Precision steel tube parts machining process innovation research

Precision Steel Tube PartsProcessingInnovative research

With the rapid development of high-end equipment manufacturing, aerospace, new energy vehicles and other industries, the dimensional accuracy of precision steel tube parts, surface quality, mechanical properties and production efficiency put forward higher requirements, the traditional precision steel tube processing technology, such as cold drawing, general turning, grinding, etc., has been difficult to meet the complex structure, ultra-thin-walled, ultra-precision and other special parts processing needs, and there are low material utilisation, processing In view of this, the precision steel tube parts processing technology innovation research, with the help of technological breakthroughs to optimise the processing process, improve processing quality, reduce production costs, to promote the upgrading of the industry has become a key path. This article, combined with the current trend of development of processing technology, from a variety of dimensions, analysis of precision steel tube parts processing technology innovation direction, as well as technical principles, and application effects.

I. Material pretreatment process innovation: building a solid foundation for precision machining

Precision steel tube parts processing quality can be guaranteed, material pretreatment is indispensable, at the forefront of the key link, the traditional pretreatment process, such as single pickling, annealing, with insufficient surface quality control, poor organisational uniformity and other conditions. Over the years, the innovation of pretreatment process are all focused on “precise temperature control, green and efficient, organisation optimisation” which are the three most core aspects, so as to provide excellent quality blanks for the subsequent processing.

In the surface purification treatment of this aspect of performance, innovative use of “pickling, then phosphating, then passivation” such a composite process, as an alternative to the traditional single pickling operation. This process with the help of precise control of the concentration of acid, such as hydrochloric acid concentration in the range of 15% to 20%, as well as the temperature of phosphating, is 50 ℃ to 60 ℃ between, and passivation time, for 3 minutes to 5 minutes, can form a layer of uniform and dense phosphate film on the surface of the steel pipe. This layer of phosphating film can not only oxidation, rust and many other defects to be completely removed, but also allows subsequent processing of lubricating properties and clamping stability has been improved. Compared with the traditional process, after the composite pretreatment of steel pipe, its surface roughness Ra value can be reduced to below 0.2μm, cold working process in the mould wear will be reduced by more than 30%. Moreover, environmentally friendly chrome-free passivator can be applied, the pollution problem of traditional chromate passivation has been solved, which is in line with the requirements of green manufacturing.

In the field of organisation optimisation, the ultra-rapid annealing process has evolved into a focus of innovation. The process uses induction heating to achieve a rapid warming of the tube, at a rate of up to 100°C/s, and precise temperature control, with the aid of adjustable austenitising temperatures in the range of 850 - 950°C, and holding times of 10 to 30 s. The process is capable of significantly improving the plasticity and toughness of the material, with grain refinement of more than 10 grades. - 30s, the grain can be refined to more than 10 levels, significantly improving the plasticity and toughness of the material. A group of experimental data show that the use of ultra-rapid annealing process for precision steel tubes, cold drawing processing of the broken tube rate from 5% reduced to 0.8%, and after the completion of the processing of the tensile strength of the parts increased by 15% - 20%. In addition, for the existence of thin-walled steel tubes are prone to deformation of the situation, the innovative research and development of the “Vacuum isothermal annealing” process can effectively reduce the temperature gradient during the heating process, prevent deformation caused by thermal stress, and protect the accuracy of billet size.

II. Core moulding process innovation: breaking through the bottleneck of complexity and precision

Precision steel tube parts of the shape and dimensional accuracy of the decision of the key link is the core forming process, the traditional forming process of complex structures, ultra-thin-walled, large aspect ratio of the parts have obvious shortcomings in the processing. In recent years, laser-assisted forming this innovative process has been applied, internal high-pressure forming this innovative process has also been applied, incremental forming this innovative process has also been applied, effectively breaking through the bottleneck of the traditional process, to obtain the high precision and that the complex structure of the parts of the efficient processing results.

