Month: May 2022
At the K-2007 exhibition, a compact, robotic 1000kN all-electric plastics injection moulding cell achieves high injection speeds, high pressures, excellent precision and dynamics and best performance
Engel, Austria showed at K-2007 plastics exhibition, Germany, a compact, all-electric e-max 200/100 plastics injection moulding machine with a clamping force of 1.000kN (100 tonf). It formed part of a ‘turnkey’ production cell featuring robot/parts removal unit Engel ERC 23 + Trayserver Engel ETS5 (for orientated parts depositing).
The cell produced mobile phone shells from a PC blend in a two-cavity mould.
The e-max machine is particularly compact, said Engel, and includes the following.
* A new die clamping unit with four tie-bars.
* A large tie-bar gap.
* A wide opening stroke.
* A generously dimensioned mould mounting space.
* Anew injection unit achieves high injection speeds, high pressures, excellent precision, excellent dynamics and high performance.
Thanks to excellent performance, the Engel e-max offers excellent cost effectiveness.
* Three-component injection moulding of switches – for the ‘teletronics’ industry, Engel demonstrated the production of a switch using Engel ‘combimelt’ three-component technology, with picking and placing and multi-component moulding.
The switch is injection moulded using a 3/4-cavity Engel mould.
An Engel ‘victory’ 330H/80W/80V/130 injection moulder with Engel ERC 63 parts removal robot produced the switch from Ultramid A3WG6 polyamide by BASF and two POM types (Delrin 577 and 500 by DuPont).
* Versatile machines, processes and applications – as well as the high-performance Engel speed injection moulding machines for the packaging industry, Engel showed a dual-platen Engel duo machine series, tiebar-less Engel victory machines, the fully-electric Engel e-motion precision machine, the compact, fully-electric Engel e-maximum and Engel elast machines, which specialise in elastomer processing
Punch level correction and adjustment method
After the press has been used for a period of time, loose parts or other problems often occur, resulting in a significant drop in its accuracy. This will seriously affect the use of the equipment. Therefore, we find that when the accuracy of the equipment decreases, effective measures will be taken to adjust its level. Our commonly used adjustment methods for level correction mainly include the following:
- 1. First, clean the punch frame thoroughly to increase the accuracy of the level reading; there is no need to feed in during debugging, but the guide screw on the guide plate must be adjusted upward, and then the equipment is slowly adjusted by elbow movement. To the bottom dead center, special attention must be paid to the guide plate not to press the floating rod too low, otherwise it will cause the floating rod to bend or break. When starting the feeder for continuous punching, the speed adjustment screw of the feeder must be rotated clockwise, and the slider moves slightly slower, so that you can see whether the nylon pad and the length fine-tuning screw are encountered when the slider moves back and forth.
- 2. The slider moves back and forth during the test machine. If you only touch the nylon washer without touching the length fine-tuning screw, this is because the floating rod has not fallen deep enough, and the bow guide screw on the punch needs to be slowly lowered. If the slider only touches the length fine-tuning screw and does not touch the nylon washer when the slider moves back and forth, this is because the floating rod has fallen too deeply, and the guide screw needs to be adjusted upward slowly.
- 3. If the slider moves between the length fine-tuning screw and the nylon washer and the distance between the two sides is equal, the speed adjustment screw should be rotated in a counterclockwise direction to make the slider speed normal, and the slider can be touched when reciprocating Nylon gasket and spacer ring. If the equipment speed does not change and the feeding distance needs to be changed from long to short, first adjust the guide screw upward to reduce the falling distance of the floating rod, and then rotate the speed adjustment screw clockwise so that the feeding can match the equipment speed.
If there is an error in the accuracy of the punch, we can adjust it according to the above method, so that it can work more accurately, improve work efficiency, and reduce work errors.
Are you be tired of messy cables under your desk?Are you be mad of your earphone cable lines knot?silicone cable organizers, let cables orgernized!How to use silicone cable organizers to organize your cables?Firstly, there will introduce two silicone cable organizers which is in different using ways: silicone cord holders and silicone cable ties bands.
Silicone Cable Tie BandsSilicone Cord Holder
Silicone cable band is a multifunctional elastic stretch cord usually be used to reseal pocket or tie cables together. It may be called at different names when they be used in different ways: silicone packbands or cables organizer band.
