China titanium piping solution supplier: www.titaniuminfogroup.com

Research on Processing Technology of Titanium Alloy Flange

Flanges are titanium alloy parts, parts material grade DMD0776 equivalent to domestic grade TC6, in the parts of the structure itself is more complex, and there are special processes shot peening process.
Procedure, to the reasonable arrangement of the process has increased the difficulty. Therefore, in the actual processing, we must go through several trial processing, data analysis of inspection results, process improvement and other technical measures to solve the parts in the process of deformation and other problems.
In the actual machining, it is necessary to go through several trial machining, data analysis of inspection results, process improvement and other technical measures to solve the problems of deformation of titanium alloy flanges during machining. This paper focuses on the whole process of titanium alloy flange processing and the solution of key problems and measures.

1. Overview

Titanium alloy flange is an important part of the engine, material DMD0776, belongs to the titanium alloy series; parts size tolerance is strict, a total of 96 holes in the circumferential direction, of which 24 holes tolerance Ф6.35 + 0.015, and the hole relative to the reference A, B, C position degree of 0.1mm; parts processing deformation is large, the parts are seriously affected by the temperature during machining, before and after the shot peening, Part state also has a large difference, is the entire development of new parts in the process of a difficult hurdle.

2. Material characteristics analysis

Titanium alloy in the DMD0776 specification for TA6, belongs to the alpha alloy, the organization is stable, but can not be heat-treated to strengthen, room temperature strength is not high. Without β-stable elements, the tensile strength is 736~981Mpa, and the plasticity is good.

3. Flange process route

After the process review, the process route is arranged as follows: rough material – repair benchmark – semi-finish turning rear end – semi-finish turning front end profile – corrosion inspection – marking – processing inner ring hole and lace – deburring – finishing turning front end – deburring – finishing turning rear end – processing outer ring hole and groove – deburring – processing rear end face groove – deburring – fluorescence inspection – cleaning – surface trimming – shot blasting – decontamination – final inspection

4. Key dimensions and machining difficulties (see Figure 1)

(1) Ф6.35+0.015 hole and hole position degree 0.1mm; (2) flatness 0.03mm; (3) 15.9±0.075mm; (4) 11±0.1,9.7±0.1mm.

20221204002415 10108 - Research on Processing Technology of Titanium Alloy Flange

Figure.1

5. Turning process analysis

5.1 Rough turning and semi-finishing turning process

The incoming state of the titanium alloy forgings after stabilization of the surface of the parts as a benchmark for the repair process, and the use of CNC horizontal turning for processing, so the use of a small margin to repair the benchmark, to ensure the technical conditions that the flatness and finish machining processing method, this approach not only ensures the flatness of the parts, but also to ensure the surface roughness of the parts.

5.2 Fine-turning process

Not only follow the finishing process of semi-finishing turning, but also follow the trend of deformation of the parts through experiment, and find the law that the size can not meet the requirements of the drawing due to the plastic deformation of the parts by the action of the tool during processing due to the soft material, and control in the program to ensure the dimensional requirements of the drawing, the program control is shown in Figure 2, and add two diagonal lines in the program to ensure the size 5±0.1mm equal thickness.

20221204002431 24781 - Research on Processing Technology of Titanium Alloy Flange

Figure.2

6. Machining allowance analysis

The material is a hard to machine material, often with a strong tendency to work hardening and high temperature strength, making its machinability even worse. Titanium alloy material thermal conductivity is poor, resulting in high cutting temperature, reducing the durability of the tool; 600 ℃ above the temperature, the formation of hard oxide layer on the surface, the knife has a strong wear effect; low plasticity, high hardness, so that the shear angle increases, the chip contact length with the front tool surface is very small, the front tool surface stress is very large, the blade is prone to breakage; low modulus of elasticity, elastic deformation, near the back of the workpiece surface rebound amount Therefore, the contact area between the machined surface and the back tool surface is large, and the wear is serious. Therefore, according to some foreign technical data, the following scheme is used for milling this part:

  • (1) Milling speed should not be too high: due to the high strength of titanium alloy, viscous, cutting easier to generate and accumulate heat in the cutting area, coupled with poor thermal conductivity, in the large removal of milling, if the milling speed is too high, there is a risk of combustion, so the parts use 120m / min.
  • (2) Try a larger depth of cut: improve the efficiency of processing can be obtained by increasing the depth of cut, in the milling process, the program each time the depth of cut up to 6 mm.
  • (3) The amount of feed per tooth should be moderate: titanium alloy cutting temperature is high, while there is the problem of hardening. Each tooth feed is too large, the cutting force is too large and lead to high cutting temperature and burn; and each tooth feed is too small, the cutting edge always work in the hardened layer and wear too fast, so the feed per tooth is 0.08-0.1mm.
  • (4) The use of downstream milling: for downstream milling, the tool teeth start cutting into the hard skin and easily lead to tool breakage; but because of the reverse milling cutting is from thin to thick, in the initial cut into the tool is easy to dry friction with the workpiece, aggravating the tool sticky chip and chipping, in the case of titanium alloy, the latter contradiction is more prominent, so in the process of processing this part, are used downstream milling.

7. The choice of drilling tools

The hole diameter and depth of the part are not high, the machine tool spindle runout is small, and the surface roughness is high, so the integral alloy drill bit is selected, for the titanium alloy heat is not easy to exclude, the internal cooling tool is selected, and the sharp cutting edge drill bit is selected, so that the hole processing is very easy.

8. Solution for deformation after blasting

Due to the special relationship between the structure of the parts and the shot, the parts after the shot deformation, the size of the larger tolerances do not have a significant impact on the tolerances and directly affected by the size of the shot serious impact, the main impact on the size of:

  • (1) Ф6.35 +0.015 hole position degree 0.1mm: before blasting hole position degree control within 0.1mm, after blasting hole position degree that there is a serious excess of poor parts.
  • (2) Ф6.35 +0.015 hole diameter, due to the hole shot, hole tolerances and strict, so in the blasting parts after the more serious excess.
  • (3) 11 ± 0.1mm, 15.9 ± 0.075mm, 9.7 ± 0.1mm and other sizes have a small change, but if the process size processing to the limit, the small change is enough to make the parts exceed the poor.

In response to the above problem, the following work was done to solve the problem:
Coordinate measuring machine to detect the position of the hole before and after the shot, to find the deformation trend of the part after the shot, through the test will be changed to the program, to the shot deformation to leave a margin, to get better results, while the hole position tolerance in the process to shrink tight, to the hole position after the shot to leave a deformation; in the process of processing, the hole position of the part is controlled at R211.98 theoretical diameter, to the shot to leave a margin of 0.02 margin, after blasting, the part deformation, hole position at R212 theoretical diameter, position degree is exactly in the qualified range; change trend is shown in Figure 4.
By comparing the data to find the deformation trend of the part, the inner ring of the part is fixed with a special fixture when shot peening, and the whole part cannot be deformed when shot peening the outer ring. Through the above control, the hole position degree is well controlled.

By comparing the data of the hole diameter before and after shot peening, the change law of the hole diameter of the part before and after shot peening is found, and the process is controlled by the machining. Fig. 3 shows the program roadmap of the rough milling lace, with a margin of 30mm and a total of 5 cuts to complete the rough machining.

20221204002451 85751 - Research on Processing Technology of Titanium Alloy Flange

Figure.3

20221204002507 12578 - Research on Processing Technology of Titanium Alloy Flange

Figure.4
11±0.1mm, 15.9±0.075mm, 9.7±0.1mm and other dimensions in the process if processed to the limit, after the shot blasting, the size is easy to exceed. The process of these three dimensions are shrunk to 11 ± 0.05mm, 15.9 + 0.075mm, 9.7 ± 0.05mm, leaving enough margin for the shot blasting, after the shot blasting, the part changes, both to ensure that the size of 11 ± 0.1mm, 15.9 ± 0.075mm, 9.7 ± 0.1mm in the tolerance range.
The above control scheme is to find the law of change before and after the blasting, using the machine processing method to control the final dimensions, and to meet the tolerance requirements of the drawings. After adopting the processing route and the adjusted parameters, the part passed the final inspection once and finally got the quality certification from the customer.

Conclusion

The machining process and the intermediate control process of the part completely guarantee the conformity of the part, and the finished part fully meets the requirements of the design drawings, and the forming process and the finished part pass the final acceptance, making a breakthrough in the machining control and special process.
SourceChina Titanium Alloy Flange Manufacurer: www.titaniuminfogroup.com

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