A control method for shortening the aging period of ultra-high strength spring steel wire

Abstract

This invention discloses a method for controlling the shortening of the aging period of ultra-high strength spring steel wire rod. The method specifically includes the following steps: S1. During rolling production, medium-temperature final rolling is used, with a sizing inlet temperature of 880±20℃; S2. During rolling production, medium-temperature wire drawing is used, with a wire drawing temperature of 870±20℃; S3. After rolling, the wire rod enters the Stellmore air-cooling line for cooling; S4. After coiling, the wire rod is hung on a C-hook for transportation, with a coiling temperature of 540-580℃. When the coiling temperature reaches 400℃, the subsequent cooling fan is turned off for 30 minutes of heat preservation before packaging. This invention successfully solves the problem of self-breakage during static storage after heat treatment, improves the performance of ultra-high strength spring steel wire rod, effectively shortens the aging period of ultra-high strength spring steel wire rod, and further alleviates storage and delivery pressures.

Description

Technical Field

[0001] This invention relates to a method for controlling the aging period of ultra-high strength spring steel wire. Background Technology

[0002] Ultra-high strength spring steel wire refers to spring steel materials with a tensile strength greater than 2000 MPa and a reduction of area greater than 40% after heat treatment. Under such high strength conditions, the quality stability during spring processing is highly sensitive to the aging time of the raw material in its hot-rolled state. Currently, the aging period of the raw material needs to reach 15 days or more. Spring steel wire with a short aging period often exhibits spontaneous breakage under static conditions after heat treatment at the customer's site. Analysis of the fracture surface reveals a finer surface microstructure and the presence of a rapidly cooled layer. Scanning analysis of the fracture surface also reveals hydrogen-induced delayed fracture morphology. To address this phenomenon, the material must be aged for more than 15 days before being shipped to the user, placing significant pressure on warehousing and delivery. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a control method for shortening the aging period of ultra-high strength spring steel wire, which can successfully solve the problem of self-breakage in the static state after heat treatment, improve the performance of ultra-high strength spring steel wire, effectively shorten the aging period of ultra-high strength spring steel wire, and further solve the pressure of warehousing and delivery.

[0004] The technical solution of this invention to solve the above technical problems is: a method for controlling the aging period of ultra-high strength spring steel wire, which specifically includes the following steps:

[0005] S1 rolling production uses medium-temperature final rolling, with a sizing inlet temperature of 880±20℃;

[0006] S2 rolling production uses medium-temperature wire drawing, with a wire drawing temperature of 870±20℃;

[0007] S3 wire rod is cooled in the Stellmore air-cooling line after rolling.

[0008] S4 reels are assembled and then hung on C-hooks for transport.

[0009] The present invention further specifies the following:

[0010] Preferably, the cooling process of the Stellmore air-cooled line in S3 is as follows: fan #1 opening at 70%, fan #2 opening at 60%, fan #3 opening at 50%, fan #4 opening at 40%, fan #5 opening at 30%, and 1-9 covers open.

[0011] Preferably, the cooling water tanks used to control the temperature before final rolling and wire drawing in S1 or S2 are two sets of water tanks, and the opening degree of the two sets of water tanks is the same, which is 40%-60%.

[0012] Preferably, in step S4, the temperature during winding is 540-580℃. When the winding temperature drops to a certain level, the subsequent cooling fan is turned off for heat preservation before packaging. Preferably, when the winding temperature drops to 400℃, the subsequent cooling fan is turned off for heat preservation for 30 minutes before packaging.

[0013] The beneficial effects of this invention are: this invention can successfully solve the problem of self-breakage in the static state after heat treatment, improve the performance of ultra-high strength spring steel wire, effectively shorten the aging period of ultra-high strength spring steel wire from 15 days to 7 days, and further solve the pressure of warehousing and delivery, and increase the turnover of warehousing circulation by 25%. Detailed Implementation

[0014] Example

[0015] This embodiment provides a method for controlling the shortening of the aging period of ultra-high strength spring steel wire, applied to ultra-high strength spring steel wire SAE9254. The method specifically includes the following steps:

[0016] S1 rolling production uses medium-temperature final rolling with a sizing inlet temperature of 880℃;

[0017] S2 rolling production uses medium-temperature wire drawing, with a wire drawing temperature of 870℃.

