The independent walking platform of CNC double-column vertical lathes produced by our company has a set of guide blocks (see Figure 1). They are connected in a straight line from end to end, and they are attached to the column and are equivalent to two rolling guides. The walking platform can be raised or lowered by rolling along the guide block to meet the use requirements. The design uses a 45-steel material with a flat butt-joint method. The hardness of the two rolling surfaces of the guide block is required to be 52 to 57 HRC. Quenching and heating the car as shown in Figure 2.
There are problems: 1 Because the original design of the 12 combined with the sinker hole from the side of only 5 mm, if the hole is made before quenching, it is easy to increase the stress deformation or even cracking, hardened surface hardness of the countersink surface is increased and difficult Processing. 2 Both ends of the quenched surface and one side are right-angled. When quenched and heated, it is easy to overheat and cause cracking or thawing deformation. The combined guide rail is a rolling guide rail. No soft space with voids and low hardness is allowed between the guide rails.
First, the solution
In response to the above issues, we take the following measures:
(1) After looking at the assembly drawing to understand how it is used, we recommend to the designer that the hole is moved inward so that the edge of the hole is more than 10 mm from the side.
(2) Communicate with the technologist and request it to be processed after countersinking.
(3) In order to ensure that the two mating surfaces meet the requirements for use, the total length of the workpiece is increased to 6 mm, and the chamfers at both ends are 3 × 45°. After quenching, they are removed by machining.
(4) For the right-angled side of the quenched surface, use a partially-inserted magnet to reduce the heating of the sharp corners (see Figure 3).
Second , the production process
The production process of the guide block is: forging → normalizing → straightening → thermal aging → machining → intermediate frequency induction quenching → straightening → tempering.
Normal fire
Normalizing after forging can refine the grain structure, increase the dimensional stability of the part, and reduce the subsequent intermediate frequency quenching deformation and cracking tendency. For a forging blank that has been bent more than 2 mm after normalizing, the flatness is to be kept within 2 mm, and the hot straightening (stress relief annealing) is performed after the straightening.
2. IF quenching
2 MPa以上。 (1) Ready to prepare a flat sensor, contour horn, plane quenching sample, start the device, adjust the sensor water pressure, so that the water spray, the water pressure in the 0. 2 MPa or more.
(2) Debugging Based on the quenched area of ​​the workpiece and the capacity of the equipment, we have improved the length of the sensor and can simultaneously inductively quench the surface of 2 to 3 workpieces. Adjust the output voltage, current, moving speed, distance from the workpiece to the workpiece and other parameters on the copy test block to meet the quenching requirements.
(3) quenching due to machining the workpiece chamfer grinding on both sides of the processing volume is too large, long production cycle, it is recommended to cancel the chamfer, direct quenching. In order to solve this problem, after several trial heating on the sample, we found a solution: align the workpiece and make a mark, the workpiece spacing is about 20 mm, adjust the gap between the sensor and the workpiece, use the starting point The wooden mat raises the sensor by 2 mm and shifts it to the right by 2 mm, as shown in Fig. 2. The sensor does not heat the sharp corner but instead heats the sharp corner by 2 mm. The heat is applied to heat the sharp corner. To the quenching temperature, pull out the wood mat, and the sensor will restore the original debugging gap. At this time, the water can spray cold on the sharp corner and start the equipment for continuous quenching. When the preheating ring has passed the termination, the induction heating is stopped. At this time, the terminal temperature has been heated to 860-880°C, and the water is continuously sprayed to complete quenching of the terminal part. (4) Turn over the workpiece, align it with the mark, repeat the above process, and complete the quenching on the other side.
3. Inspection
The hardness after quenching is 55～61HRC, there is no cracking and thawing at the sharp corners, there is no quenching soft band, the hardness is 53～55 HRC after tempering at 200°C for 3h, which meets the design and use requirements.
Third, the conclusion
Through the research on the heat treatment process of the guide block, the measures to prevent the overheating of the corners were found—the use of locally-inserted magnets and a height-increasing sensor to reduce the heating at the corners, and at the same time, an inductor was heated at the same time. A guided block process reduces the amount of machining at the machine guide, improves production efficiency, reduces production costs, and ensures product quality.
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