Preparation method of Si-Mn spring hot-rolled narrow strip steel

Abstract

The invention discloses a preparation method of Si-Mn spring hot-rolled narrow strip steel, which comprises the following steps: (1) a primary smelting furnace is used, the element mass ratio is controlled to be more than or equal to 0.10% and less than or equal to omega [C], the element mass ratio is controlled to be less than or equal to 0.015% and the element mass ratio is controlled to be less than or equal to 1600 DEG C and less than or equal to temperature T during tapping of the primary smelting furnace; the charging sequence in the tapping process is carbon powder, alloy, pre-molten slag and lime; (2) in an LF refining furnace, the initial Si content is larger than or equal to 1.2% according to the mass ratio; (3) in a vacuum refining furnace, the ultimate vacuum time is not less than 10 minutes, and the static stirring time is not less than 20 minutes; (4) continuous casting, wherein crystallizer electromagnetic stirring and tail end electromagnetic stirring are adopted in the continuous casting process; (5) heating is carried out, heating is divided into a preheating section, a first heating section, a second heating section, a third heating section and a soaking section, the third heating section and the soaking section are high-temperature sections, the in-furnace time of the high-temperature sections is smaller than or equal to 90 min, and the total in-furnace time of heating is smaller than or equal to 180 min; (6) rolling is conducted, specifically, the initial rolling temperature is 1050-1200 DEG C, the final rolling temperature is 860-950 DEG C, rapid coiling is conducted, the coiling temperature is 450-700 DEG C, and air cooling is conducted after rolling; according to the method, the components are reasonably designed, and the hot-rolled narrow strip steel with good mechanical properties and long service life is prepared by combining microalloying with smelting and rolling.

Description

Technical Field

[0001] The invention relates to a method for preparing narrow strip steel, in particular to a method for preparing Si-Mn series spring hot-rolled narrow strip steel, and belongs to the technical field of special steel production. Background Art

[0002] Si-Mn spring strip steel is a metal material with high strength, high toughness and high elasticity. It is widely used in many fields of the national economy, especially in various mechanical equipment such as automobiles, aviation, electric power, railways, medical treatment and daily hardware.

[0003] Among Si-Mn spring steels, common grades include 60Si2Mn and 60Si2MnA. Due to its high elasticity and wear resistance, Si-Mn spring strip steel is often used to manufacture springs in automotive suspension systems. These springs support the vehicle's weight and provide a comfortable ride. In brake systems, spring strip steel is used to manufacture brake shoes and other components requiring elasticity to ensure proper operation.

[0004] Si-Mn spring strip steel is commonly used in the machinery manufacturing industry to manufacture various elastic components, such as leaf springs and spring molds, for transmission, shock absorption, and support in industrial machinery. In complex mechanical equipment, spring strip steel serves as a key component in connectors and transmission mechanisms, ensuring stable operation.

[0005] Specific usage scenarios dictate that Si-Mn spring strip steel must possess both strength and toughness. Currently, numerous factors affect the strength and toughness of spring strip steel, including composition control during the smelting and casting processes, porosity and shrinkage, ferrite banding, and decarburization. Furthermore, increasingly competitive markets are placing higher demands on the production of cost-effective Si-Mn hot-rolled spring strip steel.

[0006] Patent CN111979480A discloses a hot-rolled narrow strip steel for thick-gauge washers and a preparation method thereof. Based on the carbon and manganese components, the method increases the quenching hardness and hardenability of the gasket by adjusting the carbon content and the narrow composition control range of the alloy and adding the Cr element to the hardenable alloy. This method allows for the stable and cost-effective production of hot-rolled strip steel with a hardness of less than 229 HBW and a total decarburization layer of less than 0.08 mm. The resulting washers have a quenched and tempered hardness of 50-55 HRC and are free of quenching soft spots. While the method offers excellent economic and social benefits, it only involves alloy design and lacks actual process control during primary refining and refining. Consequently, the method fails to effectively control the composition and oxygen potential of the refined slag, thus affecting the final quality. The patent CN116475252A discloses a method for controlling the decarburization layer of a hot-rolled Si-Mn hot-rolled narrow strip steel, which comprises the steps of continuous casting, step-by-step heating furnace heating, hot rolling, coiling, cooling and warehousing. By controlling the temperature and step speed of different heating intervals of the step-by-step heating furnace, the depth of the decarburization layer of the spring steel strip is reduced, and the single-side decarburization layer depth is less than or equal to 0.05 mm. Although the step-by-step heating method is disclosed, the elements are not reasonably designed, and Nb alloy is not added. Nb can be alloyed with Cr and Ni, especially during processing and heat treatment, to promote the precipitation of nanoscale secondary carbides and achieve the purpose of precipitation strengthening. There is no specific temperature limitation during rolling, and cracking phenomenon is easy to occur. The present application provides a preparation method of a Si-Mn spring hot-rolled narrow strip steel, which can solve the above-mentioned defects. SUMMARY

[0007] The present application provides a preparation method of a Si-Mn spring hot-rolled narrow strip steel, which can solve the above-mentioned defects.

