In mechanical manufacturing, deep hole machining is recognized as a machining problem due to its semi-closed or close-closed working conditions. The main difficulties are as follows: First, deep hole machining tools and shank The radial dimension is limited by the aperture and the depth must meet the technical requirements of the hole depth. Therefore, in general, the deep hole machining tool has poor rigidity and low strength, and is easy to generate vibration during cutting, and the guide is easy to deflect, thereby causing the inner wall of the hole to have low processing quality and the axis of the hole being skewed. Second, the deep hole processing, especially in the solid drilling process, the chip is more, the chip removal is not easy, the chip jam is easy to cause the chipping of the tool, and the cutting fluid is not easy to fully cool the blade, resulting in a decrease in tool life, and the spiral often appears on the inner wall of the hole. Troubles such as grooves. Third, during the deep hole machining process, the operator cannot directly observe the chip condition of the tool, so it is difficult to make a corresponding judgment and take necessary measures for the machining quality and tool wear during the cutting process.

In heavy machinery processing such as power station equipment and petrochemicals, there are often some important components, such as high-pressure heater tube sheets in thermal power units, steam generator tube sheets for nuclear power units, nuclear power units, and condenser tubes for super-supercritical unit steam turbine units. Board and so on. On these parts, there are often thousands of high-precision deep holes with small diameters that need to be machined (hole depth ratio can be 1:40~1:50). If the machining is not done properly, sometimes the quality of one hole will cause machining problems. The scrapping of the entire part will not only cause millions of tens of millions of economic losses, but also affect the production cycle of the entire product, affecting the completion of production tasks. In order to achieve efficient, high quality and low cost deep hole processing, the main measures currently taken are:

(1) Purchase and use high-precision multi-axis CNC machine tools.

(2) Select hard alloy deep hole drill (flat drill or inner chip deep hole drill, which should be selected according to the processing conditions, but generally use BTA deep hole drill mostly).

(3) In order to ensure the quality of deep hole processing, a guide sleeve with good sealing and high precision is selected.

1. Selection of guide sleeve structure

In order to obtain the effect of high-efficiency cutting, the conventional deep hole machining process uses the external chipping flat drill or the inner chip removing deep hole drilling to drill the hole. The blade material is made of cemented carbide, and the cutting fluid pressure during deep hole machining can reach 4.5. MPa, the cutting fluid flow rate is about 50 ~ 70L / min, in order to prevent the gap between the guide sleeve end face and the workpiece contact surface when the cutting fluid is cut, the leakage prevention measures are usually sealed by a sealing ring. However, the seal ring has a short service life and frequent replacement of the seal ring will greatly reduce the efficiency of the drilling process. In order to solve this processing problem, the successful development of the new guide sleeve has better solved the shortcomings and shortcomings of the deep hole machining using the seal ring seal. Because the new type of hard alloy (alloy steel) guide sleeve is the most important structural change, that is, the guide sleeve (on the end surface contacting the workpiece) is designed and manufactured with an annular V-shaped protruding surface, and the guide sleeve of this type structure is removed. It is outside the guiding action of the tool; at the same time, it can also play the role of drilling and centering and preventing the cutting fluid from leaking. The typical structure is shown in the attached drawings.

Guide sleeve structure diagram

The guiding sleeve of the type is composed of a positioning sleeve and a drill sleeve. At the same time, it can also be manufactured as a single-piece integral guiding sleeve, and its structural features are:

(1) The positioning sleeve is made of quenched medium carbon chrome steel. The drill sleeve is generally determined according to the number of deep holes to be processed. Usually, the number of machining is often hard alloy, and the alloy is small (alloy tool steel). The fit between the outer circumference of the drill sleeve and the inner bore of the positioning sleeve should be an interference fit (must ensure that the drill sleeve and the positioning ring do not move relative to each other during drilling).

