CN111394642A - Rare earth adding method for VD (vacuum distillation) process of 30CrNi2MoVA steel - Google Patents
Rare earth adding method for VD (vacuum distillation) process of 30CrNi2MoVA steel Download PDFInfo
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- CN111394642A CN111394642A CN202010349493.5A CN202010349493A CN111394642A CN 111394642 A CN111394642 A CN 111394642A CN 202010349493 A CN202010349493 A CN 202010349493A CN 111394642 A CN111394642 A CN 111394642A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/52—Manufacture of steel in electric furnaces
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/06—Deoxidising, e.g. killing
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C2007/0093—Duplex process; Two stage processes
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Abstract
The invention relates to a rare earth adding method for a VD (vacuum distillation) process of 30CrNi2MoVA (vanadium-doped vanadium) steel, belongs to the technical field of ferrous metallurgy, and solves the technical problem that no appropriate rare earth adding method for the 30CrNi2MoVA steel exists at present to improve the rare earth yield and meet the inclusion requirement2O3The sulfide inclusion is changed into round and oval rare earth oxide and rare earth sulfide.
Description
Technical Field
The invention belongs to the technical field of ferrous metallurgy, and particularly relates to a rare earth adding method for a VD (vacuum degassing) process of 30CrNi2MoVA steel.
Background
The alloy structural steel 30CrNi2MoVA is used as the manufacturing steel grade of the pump valve box of the fracturing unit, the working environment is very severe, and the alloy structural steel can bear very large impact load in the service process, so that the service life of the pump valve box can be prolonged by having high enough strength and impact performance.
The inclusion content of the alloy structural steel 30CrNi2MoVA is high, so that the quality problems of no pockmark during flaw detection, reduced impact toughness, fatigue fracture of products and the like of the 30CrNi2MoVA steel in the production process are easily caused, and the service life of the products is seriously influenced. Especially high melting point Al2O3Inclusions and sulfide-based inclusions, Al2O3The inclusions have low deformation rate during forging and rolling, so that the fatigue strength of the product is reduced, surface defects are generated, and the plasticity, toughness and fatigue resistance of the steel are reduced.
Therefore, the cleanliness of the 30CrNi2MoVA steel is improved, the inclusion content of the steel is reduced, and the method plays an important role in improving the product quality of the 30CrNi2MoVA steel. The rare earth elements have important influence on deoxidation, desulfurization, inclusion modification treatment, solidification structure and steel performance of molten steel. Research shows that rare earth elements are added into steel, so that oxide and sulfide inclusions in molten steel can be subjected to denaturation treatment, and fine and nearly spherical rare earth compounds are generated. Meanwhile, the rare earth elements can refine the structure, eliminate harmful elements such as sulfur, phosphorus and the like which are partially polymerized along the grain boundary, ensure that carbide is uniformly distributed, refine crystal grains and ensure that the structure is more uniform, thereby prolonging the service life of steel products and having very important significance for reducing the cost in the actual production process. However, no appropriate rare earth adding method exists in the smelting process of alloy structural steel 30CrNi2MoVA so far, and the requirement of inclusions is met while the yield of rare earth is improved.
Disclosure of Invention
The invention solves the technical problem that no appropriate rare earth adding method exists for 30CrNi2MoVA steel at present, and meets the requirements of flaw detection qualification and inclusion control of finished products while improving the yield of rare earth.
The invention provides a rare earth adding method for a VD (vacuum degassing) process of 30CrNi2MoVA steel, which is used for producing the 30CrNi2MoVA steel by adopting EBT (electron beam lithography) electric furnace smelting, L F refining and VD vacuum refining, wherein rare earth is added after the VD vacuum refining is broken, tapping is carried out, and die casting and pouring are carried out.
Wherein, the chemical compositions of L F after refining, deoxidation and alloying are 0.01-0.05 percent of Al, less than or equal to 0.006 percent of S and less than or equal to 0.0020 percent of O in percentage by mass.
Wherein, after VD vacuum refining is broken, rare earth is added in an adding mode of inserting an inserted rod.
Wherein the rare earth addition amount is controlled to be 0.1-0.15kg/t steel after VD vacuum refining is broken.
Wherein, after the L F refining is finished, SiO in the slag is controlled2The content of (B) is less than or equal to 10 percent by mass.
Wherein the ultimate vacuum degree of VD vacuum refining is less than or equal to 67Pa, and the holding time under the ultimate vacuum is more than or equal to 15 min.
Wherein, Ar is blown under VD vacuum refining limit vacuum, the Ar flow is more than or equal to 120L/min, about 1-2 min before breaking, and the Ar flow is adjusted to 20-40L/min.