The laser-assisted cold drawing process, an important innovation in the field of cold working, reduces the yield strength and deformation resistance of the material by localised heating of the deformed areas of the tube with the aid of the laser during the cold drawing process and, at the same time, accurately controls the heating temperature (in the range of 200 - 400°C) and the heating range to prevent deterioration of the tissue due to the overall temperature increase. At the same time, the heating temperature (in the range of 200 - 400°C) and the heating range are precisely controlled to prevent deterioration of the organisation due to the overall temperature increase. In terms of precision steel tube parts with a large L/D ratio, where the L/D ratio is greater than 50, the traditional cold drawing process is prone to large deviations in straightness, and there are uneven wall thicknesses and other issues, but laser-assisted cold drawing moulding can regulate the flow of metal with the help of localized heating, which allows the finished product to be straightness error is controlled at 0.05mm/m or less, and the accuracy of the wall thickness tolerance has been improved! 40% In addition, this process can also reduce the residual stress during cold drawing, reduce the risk of deformation during subsequent processing, especially for high-precision conduit processing in the aerospace industry.

The internal high-pressure forming process opens up new avenues for the processing of precision steel tube parts with complex cross-sections. It treats the steel tube as a billet, and by virtue of the internal high-pressure fluid (pressure up to 100 -) and the external mould work together to induce plastic deformation of the steel tube at room temperature, to fit the mould cavity to form the desired complex cross-section (such as squares, ellipses, shapes, and so on). Compared with the traditional welding forming process, internal high-pressure forming parts with no weld, uniform mechanical properties, high material utilisation (can reach 95% or more) and other advantages. For example, in the new energy vehicle battery tray frame using precision steel tube processing, internal high-pressure forming process can be completed at a time of complex shaped cross-section of the molding, shortening the processing cycle by 60%, and the impact resistance of the parts to improve more than 30%, for the thin-walled steel tube within the high-pressure forming prone to wrinkles, rupture, the innovative research and development of the “segmental pressure + temperature forming” technology, the "segmental pressure + temperature forming" technology, the "segmental pressure + temperature forming" technology, the "segmental pressure + temperature forming" technology. Temperature forming" technology, with the help of precise control of the pressure loading rate and local temperature, effectively improve the stability of forming, so that thin-walled (wall thickness <1mm) complex cross-section parts of the forming qualification rate from 60 per cent to more than 90 per cent.

To provide flexible solutions for processing small-lot, multi-species complex precision steel tube parts is the incremental forming process, which gradually processes the tube blank into the required shape with the help of point-by-point local plastic deformation of the forming tool and layer-by-layer local plastic deformation of the forming tool, which does not require special moulds, and is able to adjust the processing parameters through programming to adapt to different parts, and it can achieve high accuracy processing and controlled amount of deformation during the processing, and it is suitable for processing thin-walled and easily deformed parts. For complex curved surfaces, variable cross-section of precision steel tube parts, incremental forming process can achieve high precision machining, and the deformation in the process is controllable, it is suitable for thin-walled, easy to deform the processing of parts. For example, in the small-lot manufacturing of complex parts such as aero-engine fuel tubes, the incremental forming process can practically reduce tooling development costs, shorten machining cycle time by 50 per cent, and the dimensional accuracy of the parts can reach IT5 to IT6 level.

III. Finishing Process Innovation: Enhancing Surface Quality and Accuracy Stability

The purpose of elaborate machining process is to further improve the dimensional accuracy and surface quality of precision steel tube components to meet the assembly and use requirements of high-end equipment. The traditional precision machining process, including ordinary grinding and polishing, has high surface roughness, poor stability of precision and low machining efficiency, etc. In recent years, ultra-precision grinding, magnetorheological polishing, electrochemical-mechanical composite machining, etc. have been adopted. In recent years, the development of innovative processes such as ultra-precision grinding, magnetorheological polishing, electrochemical-mechanical composite machining and other innovative processes have achieved efficient machining of ultra-precision and low roughness surfaces.

