Spheroidal graphite cast iron steering knuckle and its preparation process

Abstract

The application belongs to the technical field of knuckle preparation, and particularly relates to a nodular cast iron knuckle and a preparation process thereof. The nodular cast iron knuckle is a nodular cast iron piece, and includes the following components by weight: C 3.75-3.95%, Mn 0.4-0.6%, Si 2.4-2.6%, S ≤0.015%, Re 0.01-0.03%, Cr ≤0.1%, Cu 0.45-0.5%, Mg 0.03-0.06%, and the balance is Fe. The high-strength and high-toughness nodular cast iron is used to replace a steel piece forging to form a forklift knuckle, thereby reducing a manufacturing process and lowering production cost. Meanwhile, a superior process forming property of casting production can conveniently manufacture a complex and optimized streamline structure piece, so as to realize structure optimization and lightening of a forklift part. The nodular cast iron is used to replace a forging to manufacture a forklift knuckle, thereby improving quality characteristics of the forklift knuckle. A large amount of graphite in the nodular cast iron exists in the form of microspheres, which not only ensures strength performance requirements of the knuckle, but also has good shock absorption, noise reduction and wear resistance, thereby greatly improving use effect and service life of the knuckle.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of knuckle preparation, and particularly relates to a nodular cast iron knuckle and a preparation process thereof. BACKGROUND

[0002] The knuckle is a key part of a turning system of a forklift. The knuckle not only bears the load of the rear part of the forklift, but also supports and drives the wheels to rotate around the kingpin to make the forklift turn. In the load driving state of the forklift, the knuckle also bears the impact load which changes, so the knuckle is required to have high strength and impact toughness. Therefore, the knuckle of the forklift is produced by using a cast steel part or a die forging part, and the production process is complicated and the manufacturing cost is high.

[0003] The knuckle is produced by using a cast iron part, which greatly reduces the production cost, simplifies the production process and improves the production efficiency. However, due to the complex structure and high mechanical performance requirement of the knuckle, it is difficult to achieve the requirements of high strength and high toughness by using the existing cast iron process. SUMMARY

[0004] In view of the problems in the prior art that the knuckle is produced by using the cast iron process, the technical scheme is proposed as follows.

[0005] The nodular cast iron knuckle is a nodular cast iron part, which comprises a knuckle main body, a connecting shaft is arranged on the knuckle main body, and a transition groove is arranged at the connecting position of the knuckle main body and the connecting shaft.

[0006] The high-strength and high-toughness nodular cast iron knuckle replaces the steel forging knuckle of the forklift, reduces the manufacturing process and lowers the production cost. Meanwhile, the cast production has excellent process formability, and can conveniently manufacture complex and optimized streamline structural parts, so as to realize the structural optimization and lightening of the forklift parts; the nodular cast iron knuckle replaces the forging knuckle of the forklift, and improves the quality characteristics of the knuckle of the forklift. A large amount of graphite in the nodular cast iron exists in the form of small globules, which not only guarantees the strength performance requirement of the knuckle, but also has good shock absorption, noise reduction and wear resistance, and greatly improves the use effect and service life of the knuckle.

[0007] The transition groove comprises a first arc-shaped part and a second arc-shaped part which are connected to each other, one end of the first arc-shaped part away from the second arc-shaped part is connected with the connecting shaft, and one end of the second arc-shaped part away from the first arc-shaped part is connected with the knuckle main body.

[0008] The shaft diameter ratio of the first arc-shaped part is 0.1, and the included angle between one end of the first arc-shaped part close to the connecting shaft and the central shaft of the connecting shaft is 6-12°.

[0009] The included angle between the connecting surface of the knuckle main body and the connecting shaft and the second arc-shaped part is -5-25°.

[0010] The transition groove is actually a combination of a transition fillet and a relief groove and an overtravel groove, and is designed as a simple curved transition groove, so that the problem of insufficient structural strength at the shaft shoulder of the knuckle after the knuckle is changed from a forged steel piece to a nodular cast iron piece is solved, and assembly interference is avoided.