Packbands SiliconeCable Band OrganizerAs for the cord holders, it usually is with notches which can be put mouse cable, power cords or earphone wires. That's why this type of cable organizer also frequently be called cable holder clip.Besides, silicone cable holder is with a suction part which make it possible to keep in place of the desktop or wall.
Link to this article：Silicone Cable Organizers, Make Your Table Organized
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Der Schlüssel zur vorbeugenden Instandhaltung von CNC-Bearbeitungsmaschinen ist die Verbesserung der täglichen Wartung. Die Hauptwartungsarbeiten umfassen den folgenden Inhalt: tägliche Inspektion, wöchentliche Inspektion, monatliche Inspektion, vierteljährliche Inspektion und halbjährliche Inspektion. Die vorbeugende Wartung von CNC-Bearbeitungsmaschinen ist wie folgt:
1. Tägliche Inspektion von CNC-Bearbeitungsmaschinen
Zu den Hauptprojekten gehören Hydrauliksysteme, Spindelschmiersysteme, Schienenschmiersysteme, Kühlsysteme und pneumatische Systeme. Die tägliche Überprüfung basiert auf den normalen Bedingungen der einzelnen Systeme. Wenn Sie zum Beispiel die Prozesserkennung des Spindelschmiersystems durchführen, sollte die Betriebsanzeige aufleuchten und die Hydraulikpumpe normal laufen. Wenn die Betriebsanzeige nicht hell ist, halten Sie die Spindel an und wenden Sie sich an den Mechaniker. Reparaturen durchführen.
2. CNC-Bearbeitung wöchentliche Prüfung der CNC-Werkzeugmaschine
Zu den Hauptbestandteilen gehören Werkzeugmaschinenteile und Spindelschmiersysteme, die wöchentlich ordnungsgemäß überprüft werden sollten, insbesondere bei Maschinenteilen, um Eisenspäne und Fremdreinigungen zu entfernen.
3. Monatliche Inspektion von CNC-Bearbeitungsmaschinen
Hauptsächlich zur Überprüfung der Stromversorgung und des Lufttrockners. Die Versorgungsspannung ist unter normalen Bedingungen mit 180 V – 220 V ausgelegt und die Frequenz beträgt 50 Hz. Wenn Anomalien vorliegen, sollte sie gemessen und eingestellt werden. Der Lufttrockner sollte einmal im Monat entfernt, gereinigt und zusammengebaut werden.
4. CNC-Bearbeitung vierteljährliche Inspektion der CNC-Werkzeugmaschine
Die vierteljährliche Inspektion sollte hauptsächlich unter drei Gesichtspunkten durchgeführt werden: Maschinenbett, Hydrauliksystem und Spindelschmiersystem. Bei der Überprüfung des Maschinenbettes ist es zum Beispiel vor allem zu prüfen, ob die Genauigkeit der Werkzeugmaschine und das Niveau der Werkzeugmaschine den Anforderungen in der Anleitung entsprechen. Wenn Probleme auftreten, wenden Sie sich sofort an den Maschinenbauer. Wenn Sie bei der Überprüfung des Hydrauliksystems und des Spindelschmiersystems Probleme feststellen, ersetzen Sie das neue Öl 6oL und 20L separat und reinigen Sie es.
5. CNC-Bearbeitung halbjährliche Inspektion der CNC-Werkzeugmaschine
Nach einem halben Jahr sollte das Hydrauliksystem der Werkzeugmaschine, das Spindelschmiersystem und die X-Achse überprüft werden, sollte bei Problemen das neue Öl ausgetauscht und anschließend gereinigt werden. Nachdem Sie das Wissen über vorbeugende Wartung gründlich kennengelernt und beherrscht haben, müssen Sie die Ursachen und die Behandlung abnormaler Phänomene im Hydrauliksystem besser verstehen und verstehen. Wenn die Ölpumpe beispielsweise kein Öl versprüht, ist der Druck anormal, es gibt Geräusche usw., sollten Sie wissen, was die Hauptgründe sind und welche Lösung dies ist.
