Method for producing rods and wires through ledeburite die steel Cr12MoV continuous casting process

Abstract

The invention provides a method for producing rods and wires through a ledeburite die steel Cr12MoV continuous casting process. The method specifically comprises the following steps of electric furnace refining, LF furnace refining, VD furnace refining, square billet continuous casting, continuous casting billet annealing, high-speed wire rod and rod rolling, annealing, inspection and warehousing. Uniformity is guaranteed, the size of carbide is smaller than that of die casting, and eutectic carbide reaches the level of die casting; continuous casting and continuous rolling processes are adopted, so that the production efficiency is improved, and the environment is benefited; a cover type annealing furnace is adopted for argon protection annealing, and a surface decarburized layer is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to a mold steel and its manufacturing method, in particular to a method for producing rod wire of ledeburite mold steel Cr12MoV by continuous casting process. BACKGROUND

[0002] Ledeburite mold steel (Cr12MoV) is one of the commonly used cold work die steels at home and abroad, which contains the following components by weight percentage: C: 1.45-1.70%; Si: ≤0.40%; Mn: ≤0.40%; P: ≤0.030%; S ≤0.030%; Cr: 11.00-13.00%; Mo: 0.40-0.60%; V: 0.15-0.30%; the balance is Fe and unavoidable impurity elements. Cr12MoV is a cold work die steel series grade in GB / T 1299-2014, which has high hardness, good wear resistance, and excellent toughness and deformation resistance, and is often used to manufacture various molds for cold working under heavy load and long service life.

[0003] The conventional (traditional) rod wire production process of cold work die steel Cr12MoV is: electric furnace→ external refining→ mold casting ingot→ cogging (forging, rolling)→ rolling rod and wire→ annealing, which has a long production process, low production efficiency, and due to the slow cooling of the mold casting ingot, the primary carbide grows seriously, there are large network eutectic carbides in the as-cast structure, which are difficult to eliminate by subsequent hot working deformation, and multiple forging and rolling deformation are required to gradually eliminate them, and the finished product still has carbide aggregation, which seriously affects the organization stability of the subsequent quenching and tempering, therefore, how to improve the production efficiency, improve the carbide size, and improve the uniformity of the organization is a technical problem to be solved. SUMMARY

[0004] To solve the above problems, the present application discloses a method for producing rod wire of ledeburite mold steel Cr12MoV by continuous casting process, which ensures uniformity, finer carbide size than mold casting, and eutectic carbide reaching the level of mold casting; the continuous casting and rolling process is adopted, the production efficiency is improved, and it is beneficial to the environment; the argon gas protection annealing of cover annealing furnace is adopted to ensure the surface decarburization layer.

[0005] A method for producing rod wire of ledeburite mold steel Cr12MoV by continuous casting process, specifically comprising the following: electric furnace→ LF furnace refining→ VD furnace refining→ continuous casting billet→ continuous casting billet annealing→ high-speed wire rolling wire rod and rod→ annealing→ inspection→ warehousing.

[0006] Further, scrap steel and high-carbon chromium iron and other alloy materials are added in the electric arc furnace for alloy melting and initial refining; the tapping temperature is ≥1590℃, P ≤0.030%, and slag needs to be removed before tapping.

[0007] Further, LF furnace smelting, adding lime, fluorite, electric slag, controlling the slag R2.5-3.5 to adjust the alloy composition, heating refining, taking silicon iron and other deoxidizers for deoxidization, the dosage is accurate to maintain white slag operation, sampling analysis, when each alloy composition reaches the standard requirement, the white slag keeps for 15 minutes, T=1625 DEG C, and then the steel is discharged to the VD station.

[0008] Further, the third step: VD furnace, slag removal is needed before entering VD, vacuum extraction, the vacuum degree reaches 67Pa and keeps for 15 minutes; after breaking the vacuum, temperature measurement, sampling and analysis are carried out, and covering agent is added, and the quenching weak argon blowing is kept for 14 minutes, and when the temperature T=1550 DEG C, the platform of the continuous casting machine is transferred to.

