FAQ
I. Product & Manufacturing Process
1. What types of grinding balls do you produce, and what are the key differences?
Chengda specializes in the production of three core series of grinding media: Forged Steel Balls , High-Chrome Cast Balls , and CADI Balls (Carbide Austempered Ductile Iron Ball ).
Forged Steel Balls:
- Key Feature: Offer excellent impact toughness and fracture resistance.
- Application: Suitable for heavy-duty applications such as semi-autogenous grinding (SAG) mills and ball mills in the mining industry.
High-Chrome Cast Balls:
- Key Feature: Rely on a high-hardness, dense wear layer.
- Application: Widely used for raw material grinding in cement plants and power generation facilities.
CADI Balls :
- Key Feature: Innovatively combine superior wear resistance with high impact toughness.
- Application: Perfectly suited for complex working conditions involving mixed materials and alternating high/low loads, precisely matching the grinding requirements of various industries.
2.What is the difference between CADI Austempered Balls and High-Chrome Cast Balls?
CADI Austempered Balls (Carbide Austempered Ductile Iron) utilize an isothermal quenching and composite toughening heat treatment process.This creates a uniform and dense austempered ductile iron microstructure.The result is a ball that not only possesses high hardness, reaching HRC 58–63, but also has excellent impact toughness.In various grinding conditions, the CADI Austempered Balls demonstrate stable performance, and their service life is significantly extended by 30–50% compared to traditional high-chrome balls.
3. What is your forging process like?
We utilize a fully automated forging production line and a high-temperature precision heat treatment system that encompass the entire process: “Heating -Forging-Quenching -Tempering”.Through a standardized, closed-loop process, we strictly control every production stage. This not only ensures that the product forms a dense and uniform internal microstructure and achieves a stable, consistent hardness distribution, but also results in high-quality performance with a fracture rate lower than 0.5%$. This provides reliable and durable grinding media for various working conditions.
4. What material grades are available for your cast balls?
Chengda’s High-Chrome Cast Balls cover the full range of chromium content ratios: High-Chrome (Cr 10–28%), Medium-Chrome (Cr 5–8%), and Low-Chrome (Cr <5%).
We precisely recommend the appropriate alloy composition scheme based on the client’s specific ore abrasiveness index, mill type (such as ball mills, SAG mills, vertical mills, etc.), and operational parameters. This ensures a high degree of matching between the grinding media and the operating conditions, achieving the optimal balance between wear resistance and cost of use.
5. How do you ensure consistent hardness from surface to core?
We utilize a four-drive automated heat treatment production line. Through precise temperature control and an intelligent, closed-loop process design, we can achieve a uniform hardened layer with a depth exceeding 15mm.
Simultaneously, we strictly guarantee product hardness consistency, controlling the hardness difference between the surface and the core to be within 2HRC. This forms the core foundation for the stable wear resistance and long service life of our grinding media.
II. Performance & Application
6. How to choose appropriate steel ball size for ball mill?
Mill Application Field | Recommended Steel Ball Diameter Range (mm) |
|---|---|
General Ball Mill | 80–150 mm |
| Mining Ball Mill | 60–120 mm |
| Cement Clinker Mill | 20–50 mm |
| Coal Mill (Power Plant) | 20–70 mm |
| Metallurgy Pelletizing Mill | 60–100 mm |
| Aggregate / Sand Line | 30–80 mm |
7. What are the differences in the breakage rate and service life among various ball materials?
| Type | Typical Breakage Rate (per 1000 hours) | Common Service Life (hours) | Applicable Scenario Characteristics |
|---|---|---|---|
Forged Steel Balls | <0.3% | 5000-8000 | Materials with medium hardness (e.g., cement clinker), moderate cost. |
High Chrome Cast Steel Balls | <0.5% | 8000-12000 | High-hardness materials (e.g., mineral ores), strong wear resistance. |
| CADI Ball Austempered Bainitic Balls | <0.2% | 6000-10000 | Balances toughness and wear resistance, suitable for complex working conditions (e.g., chemical mixtures). | |
8. Can the alloy composition and performance parameters of the steel balls be customized for specific ore types?
Yes, we can.