[0011] As an improvement of the above technical scheme, the nodular cast iron knuckle comprises the following components by weight: C 3.75-3.95%, Mn 0.4-0.6%, Si 2.4-2.6%, S ≤0.015%, Re 0.01-0.03%, Cr ≤0.1%, Cu 0.45-0.5%, Mg 0.03-0.06%, and the balance is Fe.

[0012] In the nodular cast iron smelting, 0.45-0.5% of Cu is added, and Cr ≤0.1%, Si 2.4-2.6% are controlled, so that after sufficient alloy solid solution strengthening, not only the matrix structure of the nodular cast iron is refined, the formation of pearlite is promoted, and the tensile strength of the material is improved, but also the toughness and the yield strength ratio are greatly improved and increased, so that the performance requirements of the knuckle for high strength and high toughness are met.

[0013] The preparation process of the above nodular cast iron knuckle comprises the following steps:

[0014] S1

[0015] The required raw materials are melted into an iron liquid, and the iron liquid is subjected to spheroidizing and inoculation treatment;

[0016] S2

[0017] The iron liquid is poured into a mold to be cast into a knuckle;

[0018] S3

[0019] Heat treatment.

[0020] As an improvement of the above technical scheme, in the preparation process of the nodular cast iron knuckle, in step S1, the iron liquid is subjected to spheroidizing treatment by adopting a wire feeding spheroidizing process, and the spheroidizing treatment temperature is 1460-1480℃.

[0021] The molten iron spheroidizing treatment adopts wire feeding spheroidizing, and the alloy cored wire is continuously inserted into the bottom of the molten iron, so that the spheroidizing treatment is carried out under a certain pressure and a relatively closed and oxygen-deficient atmosphere due to the pressure of the molten iron height and the blocking effect of the cover. Compared with the impingement method, the magnesium absorption rate in the molten iron is improved, the spheroidizing and inoculation treatment control is very accurate, and the nodular cast iron can be stably treated.

[0022] As an improvement of the above technical scheme, in the preparation process of the nodular cast iron knuckle, in step S1, the iron liquid is subjected to inoculation treatment by adopting wire feeding inoculation, and the inoculant is 0.3% of a silicon-calcium-barium inoculation wire.

[0023] As the improvement of the above technical scheme, in the preparation process of the spheroidal graphite cast iron knuckle, in step S2, the iron liquid is poured into the mold by using the heat preservation pouring furnace.

[0024] The pouring is performed by using the heat preservation pouring furnace, so that the pouring temperature can be strictly controlled, and the difference in the feeding efficiency caused by the temperature difference before and after pouring can be avoided; the pouring temperature that is too high or too low is not conducive to the feeding of the casting; the heat preservation pouring furnace can perform timely heat preservation and slow heating compared with the ordinary ladle, so that the problems of the too high initial pouring temperature and the too low temperature in the later pouring stage caused by the prolonging of the pouring time and the reduction of the molten iron capacity in the ladle are solved, and the shrinkage cavity and shrinkage porosity caused by the too large temperature difference before and after pouring are reduced.

[0025] As the improvement of the above technical scheme, in the preparation process of the spheroidal graphite cast iron knuckle, in step S2, the iron liquid is poured into the mold by using the heat preservation pouring furnace.

[0026] The inoculation treatment adopts the "one-time inoculation in the transfer ladle + two-time stream inoculation during pouring" to strengthen the inoculation effect, improve the graphite nucleation capacity, reduce the element segregation, avoid the generation of primary graphite and delay the growth of graphite balls.

[0027] The pouring system for the preparation process of the spheroidal graphite cast iron knuckle comprises a pouring gate, a main runner, a cavity, a riser, a bottom runner and an inner runner; the pouring gate and the main runner are communicated, the top end of the cavity is connected with the riser, the riser and the main runner are communicated, the bottom runner and the main runner are communicated, the bottom end of the cavity and one end of the inner runner are communicated, and the other end of the inner runner and the bottom runner are communicated.

