Chain Rail Link Production Process

As the core load-bearing component of the construction machinery track system, the chain rail link integrates technologies in many fields such as materials science, precision machining, and automation control. Relying on decades of accumulation of broaching technology,

Ubright Solutions has built a full-process process system covering blank preparation, precision machining, heat treatment strengthening, intelligent detection, and automated logistics. This article will deeply analyze the technical details of each link and focus on explaining the significant advantages of this process flow in precision control, production efficiency, flexibility adaptation, quality assurance, etc.

Chain Rail Link Production Process

1.Double-sided milling (datum surface processing)

• Purpose of process: Milling of datum surfaces such as the upper and lower planes of the chain rail joints, bolt hole surfaces, etc., to establish the machining coordinate system.
• Equipments: 135-280 pitch double-sided milling machine (1 set for each left/right section).
• Key parameters:
  • Processing rhythm: 50 seconds / pair (190 pitch), dry milling accuracy ≤ 0.05mm fluctuation;
  • Positioning method: positioning by bushing hole, pin hole and end face, hydraulic clamping;
  • Tool configuration: carbide face milling cutter, speed 1500-2000r/min, feed 0.2mm/z.

• Positioning clamping:
  • Main positioning: three-point positioning with blank sleeve hole, pin hole and end face (one side, two pins positioning principle);
  • Clamping method: the hydraulic pressure plate is pressed from the upper main positioning surface, the lower auxiliary support adopts adjustable rigid support nails, and the clamping force is controlled at 5-8kN to avoid deformation of the workpiece.

2. Hardening and Tempering (Heat Treatment Strengthening)

• Purpose of the process: To improve surface hardness and wear resistance by induction heating, and to eliminate internal stress by tempering.
• Heating system:Hengjin induction pass-through quenching furnace (power 200-250kW) + mesh belt tempering furnace.
  • Power supply: HKTP200kW/4-15kHz medium frequency power supply, adopting full digital phase-locked loop technology, frequency tracking accuracy ±1%;
  • Inductor: customized according to the size of the chain track section, made of purple copper tubing (wall thickness 2-3mm), hard chrome plating on the surface (thickness 0.05-0.1mm), cooling water through the interior (pressure 0.3-0.5MPa).
• Process parameters:
  • Quenching temperature: 850-900℃, depth of hardened layer 2-3mm;
  • Tempering temperature: 200-250°C, holding time 10-15 minutes;
  • Beat: 40 seconds/pair (190 pitch), supports synchronized treatment of left and right sections.

3.Rough and fine boring (key size processing)

Roughing and finishing boring all-in-one machine adopts six spindles rigid tapping + boring composite technology, realizing “one clamping, multiple holes forming”

• Process Purpose: Processing of key assembly holes such as shaft holes, bushing holes, bolt holes, etc., to ensure the matching accuracy.
• Spindle system:
  • Equipped with 6 precision spindles (diameter Φ60-Φ80mm), the front bearing adopts the combination of NN30 series double-row cylindrical roller bearings + 2344 series thrust angular contact bearings, with radial runout ≤ 0.005mm and axial runout ≤ 0.003mm;
  • Spindle motor power 11-15kW, speed range 500-3000r/min, support stepless speed change.
    
• Tool configuration:
  • Rough boring tool: carbide welded boring tool, insert angle γo=10°, αo=6°, main offset angle κr=75°, boring allowance 2-3mm;
  • Fine Boring Tools: Micro-adjustable boring tools (accuracy ±0.002mm), insert material PCBN (suitable for hardened steel) or coated carbide (suitable for cast iron), boring allowance 0.2-0.5mm;
  • Drill: high speed steel twist drill (diameter Φ10-Φ30mm), top angle 2φ=118°, helix angle β=30°, feed 0.1-0.3mm/r.
    
