12B Roller Chain Manufacturing Process

12B Roller Chain Manufacturing Process: Unveiling the Precision Production Logic of Core Industrial Transmission Components

In the global industrial transmission and material handling sector, 12B roller chains, with their wide power range, stable load capacity, and easy installation and maintenance, have become a transmission essential for mining machinery, agricultural equipment, and assembly line conveyor systems. The long-term reliability of 12B roller chains under high-load, high-frequency operation hinges on a rigorous and sophisticated manufacturing process. From raw material selection to finished product delivery, meticulous control at every stage of the process is crucial to determining the chain’s lifespan, transmission efficiency, and risk resilience. Today, we’ll delve into the complete manufacturing process of 12B roller chains, explaining the technical details behind this “high-quality chain.”

1. Process Basics: Standard Positioning and Material Selection Logic for 12B Roller Chain

Before delving into the process details, it’s important to first clarify the “process benchmark” for the 12B roller chain. As a transmission chain compliant with ANSI B29.1 (American chain standard) and ISO 606 (international chain standard), its core dimensions, such as pitch (19.05mm), roller diameter (11.91mm), and inner segment width (12.57mm), are standardized and fixed. The core goal of the process is to achieve maximum performance through materials and processing technology while meeting these standards.

1. Process Compatibility Selection of Core Materials

Different components of the 12B roller chain require differentiated materials and pretreatment processes due to their varying load scenarios:

Pins and rollers: As core components in the chain transmission that withstand impact and friction, SUJ2 high-carbon chromium bearing steel (equivalent to domestic GCr15 steel) is selected. The material must first undergo a “spheroidizing annealing” pretreatment—heating the steel to 780-820°C for 4-6 hours, then slowly cooling it to below 500°C. This process reduces the material’s hardness (Brinell hardness ≤ 207 HB), improves machinability, and lays a foundation for a uniform microstructure during subsequent heat treatment, preventing cracking during quenching.

Chain plates and bushings: Chain plates are required to withstand tensile loads, so ST52-3 low-carbon alloy structural steel (tensile strength ≥ 520 MPa) is used. A “quenching and tempering” process (quenching followed by high-temperature tempering) brings the hardness to HB220-250, ensuring both tensile strength and a certain degree of toughness to prevent fracture. Bushings are made of 20CrMnTi carburized steel, with a subsequent carburizing process to increase the surface hardness to withstand sliding friction with the pins.

II. Core Manufacturing Process: Precision Transformation from “Raw Materials” to “Chain Links”

The manufacturing of 12B roller chains involves eight core processes, each requiring strict control of process parameters to ensure precision and performance:

1. Raw Material Pretreatment: Clearing the Way for Processing

Rust and Oil Removal: Upon entering the workshop, all steel is first passed through an alkaline degreasing bath (50-60°C, soaking for 15-20 minutes) to remove surface oil. It is then pickled with hydrochloric acid (15%-20% concentration, soaking at room temperature for 8-12 minutes) to remove scale. Finally, it is rinsed with clean water and dried to prevent impurities from affecting subsequent processing accuracy.

Precision Cutting: Depending on the component size, CNC sawing or laser cutting is used for cutting. Pin cutting length tolerances must be controlled within ±0.1mm, while chain plate cutting must maintain an aspect ratio deviation of ≤0.05% to prevent deformation during subsequent stamping.

2. Precision Machining of Key Components: Millimeter-Level Precision

Chain plate stamping and punching: Chain plate stamping and punching are performed on a CNC punch press using a “continuous progressive die.” The chain plate outline is first punched out, followed by the pin holes at both ends. Hole position tolerances must be controlled to H7 (tolerance range 0-0.018mm), with a hole center distance error of ≤0.05mm to ensure subsequent precision fit with the pins. Deburring (using a grinding wheel or vibratory grinding) is required after stamping to prevent sharp edges from injuring operators or interfering with assembly. Roller Cold Forging: SUJ2 steel is formed in one step using a multi-station cold forging machine. The wire is first forged, then extruded into the roller shape, and finally punched (for insertion into the sleeve). During the cold forging process, the die temperature (≤200°C) and pressure (300-400 MPa) must be controlled to ensure the roller’s roundness error is ≤0.03mm to prevent eccentric wear during operation.
Pin Finishing: The pin is first rough-ground using a centerless grinder (with an outer diameter tolerance of ±0.05mm), then fine-ground to its final dimensions (tolerance H8, 0-0.022mm) using a cylindrical grinder. A surface roughness of Ra ≤0.8μm is maintained. This smooth surface reduces sliding friction with the sleeve, extending its service life.

