Electrical pure iron DT4C hot-rolled round steel and production process thereof

Abstract

The invention discloses electrical pure iron DT4C hot-rolled round steel and a production process thereof, and relates to the technical field of steel production, and the electrical pure iron DT4C hot-rolled round steel comprises the following chemical components in percentage by mass: less than or equal to 0.005% of C, less than or equal to 0.005% of S, 0.15-0.25% of Mn, less than or equal to 0.020% of Cr, 0.35-0.65% of Al, and the balance of Fe and inevitable impurities. After the electromagnetic performance of the obtained hot-rolled round steel finished product is annealed according to the national standard GB / T6983-2008 specification, all technical indexes completely meet the requirements of the highest-grade super electromagnetic pure iron DT4C in the standard, and the percent of pass of the coercive force, the coercive force aging increment, the maximum magnetic conductivity and the magnetic induction intensity under different magnetic fields is 100%.

Description

Technical Field

[0001] The invention relates to the technical field of steel production, in particular to electrical pure iron DT4C hot-rolled round steel and a production process thereof. Background Art

[0002] Electrical pure iron is mainly used in the manufacture of electromagnetic components, electromagnetic cores, etc. for electrical appliances, telecommunications, instruments and defense-related high-end industries. The requirements for the performance, coercive force, magnetic induction intensity and other physical quality of electromagnetic pure iron round steel are very stringent; Electrical pure iron DT4C requires low coercivity, low coercivity aging value-added and high magnetic permeability. At present, the bar products produced in China are mainly DT4 products. Compared with DT4, DT4C requires stricter composition control, low coercivity aging value-added and high magnetic permeability. The technical indicators obtained by producing round steel according to the same composition control and rolling process as DT4 cannot meet the requirements of DT4C. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the disadvantages of the prior art and provide an electrical pure iron DT4C hot-rolled round steel and a production process thereof.

[0004] In order to solve the above technical problems, the technical solution of the present invention is as follows: The invention discloses an electrical pure iron DT4C hot-rolled round steel, whose chemical composition and mass percentage are as follows: C≤0.005%, S≤0.005%, Mn: 0.15-0.25%, Cr≤0.020%, Al: 0.35-0.65%, and the balance is Fe and unavoidable impurities.

[0005] The present invention also provides a production process of electrical pure iron DT4C hot-rolled round steel, which sequentially comprises smelting, continuous casting, heating of ingots, round steel rolling and round steel cooling.

[0006] As a preferred solution of the production process of the electrical pure iron DT4C hot-rolled round steel of the present invention, the smelting process includes KR molten iron desulfurization pretreatment, converter smelting, LF refining furnace refining and RH vacuum treatment in sequence.

[0007] As a preferred solution of the production process of the electrical pure iron DT4C hot-rolled round steel of the present invention, the sulfur content in the converter smelting molten iron after the KR molten iron desulfurization pretreatment is less than or equal to 0.03%.

[0008] As a preferred solution of the production process of the electrical pure iron DT4C hot-rolled round steel of the present invention, in the ingot heating process, the temperature of the heating section is set to 1160±20°C, and the temperature of the soaking section is set to 1200±20°C.

[0009] As a preferred solution of the production process of the electrical pure iron DT4C hot-rolled round steel of the present invention, in which: in the round steel rolling process, the starting rolling temperature is set to 1100±20℃, the exiting continuous rolling temperature is set to 1000±20℃, and the entering KOCKS temperature is set to 840±20℃.

[0010] As a preferred solution of the production process of the electrical pure iron DT4C hot-rolled round steel of the present invention, in the round steel cooling process, the temperature of the upper cooling bed is controlled to be 800±20°C, and a heat preservation cover is set on the cooling bed.

[0011] As a preferred solution of the production process of the electrical pure iron DT4C hot-rolled round steel of the present invention, wherein: the coercive force Hc of the finished workpiece is ≤32A / m, and the magnetic induction intensity B 10000 ≥1.80T.

[0012] The beneficial effects of the present invention are: (1) The present invention achieves the requirements of product composition of electrical pure iron DT4C hot-rolled round steel: C≤0.005%, S≤0.005%, Mn: 0.15-0.25%, Cr≤0.020%, Al: 0.45-0.70% through smelting control of the converter process path.

[0013] (2) The present invention controls the processes such as the heating and rolling temperature of the hot-rolled round steel to achieve the performance of electrical pure iron that meets the requirements of tensile strength ≥300MPa and A ≥35%.

[0014] (3) The present invention controls the smelting and rolling round steel processes to achieve a coercive force Hc ≤ 32A / m and a magnetic induction intensity B10000 ≥ 1.80T for the finished electrical pure iron. The comprehensive performance indicators can meet the use requirements of electrical pure iron DT4C in special environments. DETAILED DESCRIPTION

[0015] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific implementation methods.

