As a core basic component of mechanical equipment, the quality of forgings directly determines the service life and operational stability of the equipment. How to prevent quality defects in forgings is the key to ensuring their quality, improving performance, reducing costs and increasing benefits.
In recent years, the Process Materials Research Institute of China National Tractor Corporation Limited has conducted in-depth research on the causes and formation patterns of quality defects in forgings. The solutions and methods it has proposed are of great significance for improving the quality of forgings in production practice.
The impact of raw material defects on the quality of forgings runs through the entire life cycle of design, production and use. By controlling the smelting process at the source, strengthening the detection methods during the process, and adapting the process to the types of defects, the negative impact of defects on the performance of forgings can be significantly reduced.
For instance, the presence of banded structure makes the steel's structure uneven and affects its performance, forming anisotropy, reducing the mechanical properties and hardenability of the steel, lowering its strength and toughness, and after quenching, it is prone to form mixed grain structure and non-martensitic structure, increasing the tendency of quenching deformation of parts, intensifying the severity of gear deformation, affecting the precision of the tooth profile after heat treatment, and increasing the ellipticity of the inner hole after heat treatment and other defects.
The forging production process has a significant impact on the quality of forgings. If the heating temperature is inappropriate, excessively high temperatures can lead to coarse grains, overheating and overburning, thereby reducing the strength and toughness of the forgings. If the temperature is too low, the plasticity will be poor, the deformation resistance will be large, and cracks are prone to occur. The distribution of flow lines during forging also affects the degree of post-heat deformation of the product. Irregular flow line distribution is prone to aggravate the amount of post-heat deformation, the irregularity of deformation and quenching defects.
For instance, for rotary products, the flow lines should be distributed as centrally and symmetrically as possible. The direction of the rear flow lines should be as consistent as possible with the main stress direction of the product, and the shear stress direction should be perpendicular to the fiber direction. For forgings like gear blanks, the bar stock should be upset to make its fibers radiate, which is beneficial for the force on the gears.
From the raw materials entering the factory to the forgings leaving the factory, the inspection process runs through the entire process. Mechanical property tests, such as tensile and impact tests, can determine the strength, toughness and other indicators of forgings, and judge whether they can withstand the specified load. Metallographic examination can observe the microstructure of forgings and detect problems such as abnormal grain size and non-metallic inclusi
If the physical and chemical inspection is not strict and substandard forgings are put into use, it is easy to cause equipment failure or even safety accidents. Strict and standardized physical and chemical inspections can provide reliable basis for the quality of forgings, ensuring their safety and stability in use.
The improvement of forging quality is the result of the coordinated optimization of raw materials, processes, and physical and chemical inspections. Henan First Tractor has demonstrated through practice that by precisely controlling chemical composition, optimizing forging processes, strictly controlling heat treatment parameters, and relying on advanced equipment and detection technologies, the internal quality and service performance of forgings can be significantly enhanced.