Spring steel wire rod with shortened aging period and production method thereof

Abstract

The invention discloses a spring steel wire rod capable of shortening the aging period and a production method thereof in the technical field of metal rolling, and the production method comprises the following steps: heating, rolling, spinning, cooling and coiling a pretreated steel billet in sequence to obtain the spring steel wire rod; wherein the tapping temperature of the heated steel billet is 970 + / -30 DEG C; the reducing and sizing inlet temperature in the rolling process is 880 + / -30 DEG C; the spinning temperature is 880 + / -30 DEG C. According to the spring steel wire with the shortened aging period and the production method thereof, the aging period of the produced spring steel wire is shortened to 7 days from 15 days, the storage and placement time is shortened, the warehouse utilization rate is increased, and the production efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal rolling, in particular to a spring steel wire with shortened aging period and a production method thereof. BACKGROUND

[0002] Currently, the ultra-high strength spring steel wire is mainly applied to the suspension system of new energy vehicles, and the tensile strength after heat treatment reaches more than 2000 MPa, and the quality level reaches the international advanced level, and is applied to the leading enterprises of new energy vehicles at home and abroad.

[0003] Under such high strength conditions, the quality stability of the spring during processing is very sensitive to the aging time of the hot-rolled raw material, and the aging period of the raw material currently needs to reach 15 days or more, otherwise quality problems such as self-breaking will occur during heat treatment; this problem brings great pressure to storage and delivery, and affects the further increment of ultra-high strength spring steel. SUMMARY

[0004] The purpose of the present application is to overcome the deficiencies in the prior art, and to provide a spring steel wire with shortened aging period and a production method thereof, wherein the aging period of the spring steel wire produced by the production method is shortened from 15 days to 7 days, the storage placement time is shortened, the warehouse utilization rate is improved, and the production efficiency is improved.

[0005] To achieve the above purpose, the present application adopts the following technical scheme:

[0006] On the one hand, the present application provides a production method of a spring steel wire with shortened aging period, the chemical composition of the spring steel wire is 0.50%-0.58% of C, 1.45%-1.75% of Si, 0.60%-0.70% of Mn, 0.60%-0.70% of Cr, and the rest is Fe and inevitable impurity elements, and the production method comprises:

[0007] The steel billet after pretreatment is sequentially subjected to heating, rolling, wire feeding, cooling and coiling to obtain a spring steel wire.

[0008] Further, the pretreatment comprises grinding and chamfering treatment of the steel billet.

[0009] Further, the cooling treatment comprises water cooling treatment and air cooling treatment.

[0010] Further, the steel wire production line adopts a water tank for water cooling treatment, the water cooling treatment includes primary water cooling treatment and finishing water cooling treatment, the rolling treatment includes rough rolling, intermediate rolling, pre-finishing rolling, finishing rolling and reducing sizing final rolling, the pretreated billet is sequentially subjected to rough rolling, intermediate rolling, pre-finishing rolling, primary water cooling treatment, finishing rolling, finishing water cooling treatment, reducing sizing final rolling, wire drawing water cooling treatment, wire drawing, air cooling treatment and coiling to obtain the spring steel wire.

[0011] The flow of the water tank for primary water cooling treatment and the water tank for finishing water cooling treatment is 2500-2850 L / m.

[0012] Further, the steel wire production line adopts a Stelmor air cooling line for air cooling treatment, the cooling speed is 6-10 ℃ / s, and after cooling to 720±15 ℃, the spring steel wire is cooled in the cover at a cooling speed of 1-3 ℃ / s.

[0013] Further, in the Stelmor air cooling line, 5-6 fans are opened, and 6-7 covers are opened.

[0014] Further, the capacity of the fan is 200,000 cubic meters per hour, and the opening degree is 30%-70%.

[0015] Further, after the coiling treatment, the coiled spring steel wire needs to be kept at 350-400 ℃ for 20-30 minutes.

[0016] On the other hand, the present application provides a spring steel wire produced by the production method.

