Preparation process of high-quality medium-manganese steel stamping part

Abstract

The application discloses a preparation process of high-quality medium-manganese steel stamping parts and belongs to the field of advanced steel materials. The application utilizes the particularity of different energy fields to avoid the problems of surface oxidation and difficult-to-ensure size precision caused by traditional heat fields by coupling a low-temperature heat field, a pulse electric field and a pressure field, and finally develops high-precision high-performance medium-manganese steel stamping parts. The specific steps of the application comprise the following steps: (1) low-temperature preheating treatment: low-temperature heating of warm-rolled medium-manganese steel; (2) pulse current rapid heating: heating of the plate by high pulse current density; (3) hot stamping: hot stamping of the medium-manganese steel by a stress field coupled pulse electric field; (4) pressure maintaining and cooling: pressure maintaining of the stamping part, taking out of the stamping part and air cooling to room temperature. The medium-manganese steel stamping part obtained by the process has a tensile strength of more than 1600 MPa and an elongation of 20%, and has small surface oxidation, small springback and high size precision.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of advanced steel material, and particularly relates to a preparation process of high-quality medium-manganese steel stamping part. BACKGROUND

[0002] Medium-manganese steel is a low-carbon medium-alloy steel, and the mass fraction of manganese is between 3% and 12%. The content of alloying elements in the medium-manganese steel is relatively low, and thus the cost is much lower than that of the second-generation advanced high-strength steel. Due to the TRIP effect of metastable austenite in the medium-manganese steel, the tensile strength thereof is about 750-2200 MPa, the total elongation is in the range of 15%-85%, and the strength-ductility product is up to 30-70 GPa·%, which is far superior to the first-generation advanced high-strength steel. Therefore, the medium-manganese steel has become the focus of the current research on high-strength and high-ductility steel iron materials. However, the high strength brings challenges to the stamping forming of the medium-manganese steel, and the existing stamping forming technology has the following problems: (1) the traditional cold stamping forming equipment has insufficient pressure, and there are problems such as die wear; and (2) the warm stamping forming can solve the problems of the traditional cold stamping, but there are problems such as surface oxidation and low stamping size precision. SUMMARY

[0003] To solve the above technical problems, the present application provides a preparation process of high-quality medium-manganese steel stamping part.

[0004] The technical scheme adopted by the present application is as follows:

[0005] A preparation process of high-quality medium-manganese steel stamping part, comprising the following steps connected in sequence:

[0006] (1) smelting and forging to obtain a steel billet.

[0007] (2) warm rolling: heating the steel billet to 600-800 DEG C, warm rolling, and then air cooling to room temperature to obtain a warm-rolled plate after pickling.

[0008] (3) low-temperature preheating treatment: heating the warm-rolled plate to 500-600 DEG C in a heat treatment furnace.

[0009] (4) pulse current rapid heating: taking out the preheated plate from the heat treatment furnace, rapidly heating it to 50-80 DEG C above the austenite transformation end temperature Ac3 by using pulse current to completely austenitize the structure.

[0010] (5) hot stamping forming: hot stamping the austenitized medium-manganese steel, and maintaining it in the range of 50-80 DEG C above Ac3 by using pulse current heating in the hot stamping process.

[0011] (6) pressure holding and cooling: pressure holding the stamping-formed medium-manganese steel, and cooling it by water to reduce the temperature to below the martensite transformation point, and then taking out the stamping part and air cooling it to room temperature.

[0012] Further, the medium manganese steel has the following mass percentage: C: 0.05-0.4%; Mn: 3-2%; Al: 1-8%, and the rest is Fe and inevitable impurities.

[0013] Further, the thickness of the warm-rolled plate obtained in step (2) is 1.5-2.0 mm.

[0014] Further, in step (4), the effective pulse current density is 10-15 A / mm 2 , and the pulse current duty cycle is 0.2.