[0009] Further, the fourth step: arc-shaped square billet continuous casting machine continuous casting, the combined mode of crystallizer and terminal electromagnetic stirring is adopted during pouring, and the casting speed is 1.0-1.2 m / min

[0010] Further, the cooling control: the three-section partition water distribution mode is adopted in the secondary cooling zone, and the specific water quantity is automatically matched with the casting speed, and the material temperature of the entry of the straightening machine is greater than 1000 DEG C; the billet is cut to size when being discharged, and the continuous casting billet with a section of 150*150 mm and a length of 6000 mm is obtained.

[0011] Further, the fifth step: continuous casting billet annealing, the continuous casting billet is immediately transferred into a chamber furnace for annealing after being cut, the annealing process is 850-860 DEG C for 6 hours, and the furnace is cooled to less than or equal to 300 DEG C and discharged.

[0012] Further, the sixth step: high-speed wire rod and bar rolling, the heating system is heated in a step-by-step heating furnace, and the heating temperature of the initial rolling square billet is controlled according to the following requirements: the preheating section is less than or equal to 850 DEG C, the heating section is 850-1100 DEG C, and the soaking section is 1080-1180 DEG C.

[0013] Further, the wire rod rolling, the opening rolling temperature is 1170 DEG C, the wire rod finishing temperature is controlled to be 950-1050 DEG C, the wire rod finishing speed is controlled to be 27 m / s, the rolling specification is Phi 9.0 mm, the hot collection enters the slow cooling tunnel furnace, the slow cooling is greater than or equal to 48 hours and then the wire rod is transferred into the annealing chamber furnace, and the hot rolling wire rod out-of-roundness is controlled to be plus or minus 0.15 mm.

[0014] Further, the bar rolling, the opening rolling temperature is 1170 DEG C, the bar rolling speed is controlled to be 1.5 m / s, the rolling specification is Phi 45 mm, the cold bed collection is immediately transferred into the annealing chamber furnace after being cut to size, and the hot rolling bar out-of-roundness is controlled to be plus or minus 0.5 mm.

[0015] The beneficial effects of the present application are as follows:

[0016] Cr12MoV adopts continuous casting 150 square billet to directly roll wire rod and bar, slag system adopts TX-2 protective slag, through two-machine two-flow arc continuous casting machine to continuously produce 150 continuous casting billet, through weak cooling of two cooling water and electromagnetic stirring, reduce the center segregation of continuous casting billet, at the same time, reduce the state of too large size of carbide and uneven distribution of carbide caused by selection of crystallization during pouring, effectively realize the fine and dispersed distribution of carbide, at the same time, continuous production improves the production efficiency and reduces the energy consumption; high-speed wire rod and bar are adopted, through 36 rolling mills, 4 water tanks and induction heating furnace to realize whole process controlled rolling and controlled cooling, effectively avoid the overheating and overheating in the center, the qualified rate of wire rod is 100% through ultrasonic flaw detection (using GB / T 4162B level flat bottom hole diameter Φ3.2mm), and the qualified rate of bar is 99%; at the same time, the wire rod is annealed in the argon protective atmosphere of cover annealing furnace instead of traditional canning annealing, effectively reduces the surface decarburization layer, the decarburization layer + transition layer is controlled to be less than or equal to 60um, and the use performance of the subsequent heat treatment cannot meet the requirements. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 , Cr12MoV Φ9.0 longitudinal metallograph 100X diagram;

[0018] Figure 2 , Cr12MoV Φ9.0 transverse metallograph 500X diagram;

[0019] Figure 3 , Cr12MoV Φ45 longitudinal metallograph 100X diagram;

[0020] Figure 4 , Cr12MoV Φ45 transverse metallograph 500X diagram. DETAILED DESCRIPTION

[0021] The present application will be further illustrated below in conjunction with the drawings and specific embodiments, and it should be understood that the following specific embodiments are only used to illustrate the present application and are not used to limit the scope of the present application. It should be noted that the words "front", "back", "left", "right", "up" and "down" used in the following description refer to the directions in the drawings, and the words "in" and "out" refer to the directions towards or away from the geometric center of a particular component.

[0022] Example 1:

[0023] Cr12MoV annealed bar and wire rod with product specifications of φ9mm and Φ45mm bar are produced, and the chemical composition thereof is shown in Table 1.