Wherein, VD vacuum refining is carried out, sampling analysis is carried out immediately after breaking the vacuum, the [ H ] is controlled to be less than or equal to 2.5ppm, then soft blowing is carried out, rare earth is added, and the soft blowing flow is 15-30L/min.
And after the VD vacuum refining is broken, soft blowing is carried out for 5-10 min, and then rare earth is added.
Wherein the soft argon blowing time is controlled within 30-50 min after the VD vacuum refining is broken.
The invention has the beneficial effects that:
the rare earth addition method is adopted to produce the 30CrNi2MoVA steel, the yield of the rare earth is more than or equal to 50 percent, and the addition of the rare earth controls the type and the appearance of inclusions in the steel from the original B type (string-shaped and chain-shaped Al)2O3) Class A (sulfide inclusion) is converted into class D (round and oval rare earth oxide, rare earth sulfide, rare earth aluminate and rare earth oxysulfide);
in the casting process, the nozzle is not easy to nodulate, the casting process is smooth, and the flaw detection qualification rate of 500mm and 600mm forged bars produced by forging steel ingots is high;
the purity of the 30CrNi2MoVA steel produced by the method is greatly improved, the type of inclusions in the steel is optimal, the size distribution is fine and dispersed, the grade of the inclusions is reduced, and the purpose of improving the product quality is finally achieved.
Detailed Description
The invention provides a rare earth adding method for a VD procedure of 30CrNi2MoVA steel, which is used for producing the 30CrNi2MoVA steel by adopting EBT electric furnace smelting, L F refining and VD vacuum refining and can be specifically carried out according to the following operation and requirements:
the process flow is EF → L F → VD → die casting.
Smelting in an EBT electric furnace:
adding raw materials according to the component requirements of steel types for smelting, after furnace burden is completely melted, when the temperature of molten steel is more than or equal to 1540 ℃, deeply blowing oxygen by a single tube at low pressure, removing Si and Mn from slag flow, fully stirring, sampling, fully analyzing, tapping after the steel types meet the requirements, and entering the next procedure, wherein the tapping conditions are 1650-;
l F refining:
carrying out the last process, deslagging the steel ladle in time after tapping, refining in L F, wherein the temperature is L F under the condition that the temperature is more than or equal to 1550 ℃, the slag thickness is less than or equal to 20mm, measuring the temperature, feeding an Al wire 100 m/furnace, adjusting the argon flow, sampling and analyzing after the reduction is completely white, controlling the chemical composition to meet the standard, and ensuring alloying, wherein [ S ] is]≤0.006％、[O]Less than or equal to 0.0020 percent, adjusting the total Al content to be within the range of 0.01 to 0.05 percent according to the sample return analysis result, and controlling SiO in the slag after L F refining is finished2The content of (A) is less than or equal to 10 percent;
VD vacuum refining:
carrying out vacuum treatment from 1/2 to VD after the temperature of the bale is 1660-1680 ℃, evacuating to require that the ultimate vacuum degree is less than or equal to 67Pa, keeping the time under the ultimate vacuum is more than or equal to 15min, blowing Ar with large flow under the ultimate vacuum (the flow of blowing Ar is more than or equal to 120L/min), blowing Ar with flow rate being adjusted to 20-40L/min before breaking, closing argon after breaking, fixing hydrogen, soft blowing argon (the flow is required to be 15-30L/min) after fixing hydrogen, soft blowing for 5-10 min, adding rare earth according to the addition of 0.125 kg/ton steel, inserting a special inserted rod in the rare earth adding mode, and controlling the soft blowing argon time to be 30-50 min after breaking;
the VD is vacuum refined and then adopts a conventional pouring process, and preferably, the VD can be carried out according to the following operations:
before pouring, argon is introduced into the injection pipe for 3-5 min, Ar gas is used for protection pouring, a water gap and a pouring gate are accurately centered, the height between the water gap and the pouring gate cannot be too high, the height is controlled to be less than or equal to 100mm after visual inspection, and secondary pollution of molten steel is reduced. The height of the used middle pouring pipe is higher than that of the ingot mold by more than 300mm so as to ensure that enough static pressure is generated during molten steel pouring, the liquid level is required to rise stably during ingot body pouring, and the feeding of a cap opening is slow and sufficient.
The invention has the advantages that the time and the condition for adding the rare earth are very critical, the rare earth is directly added after the VD vacuum refining is broken, the condition in the molten steel is the best, the content of steel grade O, S is low, and the yield of the rare earth is high. Specifically, after the rare earth is added, Al in molten steel is treated2O3Performing denaturation treatment on the MnS inclusion; secondly, further deoxidizing and desulfurizing the molten steel; thirdly, some residual rare earth is dissolved in the matrix in the steel grade in a solid way, the structure of the as-cast ledeburite is refined, harmful elements such as sulfur and phosphorus which are partially polymerized along the grain boundary are eliminated, the carbide is uniformly distributed, the crystal grains are refined, the structure is more uniform, and the mechanical property of the steel can be greatly improved.
