Research on the Law of Affecting the Quality of forging Metallurgy Quality on the Quality of Wedge Horizontal Rolling Mold

Drawing on the traditional and mature cross wedge rolling forming technology for stepped shaft parts, it is innovatively applied to the high-efficiency and low-cost manufacturing of blade preforms with special-shaped sections. Under the action of the rollers, the material undergoes radial compression deformation and axial extension deformation, and the blank changes from a uniform cross-section to a variable cross-section, which is in the shape of a stepped shaft. Forming, to prepare a blade preform with deformed cross-section characteristics. Then, the cooled blade preform is heated again and placed in a precision forging die. Under the action of the unidirectional compressive stress of the upper and lower dies, the blade preform is compressed and deformed, filling the die cavity with the smallest volume, thereby realizing precision forming of blade forgings. In the process parameters of the horizontal wedge rolling mold, the effect of forming angle has the greatest impact on center damage.


Introduction
Aero-engine forged blades are complex-shaped structural parts with tenon, thin blade body and twist angle, and even high and thin damping bosses on both sides.Forging blades abroad are also formed by billet and die forging methods.The cylindrical bar first changes its shape through the blanking process, and evolves from the original uniform cross-section to a variable cross-section to realize the pre-forming of special-shaped structures such as blade tip, blade body, tenon and damping boss [7][8].Then, through the die forging process, each part of the blade preform that has the characteristic of deformed section is further formed, so as to complete the final forming, and obtain the blade die forging with a machining allowance of 1 to 1.5 mm.
According to statistics, there are three traditional billet making methods for titanium alloy blade forgings abroad: one is extrusion + upsetting technology; the other is local aggregate upsetting technology (as shown in Figure 1); the third is cross wedge rolling technology (see Figure 1) 2).The first two technologies are general technologies, and the third cross wedge rolling technology is in the research stage, which is the direction of foreign exploration and development, and has not been applied in engineering yet.
Extrusion + upsetting technology (see Figure 1(a)), the equipment is usually an ordinary press, although the cost of a single process is low, but due to the increase in the number of processes, each time the titanium alloy blade blank is heated, only one process can be completed.It should not exceed two processes at most, that is, the simultaneous pre-forming of the blade tip, blade body, tenon and damping boss cannot be achieved at the same time.In addition, every time the titanium alloy billet is heated, a series of auxiliary processes such as sand blowing, corrosion, and glass lubricant coating need to be performed again, which increases the instability of the process and the cost of the entire process.In addition, during the extrusion process, the heat treatment technology caused by internal deformation is difficult.If the heat is not dissipated in time, it will easily lead to a large local temperature rise, which will seriously affect the microstructure of the titanium alloy extrusion.Moreover, the titanium alloy billet is in contact with the mold for a long time.Under the action of friction, the billet is easy to adhere and the mold is easily damaged.
In the localized upsetting technology (see Figure 1(b)), the equipment (flat forging machine) and the die are all dedicated, resulting in high equipment and process costs, and the microstructure is not uniform due to process characteristics.However, compared with the extrusion + upsetting technology, the local aggregation upsetting technology reduces the process and saves the material.
Figure1.Uniaxial compression deformation routing At present, the United States, Japan, Russia and other countries mainly use horizontal forging machines to carry out partial aggregate upsetting process on the blade head or crown to make blanks, while the United Kingdom, Germany and other European countries mainly use extrusion + upsetting with multiple sets of dies.The preform is obtained by the rough combined preform method [9][10][11].
In recent years, the pursuit of a short process and low cost in the manufacturing process of highperformance aero-engine components to achieve efficient and precise manufacturing has gradually become the development direction of foreign manufacturing technology [12][13].According to the research results published in 2008, two German researchers took the lead in trying to add the cross wedge rolling process to the blade preform preparation process.As shown in Figure 2, it is an optimized titanium alloy blade preparation process based on the cross wedge rolling process.The cross wedge rolling process replaces the original extrusion process and upsetting process.

Experimental materials and methods
As a traditional step shaft preparation technology, cross wedge rolling technology is applied to the preparation of blade preforms with stepped special-shaped sections, which has obvious advantages in terms of process feasibility, equipment and process costs [14][15].First, through cross wedge rolling, the original geometric shape of the raw material bar is changed, the middle is thin, and the two ends are thick, that is, the tenon, blade tip and blade body of the blade forging are preformed.Therefore, the cross wedge rolling process can achieve blade prefabrication.The requirements and effects of the specialshaped billet; second, with the help of the cross-wedge rolling process, the cross-sectional area of the blade bar along the axial direction is no longer the same, and the original material bar after rolling, presents a stepped distribution, that is, a "type" It can be seen that the cross-wedge rolling process can also meet the requirements of changing the cross-section of the blade preform; third, the cross-wedge rolling process can simultaneously complete the preparation of two or more titanium alloy blades in one process.Improve the production efficiency and reduce the cost of the preparation process; fourth, the equipment used in the cross wedge rolling process has a simple structure, and the focus is on the design of the roll shape.The cost of cross-rolling equipment can be reduced by 70-80%; fifth, through the simplification of the process, the problems of repeated heating, correction and lubrication of the billet caused by the extrusion + upsetting process no longer exist, which improves the stability of the process and reduces the The size margin of the preform is increased, and the utilization rate of the material is improved.
In order to thoroughly study the formation mechanism of central injury during the cross -rolling blank process, different degrees of damage need to be obtained.Therefore, we have chosen a broader mold process parameter (as shown in Table 1) and cause center damage under different conditions.
Table 1 The mold process parameters during the test process

