Application of NdFeB Permanent Magnet Materials in Drilling
Through the introduction of the functional characteristics and working principles of high - performance neodymium - iron - boron (NdFeB) permanent magnet materials, the feasibility and suitability of using them to make high - strength magnetic fishing tools for drilling are analyzed. The structure, specifications, usage methods, and precautions of the developed high - strength magnetic fishing tools are also explained. The high - strength magnetic fishing tool is an ideal tool for dealing with incidents where iron objects such as tooling fixtures fall into the borehole during drilling operations in various industries. It is more time - saving and safer than traditional accident - handling methods, and can greatly improve work efficiency. Therefore, the high - strength magnetic fishing tool has broad application prospects in drilling construction.
Permanent Magnet Materials
Since the 1980s, functional materials have played an increasingly important role in the modern civilization and social progress of human society. Among functional materials, permanent magnet materials occupy an important position. The per - capita consumption of permanent magnet materials in a country has become one of the measures of the country's affluence level.
Currently, the commonly used permanent magnet materials mainly include ferrite, alnico, and rare - earth permanent magnets. Rare - earth permanent magnets include SmCo, Sm₂Co, and neodymium - iron - boron (NdFeB). NdFeB has a record - high remanence (Br), high coercivity (Hcj), and magnetic energy product (BH), so it is called the "king of magnets". The iron - based permanent magnet materials represented by NdFeB are a new generation of permanent magnet materials with the highest magnetic properties (energy density), the widest application, and the fastest development speed.
China is the world's largest country in terms of rare - earth resources, and the product quality of NdFeB permanent magnet materials is at the world - leading level. The NdFeB series of permanent magnet materials are developing towards high performance and high stability, which provides reliable technical support for the popularization and application of permanent magnet materials.
Functional Characteristics of Permanent Magnet Materials
When a permanent magnet material is magnetized in an external magnetic field, the work done by the external magnetic field on the permanent magnet material is called the magnetization work. For a closed - circuit permanent magnet, the magnetization work is stored in the permanent magnet material in the form of magnetic energy (BH). For an open - circuit permanent magnet, part of the magnetization work is stored inside the rare - earth permanent magnet, and the other part is stored in the space near the two magnetic poles in the form of a magnetic field. The magnetic field energy stored by a permanent magnet in the air gap is proportional to the magnetic energy product of the permanent magnet. A permanent magnet is an energy storage device. By using the interaction of the magnetic poles of the permanent magnet and the magnetic field in the air gap, the mutual conversion between mechanical energy and electromagnetic energy can be realized, and a variety of functional devices can be made.
The application of permanent magnet materials mainly utilizes the magnetic field Hg in the air gap, and the magnitude of Hg is proportional to the square root of the maximum magnetic energy product (BH)max of the permanent magnet material. NdFeB has a record - high remanence (Br), high coercivity (Hcj), and magnetic energy product (BH)max. Therefore, the emergence of NdFeB has created conditions for the miniaturization, applicability, and reliability of many functional devices. At the same time, due to the high Curie temperature Tc and good temperature stability (- 0.3%/°C) of NdFeB, it can be used at a certain ambient temperature.
NdFeB High-Strength Magnetic Fishing Tool
Structural Design of the Fishing Tool
During the drilling process, especially in large - diameter hydrogeological drilling, it is often necessary to deal with incidents where iron objects (or steel shots) fall into the borehole. If traditional methods such as fishing with a casing, layer - by - layer stripping with an iron - sweeping bit, or grinding with a roller bit are used, it not only takes a long time and is costly but also may induce drilling accidents in extreme cases. If an NdFeB high - strength magnetic fishing tool is used, the above - mentioned disadvantages can be avoided, and work efficiency can be greatly improved.
Since the fishing tool will be affected by harsh conditions such as high temperature, friction, and extrusion in water, to fully exert its function, be durable, and have the maximum lifting weight, its design fully considers the above - mentioned factors. First, products with a grade of NdFeB320/160 or higher are selected as materials, and they are subjected to temperature - resistant aging treatment. Second, the magnets are reasonably distributed and inlaid on the working surface. Through optimized structural design, the maximum theoretical lifting weight can reach 1:500, that is, 1 kg of magnet can lift 500 kg of heavy objects.
After continuous experiments and optimized structural design, our institute has finally developed two standardized products: the flat - body type (see schematic diagram 1 - 1) and the inclined - body type (see schematic diagram 1 - 2), with patent numbers ZL98249303.7 and ZL200620024646.4 respectively. The specifications, dimensions, and performance are shown in Table 1.
The main functions and characteristics of this series of high - strength magnetic fishing tools are as follows: First, the "king of magnets" NdFeB is used, and the magnetic circuit is scientifically designed and specially treated, so the magnetic field is strong and the suction force is large, which greatly enhances the fishing ability of the fishing tool. After testing, the maximum suction force of the φ89 fishing tool is 100 kgf, and that of the φ194 fishing tool is 400 - 500 kgf. Second, the suction force is concentrated without external leakage. Through the scientific design of the magnetic circuit, there is no magnetic field diffusion on the non - working surface of the fishing tool, and the magnetic field is all concentrated on the bottom surface of the fishing tool, that is, the working surface. Third, this series of fishing tools can be directly connected to the drilling tool, and there is a water - way design, which can ensure that water can be sent at any time to flush the bottom of the borehole during the fishing process.
| Model | Outer diameter/mm | Maximum suction force/kgf | Lock - nut specification |
|---|---|---|---|
| QCL - 1 | φ56 | 30 | φ42 |
| QCL - 2 | φ73 | 60 | φ50 |
| QCL - 3 | φ89 | 100 | φ63.5 |
| QCL - 4 | φ108 | 160 | φ63.5 |
| QCL - 5 | φ127 | 210 | φ63.5 - φ89 |
| QCL - 6 | φ146 | 280 | φ63.5 - φ89 |
| QCL - 7 | φ194 | 450 | φ89 |
| QCL - 8 | φ245 | 800 | φ89 |
Combination of the Fishing Tool and the Drilling Tool
In order to meet the needs of different borehole diameters and various down - hole situations in drilling, the fishing tools are available in a wide variety of specifications - multiple borehole diameters and multiple varieties. The specifications range from φ56 to φ425, and there are two varieties: the flat - body type and the inclined - body type. The combination of the fishing tool and the drilling tool is simple and reliable. The non - working surface of the fishing tool is machined with a standard - sized lock - nut joint, which can be directly connected to the drilling tool through a reducer sub, and it is safe, reliable, and easy to assemble and disassemble.
Precautions for Using the Fishing Tool
- Before use, wipe the bottom surface (working surface) clean to ensure full contact with the object to be attracted.
- When not in use, wipe the working surface clean and apply anti - rust material for protection.
- Avoid exposing it to the sun as much as possible, and it is strictly prohibited to bake it at a temperature above 100°C, otherwise, the magnet will be demagnetized and lose its working ability.
- The NdFeB high - strength magnetic material is hard and brittle, so avoid knocking and strong impact during use.
- When handling, keep the working surface more than 0.5 meters away from magnetically - susceptible materials to avoid strong adsorption and accidents.
The NdFeB high - strength magnetic fishing tool is widely used in drilling operations in various industries such as geology, metallurgy, coal, petroleum, and hydrogeology. It can attract various magnetically - susceptible materials at the bottom of the borehole, such as steel shots, iron blocks, iron sheets, and various iron tools that have fallen into the borehole. Field use by our institute and many sister units has proved that the high - strength magnetic fishing tool is one of the indispensable practical tools in drilling construction.