Preferably, the rare earth is added after VD vacuum refining is broken, soft blowing is carried out for 5-10 min, and the aim is to enable alumina inclusions in steel to float upwards for a while, so that the rare earth content required by the modified alumina inclusions after the rare earth is added is low, the rare earth yield is improved, and inclusions generated by the rare earth are reduced. The addition of rare earth is the residual content of rare earth in steel plus inclusion containing rare earth, and the yield of rare earth is the residual content of rare earth in steel/addition of rare earth.
Except the adding time and condition of the rare earth, the rare earth content is low, the residual rare earth is remained in the steel after the rare earth is used for desulfurization, deoxidation and deformation of impurities, the residual rare earth content in the steel is low, the beneficial effect of the rare earth is insufficient, the rare earth content is high, the content of the residual rare earth impurities in the steel is increased, and the flaw detection and the performance of the finished steel are adversely affected.
In addition, the rare earth is added in a manner of inserting the inserted rod, the yield of the rare earth is higher, the high yield of the rare earth indicates that the rare earth-containing inclusions produced by the rare earth in the steel are less, and both the residual content of the rare earth and the content of the rare earth inclusions in the steel play decisive factors for the performance of the rare earth steel.
The invention is further illustrated and described by the following examples
Example 1
Furnace number 419V2-1885, steel grade 30CrNi2 MoVA;
fully melting EF furnace burden at 1635 ℃, deeply blowing oxygen by a single tube at low pressure, removing Si and Mn from the slag, fully stirring, flushing steel from steel slag at 1665 ℃, removing slag from steel ladles in time, refining at L F under the condition of L F, wherein the temperature is 1588 ℃, and the slag thickness is 20 mm;
l F is fed into an Al wire 100m/40t furnace, the argon flow is adjusted to be 30L/min, L F is reduced completely, slag is white, after sampling analysis (including all Al), the sample returns, all Al is 0.015%, L F tapping is carried out, namely, a ladle is hoisted to the next station, and the components of C0.30, Cr0.87, Ni1.79, Mo0.41, V0.11, S0.0030 and P0.012 and L F are hoisted to VD temperature 1579 ℃;
VD ultimate vacuum pressure 67pa, ultimate vacuum time 25min, large flow Ar blowing under ultimate vacuum, Ar blowing flow rate 150L/min, 2min before breaking, Ar blowing flow rate 30L/min, measuring temperature of the molten steel in time after breaking, taking an [ H ] sample, wherein the [ H ] is 1.0ppm, adding rare earth into the molten steel in an insertion rod insertion manner after breaking soft argon blowing for 8 min, wherein the adding amount is 5kg/40t of furnace, controlling total soft blowing time after VD breaking to 35min, ladle tapping at 1550 ℃, die casting and pouring.
The yield of the rare earth of the 30CrNi2MoVA steel produced by the control method is 61 percent. Inspecting the finished product inclusion according to GB/T10561-2005A method and grading: the A-type (sulfide-type) inclusion fine system and the A-type (sulfide-type) inclusion coarse system are both 1.0 grade; the fineness of the B-type (alumina-type) inclusions is 1.0 grade, and the thickness thereof is 0.5 grade; the fineness of the D-type (single-particle spherical) inclusions is 1.0 grade, and the thickness thereof is 1.0 grade. The flaw detection qualification rate is 100 percent.
Example 2
Furnace number 419V2-1886, steel grade 30CrNi2 MoVA;
fully melting EF furnace burden at 1630 ℃, deeply blowing oxygen by a single tube at low pressure, removing Si and Mn from the slag, fully stirring, flushing steel from steel slag at 1660 ℃, removing slag from steel ladles in time, refining at L F under the condition of L F, wherein the temperature is 1583 ℃, and the slag thickness is 20 mm;
l F is fed into an Al wire 100m/40t furnace, the argon flow is adjusted to be 30L/min, L F is completely reduced, slag is white, after sampling analysis (including all Al), the sample is returned to be 0.015 percent of all Al, L F tapping is carried out, namely, a ladle is hoisted to the next station, and the components of C0.29, Cr0.85, Ni1.80, Mo0.40, V0.10, S0.0045, P0.013 and L F are hoisted to the VD temperature of 1580 ℃;
VD ultimate vacuum pressure 67pa, ultimate vacuum time 25min, large flow Ar blowing under ultimate vacuum, Ar blowing flow rate 150L/min, 2min before breaking, Ar blowing flow rate 30L/min, measuring temperature of the molten steel in time after breaking, taking an [ H ] sample, wherein the [ H ] is 1.1ppm, adding rare earth into the molten steel in an insertion rod insertion manner after breaking the air and blowing the argon for 10min, wherein the adding amount is 5kg/40t of furnace, controlling total soft blowing time after VD breaking to 35min, carrying out ladle tapping at the temperature of 1550 ℃, and carrying out die casting.
