Effect of temperature control on deformation during roller chain welding

Effect of temperature control on deformation during roller chain welding

Introduction
In modern industry, roller chain is a mechanical component widely used in transmission and conveying systems. Its quality and performance directly affect the operating efficiency and reliability of mechanical equipment. Welding is one of the key links in the manufacturing process of roller chains, and temperature control during welding has a vital impact on the deformation of roller chains. This article will deeply explore the influence mechanism of temperature control on deformation during roller chain welding, common deformation types and their control measures, aiming to provide technical references for roller chain manufacturers, and also provide a basis for quality control for international wholesale buyers.

Temperature control during roller chain welding
The welding process is essentially a process of local heating and cooling. In roller chain welding, arc welding, laser welding and other welding technologies are usually used, and these welding methods will generate high-temperature heat sources. During welding, the temperature of the weld and the surrounding area will rise rapidly and then cool down, while the temperature change of the area away from the weld is small. This uneven temperature distribution will cause uneven thermal expansion and contraction of the material, thereby causing deformation.
Effect of welding temperature on material properties
Excessively high welding temperature may cause the material to overheat, making its grains coarse, thereby reducing the mechanical properties of the material, such as strength and toughness. At the same time, excessively high temperature may also cause oxidation or carbonization of the material surface, affecting the welding quality and subsequent surface treatment. On the contrary, too low welding temperature may lead to insufficient welding, insufficient weld strength, and even defects such as unfusion.

Control method of welding temperature
In order to ensure the welding quality, the welding temperature must be strictly controlled. Common control methods include:
Preheating: Preheating the parts to be welded of the roller chain before welding can reduce the temperature gradient during welding and reduce thermal stress.
Interlayer temperature control: In the process of multi-layer welding, strictly control the temperature of each layer after welding to avoid overheating or overcooling.
Post-heat treatment: After welding is completed, the welding parts are subjected to appropriate heat treatment, such as annealing or normalizing, to eliminate the residual stress generated during welding.

Types and causes of welding deformation
Welding deformation is an inevitable phenomenon in the welding process, especially in relatively complex components such as roller chains. According to the direction and form of deformation, welding deformation can be divided into the following types:
Longitudinal and transverse shrinkage deformation
During the welding process, the weld and its surrounding areas expand when heated and shrink when cooled. Due to the shrinkage in the weld direction and transverse shrinkage, the weldment will produce longitudinal and transverse shrinkage deformation. This deformation is one of the most common types of deformation after welding and is usually difficult to repair, so it needs to be controlled by precise blanking and reserved shrinkage allowance before welding.
Bending deformation
Bending deformation is caused by the longitudinal and transverse shrinkage of the weld. If the distribution of the weld on the component is asymmetrical or the welding sequence is unreasonable, the weldment may bend after cooling.
Angular deformation
Angular deformation is caused by the asymmetric cross-sectional shape of the weld or unreasonable welding layers. For example, in T-joint welding, the shrinkage on one side of the weld may cause the weldment plane to produce transverse shrinkage deformation around the weld in the thickness direction.
Wave deformation
Wave deformation usually occurs in the welding of thin plate structures. When the weldment is unstable under the compressive stress of the welding internal stress, it may appear wavy after welding. This deformation is more common in the welding of thin plate components of roller chains.

The influence mechanism of temperature control on welding deformation
The influence of temperature control in the welding process on welding deformation is mainly reflected in the following aspects:
Thermal expansion and contraction
During welding, the temperature of the weld and the surrounding areas rises, and the material expands. When welding is completed, these areas cool and contract, while the temperature change of the area far away from the weld is small and the contraction is also small. This uneven thermal expansion and contraction will cause the weldment to deform. By controlling the welding temperature, this unevenness can be reduced, thereby reducing the degree of deformation.
Thermal stress
The uneven temperature distribution during welding will produce thermal stress. Thermal stress is one of the main causes of welding deformation. When the welding temperature is too high or the cooling speed is too fast, the thermal stress will increase significantly, resulting in greater deformation.
Residual stress
After welding is completed, a certain amount of stress will remain inside the weldment, which is called residual stress. Residual stress is one of the inherent factors of welding deformation. Through reasonable temperature control, the generation of residual stress can be reduced, thereby reducing welding deformation.

Control measures for welding deformation
In order to reduce welding deformation, in addition to strictly controlling the welding temperature, the following measures can also be taken:
Reasonable design of welding sequence
The welding sequence has a great influence on welding deformation. A reasonable welding sequence can effectively reduce welding deformation. For example, for long welds, the segmented back-welding method or the skip welding method can be used to reduce heat accumulation and deformation during welding.
Rigid fixation method
During the welding process, the rigid fixation method can be used to limit the deformation of the weldment. For example, a clamp or support is used to fix the weldment in place so that it is not easily deformed during welding.
Anti-deformation method
The anti-deformation method is to apply a deformation opposite to the welding deformation to the weldment in advance to offset the deformation generated during welding. This method requires accurate estimation and adjustment according to the law and degree of welding deformation.
Post-welding treatment
After welding, the weldment can be properly post-processed, such as hammering, vibration or heat treatment, to eliminate the residual stress and deformation generated during welding.

Case analysis: roller chain welding temperature control and deformation control
The following is a real case that shows how to improve the welding quality of roller chains through temperature control and deformation control measures.
Background
A roller chain manufacturing company produces a batch of roller chains for conveying systems, requiring high welding quality and small welding deformation. In the early production, due to improper control of welding temperature, some roller chains were bent and deformed at an angle, which affected the quality and service life of the product.

Solution
Temperature control optimization:
Before welding, the roller chain to be welded is preheated, and the preheating temperature is determined to be 150℃ according to the thermal expansion coefficient of the material and the welding process requirements.
During the welding process, the welding current and welding speed are strictly controlled to ensure that the welding temperature is within the appropriate range.
After welding, the welding part is post-heat treated, and the annealing process is adopted. The temperature is controlled at 650℃, and the insulation time is determined to be 1 hour according to the thickness of the roller chain.
Deformation control measures:
The segmented back-welding method is used for welding, and the length of each welding section is controlled within 100mm to reduce heat accumulation during welding.
During the welding process, the roller chain is fixed in place with a clamp to prevent welding deformation.
After welding, the welding part is hammered to eliminate the residual stress generated during welding.

Result
Through the above measures, the welding quality of the roller chain has been significantly improved. Welding deformation has been effectively controlled, and the incidence of bending deformation and angular deformation has been reduced by more than 80%. At the same time, the strength and toughness of the welding parts have been guaranteed, and the service life of the product has been extended by 30%.
Conclusion
The influence of temperature control on deformation during roller chain welding is multifaceted. By reasonably controlling the welding temperature, welding deformation can be effectively reduced and welding quality can be improved. At the same time, combined with reasonable welding sequence, rigid fixation method, anti-deformation method and post-welding treatment measures, the welding effect of roller chain can be further optimized.