[0015] Further, in step (5), the effective pulse current density is 8-10 A / mm 2 , and the pulse current duty cycle is 0.2.

[0016] Further, in step (5), the pressure of the hot stamping is not less than 150 Kg.

[0017] Further, in step (6), the pressure holding time is not less than 20 s, and the cooling speed during the pressure holding process is not less than 30℃ / s.

[0018] The present application has the following advantages:

[0019] (1) The warm-rolled plate is used, which can take advantage of the warm-rolled plate structure to improve the performance of the stamping part, and the warm-rolled plate resistance point is beneficial to the rapid heating of the pulse electric field, avoiding oxidation.

[0020] (2) In the low-temperature preheating stage, compared with the traditional medium manganese steel heating temperature (Ac3+50-80℃), the present application only heats to 500-600℃ through a muffle furnace and other devices, which can effectively avoid the oxidation of the plate and other phenomena.

[0021] (3) In the pulse current rapid heating stage, the present application ingeniously uses the characteristics of the pulse electric field rapid heating and the high resistance characteristics of the warm-rolled medium manganese steel, so that the plate can quickly reach the predetermined temperature without oxidation.

[0022] (4) In the stamping stage, the traditional stamping does not have heat supplement, and the present application uses electric pulse assistance to generate different temperatures under different deformation amounts, thereby realizing high-precision forming preparation.

[0023] (5) In the cooling stage, the present application uses rapid heating and long-time pressure holding, which effectively improves the precision of the stamping part.

[0024] In summary, the present application adopts the idea of synergistic regulation of multiple energy fields, introduces pulsed electric field into the stamping preparation process of medium manganese steel, on the one hand solves the problem of insufficient pressure of traditional equipment, and on the other hand also avoids the problems of oxidation and low dimensional accuracy, through the ingenious coupling design of pulsed electric field, stress field and low-temperature thermal field, the medium manganese steel prepared by low-temperature drawing is stamped and formed, the unique advantages of different energy fields are utilized, the preparation of high-quality medium manganese steel stamping parts is realized, and a new idea is provided for the industrialized forming preparation of medium manganese steel stamping parts. The medium manganese steel stamping part obtained by the present application has a tensile strength of more than 1600 MPa and an elongation of more than 20%, and has small surface oxidation, small springback, high dimensional accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is the microstructure of the medium manganese steel stamping part of Comparative Example 1 after the traditional process.

[0026] Figure 2 is the microstructure of the medium manganese steel stamping part of Example 1 after the process of the present application.

[0027] Figure 3 is the surface morphology of the medium manganese steel stamping part of Example 1 after the process of the present application.

[0028] Figure 4 is the surface morphology of the medium manganese steel stamping part of Comparative Example 1 after the traditional process. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be described clearly and completely below in combination with the drawings and a preferred embodiment.

[0030] Example 1

[0031] A preparation process of high-quality medium manganese steel stamping part, the specific steps of which include:

[0032] (1) Smelting: smelting and casting to obtain a steel ingot; the composition of the medium manganese steel is C: 0.2wt.%; Mn: 5wt.%; Al: 1wt.%

[0033] (2) Forging: heat the steel ingot to 1200℃, keep for 3h, and forge into a billet;

[0034] (3) Warm rolling: heat the billet to 600℃-800℃, keep for 2h, warm rolling by 6-7 passes with high differential speed ratio, the rolling temperature interval is 500℃-700℃, the total reduction is 80%, the rolling thickness is 1.5mm, and then air cooling to room temperature, and obtaining a warm rolling plate after pickling.

