Analysis of Boring Rolling Process for Cylinder Processing

The cylinder tube is used as the main component of the cylinder, the single column for the mine, the hydraulic support, the gun tube and other products. The quality of the processing directly affects the life and reliability of the entire product. The cylinder tube requires high processing, and the inner surface roughness is required to be Ra 0.4-0.8 μm, and the coaxiality and wear resistance are strictly required. The basic feature of the cylinder barrel is deep-hole machining, and its machining has always plagued the processing personnel. The use of rolling processing, due to surface residual compressive stress left on the surface, contribute to the closure of surface micro-cracks and hinder the expansion of erosion. In order to improve the corrosion resistance of the surface and delay the generation or expansion of fatigue cracks, the fatigue strength of the cylinder is improved. Through roll forming, the rolling surface forms a layer of cold hardened layer, which reduces the elastic and plastic deformation of the contact surface of the grinding pair, thereby improving the wear resistance of the inner wall of the cylinder barrel and avoiding the burn caused by grinding. After rolling, the decrease of the surface roughness value can improve the blending properties. 1 Design of Rolling Tools The Ø160mm combination boring hob designed by us is used as an example to illustrate the tool design and process. As shown in the structure diagram, the protective cap 1 is used to protect the reference position of the spindle head tool setting tool. The role of the support pad 4 and the support pin 6 is to protect the retainer (ZQSn6-6-3) from the axial pressure of the roller. The support sleeve 11 is made of GCr15 and is required to have an interference fit with the mandrel 15 and is assembled and ground. The roller material is GCr15 or high speed steel W18Cr4V, 62~65HRC. Roller rolls and guides in the hob. The reason for using roller rolling is that it has a larger working contact area than the ball rolling and can withstand large rolling pressures. Larger feed rates can be used to increase productivity. For thin-walled and low-rigidity workpieces, a roller with a smaller diameter and a longer length should be selected. When the roller diameter is small, a small surface roughness value can be obtained. Here, we choose a Ø13 mm roller. Roller fillet radius r affects the surface roughness within a certain range, reduces the fillet radius, increases the unit stress accordingly, and can reduce the surface roughness value and improve the surface cold hardness. An increase in the number of rollers z reduces the roughness value of the rolling, but the required rolling pressure increases. Generally take 5 to 10, we take 6. Increasing the roller rolling angle a can reduce the surface roughness value, but a too large and easy to form an over-cold state, damage the surface layer, generally take a ≤ 1 °. Roller diameter in different directions will cause stuck, vibration, and strain on the machining surface, so the difference in diameter is not more than 0.03mm.

skills requirement:
(1) After the assembly, rotate the rear gear ring, the holder frame and the roller surface to slide freely
(2) When retracting, ensure that the cutting edge is upward to avoid pulling

1. Protective cap 2. Set screw 3. Cage 4. Bearing pad 5. Roller 6. Bearing pin 7 Bearing 8. Rear gear ring 9. Front gear ring 10. Small set 11. Bearing sleeve 12. Bolt 13. Body 14. Machine Cutter Block 15. Mandrel

Combination hob cutter structure diagram

Rolling is completed, when the knife is retracted, the rear gear ring 8 is hooked to make the front and rear gear rings into an engaged state. A half circle is inserted between the cage 3 and the mandrel 15 (the length is the basic length of the roller Therefore, the cage is driven to move back along the taper of the support sleeve 1:40, and is withdrawn into the support sleeve groove to disengage the roller from the cylinder tube and achieve retraction. The rollers, support sleeves, and cages of the hob cutter are wearing parts. Each pair of consumables can be rolled by approximately 150 cylinders of Ø90m×2150m (calculated by stroke). 2 Influencing factors of rolling analysis The workpiece material rolling is suitable for carbon steel below 50. The lower the carbon content is, the smaller the hole expansion is. The lower the material hardness, the higher the plasticity, the better the rolling surface quality. Although the hardness after rolling can reach 400HB, but starting from 280HB, the effect after rolling significantly reduced, therefore, the hardness of the workpiece material before rolling is generally not less than 140HB. Pre-machining generally uses turning or boring. The accuracy of the workpiece geometry is guaranteed by pre-machining. It generally requires pre-machining Ra 0.25 ~ 5μm, boring rolling mill margin of about 0.5mm. Rolling times The first time in the rolling process, the plastic deformation is most significant and full, and the surface quality is significantly improved. As the number of rolling times increases, the surface will generate excessive compressive stress, which will destroy the surface obtained by the first rolling. Quality, that is, destruction of rolling chilled layer, resulting in peeling phenomenon, so the combination of the number of rolling hob rolling election once. The larger the feed amount f for cutting, the larger the surface roughness value; the rolling speed v has little to do with the surface quality. Rolling head interference generally takes about 0.15mm (ordinary Ø60 ~ 200mm aperture cylinder), rolling amount 0.02 ~ 0.04m. Taking Ø160mm hole machining as an example, we take v=30-40m/min, f=0.1-0.25mm/r. Cooling and cleaning we use HT-40 mechanical oil: kerosene (GB258-64) = 1:1, can also be used vulcanized oil: diesel = 1:1 formula. During processing, the pressure oil rushes from the rear of the rolling head to the hob hob, and is discharged from the bed side to the oil trough on the unprocessed surface, so that the detached chips do not scratch the processed surface. In the design of the fuel tank, the main problem is cleaning, precipitation and not cooling, because the cutting oil is circulated once every 20 minutes, it is too late to precipitate, and increasing capacity is not the method. Filtration problems are mainly ensured by the selection of suitable filter equipment and process. The field proved that the pores of the filter were too large and the pores of the felt were too small to clog. Cylinder roll processing common problems and solutions: size over tolerance: the tool is not allowed, the tool or rolling head wear; internal surface vibration ripple: the material is too hard, speed is too high; obvious knife pattern: large feed rate, The cutting depth is too large; the groove is pulled: the blade is broken, the amount of cutting fluid is small, and the cutting fluid temperature is too high. 3 Application Examples The boring and rolling process is an efficient and high-quality process measure. The 镗160mm health roller head (45 seamless steel pipe) is used as an example to demonstrate the effect of rolling. After rolling, the surface roughness of the hole is reduced from Ra3.2 to 6.3 μm before rolling to Ra0.4 to 0.8 μm, the surface hardness of the hole is increased by about 30%, and the fatigue strength of the inner surface of the cylinder is increased by 25%. If the service life of the cylinder only considers the effect of the cylinder, it is increased by 2 to 3 times. The boring and rolling technology is about 3 times more efficient than the grinding process. The above data shows that the boring rolling process is efficient and can greatly improve the surface quality of the cylinder barrel.

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