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Many countries in the world have cultivated 3D printing as a new growth point for future industrial development. As early as 2012, the United States identified “Additive Manufacturing Technology” as the first manufacturing innovation center (later renamed “Made in the United States”), and the European Union, South Korea, Japan, Singapore, Russia and other countries also adopted various measures to promote 3D printing China Industry moving forward
Since the rise of 3D printing, China has successively promulgated a number of policies to support the development of the 3D printing industry. With the support of policies, 3D printing companies have sprung up like mushrooms after a rain, and are growing rapidly. The development of the 3D printing industry in Beijing, Guangdong, Zhejiang, Shaanxi and other places has also made significant progress. According to statistics, there are more than 400 companies engaged in 3D printing business in Guangdong Province alone, with multiple 3D printing industrial parks.
With the rapid development of 3D printing, whether traditional subtractive manufacturing methods such as Cnc Machine tools will be replaced has also become a hot topic of discussion among people from all walks of life. In recent years, the technology of China’s CNC machine tools has been improving day by day, and 3D printing has found their own scenes. Generally speaking, CNC machine tools need to program in advance and continuously cut to realize the forming of objects. The working principle of a 3D printer is similar to that of a CNC machine tool, and it also works according to computer instructions. The difference is that it builds products by stacking layers of raw materials. So 3D printing is also called “additive manufacturing.”
The significant difference between 3D printing and traditional manufacturing lies in the process of product molding. In the traditional manufacturing industry, the entire manufacturing process generally needs to be formed through such processes as mold opening, cutting, casting or forging, and component assembly. 3D printing eliminates complicated processes, no molds, and one-time molding. Therefore, 3D printing can overcome some designs that cannot be achieved in traditional manufacturing and produce more complex structures.
On the other hand, CNC machine tools are a type of computer numerical control (CNC), which can process complex, precise, and various parts. Generally speaking, CNC machining tools use computer-designated programs to remove excess materials through laser cutting, milling and other steps to reach the final product, which is a typical subtractive manufacturing.
On the one hand, traditional manufacturing is characterized by “global procurement, division of labor and collaboration”. Different parts of a product are often produced in different places and then shipped to the same place for assembly. And 3D printing is “integral manufacturing, one-time molding”, which eliminates the logistics link and saves cost and time.
On the other hand, the traditional manufacturing industry takes production lines as the core, factories as the main carrier, and highly concentrated production equipment. And 3D printing embodies the integration of a new generation of information technology and manufacturing represented by cloud computing, big data, Internet of Things, and mobile Internet.
As a major product of the development of traditional manufacturing, machine tools are very different from the new generation of 3D printing manufacturing methods. The machine tool is the mother machine of the manufacturing industry. If 3D printing technology can be integrated into the machine tool field, it will undoubtedly be even more powerful. The combination of the two not only improves the production efficiency, but also completes many manufacturing problems.
The special machine tool in the machine tool can be customized with functions according to customer requirements, but the functions are not powerful enough and rich, and may not be designed and manufactured as one wishes. However, with the introduction of 3D printing, the popularity and application of machine tool products may be greatly improved.
It is understood that 3D printing technology has already been applied in China’s industrial parts manufacturing, but has not yet entered large-scale industrial applications. Its process and equipment, as well as applications in medical, aerospace and other fields need to be further developed. Judging from the current situation, 3D printing technology does not have the conditions to replace traditional manufacturing. In terms of mass manufacturing, the high-efficiency and low-cost traditional subtractive manufacturing method embodied by machine tool manufacturing is even better.
Of course, with the emphasis on metal additive manufacturing, more and more equipment manufacturers in the field of traditional machine tool manufacturing have entered the field of additive manufacturing. Some have launched hybrid additive manufacturing equipment based on Cnc Machining centers, and some simply Directly enter the new field of additive manufacturing. For example, Japanese Mazak. Mazak launched the Integrex i-400am (additive manufacturing) compound processing equipment. Integrex i-400am is a complete set of equipment, which is more suitable for processing materials for small batch production, such as the processing of heat-resistant alloys for aerospace parts, and the processing of high-hardness materials for parts.
The long-term coexistence of subtractive manufacturing and growth manufacturing methods is a trend that can be met. However, in the future, this situation may change. In any case, the way to achieve refined, automated, and efficient manufacturing of products will be expected to be diversified.
Link to this article：Do 3D Printing And CNC Machine Coexist Or Compete?