[0035] (4) Low temperature preheating: the 1.5mm thick warm-rolled medium manganese steel is placed in a muffle furnace for low temperature heating, heated to 500℃;

[0036] (5) Pulse current rapid heating: the preheated warm-rolled plate is heated to 650℃ by pulse current; the effective current density of the pulse current is 15A / mm 2 , and the current duty cycle is 0.2;

[0037] (6) Hot stamping: the heated plate is hot stamped by using a 150Kg loading force, and the pulse current is used for heating during the stamping process to keep it in the range of 50℃-80℃ above Ac3; the effective current density of the pulse current is 8A / mm 2 , and the current duty cycle is 0.2;

[0038] (7) Pressure holding cooling: the medium manganese steel formed by stamping is pressure held for 20s, and water cooling is performed at the same time to reduce the temperature below the martensite phase transition point, then the stamped part is taken out, and air cooling is performed to room temperature to obtain a high-quality medium manganese steel stamped part; the cooling speed of water cooling is 30℃ / s.

[0039] Comparative Example 1

[0040] The preparation process of the medium manganese steel stamped part includes the following specific steps:

[0041] (1) Smelting: smelting and casting to obtain a steel ingot; the composition of the medium manganese steel is C: 0.2wt.%; Mn: 5wt.%; Al: 1wt.%

[0042] (2) Forging: the steel ingot is heated to 1200℃, and held for 3h, and forged into a billet;

[0043] (3) Warm rolling: the billet is heated to 600℃-800℃, and held for 2h, and subjected to 6-7 passes of high differential speed ratio warm rolling, the rolling temperature interval is 500℃-700℃, the total reduction is 80%, and the thickness is rolled to 1.5mm, and then air cooled to room temperature, and the warm-rolled plate is obtained after pickling.

[0044] (4) Hot stamping: the plate is directly heated to 700℃-800℃, and held for 2min-5min, and the heated plate is hot stamped by using a 150Kg loading force, and the pulse current is used for heating during the stamping process to keep it in the range of 50℃-80℃ above Ac3; the effective current density of the pulse current is 8A / mm 2 , and the current duty cycle is 0.2;

[0045] (6) Pressure holding cooling: the medium manganese steel formed by stamping is pressure held for 20s, and water cooling is performed at the same time to reduce the temperature below the martensite phase transition point, then the stamped part is taken out, and air cooling is performed to room temperature to obtain a high-quality medium manganese steel stamped part; the cooling speed of water cooling is 30℃ / s.

[0046] A 10mm x 10mm sample was cut from the stamping of Comparative Example 1 and Example 1 by wire cutting, the sample was ground to 2000# by different types of sandpaper in stages, and then polished and corroded; the sample was micro-characterized by SEM, and the characterization results are shown in Figure 1 and Figure 2 The results show that, compared with the traditional process, i.e., Comparative Example 1, the grain size of the material prepared by the application can ensure sufficient austenite content.

[0047] The mechanical properties of the above two stampings were then tested, and the results show that the tensile strength of the sample prepared by the application is 1623MPa, and the elongation is 20.5%. The tensile strength of the sample prepared by Comparative Example 1 is 1586MPa, and the elongation is 18%.

[0048] In addition, it can be seen from Figure 3 that the medium manganese steel stamping prepared by the application has almost no oxidation, and the springback angle is less than 0.1°. It can be seen from Figure 4 that the medium manganese steel stamping prepared by the traditional process is severely oxidized, and the springback angle is greater than 5°.

[0049] Example 2

[0050] A preparation process of a high-quality medium manganese steel stamping, the specific steps of which include:

[0051] (1) Smelting: smelting and casting to obtain a steel ingot; the composition of the medium manganese steel is C: 0.4wt.%; Mn: 12wt.%; Al: 8wt.%;

[0052] (2) Forging: heat the steel ingot to 1100℃, and keep for 4h, and forge into a billet;

[0053] (3) Warm rolling: heat the billet to 600℃-800℃, and keep for 2h, and warm roll by 6-7 passes at a high differential speed ratio, the rolling temperature interval is 500℃-700℃, the total reduction is 70%, and roll to 2mm thick, and then air cool to room temperature, and obtain a warm rolled plate after pickling.

