阅读说明：本技术 一种电炉初炼低磷15-5ph不锈钢母液及其冶炼方法 (Electric furnace primary smelting low-phosphorus 15-5PH stainless steel mother solution and smelting method thereof ) 是由 钱德桥 钱强 常立忠 于 2020-04-30 设计创作，主要内容包括：本发明公开一种电炉初炼低磷15-5PH不锈钢母液及其冶炼方法,属于金属冶炼技术领域；本发明电炉初炼的15-5PH不锈钢母液中P含量可以控制到0.015％以下,为后续冶炼出低P15-5PH不锈钢创造条件；通过将渣料和废钢加入至电炉中通电熔化,熔化后再加入渣料,渣料熔化后再加入合金料,进一步加热保温后进行出钢；其中渣料包括石灰和萤石,渣料加入至电炉前其表面采用雾化加湿处理；本发明通过上述工艺以及渣料表面的雾化加湿处理,使得在后续电炉冶炼过程中改善钢液中物化反应条件,促进钢液中P元素的降低,同时有利于钢液中O、N、H等杂质的去除。(The invention discloses an electric furnace primary smelting low-phosphorus 15-5PH stainless steel mother liquor and a smelting method thereof, belonging to the technical field of metal smelting; the P content in the 15-5PH stainless steel mother liquor primarily smelted by the electric furnace can be controlled to be below 0.015 percent, so that conditions are created for subsequently smelting low P15-5PH stainless steel; adding slag and scrap steel into an electric furnace, melting by electric conduction, adding the slag after melting, adding alloy material after melting the slag, further heating and preserving heat, and then tapping; wherein the slag material comprises lime and fluorite, and the surface of the slag material is subjected to atomization and humidification treatment before the slag material is added into the electric furnace; through the process and the atomization and humidification treatment on the surface of the slag charge, the physicochemical reaction condition in the molten steel is improved in the subsequent electric furnace smelting process, the reduction of the P element in the molten steel is promoted, and meanwhile, the removal of O, N, H and other impurities in the molten steel is facilitated.)

1. A method for primary smelting of stainless steel mother liquor with low phosphorus content of 15-5PH by an electric furnace is characterized in that slag and waste steel are added into the electric furnace to be melted, then the slag is added after melting, then alloy material is added after the slag is melted, and tapping is carried out after further heating and heat preservation; wherein the slag comprises lime and fluorite, and the surface of the slag is treated by atomization and humidification before the slag is added into the electric furnace.

2. The method for primary refining of the stainless steel mother liquor with low phosphorus content of 15-5PH by the electric furnace as claimed in claim 1, wherein the slag charge atomized water is added in a proportion of 1-5% by weight.

3. The method for primary smelting of the stainless steel mother liquor with low phosphorus content of 15-5PH by the electric furnace according to claim 1 is characterized by comprising the following specific steps:

firstly, stacking slag making materials and waste steel in layers in an electric furnace, wherein the waste steel accounts for 3/4 of total metal materials fed into the furnace;

step two, electrifying and melting;

step three, after the melting is finished, removing the slag, deoxidizing, adding the slag, and adding an alloy material after the slag is completely melted;

and step four, further heating and preserving heat, tapping after the components and the temperature are qualified, and transferring to a refining process.

4. The method for primary smelting of stainless steel mother liquor with low phosphorus content of 15-5PH by an electric furnace as claimed in claim 3, wherein in the first step, lime and iron scale are laid on the bottom of the furnace, scrap steel accounting for 3/12-5/12 of the total amount of scrap steel is added, fluorite is added, scrap steel accounting for 3/12-5/12 of the total amount of scrap steel is added, electrolytic copper and electrolytic nickel are added, lime and steel rolling iron scale are added, and the rest scrap steel is added.

5. The method for primary smelting of stainless steel mother liquor with low phosphorus content of 15-5PH in an electric furnace as claimed in claim 3, wherein in the first step, lime is added in an amount of 3-4% by weight of the scrap, fluorite is added in an amount of 0.5-1.0% by weight of the scrap, and iron oxide scale is added in an amount of 0.5-1.0% by weight of the scrap.