(2) The end face of the drill sleeve (guide sleeve) (which is in contact with the end face of the workpiece to be machined) has a 90° annular boss, which acts as a seal for the end face of the drill sleeve and the end face of the workpiece without any gap (actually It is a replacement seal ring). The 90° boss cannot be a sharp edge. Considering the poor strength of the cemented carbide drill sleeve, the sharp edge can make the centering accuracy contradictory. The 90° cutting edge generally needs a ring facet of about 0.1mm width.

(3) In order to ensure the design and manufacturing precision of the hole, the end face of the drill sleeve, the end face of the guide sleeve and the inner hole of the drill sleeve, the verticality of the reference plane of the positioning sleeve, the coaxiality of the inner and outer circles of each drill sleeve and the positioning sleeve, and the inner hole of the drill sleeve And the surface roughness of the outer circle reference plane of the positioning sleeve has strict technical requirements, and the specific values ​​thereof can be seen as the standard of the guide sleeve position tolerance and the surface roughness value in the figure.

Due to the outstanding advantages of the new structural guide sleeve, it has been widely used in deep hole drilling in foreign countries. In China, the structure has also been used in Shanghai Power Station Auxiliary Machinery Factory, Harbin Electric Group (Qinhuangdao) Heavy Equipment Co., Ltd., Harbin Turbine plant and other units are used for processing deep-hole parts such as nuclear power and nuclear islands.

2. Development of localization of guide sleeves

The guide sleeve is an important part of the whole deep hole processing system. Most of the units of the new guide sleeves are currently supplied by foreign tool companies. However, the price is expensive, especially for some non-standard guide sets. Due to the small number of orders, foreign companies are not willing to provide them. At the same time, domestic enterprises in the current production situation have reduced cost and efficiency as an important measure to develop production. Therefore, the localization of the new guide sleeves is mentioned on the agenda, but it is not easy to overcome this problem. The new guide sleeve has high design and manufacturing precision, and has high risk of manufacturing and use. At present, Mudanjiang Tools Co., Ltd. has cooperated with Harbin Electric Group (Qinhuangdao) Heavy Equipment Co., Ltd. to develop the localization of new guide sleeves to meet the needs of domestic users. The main contents of the development are as follows:

(1) Selection of structure: There are two types of guide sleeves developed, one is the structure of carbide drill sleeve and alloy steel positioning set, and the other is the whole alloy steel guide sleeve (both forms have Standard length and extended specifications). The self-developed guide sleeve structure is a typical new type of carbide guide sleeve structure recommended in the drawing.

(2) Guide sleeve material and heat treatment: The main requirements of the guide sleeve material are high wear resistance and deformation during use without causing deformation due to materials and heat treatment, thus affecting the machining accuracy and shape tolerance. The self-developed guide sleeve (positioning sleeve) is made of alloy steel. After several aging treatments, the internal stress is removed to prevent future deformation. The drill sleeves with the guide sleeves are made of ISO Class K hard alloys with high hardness and wear resistance. The hardness of the overall alloy steel guide sleeves is 62HRC.

(3) Guarantee of manufacturing quality of guide sleeve: The processing difficulties of guide sleeve manufacturing mainly include the following three aspects: one is the guarantee of the vertical hole of the drill sleeve and the vertical plane of each reference plane; the other is the coaxiality of the inner hole and the outer circle of the guide sleeve. Guaranteed; the third is that the surface roughness values ​​of the inner and outer circle and the positioning end face are required to reach a value of 0.4 μm.

The main measures taken in the process are to use the tooling once in the finishing process and then repeat the processing. Finally, employ skilled technicians to carry out manual grinding to meet the technical requirements of the drawings. It is worth noting that sophisticated inspection tools are also essential in manufacturing.

3. Conclusion

The development of the guide sleeve has overcome many difficulties through the cooperation and cooperation of the user and the manufacturer for more than half a year. After the test, the improvement rate of the guide sleeve has been improved from the original 30% to the current 70%. Mudanjiang Cemented Carbide Tools Co., Ltd. has provided various types of guide sleeves to Harbin Electric Group (Qinhuangdao) Heavy Equipment Co., Ltd., and has been stably used in production. The domestically produced guide sleeves have basically reached the foreign guide sleeves. The same level.

R421a , replacement for R22