[0008] The technical scheme for solving the above technical problems is as follows: A preparation method of a Si-Mn spring hot-rolled narrow strip steel, the process comprising an initial smelting furnace, an LF refining furnace, a vacuum refining furnace, continuous casting, billet treatment, heating, rolling and cooling. (1) Initial smelting furnace The initial smelting furnace is controlled to have an element mass ratio of 0.10%≤ω[C] and 0.015%≤ω[P] at a temperature of 1600℃. The initial smelting furnace is added with carbon powder, alloy, pre-melted slag and lime in sequence during tapping. (2) LF refining furnace The initial Si content is greater than or equal to 1.2% by mass ratio, the lime addition amount is less than or equal to 3 kg / t during refining, and the diffusion deoxidizer addition amount is less than or equal to 2 kg / t. (3) Vacuum refining furnace The limiting vacuum time is greater than or equal to 10 min, and the static stirring time is greater than or equal to 20 min. (4) Heating The heating process comprises a preheating section, a first heating section, a second heating section, a third heating section and a soaking section. Preheating section furnace temperature is less than or equal to 750 DEG C, heating first section furnace temperature is 700-1050 DEG C, heating second section furnace temperature is 950-1150 DEG C, heating third section furnace temperature is 1000-1200 DEG C, soaking section furnace temperature is 1100-1250 DEG C; Heating third section and soaking section are high temperature sections, high temperature section time is less than or equal to 90 min, total heating time is less than or equal to 180 min; (5) Rolling Opening rolling temperature is 1050-1200 DEG C, finishing rolling temperature is 860-950 DEG C, fast coiling, coiling temperature is 450-700 DEG C, air cooling after rolling.

[0009] The further defined technical solutions of the present application are: Further, the preparation method of the Si-Mn spring hot-rolled narrow strip steel comprises the following components in percentage by mass: C: 0.50%-0.70%, Si: 1.60%-1.90%, Mn: 0.70%-1.00%, P≤0.020%, S≤0.015%, Cr: 0.10%-0.50%, Ni≤0.30%, Nb≤0.05%, the balance being Fe and inevitable impurities, and the sum of the above components is 100%.

[0010] In the preparation method of the Si-Mn spring hot-rolled narrow strip steel, the pre-melted slag is added in an amount of 2-6 kg / t, and the lime is added in an amount of 3-6 kg / t, and the above amounts are the proportion of the added material in the weight of the molten steel.

[0011] In the preparation method of the Si-Mn spring hot-rolled narrow strip steel, the vacuum refining equipment in step (3) is a VD furnace or an RH furnace.

[0012] In the preparation method of the Si-Mn spring hot-rolled narrow strip steel, the prepared product has a thickness of 1.5-8.0 mm and a width of 160-450 mm.

[0013] The beneficial effects of the present application are: The mass fraction of each element of the application is as follows: 0.50%≤ω[C]≤0.70%, 1.60%≤ω[Si]≤1.90%, 0.70%≤ω[Mn]≤1.00%, ω[P]≤0.020%, ω[S]≤0.015%, 0.10%≤ω[Cr]≤0.50%, ω[Ni]≤0.30%, ω[Nb]≤0.05%, wherein the C, Si and Mn elements mainly improve the strength and hardness of the Si-Mn spring steel through solid solution strengthening, and belong to the conventional components of the Si-Mn spring steel; the control of the harmful elements P and S is mainly to prevent these elements from reducing the performance of the spring steel; based on the personalized use scene of the Si-Mn spring steel, the alloying effects of Cr, Ni and Nb, especially the precipitation of nanoscale secondary carbides during the processing and heat treatment process, can promote the precipitation strengthening purpose.