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Titanium bars for surgical implantation, also known as medical titanium bars, are the most widely used metal for human body implantation in modern medicine. Due to its non-allergenic, carcinogenic and aberrant contact with human body, titanium can well combine with bone tissue, epithelium and connective tissue, so it is a biocompatible metal material.
It is widely used in denture porcelain, bracket, steel bracket, bone joint, surgical implantation and so on.
Guest contributors are welcome at the Alloy Wiki.It is a weekly wiki and guide on alloy information and processing technology, while also about the vast array of opportunities that are present in manufacturing. Our team of writers consists of a Machining Material Supplier / Machinist / Tool and Die Maker, a Biomedical Engineer / Product Development Engineer, a Job Development Coordinator / Adjunct Professor, and a President and CEO of a manufacturing facility.
Design of Transmission Mechanism Measurement and Control System Using NI Virtual Instrument and Electrorheological Fluid
“Electrorheological fluid (ERF) is a new type of smart substance, which can quickly realize the transition from liquid to solid under the action of a high-voltage electric field, and has a fast response speed. The dynamic characteristics of the disc-type electrorheological transmission mechanism are studied, and the NI virtual instrument is used to analyze, detect and control the mechanism. The data is obtained through experiments, and then the input torque, output torque, rotational speed and applied high-voltage electric field are analyzed. Relationship. Electrorheological fluids (ERFs) are a new class of smart materials whose viscosity and yield stress can be controlled by an applied electric field.
Electrorheological fluid (ERF) is a new type of smart substance, which can quickly realize the transition from liquid to solid under the action of a high-voltage electric field, and has a fast response speed. The dynamic characteristics of the disc-type electrorheological transmission mechanism are studied, and the NI virtual instrument is used to analyze, detect and control the mechanism. The data is obtained through experiments, and then the input torque, output torque, rotational speed and applied high-voltage electric field are analyzed. Relationship. Electrorheological fluids (ERFs) are a new class of smart materials whose viscosity and yield stress can be controlled by an applied electric field.
With the development of modern science and technology, Mechatronics has been paid more and more attention, and the fluid components and systems controlled by microcomputers have been continuously developed. The application of electrorheological fluid technology to mechanical systems and hydraulic control systems can realize mechanisms with no moving parts or few moving parts, which greatly improves the dynamic quality of the system. Electrorheological fluids have a wide range of applications, including hydraulic engineering, automotive manufacturing, robotic systems, fluid sealing, etc. in engineering applications. In the automobile manufacturing industry, it can be used for the speed regulating clutch of the cooling fan of the automobile engine, the transmission clutch, the damper with controllable damping or the suspension system controlled by the computer. The auto parts designed and manufactured by ER technology have the characteristics of excellent performance, no wear, long life, good manufacturing process and low cost, and can be directly controlled by computer without interface. Vehicles using ER technology have obvious advantages in future market competition. The automatic control system of electrorheological transmission consists of three parts, namely mechanical transmission mechanism, computer detection and control device and electrorheological fluid.
the working principle of the organization
Figure 1 shows the working principle diagram of the disc-type electrorheological transmission mechanism. The middle disc and the mandrel are connected together, the left end of the mandrel is equipped with a stepper motor, the right end of the mandrel is connected to the load, and the left and right ends are each covered with a disc, and the space between the left and right discs and the middle disc is filled with ERF. In this experiment, the ERF was selected as HITL2 ERF developed by the Institute of Composite Materials, Harbin Institute of Technology, and the applied electric field was controlled by an Electronic switch. The input signal is provided by the motor at the left end of the mandrel. Since the input signal is very small and the load is connected to the right end of the mandrel, the mandrel cannot rotate. At this time, the left and right discs are driven by the stepper motor to rotate at equal and opposite speeds ΩL and ΩR, and close the electronic switch on the side where the high-voltage power supply needs to be applied (if you want to increase the torque, close the electronic switch on the left). ), at this time, the ERF between the disc and the intermediate disc will produce a medium rheological effect, and the additional torque generated will be transmitted to the output of the intermediate disc through the disc. It can be seen from the experimental schematic diagram that a small mechanical control signal is input to the left end of the shaft of the intermediate disk, and a large torque can be output to the right end. The electric field thickens the ERF viscosity between the left disk or the right disk and the intermediate disk, resulting in large shearing stress, so that the intermediate plate overcomes the load moment and rotates according to the input signal. This is the working principle of the double disc electrorheological transmission mechanism.