6. The method for primary smelting of stainless steel mother liquor with low phosphorus content of 15-5PH according to claim 3, wherein in the second step, the temperature of the molten steel is maintained between 1580 and 1600 ℃ for 30-45 min; in the heat preservation process, a mixture of fluorite powder and iron scale is added into the slag every 4-6min, the mass ratio of the fluorite powder to the iron scale is 1 (0.8-1.2), and the adding amount is 0.5-0.8kg per ton of steel.

7. The method for primary smelting of stainless steel mother liquor with low phosphorus content of 15-5PH by an electric furnace as claimed in claim 3, wherein in the third step, after the slag is completely removed, the aluminum block is put into the molten steel, and the addition amount is 0.75-1.25 kg/ton steel; then adding slag material, wherein the weight ratio of lime to fluorite in the slag material is (3.2-4.5) to 1, and the total weight of the added slag material is 1.6-2.4% of the weight of the molten steel.

8. The method for primary smelting of stainless steel mother liquor with low phosphorus content of 15-5PH by an electric furnace according to claim 3, characterized in that in the third step, after the slag is completely melted, the alloy materials of low carbon ferrochromium (FeCr65C0.5), ferrocolumbium (FeNb50) and carbon ferromanganese (FeMn84C0.7) are added in sequence.

9. The method for primary smelting of stainless steel mother liquor with low phosphorus content of 15-5PH by an electric furnace as claimed in claim 3, wherein in the fourth step, the temperature is heated to 1650-; the mixture of aluminum particles and fluorite powder is added every 3-5 min.

10. An electric furnace primary smelting low-phosphorus 15-5PH stainless steel mother liquor is characterized in that the stainless steel mother liquor obtained after electric furnace smelting comprises the following components: 0.1-0.15% of C, 0.30-0.50% of Mn, 2.80-3.50% of Cu, 4.00-4.5% of Ni, 14.0-14.80% of Cr, 0.25-0.35% of Nb, less than or equal to 0.015% of P, less than or equal to 0.008% of S and the balance of Fe and impurities.

Technical Field

The invention belongs to the technical field of metal smelting, and particularly relates to an electric furnace primary smelting low-phosphorus stainless steel mother liquor with a pH value of 15-5 and a smelting method thereof.

Background

15-5PH is precipitation hardening stainless steel with good matching of strength and toughness and excellent corrosion resistance, and is widely applied in the fields of aviation, aerospace, ships and warships and the like; the alloy is used as a key part such as a fastener in the field of aviation, and in order to obtain good comprehensive performance, particularly fatigue resistance, the comprehensive performance of steel is improved by controlling inclusions in the steel and reducing the content of O, N, H gas elements through different smelting methods in the current smelting process. The smelting process has very important influence on the cleanliness and inclusion of steel. Compared with a double-vacuum smelting process of Vacuum Induction (VIM) and vacuum consumable electrode (VAR), the Electric Arc Furnace (EAF), vacuum blown decarburization (VOD) and vacuum consumable electrode (VAR) has lower cost and is widely applied at present, but the content of P is difficult to effectively control in the electric arc furnace smelting process, so that the content of P is difficult to reduce in the subsequent smelting process.

Through retrieval, a patent of 'super martensitic stainless steel and a manufacturing process thereof' (publication number: CN109811253A) is disclosed, wherein the manufacturing process disclosed by the patent comprises the steps of smelting, ingot casting or ingot casting cogging, hot rolling, heat treatment after rolling and acid pickling; the smelting steps are as follows: any one of a vacuum induction furnace, a vacuum induction furnace and electroslag remelting, an electric furnace and external refining, and a converter and external refining is adopted to smelt other components except rare earth elements, the rare earth elements are added before tapping casting, and the casting temperature is controlled at 1500-1650 ℃. Although the stainless steel has good performance, the process still cannot effectively control the P content.

Disclosure of Invention

1. Technical problem to be solved by the invention

The invention aims to solve the technical problem that the P content is difficult to effectively control in the prior 15-5PH stainless steel electric furnace smelting process, and provides an electric furnace primary smelting low-phosphorus 15-5PH stainless steel mother liquor and a smelting method thereof.

