阅读说明：本技术 一种18CrNiMo7-6钢的冶炼工艺及其应用 (Smelting process and application of 18CrNiMo7-6 steel ) 是由 景财年 刘磊 张志浩 于 2020-11-30 设计创作，主要内容包括：本发明涉及锻圆或齿轮轴用钢制备技术领域,尤其涉及一种18CrNiMo7-6钢的冶炼工艺及其应用。所述工艺包括：EBT电弧炉冶炼、两次LF钢包精炼炉冶炼、VD钢包精炼炉冶炼、模注锭型工艺。本发明的工艺采取两方面的技术措施解决上述问题：一、改善钢液的变质处理,采用精炼工艺处理提高钢液纯净度,降低硫和氧的含量,严格控制夹杂物的含量,避免对后期锻造质量造成不利影响。二、控制浇铸温度、浇注速度以及钢锭模的稳定性,减少裂纹产生,组织分布不均匀以及缩松、缩孔。(The invention relates to the technical field of preparation of steel for forging a circle or a gear shaft, in particular to a smelting process and application of 18CrNiMo7-6 steel. The process comprises the following steps: EBT electric arc furnace smelting, two times of LF ladle refining furnace smelting, VD ladle refining furnace smelting and mold injection ingot type process. The process of the invention adopts two technical measures to solve the problems: the method has the advantages that the modification treatment of the molten steel is improved, the purity of the molten steel is improved by adopting a refining process, the contents of sulfur and oxygen are reduced, the content of inclusions is strictly controlled, and the adverse effect on the later forging quality is avoided. And secondly, controlling the casting temperature, the casting speed and the stability of the ingot mold, and reducing the generation of cracks, uneven tissue distribution, shrinkage porosity and shrinkage cavity.)

1. A smelting process of 18CrNiMo7-6 steel is characterized by comprising the following steps:

(1) a smelting stage: the bottom of the furnace is primed by lime, the target value of the end point carbon is controlled to be more than or equal to 0.08 percent, the target value of the phosphorus is controlled to be less than or equal to 0.004 percent, the tapping temperature is controlled to be more than or equal to 1640 ℃, and a deoxidizer and slag charge are added in the smelting process;

(2) and (3) refining: transferring the molten steel in the step (1) to a refining furnace, maintaining the protective atmosphere in the furnace, adding a deoxidizing agent for deoxidation, adjusting the slag condition, turning white and reducing the color of the slag for more than or equal to 20min, at the temperature of more than or equal to 1590 ℃, adding an iron alloy and/or a recarburizing agent to adjust the components of the molten steel to a preset specification, sampling and analyzing, feeding an Al wire and a CaSi wire to adjust the slag, enabling the slag to have certain alkalinity and good fluidity, and hoisting after all chemical components enter the specification;

(3) and (3) vacuum refining: transferring the molten steel obtained in the step (2) to a vacuum refining furnace, feeding an Al wire, blowing protective gas according to the H, O content required by the steel type or ingot type, and hoisting after the completion;

(4) pouring: and (3) baking the ingot mold, using low-carbon covering slag, pouring at 1543 and 1558 ℃, controlling the pouring speed of the ingot body to be 6-8, reducing the flow speed of a riser, filling the riser by adopting medium-long flow, and annealing the obtained steel ingot, thus obtaining the steel ingot.

2. The process for smelting 18CrNiMo7-6 steel as claimed in claim 1, wherein in step (1), the deoxidizer comprises at least one or more of Al, Si, Mn and Ca; preferably, the addition ratio of the deoxidizer is 1.2-1.8 kg/ton.

3. The process for smelting 18CrNiMo7-6 steel as claimed in claim 1, wherein in step (1), the slag includes at least one of lime, dolomite and ore; preferably, the slag charge is added in a proportion of 5 to 15 kg/ton, preferably 12 to 15 kg/ton.

4. The smelting process of 18CrNiMo7-6 steel according to claim 1, wherein in step (1), the temperature of the molten pool is raised to 1560 ℃, and the slag amount is controlled to be less than or equal to 3% through full-melting analysis;

or, the molten steel components finally obtained in the step (1) are controlled within the following ranges: 0.08 to 0.12 percent of C, 0.08 to 0.12 percent of Si, 0.40 to 0.50 percent of Mn, 0 to 0.008 percent of P, 1.40 to 1.55 percent of Cr, 1.50 to 1.60 percent of Ni, 0.22 to 0.27 percent of Mo, and the balance of Fe and inevitable impurities.