System Theory Model
It behaves as a Newtonian fluid in the absence of an applied electric field. Under the action of an external electric field, it behaves like a Bingham fluid, and at a low strain rate, it has viscoelastic properties. At high electric fields, it is a viscoplastic body with high yield stress. The constitutive equation is: τ=τy+ηplγ (1) where τ is the shear stress generated by the fluid flow, τy is the yield stress generated by the gradual solidification or thickening of the electrorheological fluid under the action of the electric field, and γ is the shear stress. cut rate.
The relationship between the yield stress and the applied electric field is: τy=AE2=A(U/h)2 (2) The shear stress generated by the electrorheological effect makes the driven disc obtain the moment Me. The relationship between the current variable torque Me and τy, ηpl, the rotational speed difference ΔΩ between the left and right disks, the distance h between the disks, and the inner and outer circle radii r1 and r2 of the effective area of the disks is as follows:
According to formula (2), there is a nonlinear relationship between the shear torque and the applied voltage. Here, it is assumed that their relationship is a power relationship, as shown in the following formula:
Dynamic Analysis of Disc Electrorheological Transmission Mechanism Based on Virtual Instrument
Among them, α0, α1, α2 are obtained by experiment, U=1kV.
This is to make the coefficient dimensions consistent, and they are all moment dimensions.
Construction of transmission mechanism measurement and control system
Control, analysis and detection are carried out automatically by computer using NI virtual instrument system. In the experiment, the multi-function data acquisition board PCI-MIO-16E-1, SCXI signal conditioning system, temperature and voltage measuring instrument and dynamic signal analyzer NI-4552 are used to collect and analyze the data, and the arbitrary waveform generator PCI is used to collect and analyze the data. -5411, terminal UMI and motor control board Flexmotion-6C control the stepping motor, and the whole system is managed by the program written by the software platform LabView. Different motion signals are input by the stepper motor, and the shear field is generated by the asynchronous motor. Figure 3 is the NI virtual instrument control program written by LabView. The dynamic performance of the disc-type electrorheological transmission is analyzed by the results obtained from the experiments. In the experimental study of electrorheological transmission performance, the stepper motor is used to realize variable signal input, and the speed of the asynchronous motor is controlled to adjust the shear rate. torque and speed signals. The output of the device uses a wooden wheel and reed friction to simulate a load.
Under the action of AC electric field, for the ERF used in this experiment, its electrorheological effect is stronger than that under the action of DC electric field, and the yield stress is correspondingly larger. With the increase of the externally applied voltage, the output torque of the electrorheological transmission also increases to a certain extent, as shown in Figures 4 and 5. When the ambient temperature is 18.9°C, the applied voltage is AC 3kV, and the rotational speed of the active disk is 60r/m, the output of the stepper motor changes according to the arbitrary waveform shown in Figure 6, and the input torque and output torque of the electrorheological drive are obtained. moment. The input torque of the device changes with the change of the output speed signal of the stepper motor, and the input torque signal is related to the load and fluctuates with the change of the load.
The rotation of the active disk generates a rotating shear field for the electrorheological fluid. When the ambient temperature is 18.6°C, the direct voltage of 3kV is applied, and the input of the stepper motor is removed, the speed of the asynchronous motor is adjusted to tap the speed of the active disc of the electrorheological transmission, and the results shown in Figure 8 are obtained. It can be seen that with the increase of the rotational speed of the active disc of the electrorheological transmission device, its output torque also increases. When the rotational speed of the active disc is low, its change has little effect on the output torque; while when the rotational speed of the active disc is high, its change has a more significant impact on the output torque. According to formula (4) and the experimental data, the curve fitted by torque Me is shown in Figure 9, where α0 is 0.0611, α1 is -0.02732, and α2 is 0.00577. Through the above analysis, the following conclusions can be drawn:
Dynamic Analysis of Disc Electrorheological Transmission Mechanism Based on Virtual Instrument
Dynamic Analysis of Disc Electrorheological Transmission Mechanism Based on Virtual Instrument
(1) For the disc type electrorheological transmission device designed in this experiment, after selecting an electrorheological fluid, its transmission characteristics are only related to the external electric field.
