In oil extraction, the roller cone bit is the mainly used tool for drilling. With the development of mining technology, DTH drill bits for oil have begun to become tools for oil extraction because of their high drilling speed. The material of the drill bit is a critical factor as it directly affects its performance, service life, and durability. So how should we choose the materials of the DTH drill bit for oil in combination with its service conditions?

Service conditions of DTH drill bits for oil

When the DTH drill bit for oil is in use, the piston of the DTH hammer impacts the end face of the DTH drill bit in a high-frequency manner under the action of compressed air, and at the same time, the clamping sleeve of the DTH hammer drives the spline part of DTH drill bit to rotate. Because DTH drill bits used for oil often have to drill two or three hundred meters or even more, it has worse operating conditions than ordinary DTH drill bits.

DTH drill bits for oil are mainly bearing impact loads, torsional loads, and definite bending loads during use. Therefore, it is very critical in the selection of materials.

Factors in the selection of DTH drill bit materials for oil

1. Cutting performance of the drill bit

The material should have high hardness and strength so that the drill bit can effectively cut the rock when drilling into the formation.

2. Wear resistance

The drill bit is subject to severe wear and tear during long working hours, so it is vital to choose materials with good wear resistance.

3. Corrosion resistance

The oil drilling environment usually contains acidic or alkaline substances, so the drill bit material should have good corrosion resistance.

4. Heat stability

Drill bits may be under very high thermal loads in high-temperature environments, so it is important to select materials that remain stable under high temperatures.

5. Cost-effectiveness

In addition to material performance, cost-effectiveness is also an important consideration. When selecting materials, it is necessary to comprehensively consider performance requirements and economic feasibility to ensure that the drill bit is cost-effective.

Application of 20Ni4Mo steel in DTH drill bits for oil

20Ni4Mo steel is low-carbon alloy steel. Due to the low carbon content of this steel, after quenching, lath martensite with low brittleness and high enough plastic toughness + residual austenite film at the plate phase boundary + self-tempering precipitated carbide. After tempering at low temperatures, plasticity, and toughness are significantly higher. The addition of Ni element increases the hardenability of the steel. After carburizing and quenching, it can improve the toughness of the carburized layer and the core and reduce the toughness-brittle transition temperature. The addition of the Mo element reduces the hardenability of steel. Therefore, after carburizing and quenching + low-temperature tempering, the core of the steel has good comprehensive mechanical properties, high fatigue strength, low notch sensitivity, good impact toughness, high surface hardness after carburizing and quenching, and good resistance impact performance. Therefore, 20Ni4Mo steel can be suitable for the steel body of DTH drill bits for oil.

To sum up, choosing drill bit materials should be evaluated and selected according to the specific drilling environment and working conditions to meet the actual needs. In addition, the drill bit usually consists of several parts, which may use different materials to achieve the best overall performance.