Industry standards: ISO, SAE, etc. requirements for bucket tooth hardness and toughness

International Organization for Standardization (ISO): Performance-oriented with working condition adaptation as the core

Although ISO has not set a unified numerical standard for bucket tooth hardness and toughness, it has established the core principle of "performance adaptation to working conditions" in a series of standards such as "General Safety Requirements for Earthmoving Machinery" and "Terms and Definitions of Working Devices for Earthmoving Machinery".

In terms of hardness, ISO requires that the hardness of bucket tooth materials must match the hardness of the working material: for low-hardness materials such as soft soil and sand and gravel, the surface hardness of the bucket teeth must reach 250-350HB (Brinell hardness) to balance wear resistance and processing costs; for high-strength materials such as rocks and concrete blocks, the hardness of the tooth tip must be increased to 400-500HB to ensure that plastic deformation is not easily generated during the cutting process. At the same time, it is clearly stipulated that the hardness of the bucket tooth body (non-tooth tip area) must be 30-50HB lower than the tooth tip, forming a "gradient hardness structure" to reserve space for subsequent toughness assurance.

The toughness requirement is reflected by the "impact failure resistance" index: ISO stipulates that bucket teeth must pass the 15J impact energy test (Charpy V-notch test) in the temperature range of -20℃ to 40℃, that is, after being subjected to an impact equivalent to 15 joules of energy, no through cracks or fractures should occur. This requirement is intended to cope with operating scenarios under extreme temperature differences - such as low temperature impact at northern construction sites in winter, or thermal fatigue of materials during continuous operation in summer.

Society of Automotive Engineers (SAE): Dual specifications of quantitative indicators and process adaptation

The SAE standard features "precise quantification" and "process adaptation", and its J2575 "Engineering Machinery Bucket Teeth Material Specification" has extremely strong practicality in terms of hardness and toughness.

The hardness index uses Rockwell hardness (HRC) as the core parameter: the hardness of the working area of the tooth tip (within 50mm from the tip) needs to be controlled at 45-50HRC. This range can not only ensure the "piercing force" during cutting (hardness below 45HRC is prone to tooth tip curling), but also avoid the risk of brittleness caused by excessive hardness (over 50HRC); the hardness of the area where the root of the bucket tooth connects to the bucket needs to be reduced to 30-35HRC. By reducing the hardness, the ductility of the material is improved to prevent the root from breaking due to stress concentration during operation.

The toughness requirements are refined to different types of operations: general-purpose bucket teeth need to meet 20J impact energy at 20℃, and mining-specific bucket teeth (for high impact conditions) need to be increased to 30J, and it is clearly stipulated that the crack length after the impact test shall not exceed 10mm. In addition, SAE also requires bucket tooth materials to pass the "hot and cold cycle toughness test" - after a temperature cycle from -30℃ to 60℃, the impact energy retention rate must reach more than 80% to adapt to the operating requirements in extreme climates.

China National Standard (GB/T 25628-2023): Adaptability optimization combined with local working conditions

GB/T 25628-2023 "Earthmoving Machinery Bucket Teeth" refers to international standards and combines typical working conditions of Chinese engineering construction (such as mixed materials in infrastructure projects, high-intensity impact in mining operations, etc.) to form more targeted requirements.

The hardness standard adopts "dual indicators in parallel": Brinell hardness (HB) is used for overall evaluation (tooth tip ≥400HB, body ≥320HB), and Vickers hardness (HV) is used for microscopic area detection (within 1mm depth of the tooth tip surface, hardness fluctuation must be ≤50HV). This dual index can effectively avoid the problem of "hardening the surface but insufficient internal strength" - for example, some inferior bucket teeth meet the hardness requirements through surface quenching, but the internal material is loose, and "surface peeling" is easy to occur in actual operation.

The toughness requirement highlights the ability to "resist repeated impact": in addition to the conventional 20℃, 20J impact test, a "10-cycle impact test" is added - after 10 consecutive 10J energy impacts, the bucket teeth must not have cumulative cracks. This requirement is aimed at the common "intermittent operation" scenarios (frequent start and stop, intermittent impact of materials) on Chinese construction sites to prevent "fatigue fracture" caused by repeated impacts. At the same time, the standard specifically stipulates that bucket teeth used in plateau areas (above 3000m above sea level) must pass the -30℃ low-temperature toughness test to adapt to the high-altitude and low-temperature environment.

The core logic behind the standard: dynamic balance between hardness and toughness

Whether it is ISO's "condition adaptation", SAE's "quantitative control", or GB's "local optimization", the core logic revolves around the "dynamic balance between hardness and toughness" - insufficient hardness will cause the bucket teeth to wear quickly and lose cutting ability; insufficient toughness will easily cause cracking and fracture, resulting in equipment shutdown.

These standards are not "restrictions", but the "safety bottom line" established for bucket tooth performance: when the bucket teeth meet the hardness and toughness requirements at the same time, they can maintain a service life of 800-1200 hours in routine operations (floating according to the hardness of the material), and reduce the risk of failure in sudden impacts (such as accidental contact with rocks and steel bars). For users, choosing bucket teeth that meet the standards means lower replacement frequency, more stable operating efficiency, and lower comprehensive use costs.

From international to domestic, the evolution of bucket tooth standards has always been synchronized with engineering needs. Understanding the logic behind these standards can not only help users accurately select products that suit their working conditions, but also promote the industry's continued pursuit of "performance balance" - after all, a qualified bucket tooth must be as tough as steel and also know how to "buffer" like a spring.