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Mining forum's drilling tools series: cold pressing process of bit teeth
02 Apr 2022
For a long time engaged in the rock drill steel, drilling tools, drilling tools said that export drilling head, the bottom of the carbide carbide used by the drill bit inserted into the alloy steel body part, It is longer than the drill bit used in domestic mining wells.
Major foreign mining projects like alloy grinding to prolong the life of rock drilling and save the cost of rock drilling. If the drill bit purchased at the same price is drilled one meter more, it will create one meter of value for customers.
Foreign trade companies develop many overseas customers every day, but also in the face of many domestic production enterprises, how to choose the right products for accurate mine owners, is the basic skills of every foreign trade personnel. A professional drill business personnel can not only have a set of universal sales skills articulate.
I also know the knowledge of drill tools, production process, processing technology, material alloy, machining, heat treatment, etc., to form a systematic and modular professional SOP, to provide strong theoretical, practical and scene technical support for pre-sale, in-sale and after-sale, so as to increase the chances of winning in marketing and sales.
Today we are going to talk about the topic of bit failure: Button Bit carbide fixing process , which is often encountered by our business personnel.
The main failure modes of drill bits are: cemented carbide teeth wear, fracture and fall off, which is not only related to the bad service conditions in the process of drilling, but also has a great relationship with the technology of fixing drill teeth.
At present, there are three methods for fixing spherical bit teeth in China: cold pressing, brazing and hot insert. No matter what kind of fixation technology is adopted, it is necessary to ensure that the bit does not lose teeth in the process of use, which is the key problem of spherical button bit, so it is very important to study the fixation technology of bit.
At present, the fixed tooth technology of DTH bit is mainly used: cold pressing fixed tooth, Cold pressed fixed teeth belong to press fit fixed teeth, and its peripheral tooth force is composed of cemented carbide teeth、Interference between fixed holes，It is provided by the elastic-plastic deformation caused by the steel body of the tooth hole wall.
The process flow of cold pressing fixed tooth: fixed tooth hole drilling machine processing a bit body heat treatment a fixed tooth hole reaming a measuring aperture a hard alloy grinding tooth pressing tooth.
The following points should be paid attention to during the whole cold pressing process:
(1) the drilling and reaming of fixed tooth holes should improve the machining accuracy and the surface finish of hole wall as far as possible, so as to improve the fixing force of alloy teeth. According to the hardness of different materials, is divided into the first drilling, heat treatment rereaming and first heat treatment after drilling, reaming 2 processing methods.
(2) Aperture measurement using buoy type air momentum meter to measure the hole, the accuracy of 0.001mm(micron) level, and do the corresponding data record statistics, and each hole annotation. Data recording statistics is to prepare for subsequent carbide grinding, marking each hole is to prepare for pressing teeth.
(3) Grinding teeth according to the data of measurement hole statistics, plus the determined interference amount, in the hydraulic grinding machine, from large to small step by step grinding teeth, the accuracy of 0.001mm(micron) level. After grinding cemented carbide teeth, the alloy teeth need to be cleaned with diesel.
(4) When pressing teeth, we must try to ensure that the center line of pressing head, hard alloy teeth and tooth hole coincide.
On the basis of paying attention to the above points, the selection of interference size is the key to cold pressing teeth. If the interference is too small, the tightening force provided is small, and the hard alloy teeth are easy to fall off in the process of drilling. Too much interference, it is difficult to fix teeth, and easy to cause cemented carbide teeth broken, or drill body hole wall cracking.