[0028] As the improvement of the above technical scheme, the cavity is two and is respectively located on the two sides of the main runner, and the riser and the inner runner are correspondingly provided with two.

[0029] As the improvement of the above technical scheme, the riser is circular, and the ratio of the water inlet area of the neck of the riser to the water inlet area of the inner runner is 1.5:8.

[0030] The water inlet is arranged at the bottom of the inner runner, the double-layer pouring feeding system of the top riser of the casting is adopted, the water inlet speed of the casting is improved, the riser neck is prevented from being in the high-temperature state during the pouring process, the sand washing defect of the top riser is reduced, the pouring temperature is reduced, the iron liquid enters the riser from the main runner and finally enters the cavity, and the feeding efficiency of the riser is improved.

[0031] The beneficial effects of the present application are as follows:

[0032] (1) High-strength and high-toughness nodular cast iron is used to replace forged steel to cast the steering knuckle of a forklift, thereby reducing the manufacturing process and production cost. Meanwhile, the superior process formability of the casting production can facilitate the manufacture of complex and optimized streamline structural parts, so as to realize the structural optimization and lightening of the forklift parts; the nodular cast iron is used to replace the forged steel to manufacture the steering knuckle of the forklift, thereby improving the quality characteristics of the steering knuckle. A large amount of graphite in the nodular cast iron exists in the form of microspheres, which not only ensures the strength performance requirement of the steering knuckle, but also has good shock absorption, noise reduction and wear resistance, thereby greatly improving the use effect and service life of the steering knuckle;

[0033] (2) The transition groove is actually a combination of a transition fillet, a tool withdrawal groove and an over-travel groove, and is designed as a simple curved transition groove, which solves the problem of insufficient structural strength at the shaft shoulder of the steering knuckle after the steering knuckle is changed from a forged steel part to a nodular cast iron part, and avoids assembly interference at the same time;

[0034] (3) In the nodular cast iron smelting, 0.45-0.5% of Cu, 0.1% or less of Cr and 2.4-2.6% of Si are added, and after sufficient alloy solid solution strengthening, the matrix structure of the nodular cast iron is refined, the formation of pearlite is promoted, the tensile strength of the material is improved, the toughness and yield strength ratio are greatly improved, and the performance requirements of high strength and high toughness of the steering knuckle are met;

[0035] (4) The molten iron is treated by wire feeding nodularization, and the alloy cored wire is continuously inserted into the bottom of the molten iron. Due to the pressure of the molten iron and the blocking effect of the cover, the nodularization treatment is carried out under a certain pressure and a relatively closed and oxygen-deficient atmosphere. Compared with the impingement method, the magnesium absorption rate in the molten iron is improved, the nodularization and inoculation treatment control is very accurate, and the nodular cast iron can be stably treated;

[0036] (5) The bottom ingate is used for water inlet, and a double-layer pouring and feeding system is used for the top riser of the casting, so as to improve the water inlet speed of the casting, avoid the riser neck in a high-temperature state during pouring, reduce the top riser sand washing defects, reduce the pouring temperature, and finally improve the riser feeding efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 Fig. 1 shows a structural schematic diagram of a nodular cast iron steering knuckle as one specific embodiment of the present application;

[0038] Figure 2 Fig. 2 shows a structural schematic diagram of a transition groove as one specific embodiment of the present application;

[0039] Figure 3 Fig. 3 shows a structural schematic diagram of a pouring system as one specific embodiment of the present application;

[0040] Figure 4The figure shows the mechanical property detection result of the ductile iron knuckle of the application.

