Side Column Manufacturing Process Research
The side column is the key part of the side wall of the railroad wagon open car, is the main stress parts in the side wall, the cross section is mostly cap type. In the company’s export railroad wagons, for the first time, 12mm thick cap steel side columns are used, and the manufacturing of the side columns has become one of the main difficulties of the car.
Side Column Structure Analysis
The part diagram of the side column of the export railroad wagon is shown in Figure 1, the material is Q450NQR1 and the quantity is 4 pieces/vehicle. The manufacturing difficulty of this part is that the plate is thicker and the cap section forming is very difficult.
- Side column manufacturing solution determination
- Cap section steel side column manufacturing scheme mainly has two kinds of cold-formed steel scheme and bending scheme.
Cold-formed steel solution
Cold-forming is the continuous lateral bending of coils, strips and other metal strips through sequential configuration of multiple forming rolls to make profiles with specific cross-sections. The sections made by cold-forming are called cold-formed sections. In China’s railroad wagons open car, from 60t open car to 70t open car, and even 80t open car, cap steel side column mostly using cold-formed steel. In the export car, the cap steel side columns also mostly use cold-formed steel. In view of this, at the early stage of the design of the car, the three parties, design, technology and material, specified the manufacturing process plan of cold-formed steel for the cap section steel side columns.
The previous cold-formed steel side columns had a maximum thickness of 8 mm and a maximum yield strength of 450 MPa, while the side columns had a thickness of 12 mm and a yield strength of 450 MPa, which required new shaped rolls to manufacture. The main advantage of this solution is the stable manufacturing quality and high production efficiency. The disadvantage of this solution: First, the manufacturing cycle is long, the manufacturing cycle of new shaped rolls is about 1 month, and the manufacturing cycle of cold-formed steel side column is about 1 month after manufacturing and shipping, so the manufacturing cycle takes about 2 months in total; second, the manufacturing cost is high, the price of cold-formed steel per ton is about 1500 yuan higher than steel plate, and the side column needs new shaped rolls, so the manufacturing cost is higher. The production schedule of the car is urgent, requiring 1 month to complete the trial production, and then immediately followed by mass production, therefore, the cold-formed steel program was rejected because the production schedule could not be guaranteed.
Bending And Pressing Solution
In the historical model, the side pillars of the cap section steel are manufactured by bending process, the thickness of the side pillars is 6mm, and the material is Q450NQR1. In the second bend of the inside of the side pillar bending, in order to avoid interference, the bending upper die as shown in Figure 2 must be used, this type of bending upper die is called gooseneck bending die, commonly known as crooked neck tire. Crooked neck tire in the bending process, the state of force is poor, there is a tendency to break, so the use of crooked neck tire bending cap steel side column is generally thin, not more than 8mm. crooked neck tire cross-section shape size is generally referred to the previous bending parts, and then combined with the actual production experience.
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In the beginning of the design of the side column of the export railroad wagon thickness 12mm, had considered using the bending program manufacturing, but because there is no suitable crooked neck tire, and there is no precedent of using crooked neck tire bending, crooked neck tire is likely to break, there is a great safety risk, so give up the bending program, using cold-formed steel program.
After the cold-formed steel solution was rejected, the bending solution was put back on the agenda and the feasibility of the bending solution was studied and analyzed urgently.
The bending solution requires new crooked neck tires, and the production cycle is about 25 days, which can meet the schedule requirements of trial production and mass production: the new crooked neck tires of the bending solution need to cost 40,000 yuan for tooling, and the cost of bending side columns is lower than that of cold-formed steel side columns by about 1,000 yuan per ton, and the completion of mass production can greatly reduce the manufacturing cost, which is feasible from the cost analysis.
Through the above analysis, the bending and pressing program becomes the only side column manufacturing. Process solution. The key problem to be solved in the bending solution is to design and manufacture suitable crooked neck tires and to avoid the risk of breaking the crooked neck tires.
Side Pillar Manufacturing Process Development
Bending Machine or Press Brake Selection
By analyzing the side column parts diagram, combined with the bending lower die, using the empirical formula to calculate the bending force, and then according to the bending, force selection CNC bending machine.
Side column parameters b = 2530mm, = 12mm, = 600MPa, L = 100mm, calculated P ≈ 3240000N, that is, the need for 324t bending force, so the choice of CNC bending machine rated bending force should be greater than 324t.
2. The length of the side column is 2530mm, so the effective bending length of the selected CNC bending machine should be greater than 2530mm.
3. The weight of the side column is 102.23kg, so the corresponding tooling should be considered to reduce the labor intensity of the operator.
4. Comprehensive above factors, we choose 500t CNC bending machine. The bending machine has a rated bending pressure of 500, an effective bending length of 5m, and a hydraulic lifting platform.
Crooked Neck Tire Bending Mold Design
The Creo software was used to design the crooked neck tire. The side column was used as the design reference, and the whole side column was rotated to the vertical position of the corner parallels of the second inner bend, which is the center line of the pressure of the crooked neck tire, and the shape of the crooked neck tire section was designed by considering the rebound of the side column. At the same time, in order to facilitate the operator to remove and replace the crooked neck tire, the crooked neck tire should be designed in pieces, the number of pieces should not be too many, and the weight of each piece should not be too heavy.
The maximum stress must be less than the yield strength of the crooked neck tire material, and the strength of the crooked neck tire should be checked according to this.
According to the above process, after repeated corrections, a reasonable crooked-neck tire is obtained, which has sufficient strength, safe and reliable, and can be easily dismantled and replaced. The schematic diagram of design and strength check is shown in Figure 3.
Side Column Production Site Process Control
According to the side column parts diagram, according to the neutral layer theory, the unfolding size and the bending line size of each bend are calculated. After the crooked neck tire is manufactured, it is installed on the CNC bending machine and bent according to the unfolded size and the bending line size of each bend. When bending the first bend, gradually increase the bending pressure. Until it can be folded and formed, according to the actual folding pressure of the CNC folding machine and the experience formula calculated folding pressure for comparison, to verify the accuracy of the experience formula.
When the folding pressure is set to 300t, can be folded and formed, verify the empirical formula is more accurate, in order to improve the efficiency of folding, the actual production folding pressure is set to 400t. record each bend folding pressure on the block size data, folding pressure when using the sample plate test folding angle and shape. After the trial bending of the side columns is completed, the dimensions are checked to verify the accuracy of the unfolded dimensions and the bending line of each bend, and according to the corrected data, the bending dimension data of each bend is adjusted and recorded. During batch production, the parameters of the trial production were called and the pair of block folding was pressed as shown in Figure 4, which significantly improved the production efficiency and successfully completed the production of 200 Argentine coke open wagons.
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