[0017] Compared with the prior art, the present application has the following beneficial effects:

[0018] The spring steel wire with shortened aging period and the production method thereof provided by the present application shorten the aging period of the spring steel wire from 15 days to 7 days by adjusting the process parameters in the production method of the spring steel wire, shorten the storage time, improve the utilization rate of the warehouse, and improve the production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is the metallographic diagram of the cross section of the spring steel wire provided by the comparative example of the present application;

[0020] Figure 2 is the metallographic diagram of the cross section of the spring steel wire provided by the embodiment of the present application;

[0021] Figure 3 is the scanning electron microscope diagram of the fracture of the spring steel wire provided by the comparative example of the present application. DETAILED DESCRIPTION

[0022] The application will be further described below with reference to the drawings. The following examples are only used to more clearly illustrate the technical solutions of the application, and cannot be used to limit the protection scope of the application.

[0023] Embodiment 1

[0024] The embodiment provides a spring steel wire with shortened aging period, which is a φ15mm specification ultra-high strength spring steel wire, and the strength after heat treatment reaches 2000Mpa, and is mainly used for automobile suspension system springs.

[0025] In the embodiment, the spring steel wire is obtained by heating, controlled temperature rolling, wire drawing, controlled cooling, coiling and packing after pretreatment of the steel billet. The steel wire production line used in the embodiment adopts a water tank for water cooling treatment and a Stelmor air cooling line for air cooling treatment.

[0026] The production method comprises:

[0027] (1) the steel billet is pretreated, including grinding and chamfering treatment;

[0028] (2) the pretreated steel billet is heated to 970±30℃, and then enters rough rolling, and is rolled into a φ70mm round bar, and then enters medium rolling, and is rolled into a φ32mm round bar, and then enters pre-finishing rolling, and is rolled into a φ21mm round bar, and then enters a finishing mill after initial cooling in a water tank, and enters a reducing final rolling after cooling in a finishing water tank, in the embodiment, the water tank group for initial water cooling treatment comprises one water tank, the water tank group for finishing water cooling treatment comprises two water tanks, the opening of the water tank for initial water cooling treatment is adjusted to 55%, so that the flow of the water tank for initial water cooling treatment is 2580L / m, the opening of the water tank for finishing water cooling treatment is adjusted to 40%, so that the flow of the water tank for finishing water cooling treatment is 2660L / m, to ensure the uniformity of the wire cooling, reduce the stress generated in the cooling process, and the reducing inlet temperature is 890±10℃;

[0029] (3) the steel billet after reducing final rolling is cooled in a final rolling water tank, and then wire drawing is performed, and the wire drawing temperature is 885±10℃;

[0030] (4) the steel wire after wire drawing enters a Stelmor air cooling line for air cooling, in the embodiment, the Stelmor air cooling line is opened with 5 air blowers and 7 cover caps, the flow of the air blowers is 200000 cubic meters per hour, wherein the opening of the 1# air blower is 70%, the opening of the 2# air blower is 60%, the opening of the 3# air blower is 50%, the opening of the 4# air blower is 40%, and the opening of the 5# air blower is 30%, so that the steel wire is rapidly cooled to 720±15℃ at a cooling speed of 8℃ / s in the Stelmor air cooling line, enters the holding cover cap to perform structure transformation at 3℃ / s, and is cooled to 570℃ to perform coiling;

[0031] (5) The coiled spring steel wire is naturally cooled in air, and when the temperature of the coiled spring steel wire is cooled to 350℃, the coiled spring steel wire is kept for 30 minutes, and then is cooled and packaged, so as to obtain the spring steel wire.

[0032] Embodiment 2

[0033] The embodiment provides a spring steel wire with shortened aging period and a production method thereof. The spring steel wire is also a φ15mm specification ultra-high strength spring steel wire, the strength of the spring steel wire after heat treatment reaches 2000Mpa, and the spring steel wire is mainly used for automobile suspension system springs.

[0034] In the embodiment, the spring steel wire is obtained by the pretreated steel billet being subjected to heating, temperature control rolling, wire drawing, controlled cooling, coiling and packaging. The steel wire production line used in the embodiment adopts a water tank for water cooling treatment and a Stelmor air cooling line for air cooling treatment.

[0035] The production method comprises the following steps.