[0054] (4) Low-temperature preheating treatment: place the 2mm thick warm rolled medium manganese steel in a muffle furnace for low-temperature heating, and heat to 600℃;

[0055] (5) Pulse current rapid heating: heat the preheated warm rolled plate to 800℃ by pulse current; the effective current density of the pulse current is 10A / mm 2 , and the current duty ratio is 0.2;

[0056] (6) hot stamping: hot stamping the heated sheet material with a 200 Kg loading force, and using pulse current heating to keep it at 50℃-80℃ above Ac3 during stamping; the effective current density of the pulse current is 10 A / mm 2 , and the current duty cycle is 0.2;

[0057] (7) pressure holding cooling: pressure holding the stamped medium-manganese steel for 25 s, and cooling it by water flow to reduce its temperature to below the martensite phase transition point, then taking out the stamped piece and air cooling it to room temperature to obtain a high-quality medium-manganese steel stamped piece; the cooling speed of the water flow cooling is 40℃ / s.

[0058] Mechanical property testing of the above stamped piece shows that the tensile strength of the sample prepared by the present application is 1701 MPa, and the elongation is 24%. In addition, the medium-manganese steel stamped piece prepared by the present application has almost no oxidation, and the springback angle is less than 0.1°.

[0059] Example 3

[0060] A preparation process of a high-quality medium-manganese steel stamped piece, which comprises the following specific steps:

[0061] (1) smelting: smelting and casting to obtain a steel ingot; the composition of the medium-manganese steel is C: 0.05wt.%; Mn: 3wt.%; Al: 8wt.%;

[0062] (2) forging: heating the steel ingot to 1150℃, holding for 3 h, and forging it into a billet;

[0063] (3) warm rolling: heating the billet to 600℃-800℃, holding for 2 h, and warm rolling it by 6-7 passes at a high differential speed ratio, the rolling temperature interval is 500℃-700℃, the total reduction is 75%, the rolling thickness is 1.8 mm, and then air cooling it to room temperature, and obtaining a warm-rolled sheet after pickling.

[0064] (4) low-temperature preheating treatment: placing the 1.8 mm thick warm-rolled medium-manganese steel in a muffle furnace for low-temperature heating, and heating it to 550℃;

[0065] (5) pulse current rapid heating: heating the preheated warm-rolled sheet to 700℃ by pulse current; the effective current density of the pulse current is 10 A / mm 2 , and the current duty cycle is 0.2;

[0066] (6) hot stamping: hot stamping the heated sheet material with a 200 Kg loading force, and using pulse current heating to keep it at 50℃-80℃ above Ac3 during stamping; the effective current density of the pulse current is 8 A / mm 2 , and the current duty cycle is 0.2;

[0067] (7) pressure holding cooling: the pressure holding of the middle-manganese steel formed by the stamping is 20s, and the water cooling is conducted to reduce the temperature below the martensite phase transition point, then the stamping part is taken out and air-cooled to room temperature to obtain the high-quality middle-manganese steel stamping part; the cooling speed of the water cooling is 30℃ / s.

[0068] The mechanical property test is conducted on the above stamping part, and the result shows that the tensile strength of the sample prepared by the present application is 1656MPa, and the elongation is 23.2%. In addition, the middle-manganese steel stamping part prepared by the present application has little oxidation, and the springback angle is lower than 0.1°.

[0069] Example 4

[0070] A preparation process of a high-quality middle-manganese steel stamping part, and the specific steps include:

[0071] (1) smelting: smelting and casting to obtain a steel ingot; the composition of the middle-manganese steel is C: 0.05wt.%; Mn: 3wt.%; Al: 8wt.%;

[0072] (2) forging: the steel ingot is heated to 1150℃, and held for 2h to be forged into a steel billet;

[0073] (3) warm rolling: the steel billet is heated to 600℃-800℃, and held for 2h, and then is warm rolled by 6-7 passes at a high differential speed ratio, the rolling temperature interval is 500℃-700℃, the total reduction is 75%, and the rolling thickness is 1.8mm, and then air-cooled to room temperature, and the warm rolling plate is obtained after pickling.

