Uses and Classification of Steel Grit
Steel grit is an angular, high-hardness metallic abrasive whose core applications focus on metal surface cleaning, strengthening, pre-treatment for coating and plating, and wear-resistant engineering. It is classified by material, hardness, particle size, shape and manufacturing process to suit different industrial scenarios. Details are as follows:
I. Core Applications
Metal Surface Cleaning and Rust RemovalUsed for descaling castings, removing oxide scale from forgings, and derusting steel plates/steel structures. Rust, oil stains and old coatings are removed via shot blasting or sand blasting to lay a foundation for subsequent processes. It is commonly applied in the maintenance of ships, bridges and chemical equipment.
Surface Strengthening and ModificationCreates residual compressive stress on the workpiece surface through shot blasting, improving fatigue strength and wear resistance. It is suitable for key components such as gears, springs, bearings and crankshafts to extend their service life.
Pre-treatment for Coating and PlatingIncreases the roughness of the metal surface to enhance coating adhesion and ensure anti-corrosion effects of the coating. It is used in pre-treatment procedures for coating and plating in the fields of automobile manufacturing, engineering machinery and steel structures.
Wear-resistant Engineering and Building Material ProcessingAdded to concrete/mortar wear-resistant layers (e.g., coal bunkers, hoppers, chutes) to improve compressive and impact resistance. It is also used for cutting and grinding decorative stones such as marble and granite.
Grinding and PolishingSuitable for grinding and polishing hardware, glass, gems, etc. Some high-precision steel grit can be used in the precision processing of auto engine blocks, chip housings and other components to achieve the required surface finish.
Special Industrial ApplicationsServes as a metallurgical deoxidizer, high-temperature resistant material, or for pipeline internal cleaning and mold cleaning.
II. Classification System
1. Classification by Material and Manufacturing Process
| Type | Material & Manufacturing Process | Performance Characteristics | Application Scenarios |
|---|---|---|---|
| Cast Steel Grit | Made by melting waste steel, atomizing, crushing, quenching and tempering | Hardness HRC 45–55, moderate toughness, high cost-performance ratio | Casting descaling, steel derusting, pre-treatment for coating and plating |
| Alloy Steel Grit | Added with alloying elements such as chromium, molybdenum and nickel | High hardness (HRC 58–65), excellent wear resistance, good low-temperature toughness | Wind power towers, low-temperature pipelines, mining machinery |
| Bearing Steel Grit | Processed from bearing steel scrap with special quenching and tempering | Hardness HRC 60–65, wear-resistant, significant strengthening effect | Strengthening of precision components like gears and bearing rings |
| Angular Steel Grit | Retains multiple edges (≥8) after crushing | Strong cutting force, high cleaning efficiency | Removal of thick oxide scale, stone cutting |
2. Classification by Hardness (GB/T 18838.3)
| Hardness Grade | Code | Hardness Range (HRC) | Characteristics | Application Scenarios |
|---|---|---|---|---|
| High Hardness | GH/H | 52–60 | Fast cleaning speed, relatively high crushing rate | Rapid removal of thick rust and oxide scale |
| Medium Hardness | GP/P | 45–52 | Balanced toughness and service life, high versatility | Regular derusting, descaling, pre-treatment for coating and plating |
| Low Hardness | GL/L | 40–45 | Minimal surface damage, uniform roughness | Cleaning and strengthening of precision and thin-walled workpieces |
3. Classification by Particle Size (GB/T 18838.3 Standard)
Common particle size grades include 2, 3, 4, 7, 10, 12, 14, 17, 20, 25, etc., corresponding to particle sizes of approximately 0.2–3.0 mm. Coarse grit is used for removing thick oxide scale and welding slag, medium grit for regular cleaning, and fine grit for fine processing and polishing.
4. Classification by Shape
Angular Steel Grit: Multi-angular after crushing, with strong cutting force, suitable for rust removal, descaling and strengthening.
Rounded Steel Grit: Edges passivated after tempering, causing minimal surface damage, applicable to thin-walled workpieces and those requiring high surface finish.
5. Classification by Quality Grade
Premium Grade: Low impurity content, low porosity, uniform particle size, suitable for aerospace and high-end automobile manufacturing.
Grade I: Stable performance, used in general industrial manufacturing.
Qualified Grade: Meets basic cleaning requirements, used for rough cleaning of ordinary steel structures and castings.
III. Selection Essentials
Match Workpiece Material and Purpose: Choose GP medium-hard grit for carbon steel workpieces; GL low-hard grit or rounded grit for high-strength steel/precision components; angular grit or GH high-hard grit for removing thick oxide scale or cutting stones.
Particle Size Matching: Coarse grit (e.g., Grade 25) for thick rust/oxide scale; medium grit (e.g., Grade 10, 12) for regular cleaning; fine grit (e.g., Grade 2, 3) for fine pre-treatment and polishing.
Refer to Standards: Comply with GB/T 18838.3, SAE J827, etc., and check the content of carbon (0.85%–1.20%), manganese and silicon to ensure a balance between hardness and toughness.