We precisely adjust the ball’s alloy composition (such as the content of key elements like Chromium, Manganese, and Molybdenum) and the heat treatment process (such as quenching temperature and tempering time) based on the core characteristics of the customer’s ore (including ore hardness, slurry pH value, and the content of corrosive elements like sulfur/chlorine). We also take the mill’s operating conditions (such as rotational speed, filling rate, and grinding method) into account.
Through this customized solution, we enhance the ball’s wear resistance, corrosion resistance, and impact toughness, ensuring that the balls are highly matched to the ore characteristics and mill operating conditions. This maximizes grinding efficiency and optimizes the total cost of ownership.
9.What are the core differences in steel ball selection between wet grinding and dry grinding conditions? Which type of steel ball is recommended for each?
Wet Grinding
- Core Operating Conditions：1. Slurry/material contains moisture; some scenarios include corrosive elements like sulfur/chlorine (slurry pH may be acidic/alkaline). 2. Balls are subject to the dual effects of impact and corrosion from wet material, requiring resistance to fracture and spalling.
- Core Steel Ball Performance Requirements：High toughness, corrosion resistance, resistance to impact fatigue.
- Recommended Steel Ball Type：Forged Steel Balls / CADI Austempered Bainitic Balls
- Selection Rationale：1. Forged Steel Balls: Excellent toughness (Impact Value ≥12J/cm²), can withstand repeated impact in wet grinding, resistant to fracture, and the dense surface provides better corrosion resistance than standard cast balls. 2. CADI Austempered Bainitic Balls: Combines medium hardness (HRC58-62) with high toughness (Impact Value ≥8J/cm²), demonstrating outstanding anti-corrosion and anti-spalling performance, suitable for complex wet grinding scenarios with corrosive media (e.g., non-ferrous metal ore wet grinding, chemical raw material wet grinding).
Dry Grinding
- Core Operating Conditions：1. No moisture involvement; material is dry with a high friction coefficient; balls mainly endure abrasion wear and light impact. 2. Focus is on minimizing ball wear rate, extending service life, and reducing ball replenishment frequency.
- Core Steel Ball Performance Requirements：High hardness, high wear resistance.
- Recommended Steel Ball Type：High Chrome Cast Steel Balls (Cr content ≥10%)
- Selection Rationale：High Chrome Cast Steel Balls, through proper chrome-carbon ratio design, can achieve a hardness of HRC60-65. The wear-resistant layer is uniform and effectively resists the intense friction and abrasion wear typical of dry grinding. Compared to other types, they offer a longer service life in dry grinding applications (e.g., cement clinker dry grinding, iron ore dry grinding, pulverized coal dry grinding), significantly reducing the cost of steel ball consumption per unit of grinding output.
III. Quality Control & Testing
10. To ensure the purity of the steel ball material, its mechanical properties, and its usage reliability, what professional testing equipment has your company been furnished with?
Our company has established a comprehensive quality inspection system for steel balls, equipped with various types of high-precision professional testing equipment. This equipment covers the inspection of core indicators such as chemical composition, hardness, toughness, wear resistance, and microstructure. The specific equipment and their testing purposes are as follows:
Spectroscopic Analyzer：
Rapidly and accurately determines the steel ball’s alloy composition, testing the content of key elements such as Carbon, Chromium, Manganese, and Molybdenum, ensuring compliance with customization requirements.
Carbon-Sulfur Analyzer：
Specifically measures the precise content of Carbon and Sulfur elements in the steel ball, preventing the imbalance of the Carbon-Sulfur ratio from affecting the match between hardness and toughness.
Rockwell Hardness Tester + Brinell Hardness Tester：
Dual testing of the steel ball’s surface and core hardness. The Rockwell tester focuses on precise readings (suitable for high-hardness steel balls), while the Brinell tester is suitable for low-hardness material testing, ensuring uniform and compliant hardness levels.
Impact Testing Machine：
Simulates mill conditions to test the steel ball’s impact toughness. Uses the Charpy impact test to evaluate the ball’s fracture resistance under impact loading.
Wear Testing Machine：
Simulates dry grinding and wet grinding environments to conduct wear resistance tests and quantify the steel ball’s wear rate, ensuring service life stability in actual use.
Metallographic Microscope：
Observes the steel ball’s microstructure (e.g., Martensite, Carbide distribution), detects internal defects such as segregation and cracks, and verifies the effectiveness of the heat treatment process.