(2) The electrorheological effect of HITL2 electrorheological fluid is stronger under the action of AC electric field than under the action of DC electric field. Moreover, with the increase of the applied electric field, the yield stress caused by the electrorheological effect also increases.
(3) The curve of the output torque of the electrorheological transmission is fluctuating. Because the load changes, the output torque should match the load, so the output torque should also change with the change of the load, that is, in a waveform state.
(4) The input torque of the electrorheological transmission device is to follow the speed signal of the stepping motor, but there is a certain lag, because the elastic coupling is used in the mechanism.
(5) For the control of electrorheology, the mechanical structure of double active disc is adopted, so that the influence of shear speed change on the transmission torque can be ignored. Electrorheological drives can be controlled as long as the electric field is controlled.
The Suprema is a one-piece ‘Tee Bed’ designed, robustly constructed, cylindrical grinder that can accommodate one-off, batch, or high-volume production.
Direct coupled digital servo motors and rotary encoders from GE-Fanuc, ensure geometric accuracy, while the machine benefits from Jones and Shipman’s proprietary software that removes the requirement for operators to input code, instead providing a highly flexible icon-based user interface Built around a GE-Fanuc Touchscreen the Easy Control system reduces the need for operator training and dramatically cuts set-up and changeover time.
Full manual control of the Suprema is also straightforward and intuitive thanks to the machine’s twin membrane panel controls.
The left-hand panel contains the Z axis manual control via a Hand Pulse Generator (HPG), together with the touchscreen display panel and ancillary controls.
The right-hand panel has a similar HPG and digital read out for X axis control.
The modular configuration of the Suprema designed using the latest 3D CAD technology, has allowed Jones and Shipman to offer the machine with a comprehensive range of options and additions to suit the most demanding user requirements.
The Suprema incorporates a Universal Wheelhead and has a grinding capacity of 300mm x 650mm diameter between centres.
Models are also available in 1m and 1.5m table capacities.
While this model with its universal wheelhead allows for internal and external grinding, plain straight approach and angle head options are also available; all achieved with very low capital outlay, ensuring fast payback for users.
related catagory Machine & Machinery
Alternate vehicles, transportation equipment and field work machine oil in all seasons adapt to changes in temperature
Foreign oil companies adopt tracking services for key users. Whenever the oil change period is approaching and users need to buy oil, they will test the oil for free in advance, issue an inspection report, and actively provide key users with a scientific basis for oil change. This kind of thoughtful service not only shortens the distance with users, but also improves the credibility of the brand.
The alternation of the four seasons requires the oil used in vehicles, transportation equipment and field work tools to adapt to changes in temperature, especially in the north. Lubricants of different viscosity grades are usually replaced at the end of autumn and spring, thus forming a peak season for lubricating oil sales. Foreign oil companies attach great importance to the promotional activities in these two seasons. In the autumn, they launched low pour point, low viscosity grades of multi-grade antifreeze and antifreeze, and accompanied the promotion activities to choose gifts that reflect the characteristics of winter; at the turn of spring and summer, they also promote high viscosity grade oils, and there are also optional gifts. Summer characteristics.
Lubricant is a product with high technical content. General users often don’t know the reason for their complicated technical performance, and they don’t know how to choose various brands. For this reason, foreign oil companies often adopt methods such as holding technical exchange meetings, distributing easy-to-understand oil user manuals, and returning visits to answer questions, etc., to conduct extensive and in-depth knowledge marketing.
The automotive parts and parts machining, PTJ Shop offers the highest degree of OEM service with a basis of 10+ years experience serving the automotive industry. Our automotive precision shop and experts deliver confidence. We have perfected the art of producing large component volumes with complete JIT reliability, backed by the quality and long-term reliability our customers expect.
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1 The solidification characteristics of ductile iron
The different solidification methods of nodular cast iron and gray cast iron are caused by the different growth methods of nodular graphite and flake graphite.
In hypoeutectic gray iron, graphite begins to precipitate at the edge of primary austenite. The two sides of the graphite sheet are surrounded by austenite and absorb graphite from the austenite to thicken. The tip of the graphite sheet is in the liquid. It grows by absorbing graphite.