[0041] wherein, Figure 4 The mechanical property detection basis is GB / T228.1-2010 and GB / T231.1-2018; the testing instrument is WEW-1000 screen display type hydraulic universal testing machine and HB-3000B-I cloth type hardness tester. DETAILED DESCRIPTION

[0042] To make the purpose, technical scheme and advantages of the embodiments of the application clearer, the technical scheme of the application will be described clearly and completely below with reference to the embodiments.

[0043] Embodiment 1

[0044] Figure 1 The figure shows the structural schematic diagram of the ductile iron knuckle as one specific embodiment of the application; Figure 2 The figure shows the structural schematic diagram of the ball transition groove as one specific embodiment of the application. Figure 1 、 2 In the ductile iron knuckle, the ductile iron knuckle is a ductile iron piece, comprising a knuckle body 1, a connecting shaft 2 is arranged on the knuckle body 1, and a transition groove 3 is arranged at the connecting position of the knuckle body 1 and the connecting shaft 2.

[0045] The high-strength and high-toughness ductile iron cast replaces the steel piece forging forklift knuckle, reduces the manufacturing process and lowers the production cost. Meanwhile, the casting production has superior process formability, can conveniently manufacture complex and optimized streamline structural pieces, thereby realizing the structural optimization and lightening of the forklift parts; the ductile iron replaces the forging piece to manufacture the forklift knuckle, improves the quality characteristics of the forklift knuckle. A large amount of graphite in the ductile iron exists in the form of microspheres, which not only guarantees the strength performance requirement of the knuckle, but also has good shock absorption, noise reduction and wear resistance, greatly improves the use effect and service life of the knuckle.

[0046] The transition groove 3 comprises a first arc-shaped part 31 and a second arc-shaped part 32 connected with each other, one end of the first arc-shaped part 21 away from the second arc-shaped part 32 is connected with the connecting shaft 2, and one end of the second arc-shaped part 32 away from the first arc-shaped part 31 is connected with the knuckle body 1.

[0047] The shaft diameter ratio of the first arc-shaped part 31 is 0.1, and the included angle between one end of the first arc-shaped part 31 close to the connecting shaft 2 and the central shaft of the connecting shaft 2 is 6-12°.

[0048] The included angle between the connecting surface of the knuckle body 1 and the connecting shaft 2 and the second arc-shaped part 32 is -5-25°.

[0049] In order to eliminate the stress failure at the axle shoulder of the knuckle (the joint of the knuckle body 1 and the connecting shaft 2) and avoid assembly interference, the transition fillet test at the axle shoulder is designed as a simple curve transition groove 3, wherein the first arc part 31 determines the structural strength of the axle shoulder of the knuckle, the shaft diameter ratio of the first arc part 31 is designed as 0.1, the stress concentration is reduced, the structural strength is ensured, and the assembly interference is avoided; that is, the transition groove 3 is actually a combination of the transition fillet, the relief groove and the overtravel groove, the simple curve transition groove 3 is designed, and the problem of insufficient structural strength at the axle shoulder of the knuckle after the knuckle is changed from a forged steel part to a nodular cast iron part is solved.

[0050] As an improvement of the above technical solution, the nodular cast iron knuckle comprises the following components by weight: C 3.75-3.95%, Mn 0.4-0.6%, Si 2.4-2.6%, S ≤0.015%, Re 0.01-0.03%, Cr ≤0.1%, Cu 0.45-0.5%, Mg 0.03-0.06%, and the balance is Fe.

[0051] In the nodular cast iron smelting, 0.45-0.5% of Cu is added, Cr ≤0.1%, and Si 2.4-2.6%. After sufficient alloy solid solution strengthening, not only the matrix structure of the nodular cast iron is refined, the formation of pearlite is promoted, and the tensile strength of the material is improved, but also the toughness and yield strength ratio are greatly improved, meeting the performance requirements of the knuckle for high strength and high toughness.

