The Threaded Self-Locking Structure Design of Track Spikes and its Role in Enhancing the Reliability of Track Anchorage
What are the core design parameters of the self-locking thread structure of railway spikes?
The core design parameters of the self-locking thread structure of railway spikes include thread lead angle, thread profile bevel angle and thread helix angle, and these three parameters jointly determine the quality of self-locking performance. The thread lead angle should be controlled between 3° and 5°, which is smaller than the friction angle of the thread pair, so that self-locking can be achieved by friction force to avoid loosening caused by vibration. The thread profile bevel angle is designed to 15°, compared with the 30° bevel angle of ordinary threads, it can increase the contact area between thread teeth and improve the bearing capacity. The thread helix angle must match the lead angle to ensure that after the spike is tightened, the force direction of the thread teeth is perpendicular to the contact surface, reducing the impact of lateral component force on self-locking performance. The design of these parameters needs to be adjusted according to the spike material and ballast bed type, and the lead angle of spikes for heavy-haul lines can be appropriately reduced to 3° to further enhance the self-locking effect.
What are the performance differences between the self-locking thread structure and ordinary thread structure of railway spikes?
The performance differences between the self-locking thread structure and ordinary thread structure of railway spikes are mainly reflected in three aspects: anti-loosening ability, bearing strength and durability. Under the high-frequency vibration of trains, the friction force of the thread pair of self-locking structure spikes will not attenuate with vibration, but will increase due to load extrusion, which can maintain long-term anchoring force; the friction force of ordinary thread spikes is easy to decrease under the influence of vibration, and loosening problems occur frequently. The contact area of the thread teeth of the self-locking structure is 20%-30% larger than that of ordinary threads, with higher bearing strength, which can withstand the impact load of heavy-haul trains; the force of ordinary thread spikes is concentrated on a few thread teeth, which is prone to thread profile fracture. In terms of durability, the thread wear rate of self-locking structure spikes is 40% lower than that of ordinary threads, and the service life can be extended to more than 10 years, while the service life of ordinary thread spikes is only 5-6 years, which needs to be replaced frequently.
What are the adaptation requirements of self-locking thread structures of railway spikes for different ballast bed types?
The adaptation requirements of self-locking thread structures of railway spikes for different ballast bed types are significantly different, and the core is to match the stiffness and stress characteristics of the ballast bed. The integral ballast bed has high stiffness and small deformation, and has high requirements for the pull-out resistance of spikes, so it is necessary to adopt large thread profile self-locking threads with a thread tooth height ≥3mm to increase the occlusal depth with concrete, and the pull-out resistance should be ≥80kN. The crushed stone ballast bed has low stiffness and is easy to deform, so it has higher requirements for the anti-loosening ability of spikes, so it is necessary to adopt double-lead self-locking threads, which can disperse vibration stress through double-lead design to prevent gaps between spikes and sleepers. The spikes of slab ballast bed need to pass through the track slab for anchoring, so it is necessary to adopt fine-pitch self-locking threads. The fine-pitch threads have better sealing performance, which can prevent rainwater from seeping into the anchoring holes and causing concrete corrosion. At the same time, the self-locking performance of fine-pitch threads is more stable, adapting to the high-precision installation requirements of slab ballast bed.
What are the key points of the processing technology for the self-locking thread structure of railway spikes?
The key points of the processing technology for the self-locking thread structure of railway spikes are concentrated in two links: thread rolling and heat treatment, which directly affect the stability of self-locking performance. The thread rolling adopts the cold rolling process, the rolling temperature is controlled at room temperature to avoid thread profile deformation caused by high temperature, and the rolling pressure should be applied evenly to ensure that the precision deviation of the thread profile is ≤0.05mm. The rolled spikes need to be quenched and tempered, the quenching temperature is 850-880℃, and the tempering temperature is 450-500℃, so that the hardness of the thread part reaches HRC35-40, improving wear resistance and impact resistance. After heat treatment, the threads need to be surface phosphated, and the thickness of the phosphating film is controlled at 5-8μm to enhance the friction force of the thread pair and further strengthen the self-locking effect. After processing, the go-no-go gauge inspection should be carried out to ensure that the go gauge of the thread passes and the no-go gauge does not pass. At the same time, the anti-loosening test should be carried out to verify that the anchoring force loss rate after vibration is ≤5%.
What are the on-site installation precautions for the self-locking thread structure of railway spikes?
The on-site installation of the self-locking thread structure of railway spikes needs to focus on three aspects: anchoring hole cleaning, tightening torque control and installation verticality. Before installation, it is necessary to clean the dust and debris in the anchoring hole, which can be purged with a high-pressure air gun to ensure that the hole is clean and avoid debris affecting the occlusion between the spike and concrete. The tightening torque should be adjusted according to the ballast bed type, the tightening torque of spikes for integral ballast bed is 300-350N·m, and that for crushed stone ballast bed is 250-300N·m. Excessive torque is easy to cause thread profile damage, and insufficient torque cannot achieve effective self-locking. The installation verticality deviation of the spike should be ≤1°, which can be calibrated with a level ruler. Excessive verticality deviation will lead to uneven stress on the spike, reducing the pull-out resistance and anti-loosening ability. After installation, the pull-out test should be carried out, the sampling ratio is 3 pieces per thousand pieces, and the pull-out resistance should reach more than 100% of the design value to ensure anchoring reliability.