In the deep mining of mineral resources and construction projects under various complex geological conditions, rock drilling tools are core tools, and the stability and durability of their performance are directly related to the efficiency and safety of the project. However, in practical applications, the 23CrNi3Mo steel shank adapter often experiences collapse at the end. It impacts the rock drilling tool’s service life and raises construction costs and safety risks. This paper aims to investigate the causes of this collapse and propose optimization strategies. The findings will serve as a valuable reference for professionals in relevant industries.
Overview
Rock drilling tools are composed of various components, including drill bits, drill rods, coupling sleeves, and shank adapters. The shank adapter, in particular, plays a crucial role as it is responsible for withstanding high-frequency impact loads. As a high-quality carburized steel, 23CrNi3Mo steel is widely used in the manufacture of rock drilling tools due to its high strength, wear resistance, and toughness. However, even based on such high-quality materials, the collapse of the end of the shank adapter is still difficult to avoid.
Analysis of causes of collapse
Fatigue strength reaches its limit
During the rock drilling, the shank adapter is exposed to thousands of impact loads per minute. This constant alternating stress causes the material to gradually approach its fatigue limit, leading to failure. The caving phenomenon becomes more severe in long-term rock drilling service life, as the accumulated damage over time causes the material properties to deteriorate gradually.
Problems with the transition zone between the carburized layer and the matrix
The transition layer between the carburized layer and the matrix is
Differences in material organization and properties
There may be differences in the microstructure, grain size, and hardness distribution of 23CrNi3Mo steel from different batches or heat treatment processes. These differences will directly affect the fatigue resistance of the material. For example, the finer the austenite grains, the better the strength and toughness of the material, the stronger the fatigue resistance, and the longer the rock drilling service life; conversely, coarse grains will easily lead to premature failure of the material.
Effect of retained austenite
While the retained austenite in the carburized layer can enhance the material’s strength and toughness, an excessive content can diminish wear resistance and elevate the risk of collapse. In addition, the presence of retained austenite will also affect the hardness distribution and stability of the carburized layer.
Optimization scheme
Optimize the heat treatment process
By adjusting the parameters of the heat treatment process, such as carburizing, quenching, and tempering, we can refine the austenite grains, improve the hardness and toughness of the carburized layer, and reduce the content of residual austenite. Additionally, we can use surface strengthening techniques such as shot peening and nitriding to enhance surface hardness and fatigue resistance.
Increasing material grain size
Refining austenite grains is an effective way to improve the fatigue resistance of 23CrNi3Mo steel. With the use of advanced controlled rolling and cooling processes, we can ensure the strength of the material at the same time, refine the grain, and improve the toughness and fatigue resistance of the material. Additionally, considering the addition of micro alloying elements can further refine the grain structure.
Improve material ratio
Adjust the chemical composition of 23CrNi3Mo steel and appropriately increase the content of alloying elements such as carbon and manganese to improve the hardness and wear resistance of the material. At the same time, maintain a reasonable chemical composition ratio to avoid excessive residual austenite content.
Optimize structural design
Optimize the structural design of the shank adapter, reduce the stress concentration area, and enhance the strength of the transition layer. For example, a gradual transition design can be used to make the hardness change between the carburized layer and the matrix smoother, thereby reducing the risk of collapse.
Strengthen quality inspection
In production, we should enhance the quality inspection of raw materials and finished products. Through advanced equipment such as optical microscopes and scanning electron microscopes, the microstructure, grain size, and hardness distribution of the materials are accurately analyzed to ensure that the product quality meets the standard requirements. At the same time, establish a perfect quality traceability system to trace and deal with problematic batches in time.
Improve the design and reasonable use
In addition to the problems of the material itself, design and use are also important factors affecting the collapse of the shank adapter. In the design stage, technicians should fully consider the stress situation and working environment of the shank adapter and reasonably design the structure size and shape. In the use stage, the operation should be carried out strictly by the operating procedures to avoid overload and improper operation. Use advanced testing equipment to detect and analyze the microstructure and hardness distribution of the shank adapter to provide data support for the optimization plan.
Conclusion
The collapse of the end of the 23CrNi3Mo steel shank adapter is a complex problem involving materials, processes, design, and use. By analyzing the causes of the collapse and taking effective optimization measures, we can effectively improve drilling service life and safety of drill bits and reduce construction costs. In the future, with the continuous advancement of material science and manufacturing technology, we have reason to believe that the performance of 23CrNi3Mo steel drill bits will be further improved, providing more reliable support for various types of mining and excavation operations.
