Proceso de producción de cadenas de oruga

The track walking chain (commonly known as chain tracks) is the “core of the walking system” for tracked engineering machinery such as asphalt pavers and road milling machines, bearing the entire weight of the machine and significant impact forces during operation. Its production process integrates key technologies including precision forging, CNC machining, heat treatment strengthening, and automated assembly. Below is a detailed breakdown of the production process based on modern manufacturing techniques:

Step 1: Raw Material Preparation and Cutting

The manufacturing of rail links begins with rigorous selection of raw materials. Manufacturers usually choose high-strength alloy steel as raw materials, such as 35MnBM and CrNiMo series steel, which have excellent hardenability and impact toughness, and can meet the wear and fatigue resistance requirements of tracks under harsh working conditions.

• Smelting and rolling: Smelting is carried out by electric furnace or converter, and then subjected to LF refining and VD vacuum degassing treatment to remove harmful gases and non-metallic inclusions in the steel, ensuring the purity of the internal structure of the steel.
• Cutting: Cut the hot-rolled round or square steel into sections according to the calculated volume, and use them as billets for individual chain rail segments. Modern production lines often use automatic shearing machines to ensure cutting accuracy and weight consistency.

Step 2: Heating and Precision Forging

Forging is a key process that determines the internal structure and external contour of the chain rail joint. In order to obtain dense metal flow lines, hot forging presses are commonly used for automated forging.

• Heating: The billet is quickly heated to 1100-1250 ℃ by an intermediate frequency induction heating furnace, equipped with a temperature control sorting system to automatically remove billets with unqualified temperature, ensuring accurate forging temperature.
• Blanking and Forming: The heated billet undergoes flattening, pre forging, and final forging processes in sequence. A large press (such as a 3150 ton hot forging press) applies tremendous pressure to cause the metal to flow and form in the mold cavity, forming the basic contour of the chain rail joint.
• Precision cutting (edge cutting and punching): The formed forging has burrs and continuous skin. Use composite molds for edge cutting and punching, and remove excess waste materials. The advanced technology adopts a dual station composite mold of general cutting and precision cutting, which can control the displacement within 0.3mm and significantly improve production efficiency.

Step 3: Heat treatment process

Heat treatment is the core link that determines the wear resistance and service life of track chains. In order to achieve the properties of external hardness and internal toughness, modern processes usually use methods such as waste heat quenching or overall tempering+local strengthening.

• Whole quenching and tempering: Heat the forging and quench it (water quenching or oil quenching) to obtain martensitic structure, followed by high-temperature tempering to achieve an overall hardness of HRC 25-40 and ensure core toughness.
• Localized hardening: The support surface of the chain rail joint (in contact with the supporting wheel) is the most severely worn area. After overall heat treatment, the area needs to be subjected to medium frequency or high-frequency induction quenching to form a hardened layer with a depth of 5-15mm and a hardness of HRC 45-55, greatly improving wear resistance.
• Stress relief: For high stress areas such as pin holes and liner holes, local tempering treatment is required to control the hardness below HRC 40 to prevent “blocking failure” (fracturing) due to hardness.

Step 4: Precision machining

The chain rail joint after heat treatment will undergo slight deformation and requires precision machining to ensure assembly accuracy.

• Flat machining: milling the support surface of the chain rail joint and the installation surface of the track plate to ensure that the flatness meets the requirements.
• Hole processing: Processing pin holes and liner holes. The coaxiality requirement for these two holes is extremely high, usually controlled within 0.05mm, to ensure the rotational flexibility and service life of the pin shaft and bushing after being pressed in.
• Drilling: Drilling bolt holes for fixing track plates and machining nut fitting surfaces.

Step 5: Manufacturing of Pin Shaft and Lining

The articulated part of the track chain is composed of a pin shaft and a bushing, which also require extremely high hardness and wear resistance.

• Manufacturing: The shafts and bushings are usually made of medium carbon alloy steel or carburizing steel.
• Heat treatment: They are usually treated with surface carburizing or overall hardening, with extremely high surface hardness (up to HRC 58-62), and the core maintains toughness to resist bending and impact.
• Surface treatment: For Sealed and Lubricated Track (SALT), special treatment is applied to the surface of the pin shaft and liner, and lubricating grease is filled to extend the wear life.

Step 6: Assembly and Pre tightening

Combine the processed chain rail joints, pin shafts, and bushings together.

• Press fit: Use a dedicated press fit machine to press the liner into the liner hole of the chain rail joint, and press the pin shaft into the pin hole of another chain rail joint. Usually, interference fit is used to ensure that the connection is firm and not loose.
• Sealing: In sealed lubrication tracks, a two-stage sealing system (such as butterfly seals) needs to be installed at the connection to prevent mud and grease from entering and leaking, which is crucial for equipment operating in muddy and gravel environments.

Step 7: Painting and Final Inspection

• Painting: The assembled track chain needs to undergo rust removal and cleaning before entering the dipping line. To prevent corrosion, overall immersion painting or spraying treatment is usually carried out. Modern factories adopt environmentally friendly exhaust gas collection and catalytic combustion systems to ensure clean production。
• Final inspection:
  • Dimensional inspection: Check the pitch, straightness, and lateral clearance of the chain.
  • Hardness and testing: Perform magnetic particle testing on key stress areas to check for surface cracks.
  • Performance testing: Conduct static load testing (with a bearing capacity of not less than 85kN) and fatigue testing (with a minimum of 5 million cycles).

A high-quality track walking chain requires full process control from material modification, precision forging, differential heat treatment to high-precision assembly. The current industry is developing towards automation and intelligence, with a large number of industrial robots and 3D vision technology being used to improve production efficiency while ensuring product consistency and reliability