5. The process for smelting 18CrNiMo7-6 steel as claimed in claim 1, wherein in the step (2), the deoxidizer comprises Si powder and Al powder; preferably, the addition ratio of the Si powder is 0.5 to 1 kg/ton, and the addition ratio of the Al powder is 1 to 2 kg/ton.

6. A smelting process of 18CrNiMo7-6 steel according to claim 1, wherein in the step (2), the sampling analysis must be carried out after the ferroalloy and carburant are added for more than or equal to 8 min;

preferably, the recarburizing agent comprises at least one of wood carbon, coal carbon, coke and graphite;

preferably, the ferroalloy comprises at least one of ferromanganese, ferrosilicon, ferrochrome, ferromolybdenum, and ferronickel.

7. The process for smelting 18CrNiMo7-6 steel as claimed in claim 1, wherein in step (2), the Al wire is added at a ratio of 1-2m/T, Ca-Si wire of 1.8-2.3 m/ton;

or in the step (2), the temperature of the bale is 1630-1640 ℃.

8. A process for smelting 18CrNiMo7-6 steel as claimed in any one of claims 1 to 7, wherein in step (3), the vacuum degree in the vacuum refining furnace is less than or equal to 66.7Pa, the holding time is more than or equal to 18 minutes, and Al wire is fed until the Al content in the molten steel is more than or equal to 0.025%.

9. The process for smelting 18CrNiMo7-6 steel as claimed in any one of claims 1-7, wherein in step (4), the ingot mold is baked to 200 ℃ at 100 ℃ for not less than 3 hours, and the ingot mold is fully baked to slow down the cooling of the ingot, reduce the thermal stress generated by the lower temperature of the ingot mold, improve the molten steel feeding, and effectively reduce the inter-branch microcracks; the annealing temperature is 670-700 ℃, the ingot type is less than 10T for annealing for 15 hours, 10-25T for annealing for 20 hours, and 25-50T for annealing for 25 hours.

10. Use of the process for the production of steel for forging of round or gear shafts according to any one of claims 1 to 9 from 18CrNiMo7-6 steel.

Technical Field

The invention relates to the technical field of preparation of steel for forging a circle or a gear shaft, in particular to a smelting process and application of 18CrNiMo7-6 steel.

Background

The following in the background art merely refers to information that is understood by the inventor to be relevant to the present invention and is intended to augment understanding of the present invention through a description of some basic technical knowledge related to the present invention, which information does not necessarily have to constitute knowledge that is well known by those of ordinary skill in the art.

18CrNiMo7-6 and 17CrNiMo6 are respectively forged round or gear shaft steel represented by the trade marks in EN standard and DIN standard, the two are not essentially different, and the two gradually form a uniform trade mark of 18CrNiMo7-6 at present. The carbon content of the 18CrNiMo7-6 material is 0.15-0.21%, the Cr content is 1.5-1.8%, the Ni content is 1.4-1.7%, and the Mo content is 0.25-0.35%.

18CrNiMo7-6 is used as a leading application material of key parts such as forged circles or gear shafts, and in order to ensure the high-efficiency and safe operation of products, users continuously put forward new requirements on technical indexes of material quality. In the process of smelting and solidifying a casting blank, the conventional large forged round is easy to generate horizontal and longitudinal cracks on the surface, and gray inclusions are easy to exist near the cracks: S-Mn inclusions, quenching cracks, coarse grains, quality problems of white spots, uneven distribution of internal structures, shrinkage porosity, shrinkage cavity and the like. The generation of transverse and longitudinal cracks is caused by the factors of the quality of the inner wall of an ingot receiving mould in steel ingot casting, the swing of molten steel, the casting of the steel ingot and the ingot mould, high-temperature and high-speed casting, improper demoulding and cooling of the steel ingot or early demoulding; when the steel ingot is cooled, shrinkage holes are not concentrated on the cap opening part, the head cutting amount of the forged cap opening end is too small, so that secondary shrinkage holes or residual shrinkage holes exist at the end, close to the cap opening, of the blank, and longitudinal cracks are caused during forging.

Disclosure of Invention

Aiming at the problems, the invention provides a smelting process of 18CrNiMo7-6 steel and application thereof, and the process adopts two technical measures to solve the problems: the method has the advantages that the modification treatment of the molten steel is improved, the purity of the molten steel is improved by adopting a refining process, the contents of sulfur and oxygen are reduced, the content of inclusions is strictly controlled, and the adverse effect on the later forging quality is avoided. And secondly, controlling the casting temperature, the casting speed and the stability of the ingot mold, and reducing the generation of cracks, uneven tissue distribution, shrinkage porosity and shrinkage cavity.