2. Technical scheme

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

the invention relates to stainless steel mother liquor with low phosphorus content of 15-5PH, which is prepared by electric furnace smelting, and comprises the following components: 0.1-0.15% of C, 0.30-0.50% of Mn, 2.80-3.50% of Cu, 4.00-4.5% of Ni, 14.0-14.80% of Cr, 0.25-0.35% of Nb, less than or equal to 0.015% of P, less than or equal to 0.008% of S and the balance of Fe and impurities.

The invention relates to a method for primary smelting of stainless steel mother liquor with low phosphorus content of 15-5PH by an electric furnace, which comprises the steps of adding slag and waste steel into the electric furnace, introducing the slag into the electric furnace for electric melting, adding slag after melting, adding alloy after melting the slag, further heating and preserving heat, and then tapping; wherein the slag comprises lime and fluorite, and the surface of the slag is treated by atomization and humidification before the slag is added into the electric furnace.

Preferably, the slag atomized water is added in a proportion of 1-5% of the weight of the slag atomized water.

Preferably, the specific steps are as follows:

firstly, stacking slag making materials and waste steel in layers in an electric furnace, wherein the waste steel accounts for 3/4 of total metal materials fed into the furnace;

step two, electrifying and melting;

step three, after the melting is finished, removing the slag, deoxidizing, adding the slag, and adding an alloy material after the slag is completely melted;

and step four, further heating and preserving heat, tapping after the components and the temperature are qualified, and transferring to a refining process.

Preferably, in the first step, lime and iron scale are paved at the bottom of the furnace, then scrap steel accounting for 3/12-5/12 of the total amount of the scrap steel is added, fluorite is added, then scrap steel accounting for 3/12-5/12 of the total amount of the scrap steel is added, electrolytic copper and electrolytic nickel are added, lime and steel rolling iron scale are added, and finally the rest scrap steel is added.

Preferably, in the step one, the lime accounts for 3-4% of the weight of the waste steel, the fluorite accounts for 0.5-1.0% of the weight of the waste steel, and the iron oxide scale accounts for 0.5-1.0% of the weight of the waste steel.

Preferably, in the second step, the temperature of the molten scrap steel is kept between 1580 ℃ and 1600 ℃ for 30-45 min; in the heat preservation process, a mixture of fluorite powder and iron scale is added into the slag every 4-6min, the mass ratio of the fluorite powder to the iron scale is 1 (0.8-1.2), and the adding amount is 0.5-0.8kg per ton of steel.

Preferably, in the third step, after the slag materials are completely removed, the aluminum blocks are put into the molten steel, and the adding amount is 0.75-1.25kg per ton of steel; then adding slag material, wherein the weight ratio of lime to fluorite in the slag material is (3.2-4.5) to 1, and the total weight of the added slag material is 1.6-2.4% of the weight of the molten steel.

Preferably, in the third step, after the slag is completely melted, the alloy materials of low-carbon ferrochromium (FeCr65C0.5), ferrocolumbium (FeNb50) and carbon ferromanganese (FeMn84C0.7) are added in sequence.

Preferably, in the fourth step, the steel is heated to 1650-; the mixture of aluminum particles and fluorite powder is added every 3-5 min.

3. Advantageous effects

Compared with the prior art, the technical scheme provided by the invention has the following remarkable effects:

according to the electric furnace primary smelting low-phosphorus 15-5PH stainless steel mother liquor and the smelting method thereof, the P content in the electric furnace primary smelting 15-5PH stainless steel mother liquor can be controlled to be below 0.015 percent, and conditions are created for subsequent smelting of low-P15-5 PH stainless steel; adding slag and scrap steel into an electric furnace, melting by electric conduction, adding the slag after melting, adding alloy material after melting the slag, further heating and preserving heat, and then tapping; wherein the slag material comprises lime and fluorite, and the surface of the slag material is subjected to atomization and humidification treatment before the slag material is added into the electric furnace; through the process and the atomization and humidification treatment on the surface of the slag charge, the physicochemical reaction condition in the molten steel is improved in the subsequent electric furnace smelting process, the reduction of the P element in the molten steel is promoted, and meanwhile, the removal of O, N, H and other impurities in the molten steel is facilitated.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments, but not all embodiments, of the present invention; moreover, the embodiments are not relatively independent, and can be combined with each other according to needs, so that a better effect is achieved. Thus, the following detailed description of the embodiments is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention relates to a method for primary smelting of stainless steel mother liquor with low phosphorus content of 15-5PH by an electric furnace, which comprises the steps of adding slag and waste steel into the electric furnace, introducing the slag into the electric furnace for electric melting, adding slag after melting, adding alloy after melting the slag, further heating and preserving heat, and then tapping; wherein the slag comprises lime and fluorite, and the surface of the slag is treated by atomization and humidification before the slag is added into the electric furnace. The slag atomized water is added in a proportion of 1-5% of the weight of the slag atomized water.

Comprises the following specific steps

Firstly, stacking slag making materials and waste steel in layers in an electric furnace, wherein the waste steel accounts for 3/4 of total metal materials fed into the furnace; firstly, lime and iron scale are paved at the bottom of the furnace, then scrap steel accounting for 3/12-5/12 of the total amount of the scrap steel is added, fluorite is added, then scrap steel accounting for 3/12-5/12 of the total amount of the scrap steel is added, electrolytic copper and electrolytic nickel are added, lime and steel rolling iron scale are added, and finally the rest scrap steel is added; the added lime accounts for 3-4% of the weight of the waste steel, the fluorite accounts for 0.5-1.0% of the weight of the waste steel, and the iron scale accounts for 0.5-1.0% of the weight of the waste steel.

Step two, electrifying and melting; the temperature of the molten scrap steel is kept between 1580 and 1600 ℃ for 30-45 min; in the heat preservation process, a mixture of fluorite powder and iron scale is added into the slag every 4-6min, the mass ratio of the fluorite powder to the iron scale is 1 (0.8-1.2), and the adding amount is 0.5-0.8kg per ton of steel.

Step three, after the melting is finished, removing the slag, deoxidizing, adding the slag, and adding an alloy material after the slag is completely melted; after slag materials are completely removed, putting an aluminum block into the molten steel, wherein the adding amount is 0.75-1.25 kg/ton of steel; then adding slag materials, wherein the weight ratio of lime to fluorite in the slag materials is (3.2-4.5) to 1, and the total weight of the added slag materials is 1.6-2.4% of the weight of the molten steel. After the slag is completely melted, alloy materials of low-carbon ferrochromium (FeCr65C0.5), ferrocolumbium (FeNb50) and carbon ferromanganese (FeMn84C0.7) are sequentially added.

And step four, further heating and preserving heat, tapping after the components and the temperature are qualified, and transferring to a refining process. Heating to 1650-; the mixture of aluminum particles and fluorite powder is added every 3-5 min.

The stainless steel mother liquor with the pH of 15-5 prepared by the steps comprises the following components after being smelted by an electric furnace: 0.1-0.15% of C, 0.30-0.50% of Mn, 2.80-3.50% of Cu, 4.00-4.5% of Ni, 14.0-14.80% of Cr, 0.25-0.35% of Nb, less than or equal to 0.015% of P, less than or equal to 0.008% of S and the balance of Fe and impurities.

Preparing 15-5PH stainless steel electroslag ingots by using the method for primarily smelting low-phosphorus 15-5PH stainless steel mother liquor by using the electric furnace, performing first electric furnace smelting on steelmaking raw materials in the electric furnace, performing first LF refining after one-time electric furnace smelting tapping, performing VOD refining after steel checking after one-time LF refining, performing second electric furnace smelting on the tapped steel after VOD refining, performing second LF refining after second electric furnace smelting, performing VD vacuum refining after the second LF refining, then casting molten steel, and performing electroslag remelting on cast blanks after casting to obtain 15-5PH stainless steel electroslag ingot finished products.

