersect orthogonally.
III.Bite Depth and Clearance: Edge engagement requires a balance of tightness and depth. Clearance and depth affect the sheared cross-section and blade life and must be analyzed based on the shearing method, tool dimensions, and sheet thickness.
IV.Shear Root Design: Improper shear root height compromises the knife cutting edge. Thicker sheets generally need larger knives, and design thickness should be at least three times the material thickness. If the knife's outer diameter or width is larger than expected, this proportion can be reduced accordingly.

Manufacturing and Process Challenges: Material selection, forging, heat treatment, and grinding. These complex processes rely heavily on extensive production experience.

Operational Issues:
I.Blunting and Wear: Low fatigue strength leads to edge wear and localized chipping, requiring frequent replacement or removal of large fatigue layers, which severely reduces productivity.
II.Brittle Fracture Failure: This is the most severe failure mode on the knife working. While fatigue failure indicates poor wear resistance, brittle fracture can cause catastrophic interruptions in steel sheeting production or safety incidents and is closely tied to material selection.

2.Breakthrough Solution: The Advantages of LD Die Steel

When shearing thick plates such as 6–8mm Q345 low-alloy high-strength structural steel, slitting blades must withstand extreme impact loads and frictional shear forces. The previous material choice favored M2 high-speed steel or SKD11 die steel, but these conventional materials could not fully meet the working conditions.
W6 High-Speed Steel: Although it offers high hardness and red hardness for knife cutting or slitting, insufficient toughness causes knife edge chipping under intense cyclic impacts from thick plates.
SKD11 Steel: While it offers good wear resistance, its impact toughness falls short of continuous thick-plate shearing demands, often causing premature tool failure.

From a material selection perspective, these conventional metals are premium grades, but their performance metrics do not fully match actual failure modes under working conditions. To resolve this industry bottleneck, the Licheng Blade technical team selected advanced high-alloy cold-work die steel LD (7Cr7Mo2V2Si) as the core solution.

LD steel integrates high wear resistance with high toughness:
Superior Toughness: Its impact toughness exceeds traditional cold-work die steels and high-speed steels, helping resist heavy mechanical shocks during thick-plate blanking and prevent edge chipping.
Exceptional Wear Resistance: Proper carbon and alloy content ensures sustained anti-wear performance during continuous slitting operations.
Furthermore, LCKNIFE selects high-quality LD material from steel mills, such as premium electro-slag remelted (ESR) LD steel, with minimized harmful elements such as sulfur and phosphorus, and with inclusions and segregation defects eliminated. Raw materials are selected with dimensions smaller than the finished blade to enforce a strict forging ratio during blank formation. Real-world validation confirms that LD steel blades achieve up to a 4-times increase in lifespan over W6 high-speed steel.

3. Core Heat Treatment Process Analysis

Premium material of blade requires precise heat-treatment steps to reveal its character as intended. For cutting blades here, LCKNIFE streamlined a reasonable heat-treatment processing specification for LD material as below:
Heating and Soaking: Heat LD material to 1150℃ and hold to achieve full austenitization.
Pre-cooling and Quenching: Pre-cool the raw slitter knife to 1100℃ before oil quenching to secure an ideal martensitic microstructure and target hardness.
Multiple Tempering: At least three times of tempering at 560–570℃ for knives. Sufficient tempering relieves internal residual stress in the knives, promotes secondary hardening through dispersed alloy carbide precipitation, and improves microstructural stability and thermal fatigue resistance.

Final Hardness: Stabilized in the range of HRC 58–60, achieving an optimal balance of shear knife hardness between resistance and toughness.

4. Practical Application Performance
Deployed in active production lines, Licheng LD steel slitter blades combined with optimized heat treatment show outstanding durability:
Shearing Breakthrough: After extended continuous shearing, inspection revealed only light edge wear and no chipping.
High Maintainability: Uniform wear and structural integrity on the knife surface enable quick re-grinding to restore cutting conditions, reducing tooling loss and overall operating costs.

This breakthrough delivers significant economic benefits for industrial users while confirming LD steel as a reliable material choice and process upgrade for thick-plate cutting tools.

Maanshan Licheng Blade Manufacturing Co., Ltd. uses a range of high-quality and suitable materials, along with advanced thermal treatments—including vacuum heat treatment, subzero treatment, and salt-bath treatment—to produce high-performance steel shear blades for more on stainless steel, silicon steel, Al, and Cu sheeting