[0024] Table 1 Chemical composition of Cr12MoV in Example 1

[0025]

[0026] First step: in the electric arc furnace, scrap and high carbon chromium iron alloy materials are added for alloy melting and primary refining. The tapping temperature is ≥1590℃, P≤0.030%, and slagging is needed before tapping;

[0027] Second step: LF furnace smelting, adding lime and fluorite, and electric slagging, controlling the slag R2.5-3.5 to adjust the alloy composition, temperature refining, and taking silicon iron and other deoxidizers for deoxidation, the dosage is controlled to maintain white slag operation, sampling analysis is performed, when each alloy composition meets the standard requirements, the white slag is kept for 15 minutes, T=1625℃, and then tapping is transferred to the VD station.

[0028] Third step: VD furnace, slag removal is needed before entering the VD, vacuum is extracted, the vacuum degree reaches 67Pa and is kept for 15 minutes; after breaking the vacuum, temperature measurement and sampling analysis are performed, and covering agent is added, keeping calm weak argon blowing for 14 minutes, when the temperature T=1550℃, it is transferred to the continuous casting machine platform.

[0029] Fourth step: arc-shaped square billet continuous casting, the combined mode of crystallizer and end electromagnetic stirring is adopted during pouring, and the drawing speed is controlled according to the following table:

[0030] Target temperature Target pull rate 1460-1480℃ 1.0-1.2 m / min

[0031] Cooling control: three-stage partition water distribution is adopted in the secondary cooling zone, and the specific water quantity is automatically matched with the drawing speed, the material temperature entering the straightening machine is >1000℃; when the billet is cut to size, the cross section of the continuous casting billet is 150×150mm, and the length is 6000mm.

[0032] Fifth step: continuous casting billet annealing, the continuous casting billet is immediately transferred to the chamber furnace for annealing after cutting, the annealing process is 850-860℃ for 6 hours, and the furnace is cooled to ≤300℃ before discharging.

[0033] Sixth step: high-speed wire rod and bar rolling, the heating system is adopted in the walking beam furnace, and the heating temperature of the initial rolling square billet is controlled according to the following requirements: preheating section: ≤850℃; heating section: 850-1100℃, soaking section: 1080-1180℃.

[0034] ① Wire rod rolling, the opening rolling temperature is 1170℃, the wire rod finishing temperature is controlled to be 950-1050℃, the wire rod finishing speed is controlled to be 27m / s, the rolling specification is Φ9.0mm, the hot collection enters the slow cooling tunnel furnace, the slow cooling is ≥48 hours, and then it is transferred to the annealing chamber furnace, and the hot rolling wire rod out-of-roundness is controlled to be ±0.15mm.

[0035] ② Bar rolling, the opening rolling temperature is 1170℃, the bar rolling speed is controlled to be 1.5m / s, the rolling specification is Φ45mm, and the cold bed collection is immediately transferred to the annealing chamber furnace after cutting to size, and the hot rolling bar out-of-roundness is controlled to be ±0.5mm.

[0036] Seventh step: annealing, hot rolling wire rod and bar need to be annealed,

[0037] ① Wire rod annealing, cover type annealing is adopted, nitrogen is blown before temperature rise, nitrogen protection is filled in during temperature rise, temperature keeping and temperature drop, and the flow rate is set to 15m 3 / h, the heating system is: temperature rise with furnace, the temperature rise time is ensured to be 8 hours when the temperature is raised to 880 DEG C, the temperature is kept for 10 hours at 880 DEG C, and the furnace is taken out after the temperature is cooled to below 500 DEG C, and air cooling is carried out;

[0038] ② Bar annealing, chamber furnace annealing is adopted, and the heating system is: temperature rise with furnace, the temperature rise time is ensured to be 10 hours when the temperature is raised to 880 DEG C, the temperature is kept for 10 hours at 880 DEG C, and the furnace is taken out after the temperature is cooled to below 500 DEG C, and air cooling is carried out.

[0039] Laboratory detection Cr12MoV wire rod Φ9.0, bar Φ45 carbide distribution, as Figures 1-4 shown:

[0040]

[0041] At the same time, two samples are selected in the laboratory, the tensile properties are detected by simulating customer's subsequent drawing, and the mechanical property indexes are as follows:

[0042]

[0043]

[0044] The technical means disclosed in the scheme of the application are not limited to the technical means disclosed in the above-mentioned embodiments, and also include technical solutions composed of any combination of the above technical features.