In addition, in the traditional smelting process, after VOD is finished, slag is not removed, LF heating is directly carried out, and reducing agent is added for smelting, so that TiO in the slag₂And is reduced again to make titanium enter into the steel, thereby increasing the titanium content in the steel. If the titanium content in the molten steel is to be reducedIt is necessary to add an alloy having an extremely low titanium content during alloying before VOD, which in turn causes an increase in production cost. In the traditional smelting process, slag materials in a ladle are not changed from LF to LF, so that the slag does not have the desulfurization capability any more when the sulfur content in the slag reaches a certain degree. In the patent, the separation of the steel slag is realized after VOD, and the slag is formed again in the electric furnace, so that the desulfurization capability of the slag is greatly improved.

In the traditional smelting process, after the VOD smelting technology, the LF is further heated, reduced, alloyed and the like, so that the bottom blowing gas volume of the LF ladle is generally larger, and particularly a slag hole (a place where molten steel is exposed in slag) exists, so that air is contacted with the molten steel, and oxygen, hydrogen and nitrogen are inevitably added to the molten steel.

In the patent, after VOD is finished, molten steel is put into an electric furnace, slagging is carried out again in the electric furnace, alloying is finished, and then the molten steel enters an LF furnace. Only the molten steel is heated and impurities are removed in the LF furnace, at the moment, the bottom blowing gas quantity of the LF ladle is small, only the slag surface slightly fluctuates, the molten steel is not exposed, and the contact with air is avoided, so that the oxygen increase, the hydrogen increase and the nitrogen increase are prevented.

After the VOD oxygen blowing decarburization refining, not only carbon is oxidized off, but also easily-oxidized elements, particularly Ti, are largely oxidized into TiO₂The titanium content in the steel is extremely low when entering the slag.

After VOD oxygen blowing decarburization refining, the molten steel is put into an electric furnace from a ladle sliding water gap, and finally TiO is contained₂Separating the steel slag with higher content in the steel ladle, and then reproducing new slag in the electric furnace, wherein the TiO content in the new slag₂The content is very low, thereby avoiding TiO in slag₂And (4) transition to molten steel.

The prepared 15-5PH stainless steel electroslag ingot finished product comprises the following components: 0.02-0.06% of C, 0.20-0.50% of Si, 0.30-0.80% of Mn, 2.80-4.20% of Cu, 4.00-5.30% of Ni, 14.50-15.50% of Cr, 0.08-0.15% of V, 0.30-0.43% of Nb and 0.02-0.04% of Al; the contents of impurity elements are as follows: less than or equal to 0.0015 percent of Ti, less than or equal to 0.0010 percent of S, less than or equal to 0.015 percent of P, less than or equal to 0.0018 percent of T.O, 0.015-0.025 percent of N, and less than or equal to 0.0002 percent of H.

The nitrogen content in the steel can be controlled between 0.015 and 0.025 percent. Before the molten steel is subjected to LF refining, the carbon content in the steel is controlled to be 0.15-0.20%, and the nitrogen content in the VOD oxygen blowing decarburization process is ensured to be reduced to a reasonable level without being too low or too high. In the second LF refining stage, the molten steel is not exposed, so that nitrogen is increased less. In the VD refining process, the nitrogen content is reduced by 10-20%. Due to the protective casting, the nitrogen content is basically kept unchanged in the casting and electroslag remelting stages. By the process, the nitrogen content in the electroslag ingot can be controlled within the range of 0.015-0.025%.

The slag is whitened in the later stage of the first electric furnace refining, the sulfur content is greatly reduced, and meanwhile, the slag with higher sulfur content is removed; in the first LF refining process, the white slag is fully refined, the sulfur content is further reduced, and the sulfur-containing slag is fully removed before VOD, so that resulfurization is avoided. And then the sulfur content in the steel is further reduced through second electric furnace smelting, LF refining and VD refining. Finally, after electroslag remelting, the sulfur content can be stably controlled below 0.001%.