In order to realize the purpose, the invention discloses the following technical scheme:

in a first aspect of the invention, a smelting process of 18CrNiMo7-6 steel is provided, which comprises the following steps:

(1) a smelting stage: the bottom of the furnace is primed by lime, the target value of the end point carbon is controlled to be more than or equal to 0.08 percent, the target value of the phosphorus is controlled to be less than or equal to 0.004 percent, the tapping temperature is controlled to be more than or equal to 1640 ℃, and a deoxidizer and slag charge are added in the smelting process.

(2) And (3) refining: transferring the molten steel in the step (1) to a refining furnace, maintaining the protective atmosphere in the furnace, adding a deoxidizing agent for deoxidizing, adjusting the slag condition, turning white and reducing the color of the slag for more than or equal to 20min, adjusting the temperature to be more than or equal to 1590 ℃, adding an iron alloy and a recarburizing agent to adjust the components of the molten steel to a preset specification, sampling and analyzing, feeding an Al wire and a Ca-Si wire to adjust the slag, enabling the slag to have a certain alkalinity and good fluidity, and hanging the ladle after all chemical components enter the specification.

(3) And (3) vacuum refining: and (3) transferring the molten steel finally obtained in the step (2) to a vacuum refining furnace, feeding an Al wire, blowing protective gas according to the H, O content required by the steel type or ingot type, and hoisting after the completion.

(4) Pouring: and (3) baking the ingot mold, using low-carbon covering slag, pouring at 1543 and 1558 ℃, controlling the pouring speed of the ingot body to be 6-8, reducing the flow speed of a riser, filling the riser by adopting medium-long flow, and annealing the obtained steel ingot, thus obtaining the steel ingot.

Further, in the step (1), the deoxidizer includes at least one or more of Al, Si, Mn, Ca, and the like in a composite manner. Preferably, the addition ratio of the deoxidizer is 1.2-1.8 kg/ton.

Al can eliminate the possibility of forming CO bubbles in the steel, thereby obtainingThe steel ingot with compact structure is obtained, aluminum can form stable AlN with nitrogen in the steel, the aging tendency of the steel is reduced, and fine and highly dispersed Al can be generated₂O₃These particles can become crystal nuclei for crystallization, and thus, the crystal grains can be refined. Strong deoxidation of Si, solid small particle SiO generated by single use₂Difficult to float and remove, is used in combination with Ca and Mn, and deoxidizes the product SiO₂2CaO & SiO stably combined with CaO and MnO₂、MnO·SiO₂Thereby reducing SiO₂Activity, Si deoxidation is fully carried out, and meanwhile stable bonded inclusions are easy to float upwards and be removed; mn is weaker in deoxidation, can improve the deoxidation capability of Si and Al, can be used in combination with Si and Al, and can generate a plastic inclusion MnS with a high melting point with S, so that the hot quenching tendency of steel can be reduced, and the harm of S can be reduced. Ca has the strongest deoxidizing capacity but has small solubility, and can quickly float upwards and evaporate when being used alone.

Further, in the step (1), the slag includes at least one of lime, dolomite, ore and the like. Preferably, the slag charge is added in a proportion of 5 to 15 kg/ton, preferably 12 to 15 kg/ton.

Further, in the step (1), the temperature of the molten pool is raised to 1560 ℃, and the slag amount is controlled to be less than or equal to 3 percent through full melting analysis.

Further, the molten steel components finally obtained in the step (1) are controlled within the following ranges: 0.08 to 0.12 percent of C, 0.08 to 0.12 percent of Si, 0.40 to 0.50 percent of Mn, 0 to 0.008 percent of P, 1.40 to 1.55 percent of Cr, 1.50 to 1.60 percent of Ni, 0.22 to 0.27 percent of Mo, and the balance of Fe and inevitable impurities.

Further, in the step (2), the deoxidizer comprises Si powder and Al powder, and the addition of the Si powder not only saves 50% of aluminum, but also changes Al₂0₃Behaviour, low melting product Al formed at the same time₂O₃•SiO₂Easy to float and eliminate, and has high molten steel purity and improved castability. Preferably, the addition ratio of the Si powder is 0.5 to 1 kg/ton, and the addition ratio of the Al powder is 1 to 2 kg/ton.

Further, in the step (2), the sampling analysis can be carried out only after the ferroalloy and the carburant are added for more than or equal to 8 min.

Further, in the step (2), the carburant includes at least one of wood carbons, coal carbons, coke, graphite, and the like.

Further, in the step (2), the iron alloy includes at least one of ferromanganese, ferrosilicon, ferrochrome, ferromolybdenum, ferronickel, and the like.