[0018] The cooling water tanks used for temperature control during S3 final rolling and before wire drawing consist of two sets, both with the same opening degree of 50%.

[0019] After rolling, the S4 wire rod enters the Steyrmo air-cooling line for cooling. Since the carbon content of ultra-high strength spring steel is 0.52%-0.58%, it belongs to hypoeutectoid steel. In the Steyrmo air-cooling line, the ferrite and pearlite microstructures transform. In order to ensure uniform microstructure transformation, the fans and covers are turned on appropriately when the ultra-high strength spring steel wire rod enters the Steyrmo air-cooling line after being wired. The opening of fan #1 is 70%, fan #2 is 60%, fan #3 is 50%, fan #4 is 40%, fan #5 is 30%, and 9 covers are opened. The spring steel wire rod is cooled to the phase transformation point of 720°C in the Steyrmo air-cooling line and then enters the heat-insulating cover for microstructure transformation.

[0020] After the S4 coils are assembled, they are hung on C-hooks for transportation. The temperature during assembly is 560℃. Since the removal rate of hydrogen is highest at 300℃-400℃, the solubility of hydrogen increases with temperature above this range, and the release rate of hydrogen decreases below this range. Therefore, when the coil temperature is 400℃, the subsequent cooling fan is turned off and the coil is kept warm for 30 minutes before packaging. This solves the problem of self-breakage of materials when left to stand after heat treatment.

[0021] This batch of φ15mm SAE9254 steel wire, aged for 7 days, was shipped to the user for manufacturing 2000MPa grade ultra-high strength spring steel wire. It performed well and did not experience any spontaneous breakage after heat treatment.

[0022] Table 1

[0023]

[0024] Table 2

[0025]

[0026] Table 1 shows the frequency of spontaneous breakage of materials with a short aging period of 7 days after heat treatment, as reported by customers one year before the method of this embodiment was adopted. Table 2 shows the frequency of spontaneous breakage of materials with a short aging period of 7 days after heat treatment, as reported by customers one year after the method of this embodiment was adopted. It can be seen that the present invention can successfully solve the problem of spontaneous breakage in the static state after heat treatment and can effectively shorten the aging period of ultra-high strength spring steel wire.

[0027] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method for controlling the shortening of the aging period of ultra-high strength spring steel wire, characterized in that: The method specifically includes the following steps: S1 rolling production uses medium-temperature final rolling, with a sizing inlet temperature of 880±20℃; S2 rolling production uses medium-temperature wire drawing, with a wire drawing temperature of 870±20℃; After rolling, the S3 wire rod enters the Steyrmo air-cooling line for cooling. The cooling process of the Steyrmo air-cooling line is as follows: the opening of fan #1 is 70%, the opening of fan #2 is 60%, the opening of fan #3 is 50%, the opening of fan #4 is 40%, the opening of fan #5 is 30%, and the covers are opened 1-9 times. The spring steel wire rod is cooled to the phase transformation point of 720°C in the Steyrmo air-cooling line and then enters the heat preservation cover to undergo the transformation of ferrite and pearlite structures. After the S4 coils are assembled, they are hung on C-hooks for transportation. The temperature during assembly is 540-580℃. When the coil temperature drops to 400℃, the cooling fan that serves packaging is turned off for 30 minutes to keep it warm before packaging.

2. The method for controlling the shortening of the aging period of ultra-high strength spring steel wire according to claim 1, characterized in that: The cooling water tanks used to control the temperature before final rolling and wire drawing in S1 or S2 are two sets of water tanks, and the opening degree of the two sets of water tanks is the same, which is 40%-60%.