[0052] The preparation process of the above nodular cast iron knuckle comprises the following steps:

[0053] S1

[0054] The required raw materials are melted into an iron liquid, and the iron liquid is subjected to spheroidizing and inoculation treatment;

[0055] S2

[0056] The iron liquid is poured into a mold to be cast into a knuckle;

[0057] S3

[0058] Heat treatment.

[0059] As an improvement of the above technical solution, in step S1, the iron liquid is subjected to spheroidizing treatment by using a wire feeding spheroidizing process, and the spheroidizing treatment temperature is 1460-1480°C.

[0060] The molten iron spheroidizing treatment adopts wire feeding spheroidizing, and the alloy cored wire is continuously inserted into the bottom of the molten iron. Due to the pressure of the molten iron height and the blocking effect of the cover, the spheroidizing treatment is carried out under a certain pressure and a relatively closed and oxygen-deficient atmosphere. Compared with the impingement method, the magnesium absorption rate in the molten iron is improved, the spheroidizing and inoculation treatment control is very accurate, and the nodular cast iron can be stably treated.

[0061] As the improvement of the above technical scheme, in step S1, the iron liquid is subjected to inoculation treatment by using wire feeding inoculation, and the inoculant is 0.3% silicon-calcium-barium inoculation wire.

[0062] As the improvement of the above technical scheme, in step S2, the iron liquid is poured into the mold by using a holding pouring furnace.

[0063] The pouring is performed by using the holding pouring furnace, so that the pouring temperature can be strictly controlled, and the difference in feeding efficiency caused by the temperature difference before and after pouring can be avoided. The pouring temperature that is too high or too low is not conducive to the feeding of the casting. By using the holding pouring furnace, compared with the ordinary ladle, the holding pouring furnace can be timely heated and slowly heated, so that the problems of the too high initial pouring temperature and the too low temperature in the later pouring stage are solved in the conventional pouring process along with the extension of the pouring time and the reduction of the iron liquid capacity in the ladle, thereby reducing the shrinkage hole and shrinkage porosity problems caused by the too large temperature difference before and after.

[0064] As the improvement of the above technical scheme, in step S2, during pouring, the iron liquid is subjected to secondary inoculation treatment by using pouring stream inoculation, and the inoculant is 0.1% silicon-zirconium stream inoculant.

[0065] The inoculation treatment adopts the "one-time inoculation in the transfer ladle + secondary stream inoculation during pouring" to strengthen the inoculation effect, improve the graphite nucleation capacity, reduce the element segregation, avoid the generation of primary graphite, and delay the growth of graphite balls.

[0066] Figure 3 A structure schematic diagram of a pouring system according to an embodiment of the present application is shown. Figure 3 In the pouring system for the preparation process of the ductile iron knuckle, a pouring opening 901, a main runner 902, a cavity 903, a riser 904, a bottom runner 905, and an inner runner 906 are included. The pouring opening 901 and the main runner 902 are in communication. The top end of the cavity 903 is connected with the riser 904. The riser 904 and the main runner 902 are in communication. The bottom runner 905 and the main runner 902 are in communication. The bottom end of the cavity 903 and one end of the inner runner 906 are in communication. The other end of the inner runner 906 and the bottom runner 905 are in communication.

[0067] As the improvement of the above technical scheme, referring to Figure 3 , the cavity 903 is two, and is respectively located on both sides of the main runner 902. The riser 904 and the inner runner 906 are correspondingly provided with two.

[0068] As the improvement of the above technical scheme, the riser 904 is circular. The ratio of the water inlet area of the neck of the riser 904 to the water inlet area of the inner runner 906 is 1.5:8.

[0069] The riser supplements the casting from the side of the casting, if the sand mold tightness is low, the modulus near the riser neck is the largest, when the casting production site conditions change slightly, the casting may have shrinkage defects, the original process molten iron can only enter the casting mold through the riser, the riser neck has high-temperature molten iron flowing through during the whole pouring process, and the modulus near the riser neck is increased.