In nodular cast iron, because graphite is spherical, graphite balls begin to absorb graphite around after precipitation. The surrounding liquid becomes solid austenite and surrounds the graphite balls because of the decrease in the amount of w(C); Surrounded by austenite, the only carbon that can be absorbed from the austenite is relatively limited, while the carbon in the liquid diffuses slowly into the graphite ball through the solid, and being surrounded by austenite limits its growth; so Even though the carbon equivalent of nodular cast iron is much higher than that of gray cast iron, the graphitization of nodular cast iron is more difficult, so there is not enough graphitization expansion to offset the solidification shrinkage; therefore, nodular cast iron is prone to shrinkage.
In addition, the thickness of the austenite layer that wraps the graphite ball is generally 1.4 times the diameter of the graphite ball. That is to say, the larger the graphite ball, the thicker the austenite layer, and the more difficult it is for the carbon in the liquid to transfer to the graphite ball through austenite. Great .
The fundamental reason why low-silicon ductile iron is prone to white mouth is also the solidification method of ductile iron. As mentioned above, due to the difficulty of graphitization of ductile iron, there is not enough latent heat of crystallization generated by graphitization to be released into the mold, which increases the degree of supercooling, and the graphite does not have time to precipitate to form cementite. In addition, spheroidal graphite cast iron has a rapid growth and decline, which is also one of the factors that are extremely prone to overcooling .
2 Conditions for nodular cast iron without riser casting
It is not difficult to see from the solidification characteristics of ductile iron that it is more difficult to achieve riser-free casting for ductile iron parts. Based on my many years of practical experience in production, the author has made some generalizations and summaries about the conditions required for nodular cast iron to realize the riser-free casting process, and share it with colleagues here.
2.1 Selection of molten iron composition
2.1.1 Carbon equivalent (CE)
Under the same conditions, tiny graphite is easy to dissolve in molten iron and is not easy to grow; as the graphite grows, the growth rate of graphite also becomes faster, so the primary graphite is produced before the eutectic in the molten iron to promote the solidification of the eutectic Graphitization is very advantageous. The molten iron with hypereutectic composition can meet such conditions, but the excessively high CE value causes the graphite to grow up before the eutectic solidifies, and when it grows to a certain size, the graphite starts to float, causing graphite floating defects. At this time, the volume expansion caused by graphitization will only cause the molten iron level to rise, which is not only meaningless to the feeding of the casting, but also because the graphite absorbs a large amount of carbon when it is in the liquid state, it will cause the molten iron to solidify when the eutectic is solidified. The low amount of w(C) in the medium cannot produce enough eutectic graphite, and it cannot offset the shrinkage caused by eutectic solidification. Practice has proved that it is ideal to be able to control the CE value between 4.30% and 4.50%.
2.1.2 Silicon (Si)
It is generally believed that in Fe-C-Si alloys, Si is a graphitizing element, and a high amount of w (Si) is beneficial to graphitization expansion and can reduce the occurrence of shrinkage cavities. Few people know that Si hinders eutectic solidification graphitization. Therefore, no matter from the perspective of feeding or preventing the generation of fragmented graphite, as long as the white mouth can be prevented by measures such as strengthening inoculation, the amount of w (Si) must be reduced as much as possible.
2.1.3 Carbon (C)
Under the condition of reasonable CE value, increase the amount of w(C) as much as possible. Facts have proved that the w(C) content of ductile iron is controlled at 3.60%~3.70%, and the casting has the smallest shrinkage rate.
2.1.4 Sulfur (S)
S is the main element that hinders the spheroidization of graphite. The main purpose of spheroidization is to remove S. However, the rapid growth and decline of nodular cast iron is directly related to the low amount of w (S); therefore, an appropriate amount of w (S) is necessary . The amount of w(S) can be controlled at about 0.015%, and the nucleation effect of MgS can be used to increase the graphite core particles to increase the number of graphite spheres and reduce the decline .
2.1.5 Magnesium (Mg)
Mg is also an element that hinders graphitization, so under the premise that the spheroidization rate can reach more than 90%, Mg should be as low as possible. Under the condition that the original molten iron w(O) and w(S) are not high, the residual w(Mg) content can be controlled within 0.03%~0.04% is the most ideal.
