KR100957984B1 - Friction welding process of Two-stroke Diesel engine turbocharger rotor shaft - Google Patents

Abstract

The present invention relates to a turbocharger rotor shaft friction welding method for a large diesel engine, the object of which is a turbocharger rotor for a large diesel engine that can integrate the turbocharger rotor shaft used for large engines by friction welding of disk and shaft. It is to provide a shaft friction welding method.

The present invention provides a disk forming step of forming a disk by die forging; A friction welding step of forming a rotor shaft by integrating a shaft with the disk by friction welding; And a heat treatment step of heat treating the rotor shaft integrated by the friction welding.

Rotor Shaft, Turbocharger, Disc, Shaft, Forging

Description

Friction welding process of Two-stroke Diesel engine turbocharger rotor shaft}

The present invention relates to a turbocharger rotor shaft friction welding method for a large diesel engine, and integrates a disk and a rod made of the same material by friction welding, and post-processes the material properties similar to the one-piece (mechanical properties, yield strength, The present invention relates to a turbocharger rotor shaft friction welding method for a large diesel engine having an elongation, section shrinkage, impact value, and fatigue test.

The turbocharger is a supercharger for improving engine power. It converts the exhaust gas heat energy emitted from the engine into mechanical work and rotates the compressor to inhale and compress the air in the engine room to generate high density air. To improve the combustion explosion pressure.

Rotor Shaft is the core of turbocharger components, where turbine blades, compressor wheels and bearings are assembled, exposed to high temperatures of about 450 ° C by exhaust gas on the turbine blade side, and high speed (about 15,000 on the compressor wheel side). rpm).

The material of the rotor shaft is creep-resistant forged steel, and its material name is SFCMV1, a maker's unique material, and contains 0.25% of "V" compared to general low alloy steel, so that the quenching and tempering temperature is higher than that of general alloy steel.

The conventional turbocharger rota shaft adopts an integral free forging material in order to obtain a more homogenized material suitable for a specific use environment such as about 450 ° C. and about 15,000 rpm.

However, the rotor shaft is manufactured in one piece by the free forging method, but the ingot shaft, the forging shaft, and the machining shaft must coincide with each other due to the characteristics of the rotating shaft, and the uniform forging density must be maintained over the entire surface. (Unbalance amount: Max. 1g) Since it requires high level of forging technology know-how, it is currently produced only by some overseas advanced companies, and in reality, domestic production is impossible, so we have to rely on 100% import until now. This has led to the expansion of the trade deficit and the deterioration of foreign competitiveness.

The present invention is to solve the above problems, the object of the turbocharger rotor shaft used for large-sized engine divided the disk and the shaft, the disk to obtain a uniform forging through the die forging operation, the shaft after the first forging The secondary rolling process also provides sufficient rolling ratio (13S) and circumferential and axial uniform forging density, and then provides a turbocharger rotor shaft friction welding method for a large diesel engine that can integrate the two components by friction welding.

Another object of the present invention is to establish a process and conditions for a turbocharger rotor shaft heat treatment for a large diesel engine to integrate disks and shafts of the same material by friction welding and heat them to have the same or similar quality as an integral forging material. To provide optimum friction welding conditions.

Another object of the present invention was to set the optimum heat treatment and friction welding conditions to achieve the mechanical properties and other physical properties of the friction welding part to have the most similar properties to the integral forging material.

Still another object of the present invention is to provide a turbocharger rotor shaft friction welding method for a large diesel engine, which can reduce cost cost through localization of materials and processing.

The present invention provides a disk forming step of forming a disk by die forging; A friction welding step of forming a rotor shaft by integrating a shaft with the disk by friction welding; And a heat treatment step of heat treating the rotor shaft integrated by the friction welding.

The disk forming step is to perform a die forging after the first upsetting of the material to form a disc, and to anneal the die forged disc and then rough machining.

The friction welding step includes a first welding step of welding the disc and the shaft by the rotation and inertia force of the friction welder flywheel, and a second step of pressing the disc to the disc by pressing the shaft.

In the heat treatment step, the metal properties changed at the friction surface and the heat affected portion by friction welding by the quenching and tempering process are maintained as materials inherent to the inherent mechanical properties of the raw materials.

As described above, the present invention is to form a rotor shaft by friction welding of a disk with a diameter of 400 mm to 700 mm and a shaft, and is used in a large engine without newly investing a separate forging facility for manufacturing an integral free forging material. It is possible to produce a turbocharger rotor shaft.