3. Heat Treatment: Imparting “Tough-Core Performance” to Components
Chain Plate Tempering: After stamping, the chain plates are placed in a continuous quenching furnace, held at 850-880°C for 30 minutes, then oil-quenched. They are then placed in a tempering furnace at 550-600°C for 2 hours. The final hardness reaches HB220-250, and the tensile strength is increased to ≥800 MPa, ensuring they can withstand the rated tensile load of 12B chain (≥18.8 kN). Pin and Roller Quenching + Low-Tempering: SUJ2 pins and rollers are heated to 830-850°C (holding temperature for 25 minutes) in a mesh-belt quenching furnace, oil-quenched, and then low-temperature tempered at 160-180°C for 2 hours, achieving a surface hardness of HRC 58-62 and a core hardness of HRC 30-35. This “hard exterior, tough interior” structure resists wear and cushions impact, preventing breakage. Sleeve Carburizing and Quenching: A 20CrMnTi sleeve is placed in a carburizing furnace and heated at 920-940°C for 4-6 hours with methanol and propane (carburizing agents) to achieve a surface carbon content of 0.8%-1.2%. The sleeve is then quenched (850°C oil-cooled) and low-temperature tempered (180°C). The resulting surface hardness is HRC 58-62, and the carburized layer depth is 0.8-1.2mm, effectively extending the friction life of the sleeve against the pin.

4. Modular Assembly: Ensuring Overall Chain Coordination

Inner and Outer Link Assembly: The inner link consists of a sleeve, roller, and inner link plate. First, press the sleeve into the pin hole of the inner link plate (interference fit, press-fit force 5-8kN). Then, slide the roller over the sleeve (clearance fit, clearance 0.02-0.05mm). The outer link consists of a pin and outer link plate. The pin is pressed into the outer link plate hole (interference fit). After press-fitting, check for perpendicularity (deviation ≤ 0.5°) to prevent binding during operation.​
Full Chain Assembly and Pre-Stretching: The inner and outer links are pinned together to form a complete chain. This is followed by a “pre-stretching treatment”—a tensile force of 80% of the rated load (approximately 15kN) is applied on a dedicated tensile testing machine for 30 minutes. This eliminates the chain’s initial elongation and allows the components to fit more tightly together. This allows for subsequent elongation to be controlled within 0.5% (compared to the industry average of 1%-1.5%).

III. Quality Control Process: Full-Process Inspection to Eliminate Substandard Products

12B roller chains for export undergo multi-dimensional testing to ensure compliance with international standards. Core testing steps include:

1. Dimensional Accuracy Inspection

A three-dimensional coordinate measuring machine (CMM) is used to inspect key dimensions such as the chainplate hole center distance, pin shaft outer diameter, and roller diameter. A random sampling of 20 pieces per batch is conducted, with a 100% pass rate.

A pitch gauge is used to inspect the chain pitch. The pitch deviation per meter must be ≤0.3mm to ensure accurate meshing with the sprocket.

2. Mechanical Properties Testing
Tensile Strength Test: The chain is subjected to tension on a tensile testing machine until it breaks. The breaking load must be ≥ 28.2kN (significantly exceeding the rated load of 18.8kN) to ensure safety in the event of overload.
Fatigue Life Test: The chain is mounted on a “chain fatigue testing machine” and subjected to 50% of the rated load (approximately 9.4kN) at a speed of 1500r/min. The fatigue life must be ≥ 500 hours (the industry standard is 300 hours), simulating reliability under long-term high-load conditions.

3. Surface Quality Inspection

Use a surface roughness tester to inspect the pin and roller surfaces; the Ra value must be ≤0.8μm.

Inspect the surface treatment (e.g., galvanizing, blackening): the galvanizing layer thickness must be ≥8μm and must show no rust after a 48-hour salt spray test (neutral salt spray, 5% NaCl solution). The blackening treatment must be uniform and spot-free, and adhesion must meet the GB/T 10125 standard.

IV. Craftsmanship Value: Why does high-quality craftsmanship enhance the market competitiveness of 12B roller chains?

The 12B roller chain’s technological advantages translate directly into value:

Longer lifespan: Utilizing SUJ2 material and precision heat treatment, the chain boasts an average service life of 8,000-10,000 hours, over 40% longer than conventional chains (5,000-6,000 hours), reducing replacement costs and downtime.

More stable transmission: Millimeter-level dimensional accuracy and pre-stretching ensure chain runout of ≤0.1mm during operation, maintaining a transmission efficiency above 98%, making it suitable for high-speed applications such as textile machinery and automated assembly lines.

Widely adaptable: Optional surface treatments (galvanizing, blackening, and phosphating) and customized heat treatment solutions (such as low-temperature tempering for low-temperature environments) meet diverse operating requirements. For example, galvanized chains can be used in food processing plants for rust prevention, while phosphated chains can be used in mining equipment for dust and wear resistance.

Conclusion: Craftsmanship is the “Hidden Competitive Advantage” of 12B Roller Chains

In the global 12B roller chain market, “low price” is no longer a core advantage. Instead, “process precision” and “performance stability” are key to earning the trust of overseas customers. From stringent standards in raw material selection, to millimeter-level control in the manufacturing process, to comprehensive pre-shipment inspections, every process carries a commitment to product reliability.