Ultra-precision grinding process innovation focuses on grinding wheel technology and grinding parameter optimisation, the use of cubic boron nitride, that is, CBN or diamond super-hard abrasive grinding wheels, and combined with high-speed grinding technology, the grinding speed of this technology can reach 150 to 250m/s, so that it can achieve ultra-precision machining of precision steel tube parts, through precise control of the depth of the grinding depth of microns, and the feeding By precisely controlling the grinding depth, which is micron-level, the feed speed and the rotational speed of the grinding wheel, the dimensional tolerance of the parts can be controlled within ±0.001mm, and the surface roughness Ra value can be reduced to below 0.01μm. For the thin-walled steel pipe grinding is prone to deformation such a problem, innovative research and development of the “constant pressure grinding” technology, which can real-time monitoring of the grinding force, and dynamically adjust the grinding parameters, in order to prevent deformation due to over-grinding, and thus ensure that the parts have a good cylindrical precision. In addition, the integrated application of online measurement and closed-loop control technology can provide real-time feedback on machining accuracy, and automatically adjust the grinding parameters to compensate for errors, thus further improving the stability of machining accuracy.

Magnetorheological polishing process to the precision steel tube bore and other complex surfaces of ultra-precision machining, provides an effective means of the process with the aid of magnetorheological fluid in the magnetic field under the action of the rheological properties of the formation of a certain degree of rigidity of the “flexible abrasive”, used to do the polishing of the surface of the parts, because the magnetorheological fluid has a good compatibility with the different shapes of surfaces, especially suitable for bore, curved surfaces and other parts difficult to process by conventional polishing processes. Because the magnetorheological fluid has good compliance, it can be adapted to different shapes of surfaces, especially suitable for internal holes, curved surfaces and other parts that are difficult to be processed by traditional polishing processes. In the hydraulic system used in the precision steel tube bore for finishing, magnetorheological polishing process can reduce the surface roughness Ra value of the bore from 0.8μm to 0.02μm or less, and the roundness error of the bore after polishing is less than or equal to 0.002mm, which obviously improves the sealing performance and service life of the hydraulic system. Compared with the traditional manual polishing, the processing efficiency of magnetorheological polishing has increased by more than 10 times, and the processing quality is uniform and stable, avoiding the influence of human factors.

Electrochemical-mechanical composite machining process, which combines the high efficiency of electrochemical machining, as well as mechanical machining of high-precision advantages, it is suitable for high-strength, high-hardness precision steel parts of the finishing process, the process with the help of electrochemical action, dissolve the metal material on the surface of the parts, and at the same time, the use of mechanical tools, to remove the surface of the passivation film and residual materials, in order to achieve high efficiency and high precision processing. In stainless steel, high-temperature alloys and other difficult to process material precision steel tube parts for processing, electrochemical mechanical composite processing can effectively reduce the processing force, to avoid the emergence of work hardening and surface cracks, the surface roughness of the processed parts Ra value is less than or equal to 0.03 μm, and the dimensional accuracy of the parts can reach the IT4 - IT5 level. In addition, the machining efficiency of this process is increased by 2 to 3 times compared with the traditional grinding process, and the tool wear is significantly reduced, effectively reducing the processing cost.

IV. Composite processing and intelligent process innovation: promoting efficient collaborative production

Integration of a variety of processing techniques, and the introduction of intelligent perception and control technology, the composite processing and intelligent technology integration of the application of the move, is a very important development trend of precision steel tube parts processing technology innovation level. It can reach the integration of the processing process, automation, intelligent, and then greatly enhance the production efficiency and stability of the processing quality.

Turning and milling composite machining process belongs to the typical category of composite machining field, which integrates the turning function of lathe with the milling and drilling functions of milling machine in one place, which can achieve multi-process machining of precision steel tube parts in one clamping, avoiding the positioning error caused by multiple clamping, and the turning and milling composite machining can shorten machining cycle and improve the accuracy of machining of precision steel tube parts with complex structure such as step, groove and thread. Processing accuracy. For example, in the processing of precision steel tube parts for automobile transmission shafts, mill-turn composite machining can integrate the turning process, as well as milling keyway process, and drilling process, etc., which can shorten the machining cycle by more than 40%, and the coaxiality error of the parts can be controlled within zero point one millimetre. In addition, mill-turn machine tools are generally integrated with automatic tool changer and intelligent programming system, which can realise the rapid change of multi-species parts, thus enhancing production flexibility.