2.1.6 Other elements
Mn, P, Cr and other elements that hinder graphitization are as low as possible.
Pay attention to the influence of trace elements, such as Ti. When the amount of w (Ti) is low, it is an element that strongly promotes graphitization. At the same time, Ti is an element that forms carbides and an element that affects spheroidization and promotes the production of vermicular graphite. Therefore, the lower the amount of w (Ti), the better . The author’s company once had a very mature non-riser casting process. Due to a temporary shortage of raw materials, pig iron with a w(Ti) content of 0.1% was used. Not only did the castings produced have surface shrinkage, but also concentrated types appeared inside after processing. Shrinkage.
In short, pure raw materials are beneficial to improve the self-feeding ability of ductile iron.
2.2 Pouring temperature
Experiments have shown that the pouring temperature of ductile iron from 1 350 ℃ to 1500 ℃ has no obvious effect on the shrinkage volume of the casting, but the morphology of shrinkage cavity gradually transitions from concentrated type to dispersed type. The size of graphite balls gradually increases with the increase of pouring temperature, and the number of graphite balls gradually decreases. Therefore, there is no need to demand a too low pouring temperature. As long as the mold is strong enough to resist the static pressure of the molten iron, the pouring temperature can be higher. The molten iron is used to heat the mold to reduce the degree of undercooling during the eutectic solidification, so that the graphitization has sufficient time to proceed. However, the pouring speed should be as fast as possible to minimize the temperature difference of the molten iron in the mold .
2.3 Cold iron
Based on the author’s experience in using cold iron and the above theoretical analysis, the claim that cold iron can eliminate shrinkage defects is not accurate. On the one hand, the local use of cold iron (such as perforated parts) can only transfer the shrinkage cavity rather than eliminate it; on the other hand, the use of cold iron on a large area can achieve the effect of reducing feeding or no riser. Unconsciously increasing the mold strength instead of cold iron reduces the liquid or eutectic solidification shrinkage. In fact, if the cold iron is used too much, it will affect the growth of the graphite ball and the degree of graphitization, on the contrary it will aggravate the shrinkage.
2.4 Mould strength and stiffness
Since ductile iron mostly chooses eutectic or hypereutectic composition, it takes a longer time for the molten iron to cool to the eutectic temperature in the mold, that is, the hydrostatic pressure of the mold is longer than that of the eutectic composition. If the gray cast iron is longer, the mold is more prone to compressive deformation. When the volume increase caused by graphitization expansion cannot offset the liquid shrinkage + solidification shrinkage + mold deformation volume, shrinkage cavities are inevitable. Therefore, sufficient mold rigidity and compressive strength are important conditions for realizing riser-free casting. There are many sand-coated iron casting processes to realize riser-free casting is the proof of this theory.
2.5 Inoculation treatment
The powerful inoculant and the instant delay inoculation process can not only give the molten iron a large amount of core particles, but also prevent the inoculation from declining, and can ensure that the ductile iron has enough graphite balls during the eutectic solidification; the large and small graphite balls reduce The transfer distance of C in the liquid to the graphite core speeds up the graphitization speed. In a short time, a large amount of eutectic solidification can release more latent heat of crystallization, reduce the degree of supercooling, and prevent the generation of white mouths, but also Can strengthen graphitization expansion. thus. Strong inoculation is essential to improve the self-feeding ability of ductile iron.
2.6 Liquid iron filtration
After the molten iron is filtered, some oxidized inclusions are filtered out, so that the micro-fluidity of the molten iron is enhanced, and the probability of microscopic shrinkage can be reduced.
2.7 Casting modulus
Since as-cast pearlitic ductile iron needs to add elements that hinder graphitization, this will affect the degree of graphitization and have a certain impact on the realization of self-feeding of the castings. Therefore, there are data introductions. Riser-free casting is suitable for ductile graphites below QT500. cast iron. In addition, the modulus determined by the shape and size of the casting should be at least 3.1 cm.
It is worth noting that it is difficult to achieve riser-free casting of plate castings with a thickness of less than 50 mm.
There are also information that the condition for realizing the riser-free casting process for nodular cast iron above QT500 is that its modulus should be greater than 3.6 cm.
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