Further, in the step (2), the adding proportion of the Al wire is 1-2m/T, Ca-Si wire is 1.8-2.3 m/T.

Further, in the step (2), the temperature of the bale is 1630-1640 ℃.

Further, in the step (3), the vacuum degree in the vacuum refining furnace is less than or equal to 66.7Pa, the holding time is more than or equal to 18 minutes, and an Al wire is fed until the Al content in the molten steel is more than or equal to 0.025 percent.

Further, in the step (4), the ingot mold is baked to 100-200 ℃ for more than or equal to 3 hours. The full baking of the ingot mould can slow down the cooling of the ingot, reduce the thermal stress generated by the lower temperature of the ingot mould, improve the feeding of molten steel and effectively reduce the microcracks among branches.

Further, in the step (4), the annealing temperature is 670-.

In the second aspect of the invention, the application of the smelting process of the 18CrNiMo7-6 steel in the preparation of products such as forged circles, steel for gear shafts and the like is disclosed.

Compared with the prior art, the invention has the beneficial effects that:

1. according to the invention, through the smelting in the step (1) and the two-time refining in the step (2), the purity of the molten steel is synergistically improved, and the contents of sulfur and oxygen are reduced. Meanwhile, the research of the invention finds that: the content of the inclusion can be strictly controlled by controlling the target value of the carbon content to be more than or equal to 0.08 percent, the target value of the phosphorus content to be less than or equal to 0.004 percent and controlling the addition of the Mn element to be 0.40-0.50 percent, thereby avoiding adverse effects on the later forging quality.

2. The invention can effectively reduce the micro cracks with blunt tips distributed along the branches by fully baking the ingot mould and increasing the pouring temperature. In a steel ingot, the common reasons for the intercranching cracks are as follows: the crystallization temperature range is narrow when the steel ingot is solidified, the linear shrinkage coefficient is large, and the molten steel can not be supplemented in time, so that the inside and outside temperature difference is large, therefore, the inside and outside stress of the forged circle is different, the axial tensile stress is large, and the cracks among branches develop in the subsequent forging process. The invention can slow down the cooling of the cast ingot by fully baking the ingot mould and improving the pouring temperature, reduce the thermal stress generated by the lower temperature of the ingot mould and increase the effect of supplementing the cooling retraction of the molten steel.

3. During pouring, molten steel is gradually solidified from bottom to top and from the surface to the inside, the position of a riser is finally solidified, and the Niyama criterion number of the center, the axis and the surface area of a steel ingot is less than 1.1, so that the phenomena of uneven tissue distribution, shrinkage porosity and shrinkage cavity can occur at the position due to insufficient feeding of the molten steel. Therefore, the research of the invention finds that: the casting speed of the ingot body is controlled to be 6-8, the flow speed of the riser is reduced, the riser is filled by adopting medium and long flows, the casting speed of the riser is controlled to be more than or equal to 4, the feeding capacity of molten steel is effectively enhanced, and the phenomena of shrinkage porosity and shrinkage cavity are reduced.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is a diagram showing the effects of the forged round prepared according to the first embodiment of the present invention after casting and after forging and roughing.

Fig. 2 is a structural image of a forged circle prepared according to the first embodiment of the present invention under an optical microscope.

Fig. 3 is a structural image of a forged circle prepared according to a second embodiment of the present invention under an optical microscope.

Fig. 4 is a structural image of a forged circle prepared according to a third embodiment of the present invention under an optical microscope.

Fig. 5 is a structural image of a forged circle prepared in a first experimental example of the present invention under an optical microscope.

Fig. 6 is a structural image of a forged circle prepared in a second experimental example of the present invention under an optical microscope.

Fig. 7 is a structural image of a forged circle prepared in a third experimental example of the present invention under an optical microscope.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed.

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out according to conventional conditions or according to conditions recommended by the manufacturers.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The reagents or starting materials used in the present invention can be purchased from conventional sources, and unless otherwise specified, the reagents or starting materials used in the present invention can be used in a conventional manner in the art or in accordance with the product specifications.

In addition, any methods and materials similar or equivalent to those described herein can be used in the methods of the present invention. The preferred methods and materials described herein are exemplary only, and the invention will now be further described with reference to specific embodiments.

The present invention relates to terms in heat treatment of iron-carbon alloys, and the terms are explained for the convenience of the skilled person to understand the present invention, but the contents of the explanations do not necessarily constitute the common general knowledge in the field, and specifically include:

the term "EBT electric arc furnace": the steel tapping groove of the traditional electric furnace is changed into a steel tapping box, and a steel tapping hole is vertically downward at the bottom of the steel tapping box. The lower part of the steel tapping hole is provided with a steel tapping hole opening and closing mechanism for opening and closing the steel tapping hole, and the center of the top of the steel tapping box is provided with an operation hole for facilitating the filling operation and maintenance of the steel tapping hole.