Results and Analysis
A coefficient K can be used to measure the degree of stretching and deformation in the process of compression: k = ∑ (  −   )/   =1 (1) Among them, Δ_ε i and Δ_hangti are peaks and valleys in the relative stretch and deformation phase, respectively, and Δ_εf is the final compression deformation.Compared to stretching deformation (Δ_ερi-Δ_εTi) and under the action of horizontal tensile stress, it leads to the separation of nondeformation crispy miscellaneous objects from the matrix, and it is easy to form microres.When the forging blank is rotated during the rolling process, the micro-holes repeatedly stretch-compressed deformation repeatedly under the action of horizontal stretching and radial compression, resulting in repeated opening and closing.If the K value is greater than 1, it means that the relative stretching and deformation exceeds the overall compression deformation, and the trend of the micro -hole cannot be closed at the end of the forming process, showing an absolute stretching and deformation state.Therefore The degree of damage caused by stress.
The impact of the forming angle on the central deformation is shown in Figure 3.Under the condition that the stretching angle is 10 ° and the end surface contraction rate is 75%, during the rolling process, there is a large alternate cutting deformation and relative stretch deformation.As the forming angle increases from 15 ° to 25 °, the number of cycles of alternating cutting and deformation decreases, as shown in Figure 3 (a), the compression deformation is shown in Figure 3 (b).As shown in Figure 3 (b), the K values are 15 °, 20 °, and 25 °, respectively, and 1.14, 0.85, and 0.66, respectively.When α = 15 °, K is far greater than 1, indicating that the absolute stretching and deformation state of the forging center is prone to center damage.Figure 4 represents the center damage of the forging blank at different forms of formation.When α = 15 °, there is a central injury in the forging blank, with a maximum diameter of 2.3mm, which obviously displays the form of shear damage.With the increase of the forming angle, the degree of center damage decreases.When α = 20 °, there are some micro -pores near the center, showing the macro structure of porosity.When α = 25 °, the micro -structure of the forged blank is good, and its pore degree is less than 0.5.Therefore, the number of cycles and stretching deformation coefficients alternately reduced with the increase of the forming angle, resulting in a reduction in central injury.
Figure 4.The impact of central damage when the stretching angle is 10 ° and the section of the section of 75%(A) 15 °, (B) 20 °, (C) 25 ° The impact of stretching angle on the center damage is shown in Figure 5.Under the condition that the formation angle is 15 ° and the section shrinkage rate is 75%, as the stretching angle increases, the shear deformation increases significantly, but the corresponding loop decreases proportionally, as shown in Figure 5 (a), so it is therefore shown in Figure 5 (a), so The effects of shear deformation and circulation have weakened each other.The compression deformation is shown in Figure 5 (b), of which the K values are 0.7, 0.83, and 1.14, respectively, corresponding to the stretch angles in 5 (b), respectively, respectively, respectively, respectively.With the increase of stretching angle.The impact of the stretch angle on the center injury is shown in Figure 6.All forgenal blanks formed at different tensile angles have central injuries.The maximum diameter center cavity is 0.5, 1.6, and 2.3mm, respectively, corresponding to stretch angles of 5 °, 7.5 °, and 10 °, respectively.Therefore, the increase in stretching and deformation has led to an increase in central injury, but the impact of stretching angle on center injury is far less than the effect of formation angle.The impact of section contraction rate on the central deformation is shown in Figure 7.Under the condition that the formation angle is 15 ° and the stretch angle is 10 °, as the section contraction rate increases, the shear deformation increases significantly, as shown in Figure 7.The compression deformation is shown in Figure 7 (b), of which the K value is 1.41, 0.97, 1.08, and 1, respectively, corresponding to the section contraction rate of 15%, 35%, 55%, and 75%.It is very high, so it mainly affects the beginning and growth of the micro -pores relative to stretching and deformation.In addition to the section shrinkage rate of 15%, shear deformation and stretching deformation have increased with the increase of the section contraction rate.When the sectional contraction rate is 15%, the absolute stretching and deformation of the forging center is the strongest.
The impact of the section contraction rate on the center damage is shown in Figure 8.All forging blanks formed in different areas have central injuries.The maximum diameter of the center injury is 4.6, 0.12, 0.5, and 2.3mm, respectively, corresponding to the section contraction contraction.The rate is 15%, 35%, 55%, and 75%.Except for the section shrinkage rate of 15%, it is consistent with the cutting and stretching.When the section contraction rate is 15%, the cutting deformation is less, but because it is strong Absolute stretching and deformation, micro -pores are more likely to start and grow.

Conclusions
As a traditional step shaft preparation technology, the cross wedge rolling technology is applied to the preparation of blade preforms with stepped special-shaped sections, which has obvious advantages in terms of process feasibility, equipment and process costs.This article uses scanning electron microscopy to study the micro structure and appearance of the horizontal wedge -rolled billet, and analyzes the

Figure 2 .
Figure 2. Preparation process of titanium alloy blades for aero-engine after optimization based on cross wedge rolling process of reduction in area 75 75 75 75 75 75 75 75 75 75 75 75

Figure 3 .
Figure 3.The impact of the center deformation of the center deformation when the stretch angle is 10 ° and the section shrinkage rate of 75%(A) (b) compress the deformation.

Figure 5 .
Figure 5.The impact of the central deformation of the stretching angle on the forming angle of 15 ° and the section of the section is 75%(A) shear and deformation, (b) compression deformation

Figure 6 .
Figure 6.The impact of central injury on the formation angle of the forming angle of 15 ° and the section of the section is 75%, (A) 5 °, (B) 7.5 °, (C) 10 °

Figure 7 .Figure 8 .
Figure 7.The effect of the forming angle of 15 ° and the stretch angle of 10 ° deformation of the intermittent surface deformation (A) Cut and deformation, (b) compression deformation