Processing requirements of cemented carbide tools before and after welding

The processing technology of cemented carbide welding tools can be divided into three parts according to the technological process: cemented carbide, machining before welding, welding and tool processing after welding.

Process optimization of cemented carbide and cutting tool before welding

Before welding, cemented carbide welding tools are processed separately by two parts. In order to meet the requirements of tool welding and machining after tool welding, the structure design of such tools should be considered in the design of welding tools. The top center hole shall be machined at the front end of the cutter tooth part and the rear end of the handle part of the welding tool; the joint part of the welding tool tooth and the cutter bar shall have a good welding structure.

The machining technology of cutter teeth is optimized. The cutter tooth part is made of cemented carbide. The top hole and guide part need to be processed at the left end, and the 90 ° boss and connecting rod need to be processed at the right end. The rough machining of the connecting rod is completed by using the wire feeding in use, and the 90 ° boss is processed at the right end. The fine machining of the connecting rod is completed by using a cutter grinder, and the machining of the top hole is completed by using electric pulse. The Φ 6 guide is processed by external grinding and cutter grinding machine.

The processing technology of the toolholder is optimized. The 90 ° groove at the left end is processed by using middle wire feeding, and the positioning hole is processed by lathe and Tongling.

Welding process optimization of cemented carbide and cutter bar

Through the preliminary project exploration, we have completed the research on the welding process of cemented carbide and structural steel, including the selection of solder, the selection of flux and the brazing process.

Selection of solder. ① The brazing filler metal should have good wettability to cemented carbide and steel matrix to ensure good fluidity and permeability. ② The use of cemented carbide has high red hardness, so it is necessary to ensure that the brazing seam has enough hardness at room temperature. ③ The melting point of solder should be as low as possible to reduce brazing stress and prevent cracks. However, the melting point of solder should be 300 ℃ higher than the working temperature of weld to ensure normal cutting. H62 and hag-45b were selected for the comparative experiment.

Selection of flux. The function of flux is to reduce the oxide on the tool bar and brazing surface, so that the solder can well wet the metal surface to be brazed. Generally, the melting point of flux is lower than 100 ℃ of solder, and has good fluidity and low viscosity. 842 silver flux and 201 copper flux were selected for comparative experiment. In the experiment of flux, proper amount of water should be added, heated and stirred into paste.

Brazing technology of cemented carbide and steel. (1) Preparation before welding. ① Before welding, the cemented carbide should be checked for cracks, bending and other defects to ensure that the brazed surface is flat and has a certain geometric shape, and maintains good contact with the substrate. ② The cemented carbide is sandblasted to remove the oxide layer and black letters on the brazed surface to prevent desoldering. (2) Brazing process. ① When welding cemented carbide tools, it is the basic condition to ensure the welding quality that the cutter bar and cutter head are heated evenly. If the temperature of the cemented carbide is higher than that of the tool bar, the melted solder will wet the cemented carbide but not the tool bar, and the joint strength will decrease. When the cemented carbide is sheared along the weld, the solder will not be damaged, but will be detached with the cemented carbide. On the contrary, if the phenomenon. ② Cooling after brazing. During cooling, the surface of cemented carbide produces instantaneous tensile stress, and the tensile stress is much lower than the compressive stress. Usually, the workpiece is inserted into the lime tank or charcoal powder tank immediately after welding to cool the workpiece slowly. If possible, the workpiece can be put into the furnace at 220 ℃～ 250 ℃ for 6h ～ 8h immediately after brazing. Low temperature tempering treatment can eliminate partial brazing stress, reduce cracks and prolong the service life of cemented carbide tools. ③ Cleaning after welding. The cemented carbide workpieces should be cleaned after welding, so as to clean up the residual solvent around the weld. The common cleaning method is to put the cooling workpiece after welding into boiling water for about 1-2 h, and then sandblasting, so as to remove the residual flux and oxide adhered around the weld.

Tool welding condition report. (1) Development of butt welding reamer 5880. Results of 5880 welding: 6 pieces with runout less than 0.2, 2 pieces with runout greater than 0.2 and less than 0.4, and 4 pieces with run out greater than 0.4; (2) welding condition of cabit butt welding reamer. The welding result of cabit butt welding reamer: because of the new welding structure, the welding qualified rate is 75%.

Optimization of cutting tool processing technology after welding

By studying the processing technology of welded cemented carbide, summarizing the technological characteristics of multiple processing of welding tools, a new processing technology of welding carbide tools is formulated. The machining methods of rough grinding, slotting and semi precision grinding of alloy outer diameter are used to solve the problem of difficult machining of alloy parts in external grinding. The processing methods of semi precision grinding, edge grinding and fine grinding of alloy outer diameter are used to solve the problem of alloy parts In order to solve the problem of dimension machining, the paper summarizes the experience of grinding by grinding the extra long reamer of kabi, and uses the edge grinding to process the back angle of the cutter tooth. Among them, the machining of chamfering and its back corner and grinding process need to be carried out according to the size required in the drawing, which can not rely on the operator's feeling, and need to meet the use requirements.