The yield of the rare earth of the 30CrNi2MoVA steel produced by the control method is 70 percent. Inspecting the finished product inclusion according to GB/T10561-2005A method and grading: the fine grade of A type (sulfide type) inclusion is 0.5 grade, and the coarse grade is 1.0 grade; the fineness of the B-type (alumina-type) inclusions is 1.0 grade, and the thickness thereof is 1.0 grade; class D (single-particle spherical) inclusions are 0.5 grade in fineness and 0.5 grade in coarseness. The flaw detection qualification rate is 100 percent.
Claims (10)
- The rare earth adding method for the VD procedure of the 30CrNi2MoVA steel adopts EBT electric furnace smelting, L F refining and VD vacuum refining to produce the 30CrNi2MoVA steel, and is characterized in that rare earth is added after the VD vacuum refining is broken, tapping is carried out, and die casting and pouring are carried out.
- 2. The method for adding rare earth into 30CrNi2MoVA steel in a VD procedure is characterized in that the chemical components of L F after refining, deoxidation and alloying are 0.01-0.05% of Al, less than or equal to 0.006% of S and less than or equal to 0.0020% of O in percentage by mass.
- 3. The method for adding rare earth to 30CrNi2MoVA steel in a VD procedure according to claim 1 or 2, characterized in that: and rare earth is added in an insertion mode of inserting an inserted rod after the VD vacuum refining is broken.
- 4. The method for adding rare earth into 30CrNi2MoVA steel in a VD process according to any one of claims 1 to 3, characterized by comprising the following steps: the rare earth addition amount after the VD vacuum refining is broken is controlled to be 0.1-0.15kg/t steel.
- 5. The method for adding rare earth into 30CrNi2MoVA steel in VD process according to any one of claims 1 to 4, characterized in that SiO in the slag is controlled after L F refining is finished2The content of (B) is less than or equal to 10 percent by mass.
- 6. The method for adding rare earth into 30CrNi2MoVA steel in a VD process according to any one of claims 1 to 5, characterized by comprising the following steps: the ultimate vacuum degree of VD vacuum refining is less than or equal to 67Pa, and the holding time under the ultimate vacuum is more than or equal to 15 min.
- 7. The method for adding rare earth into 30CrNi2MoVA steel in a VD process according to any one of claims 1 to 6, characterized in that Ar is blown under VD vacuum refining limit vacuum, the Ar flow rate is not less than 120L/min, about 1 to 2min before breaking, and the Ar flow rate is adjusted to 20 to 40L/min.
- 8. The method for adding the rare earth into the 30CrNi2MoVA steel in the VD procedure is characterized in that sampling analysis is carried out immediately after the VD vacuum refining is broken, the [ H ] is controlled to be less than or equal to 2.5ppm, then soft blowing is carried out, the rare earth is added, and the soft blowing flow is 15-30L/min.
- 9. The method for adding rare earth into 30CrNi2MoVA steel in a VD process according to any one of claims 1 to 8, characterized by comprising the following steps: and after the VD vacuum refining is carried out and the air is broken, soft blowing is carried out for 5-10 min, and then rare earth is added.
- 10. The method for adding rare earth into 30CrNi2MoVA steel in a VD process according to any one of claims 1 to 9, characterized by comprising the following steps: and after the VD vacuum refining is broken, the soft argon blowing time is controlled to be 30-50 min.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113025777A (en) * | 2021-03-02 | 2021-06-25 | 攀钢集团江油长城特殊钢有限公司 | 30CrNi2MoVA large-size forged material and preparation method thereof |
| CN114107602A (en) * | 2021-11-26 | 2022-03-01 | 成都先进金属材料产业技术研究院股份有限公司 | Method for adding rare earth into 00Cr18Mo2 ferrite stainless steel |
| CN114716256A (en) * | 2022-03-11 | 2022-07-08 | 钢铁研究总院有限公司 | Refractory material for smelting rare earth steel and method for improving rare earth yield |
| CN114908207A (en) * | 2022-04-18 | 2022-08-16 | 包头钢铁（集团）有限责任公司 | Method for improving rare earth yield by controlling sulfur content of molten steel |
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| CN113025777A (en) * | 2021-03-02 | 2021-06-25 | 攀钢集团江油长城特殊钢有限公司 | 30CrNi2MoVA large-size forged material and preparation method thereof |
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Application publication date: 20200710 |