The term "LF ladle refining furnace: the method is used for refining molten steel melted in a primary smelting furnace, can adjust the temperature of the molten steel, performs process buffering, and is important metallurgical equipment meeting the requirements of continuous casting and continuous rolling.

The term "VD ladle refining furnace": the refining furnace utilizes the five-stage steam jet pump to work, so that the working vacuum degree of a vacuum chamber reaches below 67Pa, and the refining purpose is achieved through the action of negative pressure.

The term "white slag": refers to slag formed during diffusion deoxidation during the reduction phase of electric arc furnace steelmaking.

The term "basicity": the mark of the free oxygen ion concentration in the slag is an index for representing the chemical property of the slag and is one of important bases for determining the slagging system of the blast furnace.

The term "purity": the quantity, the form and the distribution of non-metallic inclusions in molten steel are important factors influencing the quality of steel.

First embodiment

A smelting process of 18CrNiMo7-6 steel comprises the following steps:

(1) the smelting process of the EBT electric arc furnace comprises the following steps: 1000kg of lime at the furnace bottom, electrifying after feeding, heating the molten pool to 1560 ℃, carrying out full-melting analysis, controlling the slag amount to be 3%, adding a deoxidizer (Al ingot is 1.2 kg/T) and slag materials (lime is 15 kg/T), baking the steel ladle, ensuring normal ventilation, oxygen end, controlling the target value of end-point carbon content to be 0.08%, controlling the target value of phosphorus content to be 0.004%, controlling the tapping temperature to be 1640 ℃, and controlling the components from primary molten steel to an LF furnace to be: 0.08% of C, 0.10% of Si, 0.40% of Mn, 0.004% of P, 1.40% of Cr, 1.50% of Ni, 0.23% of Mo, and the balance of Fe and inevitable impurities.

(2) The two-time LF ladle refining furnace smelting process flow comprises the following steps: transferring the ladle car to an LF furnace, adjusting the pressure of protective gas (Ar gas), adding 0.5 kg/ton Si powder and 1.2 kg/ton Al powder for deoxidation after electrifying and slagging uniformly, adjusting the slag condition, performing white reduction on the slag for 20min at the temperature of 1590 ℃, sampling and analyzing, keeping the white slag for 25min, and protecting the reducing atmosphere in the furnace; adding ferroalloy and carburant, adjusting the components to a preset specification, adding the components for 8min, and sampling and analyzing; feeding Al wire 1m/T, feeding Ca-Si wire 2m/T, adjusting slag 5min before ladle to make it have certain alkalinity and good fluidity, and then ladle after all chemical components enter specification, wherein the ladle temperature is 1630 ℃.

(3) VD ladle refining furnace smelting process flow: checking the equipment, reserving steam pressure, keeping the vacuum pumping time for 6min, keeping the vacuum degree for 66.7Pa for 18min, keeping the Ar gas pressure for 2.0kg, sampling and analyzing, feeding an Al wire until the Al content of the molten steel reaches 0.025%, determining the content of H, O according to the requirements of steel types or ingot types, blowing Ar gas for 10min statically, and keeping the ladle temperature at 1545 ℃.

(4) The process flow of the mold injection molding is as follows: fully baking the steel ingot mould until the temperature reaches 100 ℃, continuing for 3 hours, using low-carbon mold powder, 8T ingot model, 1545 ℃ injection temperature, 6 ingot body injection speed, reducing the flow rate of a riser, filling the riser by adopting medium-length flow, 4 riser injection speed, 6.5 hours lifting time, advancing and retreating a furnace, annealing for 15 hours at 670 ℃ to obtain a forged circle, and the effect graphs after pouring and forging rough machining are shown in figure 1.

First test example

(1) The smelting process of the EBT electric arc furnace comprises the following steps: 1000kg of lime at the furnace bottom, electrifying after feeding, heating the molten pool to 1560 ℃, carrying out full-melting analysis, controlling the slag amount to be 3%, adding a deoxidizer (Al ingot is 1.2 kg/T) and slag materials (lime is 15 kg/T), baking the steel ladle, ensuring normal ventilation, oxygen end, controlling the target value of end point carbon content to be 0.08%, controlling the target value of phosphorus content to be 0.01%, controlling the tapping temperature to be 1640 ℃, and controlling the components from primary molten steel to an LF furnace to be: 0.08% of C, 0.10% of Si, 0.40% of Mn, 0.004% of P, 1.40% of Cr, 1.50% of Ni, 0.23% of Mo, and the balance of Fe and inevitable impurities.