Claims

1. A method for producing rods and wires by continuous casting of ledeburite die steel Cr12MoV, characterized in that: Specifically including the following: electric furnace → LF furnace refining → VD furnace refining → continuous casting billet → Annealing of continuous casting billets → high-speed wire rolling wire rods and bars → annealing → inspection → storage.

2. The method for producing rods and wires by continuous casting of ledeburite die steel Cr12MoV according to claim 1, characterized in that: Scrap steel, high carbon ferrochrome and other alloy materials are added to the electric arc furnace for melting and primary smelting of the alloy; the tapping temperature is ≥1590℃, P ≤0.030%, and slag removal is required before tapping.

3. The method for producing rods and wires by continuous casting of ledeburite die steel Cr12MoV according to claim 1, characterized in that: LF furnace smelting, adding lime and fluorite, electrifying slag, controlling slag R2.5-3.5 to adjust alloy composition, heating and refining, taking ferrosilicon and other deoxidizers for deoxidation, the dosage is based on maintaining white slag operation, sampling and analysis, when each alloy composition meets the standard requirements, the white slag is kept for 15 minutes, T = 1625℃ When the steel is discharged, it is transferred to the VD station.

4. The method for producing rods and wires by continuous casting of ledeburite die steel Cr12MoV according to claim 1, characterized in that: The third step: VD furnace. Before entering the VD furnace, slag removal and vacuum are required. The vacuum degree reaches 67Pa and is maintained for 15 minutes. After breaking the vacuum, temperature measurement and sampling are performed for full analysis. Covering agent is added and the furnace is kept calm and weakly blown with argon for 14 minutes. When the temperature is measured at T=1550℃, it is transferred to the continuous casting machine platform.

5. The method for producing rods and wires by continuous casting of ledeburite die steel Cr12MoV according to claim 1, characterized in that: Step 4: Continuous casting of curved billets is carried out using a continuous casting machine. A combination of a crystallizer and end-stage electromagnetic stirring is used during casting, with a casting speed of 1.0-1.2 m / min.

6. The method for producing rods and wires by continuous casting of ledeburite die steel Cr12MoV according to claim 1, characterized in that: Cooling control: The secondary cooling zone adopts a three-stage zoned water distribution method. The water volume is automatically matched with the drawing speed. The material temperature entering the drawing and straightening machine is greater than 1000℃. The billet is cut to a fixed length when it is discharged, and the continuous casting billet with a cross-section of 150×150mm and a length of 6000mm is obtained.

7. The method for producing rods and wires by continuous casting of ledeburite die steel Cr12MoV according to claim 1, characterized in that: Step 5: Annealing of continuous casting billets. After being cut, the continuous casting billets are immediately transferred to a chamber furnace for annealing. The annealing process is to keep the temperature at 850-860℃ for 6 hours, and then cool to ≤300℃ before being taken out of the furnace.

8. The method for producing rods and wires by continuous casting of ledeburite die steel Cr12MoV according to claim 1, characterized in that: Step 6: For high-speed wire rolling, the wire rods and bars are heated in a walking beam heating furnace. The heating temperature of the initial rolled square billets is controlled according to the following requirements: preheating section: ≤850℃; heating section: 850~1100℃; soaking section: 1080~1180℃.

9. The method for producing rods and wires by continuous casting of ledeburite die steel Cr12MoV according to claim 1, characterized in that: Wire rod rolling, starting rolling temperature: 1170℃, final rolling wire drawing temperature controlled at 950~1050℃, wire finishing rolling speed controlled at 27m / s, rolling specification is Φ9.0mm, heat is collected into slow cooling tunnel furnace, slow cooling ≥48 hours and then transferred to bell furnace annealing, hot rolled wire rod out-of-roundness controlled at ±0.15mm.

10. The method for producing rods and wires by continuous casting of ledeburite die steel Cr12MoV according to claim 1, characterized in that: Bar rolling, starting rolling temperature: 1170℃, bar rolling speed controlled at 1.5m / s, rolling specification is Φ45mm, after being collected and cut to length on the cooling bed, it is immediately transferred to the chamber furnace for annealing, and the out-of-roundness of the hot-rolled bar is controlled at ±0.5mm.

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