Application of non-quenched and tempered steel on the cylinder of the comber

Non-quenched and tempered steel has the advantages of saving energy, reducing cost, reducing workpiece deformation and reducing environmental pollution. Germany, Sweden and Japan are leading in the research and application of non-tempered steel in the world, and have been widely used in non-tempered steel in China. It is used in the equipment manufacturing industry and the automotive industry, but it is still relatively rare in the textile machinery industry.

1. Combing machine cylinder shaft service conditions

The main function of the combing machine in the spinning process is to eliminate the short fibers, remove the impurities such as twisted particles in the fibers, and make the fibers further parallel and parallel, and finally make a combed strip with a relatively uniform thickness.

The cylinder part is the core component of the combing machine. It is installed in the bearing part of the cylinder drive shaft in sections. During the working process, the feeding part inputs a certain length of fiber layer, and the rear end of the fiber layer is held by the nipper plate to receive the cylinder pair. The combing of the fibers. The main drive of the comber is placed on the head of the machine. The power is transmitted to the cylinder shaft by two pairs of non-circular gears. The cylinder shaft runs through the whole machine. The head section and the tail section are connected by one long and one short. The dial is the benchmark for all parts of the machine (timed positioning). In the non-circular gear transmission, the instantaneous transmission ratio is changed, so the cylinder shaft performs the shifting motion and is composed of the variable acceleration and the deceleration motion. The technical development of the comber is focused on improving the speed of the car. The speed of the combing machine of our company is initially 290 clamps/min. The newly developed JWF1278 comber is expected to increase the speed to 420 clamps/min, which leads to the original The shaft has been deformed, the keyway is "smashed" or even broken.

At present, our company's comber cylinder shaft is processed by 55 steel quenching and tempering treatment, but the quenching and tempering treatment increases the internal stress of the shaft. The cylinder shaft belongs to the slender shaft. The deformation is large during the processing, the straightening is difficult, and the efficiency is high. Low, sometimes several additional stress-relieving treatments, not only costly, but also restrict normal assembly and production schedules. Therefore, the cylinder drive shaft not only requires high hardness and wear resistance of the bearing gear, but also has certain torsion, bending strength, and good impact toughness.

2. Test process

(1) Xilin shaft process test This process test selects two parts of the two parts: JWF1276-0612Q1 cylinder drive shaft (head), specification: f30mm×1630mm; JWF1276-0610Q1 cylinder drive shaft (tail), Specifications: f30mm × 2238mm. Cylinder shaft processing process: preparation → car processing → rough grinding → segmentation high frequency induction quenching → fine grinding → milling key groove → phosphating. Technical requirements for parts: The hardness of each section of the shaft f30mm is 60-64HRC after heat treatment, the total radial runout is ≤0.050mm, the radial runout is less than or equal to 0.030mm within 1m, and the roundness requirement is ≤0.006mm.

(2) Material selection Considering the difficulty of processing the cylinder drive shaft, the internal stress is large, the deformation is large, and the straightening is difficult after quenching and tempering. By investigating the mechanical properties and processing properties of the non-quenched and tempered steel, a suitable one can be selected. Non-tempered steel is used instead of the process test. According to the national non-tempered mechanical structural steel standard GB/T15712-2008, the direct cutting processing material F45MnVST is selected. The chemical composition of raw material 55 steel and F45MnVST is shown in Table 1.

(3) Comparison of mechanical properties The mechanical properties of 55 steel and F45MnVST are shown in Table 2. It can be seen that the yield strength of the two steels is equivalent. The tensile strength of the 55 steel after quenching and tempering is quite different from that of F45MnVST, while the plasticity and toughness of F45MnVST are slightly worse, and the hardness of the two is also comparable.

(4) Test data: High-frequency induction quenching of the long shaft by double-frequency quenching machine (twisting twice), induction coil diameter 36mm, heating temperature (880±10) °C, water spray cooling, deep well furnace tempering, 150 °C insulation for 120~150min. The surface hardness after quenching requires 60~64HRC. The actual test results of the two materials are shown in Table 3, which meet the requirements.

Grinding is performed using a centerless grinding machine. Each grinding is straightened. After the grinding is completed, the radial runout and the roundness of the quenching section are checked (see attached drawing). The maximum radial runout and the roundness of the quenching section are shown in Table 4 to Table 7.

After 4 to 6 times of grinding, the dial gauge measures the radial circular runout, and the total length is 0.05mm, which meets the requirements; the dial gauge measures the roundness of the quenching section, and the required roundness does not exceed 0.006mm, which meets the requirements. The original 55 steel has a large deformation after quenching and tempering, and the roundness requirement should be relaxed to within 0.010 mm.

3. Comparison of hardened layers of two materials

After the 55 steel quenching and tempering and F45MnVST two materials, each of the f20mm×250mm test bars was fabricated. After the high-frequency induction quenching was performed on the same dual-frequency quenching machine with the same quenching parameters, the surface hardness and the hardened layer depth were analyzed. The results are shown in Table 8.

After quenching, the surface hardness of 55 steel is 890HV0.05, Rockwell hardness is 66HRC, and the hardened layer depth is 1.5mm. After F45MnVST quenching, the surface hardness is 800HV0.05, Rockwell hardness is 63HRC, and hardened layer depth is 1.75mm.

It shows that under the same quenching conditions, the hardenability of non-quenched and tempered steel is higher than that of 55 steel, and the hardenability is lower than that of 55 steel. Since non-quenched and tempered steel has a large content of Si and Mn, and a small amount of alloying elements such as V and Ti are added, the hardenability is high; and the carbon content is lower than that of 55 steel, so the hardenability is low.

4. Test results

(1) The method of F45MnVST replacing 55 steel processing comber cylinder shaft is feasible, and the data after heat treatment and machining can meet the requirements of drawings.

(2) Non-tempered steel parts have significantly reduced deformation compared with quenched and tempered parts during high-frequency induction hardening and grinding. The difficulty of straightening is reduced, the production efficiency is greatly improved, and the production cost can be reduced after batch use.

(3) Non-tempered steel has been widely used in the domestic automobile manufacturing industry, and should be vigorously promoted in the textile machinery industry, especially long-axis parts requiring micro-deformation.

About the author: Cheng Qinghong, Zhao Tingjie, Hu Liying, Jingwei Textile Machinery Co., Ltd. Yuci Branch, Technical Department.