(2) The smelting process flow of the primary LF ladle refining furnace comprises the following steps: transferring the ladle car to an LF furnace, adjusting the pressure of protective gas (Ar gas), adding 0.5 kg/ton Si powder and 1.2 kg/ton Al powder for deoxidation after electrifying and slagging uniformly, adjusting the slag condition, performing white reduction on the slag for 20min at the temperature of 1590 ℃, sampling and analyzing, keeping the white slag for 25min, and protecting the reducing atmosphere in the furnace; adding ferroalloy and carburant, adjusting the components to a preset specification, sampling and analyzing after 8min of adding the components, adjusting the slag 5min before the ladle to ensure that the slag has certain alkalinity and good fluidity, and hoisting after all chemical components enter the specification, wherein the temperature of the ladle is 1630 ℃.

(3) VD ladle refining furnace smelting process flow: checking the equipment, reserving steam pressure, keeping the vacuum pumping time for 6min, keeping the vacuum degree for 66.7Pa for 18min, keeping the Ar gas pressure for 2.0kg, sampling and analyzing, feeding an Al wire until the Al content of the molten steel reaches 0.025%, determining the content of H, O according to the requirements of steel types or ingot types, blowing Ar gas for 10min statically, and keeping the ladle temperature at 1545 ℃.

(4) The process flow of the mold injection molding is as follows: fully baking the steel ingot mould until the temperature reaches 100 ℃, continuing for 3 hours, using low-carbon covering slag, 8T of ingot type, 1545 ℃ of injection temperature, 6 of ingot body injection speed, reducing the flow rate of a riser, filling the riser by adopting medium-length flow, 4 of riser injection speed, 6.5 hours of lifting time, advancing and retreating the furnace, and annealing for 15 hours at 670 ℃ to obtain the alloy steel ingot mould.

Second embodiment

(1) The smelting process of the EBT electric arc furnace comprises the following steps: 1000kg of lime at the furnace bottom, electrifying after feeding, heating the molten pool to 1560 ℃, performing full-melting analysis, controlling the slag amount to be 3%, adding a deoxidizer (Al ingot is 1.3 kg/T) and slag materials (lime is 13 kg/T), baking the steel ladle, ensuring normal ventilation, oxygen end, controlling the target value of end-point carbon content to be 0.10%, controlling the target value of phosphorus content to be 0.003%, tapping temperature to be 1650 ℃, and controlling the components from primary molten steel to an LF furnace to be: 0.10% of C, 0.12% of Si, 0.50% of Mn, 0.003% of P, 1.45% of Cr, 1.55% of Ni, 0.22% of Mo, and the balance of Fe and inevitable impurities.

(2) The two-time LF ladle refining furnace smelting process flow comprises the following steps: transferring the ladle car to an LF furnace, adjusting the pressure of protective gas (Ar gas), adding 0.8 kg/ton Si powder and 2 kg/ton Al powder for deoxidation after electrifying and slagging uniformly, adjusting the slag condition, transferring the slag color to white and reducing for 25min, at the temperature of 1600 ℃, sampling and analyzing, keeping the white slag for 30min, and protecting the reducing atmosphere in the furnace; adding ferroalloy and carburant, adjusting components to a preset specification, adding the components for 9min, and sampling and analyzing; feeding Al wire 1.5m/T, feeding Ca-Si wire 1.8m/T, adjusting slag 5min before ladle to make it have certain alkalinity and good fluidity, and ladle after all chemical components enter specification, wherein the ladle temperature is 1635 ℃.

(3) VD ladle refining furnace smelting process flow: checking the equipment, reserving steam pressure, keeping the vacuum pumping time for 5min, keeping the vacuum degree at 66.7Pa for 19min, keeping the Ar gas pressure for 2.0kg, sampling and analyzing, feeding an Al wire until the Al content of the molten steel reaches 0.025 percent, determining the content of H, O according to the requirements of steel types or ingot types, blowing Ar gas statically for 15min, and keeping the ladle temperature at 1550 ℃.

(4) The process flow of the mold injection molding is as follows: fully baking the steel ingot mould until the temperature reaches 120 ℃, keeping for 4 hours, using low-carbon protective slag, 8T ingot type, 1550 ℃ injection temperature, 7 ingot body injection speed, reducing the flow rate of a riser, filling the riser by adopting medium-length flow, 5 riser injection speed, 6.5 lifting time, advancing and retreating a furnace, and annealing for 15 hours at 680 ℃ to obtain the alloy steel ingot mould.