[0014] The application limits the tapping conditions of the preliminary refining furnace and limits the charging sequence during the tapping process. The preliminary refining furnace includes an electric furnace and a converter, and the alloy includes various low-Al and low-Ti alloys containing Si and Mn elements. The selection of the preliminary refining furnace type is determined according to the actual working condition of the steel plant, which can be an electric furnace and a converter. The high-C content tapping and the charging process first add carbon powder, mainly to reduce the oxygen potential in the tapping molten steel, thereby reducing the generation of initial inclusions, and at the same time stabilizing the composition of the refining slag, on the one hand promoting the absorption of inclusions and improving the cleanliness of the molten steel; on the other hand, ensuring the stability of product quality. The specification of the pre-melted slag and the amount of lime added is mainly to create a suitable refining slag system, and the low-Al and low-Ti alloy is mainly used to suppress the production of hard B-type and TiN inclusions, which are harmful to the fatigue life of spring steel.

[0015] The initial Si content in the LF process is controlled to be ≥1.2%, mainly to reduce the oxygen content in the molten steel and ensure that the molten steel belongs to Si-controlled oxygen; the addition of lime is mainly to improve the basicity of the refining slag, thereby improving the absorption efficiency of inclusions; the diffusion deoxidizer is mainly to reduce the oxygen potential of the refining slag, and the diffusion deoxidizer includes SiC and carbon powder, the specific selection is determined according to the actual working condition of the steel plant, and the use of Al-containing diffusion deoxidizer is prohibited.

[0016] The selection of the vacuum equipment is determined according to the actual working condition of the steel plant, including VD and RH two types of vacuum equipment; the specification of the limiting vacuum time is mainly to reduce the content of H and N elements in the molten steel.

[0017] The heating furnace in the heating process is a step-by-step heating furnace, and the temperature setting of different heating intervals of the heating furnace is to ensure that no stress cracks are generated in the blank heating process and to quickly pass through the decarburization sensitive temperature interval of high-carbon steel, thereby reducing the occurrence of decarburization, and significantly reducing the quenching hardness of the narrow strip steel when the decarburization is more serious. Strict control of the total time in the furnace and the time in the high-temperature section is the key to ensuring the decarburized layer of the Si-Mn spring steel, and the shorter the total time in the furnace and the time in the high-temperature section, the shallower the corresponding decarburized layer depth.

[0018] The rolling process control temperature, and the setting of the rolling temperature is mainly to ensure the plate shape and the smooth progress of the rolling process, and to prevent cracking; and the setting of the coiling temperature is mainly to fully utilize the self-tempering process after coiling, to play a stress relieving role, and to prevent the unwinding cracking phenomenon from occurring in the subsequent process.

[0019] The present application combines the existing special steel smelting, rolling and heat treatment equipment, and through optimization of the smelting process and the rolling process, the development of Si-Mn spring hot-rolled narrow strip steel can be completed without the need to increase additional equipment and processes, thereby being low in cost and high in performance-price ratio. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. Embodiment 1

[0021] The present embodiment provides a preparation method of Si-Mn spring hot-rolled narrow strip steel, and the process includes an initial smelting furnace, an LF refining furnace, a vacuum refining furnace, continuous casting, blank treatment, heating, rolling and cooling. By adopting Si deoxidization process smelting, combining the process cooperation of the tapping process, the refining process, the continuous casting process, the heating process and the rolling process, the cleanliness of the molten steel is improved, the plasticity of hard inclusions is improved, and ideal plate shape and metallographic structure are obtained by combining the control of the rolling process, thereby forming a preparation method of Si-Mn spring hot-rolled narrow strip steel, wherein: The composition of the narrow strip steel includes the following components in terms of mass percentage: C: 0.50%-0.70%, Si: 1.60%-1.90%, Mn: 0.70%-1.00%, P≤0.020%, S≤0.015%, Cr: 0.10%-0.50%, Ni≤0.30%, Nb≤0.05%, and the balance is Fe and unavoidable impurities, and the sum of the above components is 100%; (1) Initial smelting furnace When tapping the primary furnace, the element mass ratio is controlled at 0.15% = ω[C], ω[P] = 0.013%, and 1630°C = temperature T; The order of charging during the tapping process of the primary furnace is: carbon powder → alloy → pre-melted slag → lime. The amount of pre-melted slag added is 2-6 kg / t, and the amount of lime added is 3-6 kg / t. (2) LF refining furnace Calculated by mass ratio, the initial Si content is 1.3%, the amount of lime added during refining is ≤3kg / t, and the amount of diffusion deoxidizer added is ≤2kg / t; The diffusion deoxidizer is a mixture of SiC and carbon powder; (3) Vacuum refining furnace The ultimate vacuum time is ≥10min, the static stirring time is ≥20min, and the vacuum refining equipment is a VD furnace or RH furnace; (4) Heating The actual furnace entry method adopts 2 empty and 1 entry, with the preheating section temperature of 500℃, the heating section temperature of 886℃, the heating section temperature of 1048℃, the heating section temperature of 1164℃, and the soaking section temperature of 1190℃. The high temperature section (including the third section and the soaking section) is in the furnace for 73 minutes, and the total time in the furnace is 176 minutes. (5) Rolling The starting rolling temperature is 1122°C, the final rolling temperature is 923°C, the rapid coiling is at a coiling temperature of 562°C, and the steel is air-cooled after rolling. The thickness of the prepared product is 2.3 mm and the width is 378 mm.