Supplementary Note: All testing equipment strictly follows national standards such as GB/T and ISO for calibration and operation. The inspection data is traceable, ensuring that the material and performance of every batch of steel balls comply with customized customer requirements and industrial usage standards.
11.To ensure product quality and compliance, does your company hold authoritative third-party certifications and relevant inspection reports?
Our company places great emphasis on the authority and compliance of product quality. We have successfully obtained multiple international and domestic authoritative certifications and can provide comprehensive inspection document support based on customer needs. This includes:
Reports: We can provide material and performance testing reports for steel balls issued by internationally renowned third-party institutions such as SGS, BV, and TUV. The testing items cover core indicators like composition analysis, hardness, wear resistance, and toughness, with results recognized globally.
Certification Certificates: We have obtained the ISO 9001 Quality Management System Certification, ensuring that the entire process—from raw material procurement, production and processing, finished product inspection, to logistics delivery—adheres to standardized quality management requirements.
Factory Inspection Certificates: Every batch of products undergoes a comprehensive internal inspection before leaving the factory. A Factory Inspection Certificate is provided with the shipment, clearly stating key information such as the product batch number, inspection data, and conformance conclusion, ensuring product traceability and verifiability.
Supplementary Note: All certifications and inspection reports are currently valid. Original scanned copies or hard copies can be provided upon customer request. We support customer on-site verification or third-party re-inspection to fully guarantee customer confidence in product quality.
12.What full-process quality inspection items are performed on each batch of steel balls before shipment to ensure stable product quality
To ensure stable product quality, our company has established a “Raw Material – Production – Finished Product” full-chain quality inspection system. Each batch of steel balls must pass the following 5 core inspection items before shipment. Only upon passing all items can the batch be released from the factory. The specific inspection contents and standards are as follows:
1.Chemical Composition Analysis :
A combined test using a Spectroscopic Analyzer and Carbon-Sulfur Analyzer is employed to accurately verify the content of key alloying elements such as Carbon, Chromium, Manganese, and Molybdenum. This ensures compliance with customized composition requirements, with the deviation controlled within ±0.05% (Referencing GB/T 17445-2019 standard).
2.Hardness Testing:
Rockwell Hardness Testers check the surface hardness (High Chrome Steel Balls≥HRC60, Forged Steel Balls≥HRC55 , CADI Balls HRC58-62). Brinell Hardness Testers verify the uniformity of the core hardness. The hardness difference within the same batch must be ≤3HRC to prevent excessively low hardness or segregation.
3.Impact Value Testing:
A Charpy impact test is conducted using the impact testing machine to determine the steel ball’s impact resistance (Forged Steel Balls≥12J/cm²，CADI Balls≥8J/cm²，High Chrome Steel Balls≥5J/cm²). This ensures resistance to fracture and spalling under mill impact conditions.
4.Size and Appearance Inspection:
① Size: High-precision calipers / micrometers are used for random inspection of the steel ball diameter (tolerance ≤±0.5mm, ) and sphericity (≤0.3mm), ensuring compatibility with mill filling requirements. ② Appearance: Manual and visual inspection is performed to ensure freedom from defects like cracks, pores, inclusions, or burrs, and to confirm surface finish meets standards.
5.Sampling Wear Test
Sampling is performed by batch (3–5 pieces per 100 tons). A wear testing machine simulates actual grinding conditions (dry/wet grinding) to test the steel ball’s wear rate. This ensures the wear quantity complies with industry standards (≤0.2g/h) and verifies the stability of the service life.
IV. Supply, Packaging & Delivery
13.What is your company's Minimum Order Quantity (MOQ) requirement for steel balls? Do you support small-batch trial orders?
To balance production efficiency with our customers’ actual needs, we have established a flexible Minimum Order Quantity (MOQ) policy:
Standard Batch Orders: The MOQ for each specification (e.g., diameter, precision) or material (High Chrome Cast Steel Balls, Forged Steel Balls, CADI Austempered Bainitic Balls) is 10 tons. This is tailored to the large-scale grinding requirements of industries such as mining, cement, and metallurgy. Customers benefit from volume purchase discounts and standardized logistics services.