In addition, the present invention can utilize the domestic production equipment and domestic friction welding technology, localization of the material is possible, not only the technical accumulation, but also to improve the quality as well as to significantly reduce the production cost cost has the effect of securing the national competitiveness. .

In addition, makers (Mitsubishi Heavy Industries) have assembled rotating bodies (campresser wheels, turbine blades, bearings) as a single type and introduced them in Korea through the localization of rotor shafts. It is also possible to secure assembly technology for rotating bodies.

In addition, the present invention is to form a rotor shaft by integrating the same material by friction welding, and to heat it, it has the same mechanical properties and quality as the rotor shaft of the same material by free forging.

In addition, since the present invention is to form a disk and a shaft, and then friction welding it, it is possible to minimize the loss of the material, to obtain a uniform forging quality, and also to reduce the time required for manufacturing, which has a significant effect on cost reduction. You can expect

In addition, the present invention can be formed of a material equivalent to the inherent mechanical properties of the raw material on the friction welding surface according to the friction welding of the same material disk and shaft through the optimum heat treatment conditions and friction welding conditions.

In addition, the present invention has a number of effects, such as to further integrate the disk and the shaft by adding a primary welding, secondary pressure welding process.

1 is an exemplary block diagram showing the flow of the manufacturing process according to the invention, Figure 2 is a photographic illustration showing the flow of the manufacturing process according to the present invention, the present invention is to form a disk by die forging Disk forming step (S100); Friction welding step (S200) of forming a rotor shaft by integrating the shaft to the disk by friction welding; It is to include a heat treatment step (S300) for heat-treating the rotor shaft integrated by the friction welding.

The disk forming step (S100) forms a disk by die forging, and after roughing the die forged die for roughing, and has a forging material of Ø400mm to 700mm diameter.

The shaft manufacturing process uses a homogeneous material having a diameter of Ø90 mm to 150 mm after the first forging with the ingot, and the second rolling, and after the roughing, friction welding with the disk.

At this time, the disk 10 and the shaft 20 has a material specification as shown in Table 1 below.

Table 1

The friction welding step (S200) consists of a primary welding step (S210) for welding the disk and the shaft by the rotational force of the disk, and the secondary welding step (S220) for welding the disk and the shaft by pressing the shaft to the disk. have.

That is, the friction welding step (S200) is to provide a rotational force to the disk, the friction welding of the disk and the shaft using the relative friction heat generated by pressing the shaft at a constant pressure.

At this time, the disk 10 has a rotational force of about 550 ~ 650rpm, the shaft 20 has a forging pressure of about 155 ~ 175 bar.

In addition, the primary welding performs friction welding of the disk and the shaft by applying a frictional pressure of 125 to 145 bar to the shaft to have an upset distance of about 1.5 to 2.0 mm.

In addition, the secondary welding firmly welds the primary welded disk and the shaft by applying the shaft in the disc direction at a forging pressure of about 155 to 175 bar. At this time, the pressure holding time is about 75 to 85 seconds, and the total upset length by the primary welding and secondary welding is about 14 to 18 mm.

That is, the present invention, as shown in Figure 2, is installed by connecting the disk 10 to the rotary shaft 31 of the flywheel friction equipment, the fixed shaft 32 is spaced apart from the rotary shaft 31 at a predetermined interval The shaft 20 is installed in each of the shafts), and the rotating shaft 31 on which the disk is installed is rotated at a rotational force of about 550 to 650 rpm, generating about 15,000 to 17,000 N inertial force, and the friction welding pressure on the fixed shaft 32. 125 to 145 bar is applied to contact the shaft 20 and the disk 10 to generate frictional heat according to the relative motion on the contact surface between the shaft and the disk to weld the disk and the shaft first. At this time, the primary welding is performed to have an upset distance of about 1.5 to 2.0 mm.

The rotational speed of the rotating shaft is gradually reduced by such primary welding, and the forging pressure of about 155 to 175 bar is applied to the shaft after the primary welding by about 75 to 85 seconds, preferably about 80 seconds to brake the rotating shaft. Simultaneously weld the shaft and disc at the same time. At this time, the secondary welding is performed so that the upset length by the primary and secondary welding has about 14-18 mm.

