Machine tool guideways induction hardening machine

Machine tool guideways

induction hardening machine

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About machine tool guideways

The guideway is an important part of the machine tool. There are guideways on the machine bed, column, beam and turntable. The accuracy, machining accuracy and service life of the machine tool depend to a large extent on the geometric accuracy and intrinsic quality of the guideway, so the guideway should have the characteristics of small change, good dimensional stability and high wear resistance.

Correct and reasonable selection of machine tool guide metals and quench hardening process is one of the important measures to improve the wear resistance, scratch resistance and fatigue strength of guideways, maintain accuracy stability and prolong service life.

Heat treatment method of inlaid tool guideway:

There are mainly integral quenching and tempering, carburizing quenching, surface induction quenching and nitriding treatment.

Technical conditions and heat treatment characteristics of cast iron guideways

Contact resistance quenching, flame quenching and high-temperature aging, etc. Surface quenching media mainly includes induction quenching medium, contact resistance quenching media and flame quenching media. details as follows:

After high-frequency induction hardening, ultra-frequency induction hardening, and medium-frequency induction hardening, the hardness of the hardened layer can reach 1-1.5mm, 1.5-2.0mm, and 2-4mm respectively. The induction hardening equipment is complex and technical, but the quenching hardness is uniform and consistent. Good performance, high productivity, suitable for mass production. Currently widely produced at home and abroad. At present, the use of rail CNC quenching machine tools, refined oil quenching inductors, so that the quality of rail quenching rate has been greatly improved.

The advantages of contact resistance heating and quenching are that the equipment and heat treatment process are simple and easy to operate. After hardened by this method, the wear resistance of ordinary gray cast iron machine tool guideways can be doubled compared with the unquenched guideways, and the scratch resistance is significantly improved. The hardness can reach 0.2-0.25mm, the hardness can reach more than 600HV, and the quenching distortion is very small. After quenching, there is no need to grind, only use the oil stone to polish the quenched pattern and it can be used.

The disadvantage is that the productivity is low, the hardened area is small, the wear resistance is lower than that of induction hardening, the hardened layer is very shallow, and it is easy to cause fire burns, so this process is mostly used for small-batch products with light guideway load or maintenance of machine tool guideways. middle.

The depth of the hardened layer obtained by flame quenching can reach 1-3mm.

However, the disadvantage is that the critical temperature is not easy to control, and it is easy to cause the phenomenon of overheating and melting. The hardness distribution is not as uniform as that of induction quenching, and the distortion of the guideway after quenching is large, which is only suitable for single-piece or small batch production. In manual operation, due to poor process stability, the temperature is difficult to control, and it has been rarely used at present.

The distortion of the guideway of laser quenching is only 1/10-1/5 of that of high-frequency induction quenching, which can greatly save the amount of grinding after haggard. The depth of the hardened layer is 0.2-1.0mm

The frequency of general high-frequency induction quenching equipment is 200 ~ 300kHz, and the frequency of super audio equipment is mostly 30 ~ 50kHz. The output power of high frequency and super audio induction equipment is 60kW, 100kW, 200kW, 250kW and so on. The frequency of intermediate frequency induction equipment is generally 2.5kHz and 8kHz, and the output power is 100kW, 200kW, 250kW and 500kW.

Inductionquenching machine tools can be divided into two types according to the fixing or moving of coils and guideways Trolley induction quenching machine and sliding induction quenching machine, etc.

The design principles of high-frequency, super-audio and medium-frequency induction quenching coils for machine tool guideways are basically the same, but they should be adjusted through tests during the specific guideway quenching process. Inductors for rail quenching can be divided into mountain-shaped coils, V-shaped coils, flat coils, and rectangular coils according to their outer shapes.

The cross-section of the XKA714 CNC milling machine guideway is shown in picture. The length of the guideway is 1040m, and the metal is HT300.

Heat treat technical requirements: Ultrasonic induction quenching on the upper steel alloys and inner side of the guideway, the hardness is 67-74HS.

As shown in above picture, in order to make the temperature of the quenching rail uniform, install the same number of magnets on the preheating group and the ring of the inductor. In order to reduce the concave distortion of the guideway after quenching, the upper guideway metal is processed into a middle convex 0.20 ~ 0.25mm before quenching.

The power of the ultrasonic induction quenching equipment is 200kW and the frequency is 30~50kHz. The guideway quenching process is: the temperature is 900-920C, and the guideway moving speed is 3.3mm/s. Electric parameters: the anode voltage is 3.5kV, the anode current is 5.5A, and the grid current is IA. The cold water spray pressure is 0.15MPa.

The cooling process is also important. Rapidly cooled after quenched is very necessary. The slower cooling rate sometimes will cause cracking. Rapidly cooling is needed. so the cooling rates have to be designed.the machine guide need rapidly cool down.

Using residual heat treating self-tempering method. The left and right guideways are quenched successively, but the direction of movement of the guideways should be the same when quenched

Towards. The maximum hardness after induction quenching is 67 ~ 74HS, and the depth of the hardened layer is > 1.5mm.

The metal of the CW61100E machine tool guideway is 68HS 6815 68HS 68UHT250 or HT300, and the guideway section and hardnesses requirements are as follows

As shown in the picture

The roughness reaches Ra≤3.2μm; the sharp corners must be chamfered with C2; the hardness of the guideway surface: when its length is 2500mm, the H is >190HBW; when the guideway length is >2500mm, or when the quality is >31, the H is ≥180HBW.

Quenching equipment: quenching medium frequency power supply + self-made mobile Nao fire machine, as shown in the picture:

The inductor is made of 10mm x 10mm square pure low carbon steel pipe, and the wall thickness is required to be 1.5mm. The effective length of the inductor should be 20-30mm longer than the width of the quench outer side. For the guideway outer side with a quenching outer side width > 180mm, the use of the inductor will cause the phenomenon of fast heat in the middle and slow heat on both sides, so the inductor should be made into an arc. The arc radius R ( mm) can be calculated by the following formula:

R=Bx10+350mm

In the formula, B is the width of the quenched outer side (mm). Take the quenching outer side width of 180m as an example, R=180mm x 10 + 350mm =2150m, the plane coil is shown in the figure

When the mountain-shaped guideway is quenched, the temperature of the root of the mountain-shaped guideway is higher than that of the upper part due to the annular effect such as heat conduction and induction heating.

Therefore, the angle of the coil should be smaller than the angle of the guideway surface in the design.

The coil is shown in the picture below.

During medium frequency induction quenching, a magnetic conductor should be installed on the inductor to strengthen the magnetic field and improve the heating speed and heating temperature uniformity.

Different quenching process parameters are selected for different types of rail surfaces.

The test results are as follows: hardenss in HBW