[0036] (1) The steel billet is pretreated, including grinding and chamfering treatment;

[0037] (2) The pretreated steel billet is heated to 980±15℃, and then is subjected to rough rolling, and is rolled into a φ70mm round bar, and then is subjected to medium rolling, and is rolled into a φ32mm round bar, and then is subjected to pre-finishing rolling, and is rolled into a φ21mm round bar, and then is cooled in an initial cooling water tank, and then is subjected to finishing rolling, and is cooled in a finishing water tank, and then is subjected to final diameter reduction rolling, in the embodiment, the water tank group for initial water cooling treatment comprises a plurality of water tanks, the water tank group for finishing water cooling treatment comprises two water tanks, the opening degree of the water tank for initial water cooling treatment is adjusted to 65%, so that the flow of the water tank for initial water cooling treatment is 2800L / m, the opening degree of the water tank for finishing water cooling treatment is adjusted to 50%, so that the flow of the water tank for finishing water cooling treatment is 2750L / m, the uniformity of the wire cooling is ensured, the stress generated in the cooling process is reduced, and the inlet temperature of the diameter reduction is 875±15℃;

[0038] (3) The steel billet after the final diameter reduction rolling is cooled in a final rolling water tank, and then is subjected to wire drawing, and the wire drawing temperature is 880±15℃;

[0039] (4) The steel wire after the wire drawing is subjected to air cooling in a Stelmor air cooling line, in the embodiment, the Stelmor air cooling line is started with five air fans and seven cover caps, the flow of the air fan is 200000 cubic meters per hour, the opening degree of the 1# air fan is 70%, the opening degree of the 2# air fan is 60%, the opening degree of the 3# air fan is 50%, the opening degree of the 4# air fan is 40%, and the opening degree of the 5# air fan is 30%, so that the steel wire is rapidly cooled to 720±15℃ at a cooling speed of 8℃ / s in the Stelmor air cooling line, is subjected to structure transformation at 3℃ / s in the cover cap, and is coiled after being cooled to 560℃;

[0040] (5) The coiled spring steel wire rod is naturally cooled in air, and when the temperature of the coiled spring steel wire rod is cooled to 400°C, the coiled spring steel wire rod is kept for 20 minutes, and then is cooled and packaged, to obtain the spring steel wire rod.

[0041] Comparative Example 1

[0042] The present comparative example provides a spring steel wire rod with a shortened aging period of φ15 mm specification and a production method thereof, the production method comprising: the pretreated billet sequentially passes through rough rolling, intermediate rolling, pre-precision rolling, initial cooling water cooling treatment, precision rolling, precision rolling water cooling treatment, reducing sizing final rolling, wire drawing water cooling treatment, wire drawing, air cooling treatment and coiling, to obtain the spring steel wire rod. Different from Example 1, in the present comparative example, the specific parameter control is as follows: the reducing sizing inlet temperature is 800±20°C; the wire drawing temperature is 800±20°C; the water tank opening degree and flow are not specifically refined as control points; in order to reduce the original rod strength, the opening degrees of 1# fan, 2# fan and 3# fan in the Stelmor air cooling line are 15%, 10% and 10% respectively, and 4 covers are opened; in order to increase the ferrite transformation amount, the wire rod is cooled to 780±20°C at a lower cooling speed of 3-5°C / s in the Stelmor air cooling line to enter the holding cover for structure transformation, and the coiled spring steel wire rod is not kept after coiling, but is naturally cooled to room temperature for collection and packaging.

[0043] After the spring steel wire rod provided in Example 1 is aged for 7 days, an ultra-high strength spring steel wire is made, and the frequency of self-breaking phenomenon in a period of time is recorded, and the results are shown in Table 1.

[0044] Table 1

[0045] Time January February March April May June July August September October November December Example 1 frequency of self-termination (%) 0 0 0 0 0 0 0 0 0 0 0 0 Example 2 frequency of self-termination (%) 0 0 0 0 0 0 0 0 0 0 0 0

[0046] As shown in Table 1, the frequency of self-breaking of the spring steel wire rod provided in Example 1 and Example 2 after heat treatment for 7 days is good, and no self-breaking phenomenon after heat treatment occurs.

[0047] After the spring steel wire rod provided in Comparative Example 1 is aged for 7 days, an ultra-high strength spring steel wire is made, and the frequency of self-breaking phenomenon in a period of time is recorded, and the results are shown in Table 2.