The heat treatment step (S300) maintains the metal properties changed in the friction surface and the heat affected by friction welding by the quenching step (S310) and tempering step (S320) of the material equivalent to the inherent mechanical properties of the raw material .

The quenching step (S310) is heat-treated at 940 ~ 960 ℃, preferably about 950 ℃ for about 3 to 5 hours, preferably about 4 hours, and then oil cooled.

The tempering step (S320) is heat-treated at about 690 to 750 ° C, preferably about 700 ° C for about 5 to 7 hours, preferably about 6 hours, and then air-cooled.

Figure 3 shows a block diagram showing a modified manufacturing process according to the present invention, the present invention can first heat the disk and the shaft, respectively, can be integrated by friction welding. That is, the present invention is a disk forming step (S`100) for forming a disk by die forging; A heat treatment step of heat treating the disk and the shaft, respectively (S′200); And a friction welding step (S`300) of forming a rotor shaft by integrating the shafts by friction welding to the respective heat-treated disks.

At this time, the heat treatment step (S`200) and the friction welding step (S`300) has the same conditions as the rotor shaft manufacturing method according to Figs. 1 and 2 described above, further description thereof will be omitted.

In addition, the present invention further includes a stress removing step (S`400) for removing the stress of the rotor shaft integrated by the friction welding in the welding method shown in Figure 3, the stress removing step (S`400) Is heat-treated at about 630 to 680 ° C. for about 5 to 7 hours, followed by air cooling to remove stress in the rotor shaft.

Hereinafter, the present invention will be described in detail by way of examples.

Example 1

Ø618 mm diameter disk is formed by die forging, connected to the rotary shaft of the flywheel friction equipment, and Ø 140 mm diameter forged round vine shafts are respectively installed on the fixed shaft spaced apart from the rotary shaft at regular intervals. Then, the rotating shaft was rotated, the friction welding pressure was applied to the fixed shaft, and the shaft and the disk were first welded. At this time, the rotating shaft is equipped with a rotational force of 600rpm, the fixed shaft was subjected to friction welding pressure 135bar, the disk and the shaft was first welded to have an upset distance of 1.75mm.

After the primary welding, the forging pressure of 165 bar was applied to the shaft for 80 seconds again to brake the rotating shaft and weld the shaft and the disk to the secondary, and the disk and the shaft were upset length by the primary and secondary welding. 16 mm will be provided.

The rotor shaft integrated by friction welding as described above was heat treated at about 950 ° C. for about 4 hours, quenched by oil cooling, and then heat-treated at 700 ° C. for about 6 hours, followed by air cooling to temper.

For the rotor shaft formed as described above, the mechanical properties of the disk, the friction welding portion and the shaft were measured, and the results are shown in Table 2 below.

[Table 2]

Example 2

After forming the rotor shaft as in Example 1, it was separated as shown in Figure 4, the specimen was taken, and the tensile and impact tests were performed for this, the results are shown in Table 3 below.

[Table 3]

Example 3

After the rotor shaft was formed in the process of FIG. 1 as in Example 1, the friction welding portion (bonding portion between the disc and the shaft) and the base material cross-sectional structure were examined, and the results are shown in FIG. 5.

Figure 5 shows the cross-sectional structure of the base material for the right / left 5mm, 10mm, 15mm around the friction welding portion, as shown in Figure 5, there is no significant difference between the disk and the shaft and the friction welding portion Able to know.

Example 4

After forming the disk of Ø618 mm by die forging, and heat-treating the disk and the forged round vine shaft of Ø 140 mm under the heat treatment condition of Example 1, the heat-treated disk and shaft were rotated and fixed shaft of the flywheel friction device. In each case, friction welding was carried out under the same conditions as in Example 1.

As described above, the rotor shaft formed by the process of FIG. 3 was examined for the friction welding portion (joint portion of the disc and the shaft) and the base material sectional structure.

Figure 6 shows the cross-sectional structure of the base material for the right / left 5mm, 10mm, 15mm around the friction welding portion, as shown in Figure 6, there is no significant difference between the disk and the shaft and the friction welding portion Able to know.

Example 5

In general, similar products made by friction welding are dissimilar metals, and there are currently no methods to verify the presence of internal defects on friction surfaces and heat affected zones. Nondestructive testing (UT) with homogeneous metals can be tried to verify internal defects. FIG. 7 illustrates an abnormal wave when an internal defect exists around a friction interface, and thus it is possible to verify whether an internal defect exists.