• Cutting parameters:
  • Rough boring: cutting speed Vc=40-60m/min, feed f=0.2-0.4mm/r, back draft ap=1-2mm;
  • Fine boring: Vc=60-80m/min (steel parts)/30-50m/min (cast iron), f=0.08-0.2mm/r, ap=0.2-0.5mm;
  • Drilling: Vc=20-30m/min, f=0.15-0.3mm/r, pecking drilling method for deep hole processing (back-off frequency 5-8 times/hole).
• Technology highlights:
  • Six spindles synchronous machining, efficiency is 2-3 times of machining center;
  • Machining accuracy: shaft hole tolerance 0~+0.05mm (H7 grade), center distance ±0.1mm;
  • Automatic tool change: preset tool life (e.g. boring tool 2000 pieces / times), expiration alarm prompts.

4.Broaching / Pushing surface (tooth surface and positioning surface processing)

The special broaching machine for chain rail joints adopts vertical broaching + hydraulic drive for machining complex surfaces such as tooth surface and nut surface

• Purpose of the process: Processing of complex surfaces such as tooth surface and nut surface of chain rail joints to ensure transmission accuracy.
• Broach design:
  • Material: high-speed steel (W18Cr4V) or cemented carbide (YT15), broach overall length 1500-2500mm, edge hardness HRC62-65;
  • Parameters of tooth shape: front angle γo=10°-15°, back angle αo=3°-5°, tooth rise 0.05-0.15mm/tooth, number of calibrated teeth 3-5.
• Broaching process:
  • Pulling force: According to the calculation of material and allowance, the pulling force of steel parts is about 150-200kN (190 pitch), the pressure of hydraulic system is 16-20MPa;
  • Speed: working stroke 1-10m/min (adjustable), return stroke 15-20m/min, shorten the non-processing time;
  • Cooling: the concentration of 10-15% of the extreme pressure emulsion, through the built-in cooling system from the center hole of the broach spray, flow ≥ 20L/min.
• Key indicators:
  • Broaching beat: 40-56 seconds / pair, surface roughness Ra <12.5μm;
  • Positioning method: positioning by the shaft hole after boring, hydraulic compression to prevent deformation.Broaching / Pushing surface (tooth surface and positioning surface processing)

5. Burr grinding and chamfering

• Purpose of process: Remove burrs from holes and edges to avoid assembly scratches and stress concentration.
• Equipment: FANUC robot + automatic chamfering unit, using imported grinding head (such as Germany Jinshibo).
• Automation: The robot grabs the workpiece to the chamfering table, and controls the trajectory of the grinding head through the servo module, with a beat of 30-40 seconds per piece.

6. Sensor technology for in-line inspection

In-line inspection equipment with integrated laser displacement sensors + contact probes for simultaneous multi-parameter measurements:

• Bore detection:
  • A total of 4 sets of laser displacement sensors T1-T4, distributed at 90°, are used to calculate the bore diameter by triangulation (accuracy ±0.005mm);
  • The moving speed of the probe is 5-10mm/s, the sampling frequency is 1000Hz, and the profile curve of the hole diameter is drawn in real time.
• Form and position tolerance detection:
  • Flatness: through 2D laser scanning, calculate the maximum deviation of the measured surface from the ideal plane (resolution 0.001mm);
  • Parallelism: take the bottom surface as the reference, measure the height difference of each point of the top surface, tolerance band ≤ 0.2mm.
• Data processing:
  • Using SPC statistical software, real-time calculation of Cp, Cpk value (required ≥ 1.33), when 5 consecutive pieces of data over ±1σ, automatically triggered equipment adjustment prompt.

7. Magnetic Particle Flaw Detection (Defect Detection)

• Process Purpose: Detect surface and near-surface cracks, slag entrapment and other defects to ensure product safety.
• Equipment: KODAK CJW-3000 Fluorescent Magnetic Particle Flaw Detection Machine, double-station design.
• Process: Manual/robot loading → magnetizing spray → UV lamp observation → demagnetization and discharging, beat 22 seconds/pair, defect recognition accuracy 0.02mm.