[0048] Table 2

[0049] Time January February March April May June July August September October November December frequency of self-termination (%) 3.6 3.4 3.8 3.2 2.8 3.0 2.6 2.8 3.0 3.2 3.3 3.6

[0050] As shown in Table 2, the frequency of self-breaking of the spring steel wire rod provided in Comparative Example 1 after heat treatment for 7 days occurs, and the self-breaking phenomenon after heat treatment occurs in a period of time.

[0051] The fracture of the self-breaking spring steel wire rod provided in Comparative Example 1 is analyzed, and the results are shown in Table 3. Figure 1As shown, the metallographic diagram shows that the surface grain size of the fracture is finer, and there is a quenching layer structure; and through scanning analysis of the fracture, as shown in Figure 3 As shown, there is a hydrogen-induced delayed fracture morphology, and the cross section of the spring steel wire provided in Example 1 is analyzed, as shown in Figure 2 As shown, the metallographic diagram shows that after improvement, the cross section of the spring steel wire provided in Example 1 has no surface quenching layer, and the structure is uniform.

[0052] The spring steel wire produced by the production method provided by the application achieves 7-day aging delivery, and improves the production capacity.

[0053] In the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like are based on the orientations or positional relationships shown in the drawings, and are only used to explain the relative positional relationships, movement conditions and the like between the components in a certain specific posture. If the specific posture changes, the directional indications also change accordingly. This is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features limited by "first", "second" and the like can be explicitly or implicitly included one or more. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0054] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, and it can be the communication between the two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0055] The embodiments of the present application are described above in combination with the drawings, but the present application is not limited to the above specific embodiments, and the above specific embodiments are only illustrative, not limiting, and those skilled in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims.

Claims

1. A method for producing spring steel wire with shortened aging period, characterized in that: The chemical composition of the spring steel wire rod is C: 0.50%-0.58%, Si: 1.45%-1.75%, Mn: 0.60%-0.70%, Cr: 0.60%-0.70%, and the remaining components are Fe and inevitable impurity elements. The production method comprises: heating, rolling, spinning, cooling and coiling the pretreated steel billet to obtain the spring steel wire rod; The tapping temperature of the heated billet is 970±30°C; the sizing inlet temperature in the rolling process is 880±30°C; and the wire drawing temperature is 880±30°C.

2. The method for producing spring steel wire with shortened aging period according to claim 1, characterized in that: The pretreatment includes grinding and chamfering the steel billet.

3. The method for producing spring steel wire with shortened aging period according to claim 1, characterized in that: The cooling treatment includes water cooling treatment and air cooling treatment.

4. The method for producing spring steel wire with shortened aging period according to claim 3, characterized in that: The steel wire rod production line uses a water tank for water cooling treatment, the water cooling treatment includes initial water cooling treatment and finishing water cooling treatment, the rolling treatment includes rough rolling, intermediate rolling, pre-finishing rolling, finishing rolling and sizing final rolling, and the pre-treated steel billet is sequentially subjected to rough rolling, intermediate rolling, pre-finishing rolling, initial cooling water cooling treatment, finishing rolling, finishing water cooling treatment, sizing final rolling, wire laying water cooling treatment, wire laying, air cooling treatment and coiling to obtain spring steel wire rod; The flow rates of the water tank for the initial water cooling treatment and the water tank for the finishing water cooling treatment are both 2500-2850 L / m.

5. The method for producing spring steel wire with shortened aging period according to claim 3, characterized in that: The steel wire production line adopts a Stelmor air cooling line for air cooling treatment, with a cooling rate of 6°C / s-10°C / s. After cooling to 720±15°C, it enters the insulation cover and is kept warm at a cooling rate of 1°C / s-3°C / s.

6. The method for producing spring steel wire with shortened aging period according to claim 5, characterized in that: In the Stelmore air cooling line, 5-6 fans are opened and 6-7 covers are opened.

7. The method for producing spring steel wire with shortened aging period according to claim 6, characterized in that: The fan has a capacity of 200,000 cubic meters per hour and an opening degree of 30%-70%.

8. The method for producing spring steel wire with shortened aging period according to claim 1, characterized in that: After the coiling process, the coiled spring steel wire needs to be kept at 350-400° C. for 20-30 minutes.

9. A spring steel wire produced by the production method according to any one of claims 1 to 8.

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