Example 6

As a result of testing to compare the fatigue strength of the integral free forging material and the fatigue strength of the friction welding portion, it can be confirmed that the fatigue strength of the base metal is higher than that of the base metal.

Example 7

The rotor shaft test pieces formed according to the heat treatment temperature conditions were confirmed through the bending test for the integrity of the friction welding portion. Table 4 below and Figure 9 show the results of the banding test.

[Table 4]

Example 8

Disc forging F.E analysis determined the most optimal process and size for forging after upsetting the diameter Ø350 mm and height 530 mm. 10 is a disc forging simulation process.

Example 9

After forming the rotor shaft as in Example 1, as shown in Table 5 shows the set temperature and the process according to the four heat treatment test conditions.

[Table 5]

Example 10

After the rotor shaft is formed as in Example 1, Figure 11 shows that the hardness of the friction welded portion in accordance with the optimum friction welding conditions, heat treatment process and temperature settings, but the hardness of the weld portion is generally higher than the base material due to the hardness and weakness A uniform hardness distribution can be seen without any difference between the base hardness.

Example 11

12 to 13 predicted the temperature distribution and the junction change process through the rotor shaft friction welding F.E simulation.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

1 is an exemplary block diagram showing the flow of the manufacturing process according to the present invention

Figure 2 is a photographic example showing the flow of the manufacturing process according to the present invention

Figure 3 is a block diagram showing a modified manufacturing process according to the present invention

Figure 4 is an exemplary view showing a sampling of the rotor shaft according to the present invention

5 is an exemplary view showing a friction welding portion and the base material cross-sectional structure according to the present invention

6 is an exemplary view showing a friction welding portion and the base material cross-sectional structure of the present invention according to FIG.

7 is a photographic illustration showing a non-destructive testing process of the rotor shaft according to the present invention.

8 is a result chart according to Example 6

9 is a bending test results according to Example 7

10 is an exemplary view showing a disk forging simulation process according to the present invention

11 is a hardness distribution diagram at the friction welding boundary in accordance with the present invention

12 to 13 are exemplary views showing the process of temperature distribution and joint change through the rotor shaft friction welding F.E simulation

* Explanation of symbols for main parts of the drawings

10: disc 20: shaft

(31): rotating shaft (32): fixed shaft

100: rotor shaft

Claims (8)

A disk forming step of forming a disk by die forging; A friction welding step of forming a rotor shaft by integrating a shaft with the disk by friction welding; A heat treatment step of heat-treating the rotor shaft integrated by the friction welding, The friction welding step is made of a first welding step and a second pressure welding step, The primary welding is subjected to friction welding of the disc and the shaft by applying a frictional pressure of 125 to 145 bar to the shaft to have an upset distance of 1.5 to 2.0 mm, The secondary welding is a turbocharger for a large diesel engine, characterized in that the primary welded disk and the shaft is firmly welded by applying the pressure to the shaft for 75 to 85 seconds in the disc direction at a forging pressure of about 155 to 175 bar. Rotorshaft friction welding method. The method according to claim 1; Turbocharger rotor shaft friction welding method for a large diesel engine, characterized in that the friction welding step so that the total upset length of the rotor shaft has a 14 to 18mm. The method according to claim 1; The heat treatment step is a heat treatment for 3 to 5 hours at 940 ~ 960 ℃, and then quenching oil cooling, Turbocharger rotor shaft friction welding method for a large diesel engine, characterized in that consisting of a tempering step of air-cooled after heat treatment at 690 ~ 750 ℃ for 5 to 7 hours. delete The method according to claim 1; It includes a stress removing step for removing the stress of the rotor shaft integrated by friction welding, the stress removing step is a large diesel engine turbo, characterized in that the air-cooled after heat treatment for 5 to 7 hours at 630 ~ 680 ℃ Charger rotor shaft friction welding method. The method according to claim 1; Turbocharger rotor shaft friction welding method for large diesel engines, characterized by a non-destructive test method for checking the presence of internal defects of friction welding surfaces and heat affected zones The method according to claim 1; Turbocharger rotor shaft friction welding method for a large diesel engine, characterized by using a disk-shaped forging material diameter Ø 350 mm, height 530 mm. The method according to claim 1; Elongation at Friction Weld Min. 13%, section shrinkage Min. Turbocharger rotor shaft friction welding method for large diesel engines, characterized by 40%.

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