Second test example

(1) The smelting process of the EBT electric arc furnace comprises the following steps: 1000kg of lime at the furnace bottom, electrifying after feeding, heating the molten pool to 1560 ℃, performing full-melting analysis, controlling the slag amount to be 3%, adding a deoxidizer (Al ingot is 1.3 kg/T) and slag materials (lime is 13 kg/T), baking the steel ladle, ensuring normal ventilation, oxygen end, controlling the target value of end-point carbon content to be 0.10%, controlling the target value of phosphorus content to be 0.003%, tapping temperature to be 1650 ℃, and controlling the components from primary molten steel to an LF furnace to be: 0.10% of C, 0.12% of Si, 0.50% of Mn, 0.003% of P, 1.45% of Cr, 1.55% of Ni, 0.22% of Mo, and the balance of Fe and inevitable impurities.

(2) The two-time LF ladle refining furnace smelting process flow comprises the following steps: transferring the ladle car to an LF furnace, adjusting the pressure of protective gas (Ar gas), adding 0.8 kg/ton Si powder and 2 kg/ton Al powder for deoxidation after electrifying and slagging uniformly, adjusting the slag condition, transferring the slag color to white and reducing for 25min, at the temperature of 1600 ℃, sampling and analyzing, keeping the white slag for 30min, and protecting the reducing atmosphere in the furnace; adding ferroalloy and carburant, adjusting components to a preset specification, adding the components for 9min, and sampling and analyzing; feeding Al wire 1.5m/T, feeding Ca-Si wire 1.8m/T, adjusting slag 5min before ladle to make it have certain alkalinity and good fluidity, and ladle after all chemical components enter specification, wherein the ladle temperature is 1635 ℃.

(3) VD ladle refining furnace smelting process flow: checking the equipment, reserving steam pressure, keeping the vacuum pumping time for 5min, keeping the vacuum degree at 66.7Pa for 19min, keeping the Ar gas pressure for 2.0kg, sampling and analyzing, feeding an Al wire until the Al content of the molten steel reaches 0.025 percent, determining the content of H, O according to the requirements of steel types or ingot types, blowing Ar gas statically for 15min, and keeping the ladle temperature at 1550 ℃.

(4) The process flow of the mold injection molding is as follows: and (3) annealing the low-carbon mold flux at 680 ℃ for 15 hours in a forward annealing furnace by using low-carbon mold flux, 8T ingot shape, 1350 ℃ injection temperature, 7 ingot body injection speed and a riser to reduce the flow speed, filling the riser by using medium-long flow, 5 riser injection speed and 6.5h hoisting time.

Third embodiment

(1) The smelting process of the EBT electric arc furnace comprises the following steps: 1000kg of lime at the furnace bottom, electrifying after feeding, heating the molten pool to 1560 ℃, carrying out full-melting analysis, controlling the slag amount to be 3 percent, adding a deoxidizer (Al ingot is 1.8 kg/T) and slag materials (lime is 12 kg/T), baking the steel ladle, ensuring normal ventilation, oxygen end, controlling the target value of end point carbon content to be 0.12 percent, controlling the target value of phosphorus content to be 0.0035 percent, controlling the tapping temperature to be 1660 ℃, and controlling the components from primary molten steel to an LF furnace to be: 0.12% of C, 0.08% of Si, 0.50% of Mn, 0.008% of P, 1.55% of Cr, 1.60% of Ni, 0.27% of Mo, and the balance of Fe and inevitable impurities.

(2) The two-time LF ladle refining furnace smelting process flow comprises the following steps: transferring the ladle car to an LF furnace, adjusting the pressure of protective gas (Ar gas), adding 1 kg/ton of Si powder and 1 kg/ton of Al powder for deoxidation after electrifying and slagging uniformly, adjusting the slag condition, transferring the color of slag to white for reduction for 30min at the temperature of 1610 ℃, sampling and analyzing, keeping the white slag for 35min, protecting the reducing atmosphere in the furnace, adding a proper amount of deoxidizer and adjusting the temperature; adding ferroalloy and carburant, adjusting components to a preset specification, adding the components for 10min, and sampling and analyzing; feeding Al wire 1.6m/T, Ca-Si wire 2.2m/T, adjusting slag 5min before ladle to make it have certain alkalinity and good fluidity, and ladle after all chemical components enter specification, wherein the ladle temperature is 1640 ℃.