The core aspect of intelligent machining process innovation lies in the existence of a “perception - decision - control” situation, which is a closed-loop synergistic state. By integrating force sensors, temperature sensors, vision sensors and other intelligent sensing elements in the machining equipment, key data such as cutting force, temperature, tool wear, part size, etc. in the machining process can be collected in real time, and the collected data can be processed and analysed by virtue of big data analysis and artificial intelligence algorithms to accurately identify abnormal states in the machining process (e.g. tool wear, part deformation) and predict the machining quality. ) and predict the machining quality, based on the analysis results, automatically adjust the machining parameters (such as cutting speed, feed, cutting fluid flow) or trigger the early warning mechanism to achieve adaptive control of the machining process. For example, in the CNC turning of precision steel tube parts, the intelligent tool wear monitoring system can monitor the tool wear status in real time, and when the wear amount reaches the threshold, it will automatically trigger the tool change procedure, so as to avoid the machining quality degradation due to the excessive tool wear, and the intelligent temperature control system can real-time adjustment of the cooling system parameters, to control the temperature of the cutting area to maintain stability, and to reduce the impact of thermal deformation on the machining accuracy. The intelligent temperature control system can adjust the parameters of the cooling system in real time to control the temperature of the cutting area to keep stable and reduce the impact of thermal deformation on machining accuracy.

Moreover, the use of digital twin technology has given a new boost to the quality and updating of precision steel tube parts processing. By building a digital twin model of the processing process, it is possible to achieve virtual simulation and visual supervision of the processing process, pre-judge the problems that may occur in the processing process (such as collision, deformation), and then optimise the processing parameters; at the same time, by means of the instant synchronisation between the virtual model and the actual processing data, it is possible to achieve the whole process of the process of the processing process of the retrospective and quality control. In large-scale manufacturing of precision steel tube parts, digital twin technology can shorten the machining process optimisation cycle time by more than 50% and increase the production pass rate by 8% to 10%.

V. Challenges and trends in the application of innovative processes

Precision steel tube parts processing process innovation has made significant progress, but in the practical application of the many problems still encountered: First, some innovative processes (such as laser-assisted forming, magnetorheological polishing) of the high cost of equipment input, resulting in small and medium-sized mass production enterprises are limited in the application of the second, the complexity of the process of parameter regulation is extremely difficult to the operator's technical level is quite high; Third, some of the innovative process of processing Third, the processing mechanism of some innovative processes is not yet comprehensive, and it is difficult to achieve accurate control of the whole working conditions.

In the future, precision steel tube parts processing process innovation will show the following development trends: one for the green, to further optimize the process, cut cutting fluid, acid and other harmful substances, the use of dry machining, low-temperature machining of such environmentally friendly processes; the second is the ultimate precision, with the help of process optimization and upgrading of equipment to achieve nanometer precision machining to meet the high-end chip manufacturing, aerospace and other fields of the The third is full-process intelligence, deeply integrating artificial intelligence, digital twin, industrial internet and other technologies to achieve unmanned and autonomous control of the processing process; the fourth is low-cost, through technology iteration and large-scale application, to reduce the equipment and operating costs of the innovative process, and increase its popularity in various industries.

VI. Conclusion

Precision steel tube parts processing technology innovation, is to deal with high-end equipment manufacturing demand for upgrading the inevitable choice, the key is to take advantage of technological breakthroughs to solve the traditional process in the lack of precision, as well as the lack of complexity, and high efficiency of the short board. From the perspective of organisational optimisation in material pretreatment, to the core forming stage of the process breakthroughs, and then to the precision of the finishing process to enhance the accuracy, as well as composite processing and intelligent synergistic empowerment, multi-dimensional process innovation, is prompting the development of the precision steel processing industry in the direction of high-quality, high-efficiency direction towards the direction of the green direction forward. In the future, it is necessary to further strengthen the mechanism research of the innovative process, but also to carry out equipment research and development, so as to reduce the application cost and enhance the maturity of the technology. At the same time, pay close attention to the integration of interdisciplinary technology applications for precision steel tube parts processing to give a more efficient, but also more accurate, but also more environmentally friendly solutions to help high-end equipment manufacturing industry continue to upgrade.