[0016] The present application provides an electrical pure iron DT4C hot-rolled round steel, whose chemical composition and mass percentage are as follows: C≤0.005%, S≤0.005%, Mn: 0.15-0.25%, Cr≤0.020%, Al: 0.35-0.65%, and the balance is Fe and unavoidable impurities.

[0017] Based on the chemical composition and mass percentage of the above-mentioned electrical pure iron DT4C hot-rolled round steel, the present application also provides a production process of electrical pure iron DT4C hot-rolled round steel, which sequentially includes smelting, continuous casting, billet heating, round steel rolling and round steel cooling.

[0018] The smelting process includes KR hot metal desulfurization pretreatment, converter smelting, LF refining furnace refining and RH vacuum treatment. The smelting process is carried out through KR hot metal desulfurization pretreatment, converter double slag operation smelting, LF furnace temperature control smelting, RH vacuum decarburization and alloying control and continuous casting protection operation to obtain qualified continuous casting billets.

[0019] In this embodiment, the size of the ingot is 250mm*300mm*10500mm.

[0020] Specifically, the KR molten iron desulfurization pretreatment is to ensure that the S of the molten iron for converter smelting is ≤ 0.003%, and to perform slag removal operations.

[0021] In the converter process, the converter uses special scrap steel and double slag operation to ensure that the converter tapping conditions meet the requirements of refined molten steel.

[0022] In the LF furnace refining process, power supply and argon blowing are used to control the transfer temperature of molten steel.

[0023] RH vacuum treatment adopts vacuum decarburization and alloying to meet the continuous casting temperature and composition requirements, and realize the design requirements of chemical composition C≤0.005%, S≤0.005%, Mn: 0.15-0.25%, Cr≤0.020%, Al: 0.35-0.65%.

[0024] The continuous casting process uses special protective slag and covering agents, continuous casting gas protection, continuous casting superheat and constant casting speed control to ensure that the surface and internal quality of the continuous casting billet meet the rolling requirements.

[0025] In the heating process of the casting, the temperature of the heating section is set to 1160±20℃, and the temperature of the soaking section is set to 1200±20℃.

[0026] The converter process mainly refers to the double-slag operation of the converter, which controls the steel-making conditions and provides good basic conditions for the subsequent molten steel refining.

[0027] In the billet heating process, the temperature of the heating section is set to 1160±20℃, and the temperature of the soaking section is set to 1200±20℃. The temperature should be raised slowly when the billet starts to be heated.

[0028] In the round steel rolling process, the starting rolling temperature is set at 1100±20℃, the exiting continuous rolling temperature is set at 1000±20℃, and the entering KOCKS temperature is set at 840±20℃.

[0029] In the round steel cooling process, the temperature of the upper cooling bed is controlled at 800±20℃, and a heat preservation cover is set on the cooling bed for slow cooling.

[0030] Through the above process, the product composition of electrical pure iron DT4C hot-rolled round steel is achieved with C≤0.005%, S≤0.005%, Mn: 0.15-0.25%, Cr≤0.020%, Al: 0.45-0.70%. At the same time, through the control of hot-rolled round steel heating and rolling temperature, the performance of electrical pure iron meets the requirements of tensile strength ≥300MPa and A≥35%. In addition, by controlling the smelting and rolling round steel process, the coercive force Hc≤32A / m and the magnetic induction intensity B 10000 ≥1.80T, the comprehensive performance indicators can meet the use requirements of electrical pure iron DT4C in special environments.

[0031] The following is an explanation through specific embodiments. Example

[0032] (1) Furnace number: 23403099, specification φ40mm.

[0033] (2) Process route: blast furnace molten iron - KR - converter → LF furnace → RH → continuous casting → continuous casting 250mm*300mm → billet heating → rolling → finished product inspection → packaging → weighing → warehousing.

[0034] (3) KR: After desulfurization, S ≤ 0.001%, slag removal.

[0035] (4) Converter: 12 tons of pure iron scrap steel was added, the converter was operated with double slag, and the converter steel output was C: 0.03%, S: 0.003%.

[0036] (5) LF furnace: refining and slag making, power supply and temperature raising.

[0037] (6) RH vacuum: vacuum cycle decarburization and alloying. After vacuum, C: 0.003%, Mn: 0.17%, Al: 0.43%, S: 0.003%.

[0038] (7) Continuous casting: Continuous casting uses pure iron special protective slag, covering agent, continuous casting billet 250*300mm, constant casting speed operation.

[0039] (8) Billet heating: The temperature of the heating section of the walking beam furnace is 1155°C, and the temperature of the soaking section is 1205°C. The temperature of the billet should be raised slowly when it starts to be heated; (9) Round steel rolling: starting rolling temperature 1115℃, continuous rolling temperature 1020℃, KOCKS temperature 860℃.