Summary Of Comprehensive Process Advantages

Technical Bottlenecks And Solutions

1.Material performance limitations

• Specific performance
  • Currently, the commonly used steel materials for chain track joints, such as 50, 50mn, 40mn2, 40mnb, etc., are susceptible to chain track breakage under the harsh working conditions faced by high-power construction machinery. It is difficult for these materials to combine high strength, high wear resistance and high impact toughness, which cannot meet the increasing engineering needs.
• Solutions
  • New alloy research and development: In-depth study of the impact of alloying elements on the performance of steel mechanism, in the smelting process targeted to add a specific proportion of alloying elements. For example, add mn, co to improve hardenability and strength; add nb, y, sc, b to purify and refine grain size and improve toughness; use al, ti to optimize strength and toughness; use w, v to increase strength, toughness and inhibit grain size, so as to enhance the overall performance of the material.
  • Customized steel supply: Establishing in-depth cooperation with steel suppliers to customize steel according to the special performance requirements of chain rail joints. We control the composition, organization and other key indexes from the source of steel making to ensure the stable quality of materials and meet the production requirements.

2. Large Pitch Chain Track Sections Heat Treatment Challenges

• Specific performance
  • Because of the large pitch, volume and thickness of the large-pitch chain rail joints, conventional heat treatment is easy to cause grain coarseness, which seriously affects the product performance. Moreover, different parts of the hardness and toughness requirements are different, a single heat treatment process is difficult to meet the complex needs.
• Solution
  • Special process design: solid solution treatment under pulsed electric field conditions is adopted to raise the temperature in stages to promote the full dissolution of components and optimize the organizational structure. Subsequently, water quenching and oil cooling, aging treatment, quenching in specific quenching solution, tempering, and finally air cooling under pulsed magnetic field conditions are carried out in order to effectively refine the grain size and improve the properties.
  • Simulation and precise control: Using simulation software to accurately simulate and analyze the temperature field and stress field of the heat treatment process. According to the performance requirements of different parts, the process parameters are precisely adjusted to realize differentiated heat treatment and ensure balanced overall performance.

3.Tool wear and short tool life

• Specific performance
  • When processing high-strength, high-hardness chain rail joint material, tool wear is fast. Especially in the processing of tooth surface, nut surface and other complex surfaces, tool life is extremely short, frequent tool change not only reduces productivity, but also affects the stability of machining accuracy.
    
• Solution
  • Upgrade of tool materials: actively use high-performance tool materials, such as coated carbide tools, through a special coating to enhance wear resistance and corrosion resistance; CBN (cubic boron nitride) tools, using its ultra-high hardness and abrasion resistance, so that the tool life is increased by 3 – 5 times.
    Optimization of process parameters: With the help of cutting simulation software, the cutting process is simulated in all aspects. By analyzing the cutting force, temperature, wear and other factors, we search for the best combination of tool geometry parameters (such as cutting angle, edge shape) and cutting process parameters (such as cutting speed, feed, backdraft) to minimize tool wear.
  • Intelligent monitoring of tool change: Tool wear monitoring sensors are installed to collect tool wear data in real time. Combined with intelligent algorithms to accurately analyze and predict the tool wear state, issue an early warning and automatically perform tool change operations to avoid excessive tool wear resulting in scrap.

4. Low productivity

• Specific performance
  • The traditional chain rail joint production is mainly based on single-machine processing, with poor connection between work processes and many artificial links. The production rhythm is long, such as 190 pitch chain rail joints shift production is only 150 – 200 sets, it is difficult to adapt to the needs of large-scale, high-efficiency production.
• Solution
  • Construction of automated production line: robots are fully introduced to participate in loading and unloading, handling and other operations. According to the characteristics of different processes, truss robots and SCARA robots are used, together with automated fixtures, to greatly improve the precision and efficiency of operation, and realize the rapid flow and seamless connection between processes.
  • Application of composite machining equipment: introduce multi-axis linkage machining centers and composite machining equipment to realize multi-process centralized machining. For example, the use of six-spindle roughing and finishing boring machine can simultaneously process multiple holes, compared with the traditional machining efficiency increased 2 – 3 times, effectively reducing the number of clamping and processing time.
  • Intelligent production management: MES (Manufacturing Execution System) is deployed for intelligent optimization of production scheduling and real-time monitoring of equipment operation status. Dynamically adjust the production plan according to the production schedule, equipment performance and other factors to improve equipment utilization and overall production efficiency.