[0022] The mechanism of the present invention is specifically as follows: First, through the design of the composition of C, Si, Mn and Cr, the selective micro-alloying effect of Ni and Nb is adopted, and the smelting and rolling processes are combined to achieve the mechanical performance and fatigue life requirements of Si-Mn spring narrow strip steel. The smelting process adopts Si deoxidation technology. By controlling the C content in the steel-tapping process, the Si content and refining slag composition in the LF refining process, the effective removal of harmful gas elements in the vacuum process, and the control of alloy component segregation in the continuous casting process, the cleanliness of the molten steel is improved, the production of hard inclusions is suppressed, and the service life of Si-Mn spring narrow strip steel is extended. The rolling process reduces the decarburization of the narrow strip steel while ensuring the dimensional accuracy and plate shape through strict control of the heating temperature and the rolling process temperature. Ultimately, the performance uniformity and machinability of the Si-Mn spring narrow strip steel are protected.

[0023] The present invention combines existing special steel smelting, rolling and heat treatment equipment, and can complete the development of Si-Mn series spring hot-rolled narrow strip steel by optimizing the smelting process and rolling process without adding additional equipment and processes.

[0024] In addition to the embodiments described above, the present application can have other implementation manners. Any technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope of the present application.

Claims

1. A method for preparing Si-Mn hot-rolled narrow strip spring steel, characterized in that: The process includes primary refining furnace → LF refining furnace → vacuum refining furnace → continuous casting → billet processing → heating → rolling → cooling, among which: (1) Primary furnace When tapping the primary furnace, the element mass ratio is controlled to be 0.10%≤ω[C], ω[P]≤0.015%, and 1600℃≤temperature T; The order of charging during the tapping process of the primary furnace is: carbon powder → alloy → pre-melted slag → lime; (2) LF refining furnace Calculated by mass ratio, the initial Si content is ≥1.2%, the amount of lime added during refining is ≤3kg / t, and the amount of diffusion deoxidizer added is ≤2kg / t; (3) Vacuum refining furnace Ultimate vacuum time ≥10min, static stirring time ≥20min; (4) Heating The heating process is divided into preheating section, heating section 1, heating section 2, heating section 3 and soaking section, specifically: The preheating furnace temperature is ≤750℃, the heating furnace temperature is 700-1050℃, the heating furnace temperature is 950-1150℃, the heating furnace temperature is 1000-1200℃, and the soaking furnace temperature is 1100-1250℃; The three heating sections and the soaking section are high temperature sections, the high temperature time in the furnace is ≤90min, and the total heating time in the furnace is ≤180min; (5) Rolling The starting rolling temperature is 1050-1200℃, the finishing rolling temperature is 860-950℃, rapid coiling, the coiling temperature is 450-700℃, and air cooling is performed after rolling.

2. The method for preparing Si-Mn hot-rolled narrow spring steel strip according to claim 1, characterized in that: The composition of the prepared narrow strip steel includes the following components by mass percentage: C: 0.50%-0.70%, Si: 1.60%-1.90%, Mn: 0.70%-1.00%, P≤0.020%, S≤0.015%, Cr: 0.10%-0.50%, Ni≤0.30%, Nb≤0.05%, the balance is Fe and unavoidable impurities, the sum of the above components is 100%.

3. The method for preparing Si-Mn hot-rolled narrow spring steel strip according to claim 1, characterized in that: In the step (1), the amount of pre-melted slag added is 2-6 kg / t, and the amount of lime added is 3-6 kg / t.

4. The method for preparing Si-Mn hot-rolled narrow spring steel strip according to claim 1, characterized in that: In the step (2), the diffusion deoxidizer is at least one of SiC and carbon powder.

5. The method for preparing Si-Mn hot-rolled narrow strip spring steel according to claim 1, characterized in that: The vacuum refining equipment in step (3) is a VD furnace or an RH furnace.

6. The method for preparing Si-Mn hot-rolled narrow strip spring steel according to claim 1, characterized in that: The thickness of the prepared product is 1.5-8.0 mm and the width is 160-450 mm.