[0040] (10) Cooling of round steel: Place the round steel on a cooling bed, cover it with an insulation cover, and cool it slowly.

[0041] (11) Round steel properties: tensile strength 320MPa, elongation after fracture 38%.

[0042] (12) Electromagnetic performance test: coercive force Hc: 19.7A / m; coercive force aging increase ∆Hc: 19.7A / m; maximum magnetic permeability: 32.99m / Hm; magnetic induction intensity B 10000 :1.9T. Example

[0043] (1) Furnace number: 23410345, specification φ65mm.

[0044] (2) Process route: blast furnace molten iron - KR - converter → LF furnace → RH → continuous casting → continuous casting 250mm*300mm → billet heating → rolling → finished product inspection → packaging → weighing → warehousing.

[0045] (3) KR: After desulfurization, S ≤ 0.001%, slag removal.

[0046] (4) Converter: 15 tons of pure iron scrap steel was added, the converter was operated with double slag, and the converter steel output was C: 0.027%, S: 0.004%.

[0047] (5) LF furnace: refining and slag making, power supply and temperature raising.

[0048] (6) RH vacuum: vacuum cycle decarburization and alloying, after vacuum, C: 0.003%, Mn: 0.16%, Al: 0.57%, S: 0.003%.

[0049] (7) Continuous casting: Continuous casting uses pure iron special protective slag, covering agent, continuous casting billet 250*300mm, constant casting speed operation.

[0050] (8) Billet heating: The temperature of the heating section of the walking beam heating furnace is 1150°C, and the temperature of the soaking section is 1210°C. The temperature of the billet should be raised slowly when it starts to be heated.

[0051] (9) Round steel rolling: starting rolling temperature 1100℃, continuous rolling temperature 1000℃, KOCKS temperature 850℃.

[0052] (10) Round steel cooling: Place on cooling bed, cover with insulation cover, and cool slowly.

[0053] (11) Round steel properties: tensile strength 311 MPa, elongation after fracture 40%.

[0054] (12) Electromagnetic performance test: coercive force Hc: 20.55A / m; coercive force aging increase ∆Hc: 0.58A / m; maximum magnetic permeability: 43.74m / Hm; magnetic induction intensity B 10000 :1.87T.

[0055] Therefore, after annealing in accordance with the national standard GB / T6983-2008, the electromagnetic properties of the hot-rolled round steel product obtained by the technical solution of the present application fully meet the requirements of the highest grade super electromagnetic pure iron DT4C in the standard, and the pass rate of coercive force, coercive force aging value, maximum magnetic permeability and magnetic induction intensity under different magnetic fields is 100%.

[0056] In addition to the above embodiments, the present invention may also have other implementation modes; any technical solutions formed by equivalent replacement or equivalent transformation shall fall within the protection scope required by the present invention.

Claims

1. A hot-rolled round steel made of electrical pure iron DT4C, characterized in that: Its chemical composition and mass percentage are as follows: C≤0.005%, S≤0.005%, Mn: 0.15-0.25%, Cr≤0.020%, Al: 0.35-0.65%, and the balance is Fe and unavoidable impurities.

2. A production process of hot-rolled round steel made of electrical pure iron DT4C according to claim 1, characterized in that: It includes smelting, continuous casting, billet heating, round steel rolling and round steel cooling in sequence.

3. The production process of electrical pure iron DT4C hot-rolled round steel according to claim 2, characterized in that: The smelting process includes KR molten iron desulfurization pretreatment, converter smelting, LF refining furnace refining and RH vacuum treatment in sequence.

4. The production process of electrical pure iron DT4C hot-rolled round steel according to claim 3, characterized in that: The sulfur content in the converter smelting molten iron after the KR molten iron desulfurization pretreatment is less than or equal to 0.03%.

5. The electrical pure iron DT4C hot-rolled round steel according to claim 2, characterized in that: In the casting heating process, the temperature of the heating section is set to 1160±20°C, and the temperature of the soaking section is set to 1200±20°C.

6. The production process of electrical pure iron DT4C hot-rolled round steel according to claim 2, characterized in that: In the round steel rolling process, the starting rolling temperature is set to 1100±20°C, the exiting continuous rolling temperature is set to 1000±20°C, and the entering KOCKS temperature is set to 840±20°C.

7. The production process of electrical pure iron DT4C hot-rolled round steel according to claim 1, characterized in that: In the round steel cooling process, the temperature of the upper cooling bed is controlled to be 800±20° C., and a heat preservation cover is provided on the cooling bed.

8. The production process of electrical pure iron DT4C hot-rolled round steel according to claim 1, characterized in that: The coercive force of the finished workpiece is Hc≤32A / m, and the magnetic induction intensity is B 10000 ≥1.80T.