(3) VD ladle refining furnace smelting process flow: checking the equipment, reserving steam pressure, keeping the vacuum pumping time for 5min, keeping the vacuum degree at 66.7Pa for 19min, keeping the Ar gas pressure for 2.0kg, sampling and analyzing, feeding an Al wire until the Al content of the molten steel reaches 0.025%, determining the content of H, O according to the steel type or ingot type requirement, blowing Ar gas statically for 20min, and carrying out ladle temperature of 1555 ℃.

(4) The process flow of the mold injection molding is as follows: fully baking the steel ingot mould until the temperature reaches 200 ℃, continuing for 5 hours, using low-carbon protective slag, 8T of ingot type, 1555 ℃ of injection temperature, 8 of ingot body injection speed, reducing the flow rate of a riser, filling the riser by adopting medium-length flow, 6 of riser injection speed, 6.5 hours of lifting time, advancing and retreating the furnace, and annealing for 15 hours at the temperature of 690 ℃.

Third test example

(1) The smelting process of the EBT electric arc furnace comprises the following steps: 1000kg of lime at the furnace bottom, electrifying after feeding, heating the molten pool to 1560 ℃, carrying out full-melting analysis, controlling the slag amount to be 3%, adding a deoxidizer (Al ingot is 1.2 kg/T) and slag materials (lime is 12 kg/T), baking the steel ladle, ensuring normal ventilation, oxygen end, controlling the target value of end-point carbon content to be 0.10%, controlling the target value of phosphorus content to be 0.003%, controlling the tapping temperature to be 1660 ℃, and controlling the components from primary molten steel to an LF furnace to be: 0.12% of C, 0.08% of Si, 0.50% of Mn, 0.008% of P, 1.55% of Cr, 1.60% of Ni, 0.27% of Mo, and the balance of Fe and inevitable impurities.

(2) The two-time LF ladle refining furnace smelting process flow comprises the following steps: transferring the ladle car to an LF furnace, adjusting the pressure of protective gas (Ar gas), adding 1 kg/ton of Si powder and 1 kg/ton of Al powder for deoxidation after electrifying and slagging uniformly, adjusting the slag condition, transferring the color of slag to white for reduction for 30min at the temperature of 1610 ℃, sampling and analyzing, keeping the white slag for 35min, protecting the reducing atmosphere in the furnace, adding a proper amount of deoxidizer and adjusting the temperature; adding ferroalloy and carburant, adjusting components to a preset specification, adding the components for 10min, and sampling and analyzing; feeding Al wire 1.6m/T, Ca-Si wire 2.2m/T, adjusting slag 5min before ladle to make it have certain alkalinity and good fluidity, and ladle after all chemical components enter specification, wherein the ladle temperature is 1640 ℃.

(3) VD ladle refining furnace smelting process flow: checking the equipment, reserving steam pressure, keeping the vacuum pumping time for 5min, keeping the vacuum degree at 66.7Pa for 19min, keeping the Ar gas pressure for 2.0kg, sampling and analyzing, feeding an Al wire until the Al content of the molten steel reaches 0.025%, determining the content of H, O according to the steel type or ingot type requirement, blowing Ar gas statically for 20min, and carrying out ladle temperature of 1555 ℃.

(4) The process flow of the mold injection molding is as follows: and fully baking the steel ingot mould to 140 ℃, keeping for 5 hours, uniformly pouring the ingot body and a riser by using low-carbon protective slag, 8T ingot type and 1555 ℃, pouring at the speed of 10, lifting for 6.5 hours, moving into and out of a furnace, and annealing at the temperature of 690 ℃ for 15 hours to obtain the steel ingot mould.

Tissue Performance testing

The results of the first, second and third examples are shown in fig. 2, 3 and 4 respectively, and it can be seen from the figures that the microstructure is uniform, no obvious crack is generated after cold heading, no obvious damage is caused during flaw detection, no shrinkage cavity and shrinkage porosity occur, and the strength and elongation after heat treatment after forging reach the standard.

The ingot of the first test example was sampled and analyzed, and the result is shown in fig. 5, from which it can be seen that the structure segregation in the steel is severe, and that individual products are cracked during cold heading; meanwhile, Ca-Si wires are not fed in the secondary refining process, calcification is not generated, the content of S is too high, and the crystal particles of individual products are separated from each other during cold heading to generate cracks and even generate hot shortness.

The second test example ingot was sampled and analyzed, and the result is shown in FIG. 6, in which it can be seen that cracks were present in the ingot, the crack tips were relatively blunt, and the cracks were mainly distributed along the dendrites.

The sampling analysis of the ingot of the third test example showed that the structure distribution was not uniform, and the shrinkage porosity and shrinkage cavity occurred locally, as shown in fig. 7.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.