How to Select Materials for Deep Hole and Large Diameter DTH Drill Bits

Table of Contents

Rock drilling tools are one of the main tools for human beings to conquer rocks and are applied widely in geology, metallurgy, coal, building materials, petroleum, and other fields. With the upgrading of rock drilling equipment and the rapid development of modernization, more types and models of rock drilling tools have been developed, such as DTH drill bits for large-diameter drilling.

The diameter of large-diameter drill bits is generally greater than 300mm, more than 500, 800, and 1000mm, and some even reach 1500~3000mm. The depth of large-diameter drilling varies depending on the application, the rock formations encountered also vary greatly, and the requirements are very demanding in most cases. Therefore, preventing the early failure of deep-hole and large-diameter DTH drill bits and ensuring the service life of the drill bit are the primary quality goals, and its material selection and heat treatment process are especially important.

Material performance requirements for deep hole and large diameter DTH drill bits

DTH drill bit

The harsh working environment puts forward very high requirements on the hardness, strength, toughness, impact resistance, wear resistance, and fatigue resistance of the DTH drill bit. Considering the performance requirements of various parts, the selection of the DTH drill bit material should meet the following aspects.

1. Higher surface hardness is required to enhance wear resistance, better toughness in the heart to enhance impact resistance, and good fracture toughness, fatigue strength, and fracture strength to avoid brittle fracture and fatigue fracture.

2. High hardenability. To meet the different requirements of the performance of each part of the drill bit, it is conducive to increasing the indicated yield strength and improving the cementing force of the buttonhole to the carbides, it can also improve the yield strength and toughness of the heart.

3. It has some corrosion resistance when encountering corrosive gas and liquid.

4. Under some high temperatures, the material has high stability of organization and hardness, not easy to soften and deform, etc.

5. Good process performance, such as having good forging performance, heat treatment performance.

6. High metallurgical quality, good structure uniformity, and high purity.

Composition of steel for rock drilling tools

DTH drilling tools

The most important alloying elements of steel for rock drilling tools include Cr, Ni, and Mo, of which chromium can increase the hardenability of steel and has a secondary hardening effect, which can improve the hardness and wear resistance of carbon steel without making the steel brittle, chromium can improve the strength and hardness of carbon steel rolling state, reduce elongation and section shrinkage; nickel can improve the strength of steel at the same time, the damage to the toughness, plasticity and other process properties of steel is smaller than other Molybdenum in steel can improve the hardenability and thermal strength, prevent tempering brittleness, increase corrosion resistance; and silicon can improve the oxidation resistance of steel at high temperatures, and greatly improve the tempering stability of steel; manganese can improve the wear resistance and hardenability of steel, and its combination with silicon can enhance the elastic limit of steel.

Of course, in addition to considering the choice of materials, the design and structure of deep hole large diameter DTH drill bits also need to be optimized according to the specific drilling requirements to improve drilling efficiency and quality. It should also be noted that the fabrication and processing of the DTH drill bit are demanding and requires the use of advanced processing technology and equipment to ensure the quality and reliable performance of the drill bit.

To sum up, a deep hole large diameter DTH drill bit is a drill bit used for drilling larger diameter. For its material selection, it needs to be considered comprehensively in various aspects such as hardness, rigidity, wear resistance, and chemical stability to meet the drilling requirements under different geological conditions. It also needs to optimize the design and structure and adopt advanced processing technology and equipment to ensure the quality and reliable performance of the drill bit to improve the drilling efficiency and quality.

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