In the second electric furnace smelting process, the white slag is kept for more than 20min, and the oxygen content in the steel is effectively reduced. White slag refining is continued in the secondary LF refining process, and since no alloy or slag charge is added, external oxygen is reduced; the bottom blowing mainly takes slight fluctuation of a ladle slag surface, and molten steel is not exposed, so that secondary pollution of air is reduced, and the oxygen content is further reduced after secondary LF refining. In the VD refining process, the oxygen content is reduced again due to the floating of the inclusion.

The electroslag ingot production method comprises the following steps:

s1, first electric furnace smelting: using common scrap steel, 15-5PH returning materials and ferroalloy as main raw materials, melting and primary smelting, pouring molten steel into a steel ladle, and preparing for first LF refining; in the first electric furnace smelting process, common scrap steel (carbon steel) is added at first, and the amount of the scrap steel is not less than 1/2 of total charging materials. The slag is a mixture of lime and fluorite powder. Before the fluorite powder is added, atomization humidification treatment needs to be adopted on the surface of the fluorite powder, and the adding proportion of atomized water is 1-5%. 20-30kg of steel slag per ton; adding lime powder in proportion: fluorite ═ 3:1-4: 1; lime particles are 20-50 mm, and Cao% is more than or equal to 96%; fluorite is powder, smaller than 100 meshes, CaF₂％≥98％；

And after the slag is completely melted, removing the slag, and slagging again, wherein 15-20kg/t of steel slag is charged. Adding 15-5PH returning materials and ferroalloy to adjust the components;

before tapping, regulating Cu, Ni, Nb, Cr and Mn in steel to the lower limit of the component range; p is less than or equal to 0.015 percent; si and V are not adjusted; 0.06-0.08% of Al; and C is 0.1-0.15%. After the components reach the target requirements, the slag is removed and tapped, and the tapping temperature is 1600-1650 ℃.

S2, first LF refining: adjusting the components and temperature of the molten steel; in the first LF refining process, lime and fluorite powder are added in the refining process, and 10-15kg of steel slag per ton; lime powder: fluorite is 3: 1-4: 1. Adding 1/2 slag materials along with the tapping process of the electric furnace, and finishing adding 1/2 slag materials in the LF furnace; in the LF refining process, the carbon content is further adjusted to 0.15-0.20%; regulating Cu and Ni to a target component range, keeping Nb and Mn at lower limits, regulating Cr to an upper limit of the component range, and not regulating other components; the LF refining process is carried out for 50-60 min, and the tapping temperature is more than or equal to 1670 ℃.

S3, VOD refining: blowing oxygen for decarburization to reduce the carbon content of the molten steel; in the VOD refining process, vacuum oxygen blowing refining is carried out; vacuum oxygen blowing time is 30min, standing for 20min after oxygen blowing is finished, and vacuum breaking. C is less than or equal to 0.02 percent after refining.

S4, smelting in an electric furnace for the second time: transferring the molten steel refined by VOD into an electric furnace to realize steel-slag separation, and slagging again and adjusting components in the electric furnace; in the second electric furnace smelting process, firstly, molten steel after vacuum oxygen blowing is put into an electric furnace, and steel slag is thoroughly separated. Then, the furnace slag is rapidly added into the electric furnace, and the TiO in the slag after the slag formation is required₂The content is less than or equal to 0.15 percent; and continuously carrying out slag removing and slag supplementing operations in the electric furnace smelting process until slag becomes white, and keeping for 20min, so that steel can be discharged, wherein the steel discharging temperature is 1600-. Before tapping, all components except Al enter target components; 0.1-0.12% of Al. Slag is not removed before tapping, and the steel slag is mixed out.

S5, secondary LF refining: adjusting the temperature, refining the white slag and not adjusting the components; in the second LF refining process, no alloy or slag is added into the LF furnace except for heating. The blowing amount of the ladle bottom in the refining process is mainly slight fluctuation of the ladle slag surface, and the molten steel is not exposed. The refining time is 30min-40min, and the refining is finished when the temperature of the molten steel reaches 1670 ℃.

S6, VD refining: vacuum refining is carried out, and the inclusion content of gas in the steel is further reduced;

s7, casting: protecting and casting the electrode bar;

s8, electroslag remelting: and refining the electrode bar.