[0074] (4) low-temperature preheating treatment: the 1.8mm-thick warm-rolled middle-manganese steel is placed in a muffle furnace for low-temperature heating, and heated to 550℃;

[0075] (5) pulse current rapid heating: the preheated warm-rolled plate is heated to 750℃ by pulse current; the effective current density of the pulse current is 8A / mm 2 , and the current duty ratio is 0.2;

[0076] (6) hot stamping: the heated plate is hot stamped by adopting a 150Kg loading force, and the pulse current heating is adopted in the stamping process to keep it in the range of 50℃-80℃ above Ac3; the effective current density of the pulse current is 10A / mm 2 , and the current duty ratio is 0.2;

[0077] (7) pressure holding cooling: the pressure holding of the middle-manganese steel formed by the stamping is 20s, and the water cooling is conducted to reduce the temperature below the martensite phase transition point, then the stamping part is taken out and air-cooled to room temperature to obtain the high-quality middle-manganese steel stamping part; the cooling speed of the water cooling is 30℃ / s.

[0078] The mechanical property test is carried out on the stamping part, and the result shows that the tensile strength of the sample prepared by the application is 1842MPa, and the elongation is 22%. In addition, the medium manganese steel stamping part prepared by the application has almost no oxidation, and the springback angle is less than 0.1o.

[0079] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements are also within the protection scope of the present application.

Claims

1. A manufacturing process for high-quality medium-manganese steel stamped parts, characterized in that, Includes the following steps for sequential connection: (1) Smelting and forging to obtain steel billets; (2) Warm rolling: The steel billet is heated to 600℃~800℃, warm rolled, then air cooled to room temperature, and pickled to obtain warm rolled plate; (3) Low-temperature preheating treatment: The warm-rolled plate is heated to 500℃~600℃ in a heat treatment furnace; (4) Rapid heating with pulsed current: Take the preheated plate out of the heat treatment furnace and rapidly heat it with pulsed current to 50°C to 80°C above the austenite transformation end temperature Ac3, so that the structure is completely austenitized. (5) Hot stamping: The austenitized medium manganese steel is hot stamped. During the hot stamping process, pulse current heating is used to keep it within the range of 50℃ to 80℃ above Ac3. (6) Pressure holding and cooling: The stamped medium manganese steel is held under pressure and cooled by water to reduce its temperature below the martensitic transformation point. Then the stamped part is taken out and air-cooled to room temperature.

2. The manufacturing process of a high-quality medium-manganese steel stamped part according to claim 1, characterized in that, The mass percentage of medium manganese steel is: C: 0.05-0.4%; Mn: 3-2%; Al: 1-8%, with the remainder being Fe and unavoidable impurities.

3. The manufacturing process of a high-quality medium-manganese steel stamped part according to claim 1, characterized in that, The thickness of the warm-rolled plate obtained in step (2) is 1.5mm to 2.0mm.

4. The manufacturing process of a high-quality medium-manganese steel stamped part according to claim 1, characterized in that, In step (4), the effective pulse current density is 10–15 A / mm. 2 The pulse current duty cycle is 0.

2.

5. The manufacturing process of a high-quality medium-manganese steel stamped part according to claim 1, characterized in that, In step (5), the effective pulse current density is 8–10 A / mm. 2 The pulse current duty cycle is 0.

2.

6. The manufacturing process of a high-quality medium-manganese steel stamped part according to claim 1, characterized in that, In step (5), the pressure of hot stamping shall not be less than 150 kg.

7. The manufacturing process of a high-quality medium-manganese steel stamping part according to claim 1, characterized in that, In step (6), the pressure holding time shall not be less than 20s, and the cooling rate during the pressure holding process shall not be less than 30℃ / s.

Images