[0070] The bottom inner gate 906 is used for water inlet, the casting top riser 904 double-layer pouring feeding system is used, the casting water inlet speed is improved, the riser neck is avoided from being in a high-temperature state during the pouring process, the top riser sand washing defect is reduced, the pouring temperature is reduced, the molten iron enters the riser 904 from the main gate 902, finally enters the cavity 903, and the riser 904 feeding efficiency is improved.

[0071] The above examples are only used to illustrate the technical solutions of the present application, but not limit it.

Claims

1. A nodular cast iron knuckle, characterized in that: The knuckle is a nodular cast iron part, comprising a knuckle body (1), a connecting shaft (2) is arranged on the knuckle body (1), and a transition groove (3) is arranged at the connecting position of the knuckle body (1) and the connecting shaft (2); The transition groove (3) comprises a first arc-shaped part (31) and a second arc-shaped part (32) connected with each other, one end of the first arc-shaped part (31) away from the second arc-shaped part (32) is connected with the connecting shaft (2), and one end of the second arc-shaped part (32) away from the first arc-shaped part (31) is connected with the knuckle body (1); The shaft diameter ratio of the first arc-shaped part (31) is 0.1, and the angle between one end of the first arc-shaped part (31) close to the connecting shaft (2) and the central shaft of the connecting shaft (2) is 6-12°; The angle between the connecting surface of the knuckle body (1) and the connecting shaft (2) and the second arc-shaped part (32) is -5-25°.

2. The ductile iron knuckle according to claim 1, wherein The following components are included by weight: C 3.75-3.95%, Mn 0.4-0.6%, Si 2.4-2.6%, S ≤0.015%, Re 0.01-0.03%, Cr ≤0.1%, Cu 0.45-0.5%, Mg 0.03-0.06%, and the balance is Fe.

3. The process for producing a knuckle of ductile cast iron according to claim 2, wherein The following steps are included: S1 Melting the required raw materials into molten iron, and performing spheroidizing and inoculation treatment on the molten iron; S2 Pouring the molten iron into a mold to cast the knuckle; S3 Heat treatment.

4. The process for producing a nodular cast iron knuckle according to claim 3, characterized in that: In step S1, the molten iron is spheroidized by using a wire feeding spheroidizing process, and the spheroidizing treatment temperature is 1460-1480℃.

5. The process for producing a nodular cast iron knuckle according to claim 3, characterized in that: In step S1, the molten iron is inoculated by using a wire feeding inoculation process, and the inoculant is 0.3% silicon-calcium-barium inoculant wire.

6. The process for producing a spheroidal graphite cast iron knuckle according to claim 3, characterized by: In step S2, the molten iron is poured into a mold by using a holding pouring furnace.

7. The process for producing a spheroidal graphite cast iron knuckle according to claim 3, characterized by: In step S2, during pouring, the molten iron is secondarily inoculated by using pouring stream inoculation, and the inoculant is 0.1% silicon-zirconium stream inoculant.

8. A gating system for the process of producing a nodular cast iron knuckle as claimed in claim 3, characterized in that: The pouring gate (901), the main sprue (902), the cavity (903), the riser (904), the bottom sprue (905) and the inner sprue (906) are included; the pouring gate (901) and the main sprue (902) are communicated, the top end of the cavity (903) is connected with the riser (904), the riser (904) and the main sprue (902) are communicated, the bottom sprue (905) and the main sprue (902) are communicated, the bottom end of the cavity (903) and one end of the inner sprue (906) are communicated, and the other end of the inner sprue (906) and the bottom sprue (905) are communicated.

9. The gating system of claim 8, wherein: The cavity (903) is two, and is respectively located on both sides of the main sprue (902); the riser (904) and the inner sprue (906) are correspondingly provided with two.

10. The gating system of claim 8, wherein: The riser (904) is circular, and the ratio of the water inlet area of the neck of the riser (904) to the water inlet area of the inner sprue (906) is 1.5:8.

Images