Small Trial Orders: For new customers testing product suitability, small-capacity operations, or special scenario verification needs, we support trial orders starting from a minimum of 1 ton (limited to a single specification / single material). Trial orders enjoy the same quality standards and inspection services as regular orders, and a complete quality inspection report will be provided with the shipment.
14. What is the Steel Ball Delivery Lead Time?
- Standard specification steel balls are usually available in stock (having completed ex-factory inspection and ready for immediate shipment).
- For large volume or multi-specification combination orders, the production lead time is 30–35 days, with the final delivery period subject to slight fluctuations.
- For customized specifications, the production cycle needs to be calculated. The specific delivery time can be confirmed with your account manager, and we will prioritize ensuring delivery efficiency.
15. Does your company provide free steel ball samples for testing?
Yes, we provide free steel ball samples to new customers to help them directly verify product quality.
Clients can use the samples for a dual verification process:Visual Inspection: To confirm the steel ball’s roundness, surface finish, and the absence of defects like cracks or pores.Professional Testing: To conduct core indicator tests on the sample, such as chemical composition analysis, hardness testing, and wear resistance evaluation, to fully verify whether the product meets their specific grinding condition requirements.
16. What is the packaging?
We can provide diverse packaging solutions that comply with industrial transportation standards, balancing safety, convenience, and customization requirements. Details are as follows:
1.Steel Drum
- Core Specification Parameters : Standard capacity 850-900kg per drum (adjustable upon request), made of thickened cold-rolled steel plate
- Key Advantages:Extremely strong sealing, providing outstanding moisture-proof, anti-corrosion, and anti-extrusion capabilities.
- Applicable Scenarios: Scenarios requiring high protection and long-term storage, such as overseas shipping or warehousing in humid environments.
2.Ton Bag Packaging
- Core Specification Parameters:Single bag load capacity of 1000 kg, made of thickened wear-resistant PP material + moisture-proof inner lining.
- Key Advantages:Cost-effective and highly efficient for loading/unloading; sealed and moisture-proof, preventing steel ball rust and wear during transport.
- Applicable Scenarios:Large-scale bulk procurement in industries like mining, cement, and metallurgy, or for long-distance land/sea transportation.
3.Customized Brand Identification Packaging
Core Specification Parameters:Supports printing brand LOGO, product specifications, batch numbers, etc., on the surface of the steel drums / ton bags.
Key Advantages:Enhances brand recognition; facilitates customer warehousing management and product traceability; value-added services like anti-corrosion coatings and reinforced strapping can be customized.
Applicable Scenarios:Scenarios with brand visibility requirements or special transportation environments (high humidity / severe turbulence).
V. Technical Support & After-Sales
17.Does your company offer on-site or remote technical support related to steel ball usage?
Yes, we provide full-cycle technical support.Our senior engineers can offer remote guidance via video, phone, and other means on issues such as steel ball selection review, charge optimization, and wear analysis.Upon client request, they can also conduct on-site services, including field inspections, gradation adjustments, and operational training, to quickly resolve practical usage pain points.
18.What is your after-sales service process if abnormal issues occur during steel ball usage (e.g., excessively fast wear, fracture rate exceeding standards)? How quickly can you respond and resolve them?
We have established an after-sales service system characterized by “Rapid Response + Closed-Loop Resolution”.
Response Time: We will respond within 1 hour of receiving feedback (during working days) and provide a preliminary solution within 4 hours.
On-Site Support: If the issue cannot be resolved remotely, we will arrange for an engineer to conduct an on-site inspection within 24–48 hours (excluding remote areas).
Resolution: For abnormalities caused by quality issues, upon verification, we offer services such as free replenishment, returns/exchanges, or customized upgrade services.
Furthermore, we provide a 1-year warranty period for all our products and offer lifetime tracking of the steel ball usage status.
19.Is your company willing to conduct joint testing or co-development collaborations with clients?
Yes, we are highly committed to engaging in joint testing and co-development collaborations with our clients.Leveraging our years of accumulated industry expertise, we have established long-term cooperative relationships with several globally renowned mining and cement groups. Together, we undertake projects such as long-term performance testing of steel balls, optimization for specific operating conditions, and innovation of new alloy materials.If you have a need for joint testing or customized development, we can assemble a dedicated technical team to coordinate with you and fully participate in the solution design, test implementation, and result translation.