阅读说明：本技术 异质铸铁中频电炉同炉熔炼的方法 (Method for smelting heterogeneous cast iron by medium-frequency electric furnace in same furnace ) 是由 刘振一 冯淑花 张燕明 胡春萍 于 2020-07-03 设计创作，主要内容包括：本发明公开了一种异质铸铁中频电炉同炉熔炼的方法,属于铸铁熔炼领域,该方法包括以下步骤：准备炉料、设备及技术文件,确定不同材料种类或不同牌号铁液熔化作业顺序,确定第一种铁液以及其他铁液熔化工艺规程,根据工艺配料单要求备料、装料并加热熔化,取样进行出炉前铁液化学成分分析和调整,出炉浇注后根据具体情况确定第二种铁液配料工艺,向炉内补加所需的金属炉料并加热熔化,进行第二种铁液取样分析和成分调整以及铁液处理和出炉浇注,重复以上步骤可进行下一种铁液的熔化生产和铁液处理。本方法可以使同炉铁液熔炼出不同材料种类或不同牌号铸铁件,有效稳定铸件质量,保证铸件合格率,便于对生产进行流程控制以及降低铸铁熔炼成本。(The invention discloses a method for smelting heterogeneous cast iron in a medium-frequency electric furnace in the same furnace, which belongs to the field of cast iron smelting and comprises the following steps: preparing furnace burden, equipment and technical files, determining the melting operation sequence of different material types or different brands of molten iron, determining the melting process procedures of the first molten iron and other molten irons, preparing materials, charging and heating for melting according to the requirements of a process batching sheet, sampling, analyzing and adjusting the chemical components of the molten iron before tapping, determining the batching process of the second molten iron according to specific conditions after tapping and pouring, supplementing required metal furnace burden into the furnace and heating for melting, performing sampling analysis and component adjustment of the second molten iron, treating the molten iron and tapping and pouring, and repeating the steps to perform the melting production and the treatment of the next molten iron. The method can smelt different material types or different brands of iron castings by the same furnace molten iron, effectively stabilize the quality of the castings, ensure the qualification rate of the castings, facilitate the flow control of the production and reduce the smelting cost of the cast iron.)

1. The method for smelting heterogeneous cast iron in the same medium-frequency electric furnace is characterized by comprising the following steps of:

(1) preparing furnace burden and equipment;

(2) determining the melting operation sequence of different material types or different brands of molten iron of the iron casting;

(3) determining a melting process of the iron casting and establishing a process list of a melting proportion of the iron casting;

(4) calculating chemical components of molten iron of the iron casting to be produced;

(5) comparing the calculation result of the chemical composition of the molten iron with the standard range value, preparing materials, charging, heating and melting after confirming that the liquefied iron composition is within an allowable error range, sampling for analyzing the chemical composition of the molten iron before tapping, adjusting the chemical composition of the molten iron before tapping according to the analysis result, and then carrying out molten iron treatment and tapping pouring;

(6) and (5) determining the melting process of the next iron casting, making a next iron casting melting batching process list, and repeating the steps (4) and (5) to finish the melting of the next iron casting.

2. The method for smelting heterogeneous cast iron by using an intermediate frequency electric furnace and the same furnace according to claim 1, is characterized in that: the furnace charge comprises pig iron, scrap steel, scrap returns, ferroalloy and auxiliary materials required by the melting production of the cast iron; the device comprises an intermediate frequency electric furnace, an iron liquid treatment bag, a crown block and detection equipment.

3. The same-furnace smelting and processing technical method of the heterogeneous cast iron intermediate frequency electric furnace according to claim 1, characterized in that: the material types of the iron casting are as follows: common grey cast iron, alloy grey cast iron, nodular cast iron and vermicular cast iron; the cast iron part has the following brands: HT200, HT250, HT300, QT400-18, QT500-7, QT600-3, RuT260, RuT300, RuT 340; the smelting sequence of molten iron of different material types is as follows: common grey cast iron, vermicular cast iron, nodular cast iron and alloy grey cast iron; the smelting sequence of molten iron with the same material and different grades is as follows: gray cast iron: HT200, HT250, HT 300; nodular cast iron: QT400-18, QT500-7 and QT 600-3; vermicular cast iron: RuT260, RuT300, RuT 340.

4. The same-furnace smelting and processing technical method of the heterogeneous cast iron intermediate frequency electric furnace according to claim 1, characterized in that: the grey iron casting, the nodular iron casting and the vermicular iron casting comprise: HT200, HT250, HT300, QT400-18, QT500-7, RuT260, RuT300, RuT 340; the qualified content range of chemical components of various iron castings before tapping is as follows: the chemical components of the grey cast iron HT200 are 3.2-3.5% of carbon, 1.2-1.6% of silicon, 0.8-1.0% of manganese, less than or equal to 0.10% of phosphorus and less than or equal to 0.10% of sulfur; the chemical components of the grey cast iron HT250 are 3.0-3.4% of carbon, 1.1-1.5% of silicon, 0.8-1.1% of manganese, less than or equal to 0.08% of phosphorus and less than or equal to 0.08% of sulfur; the chemical components of the grey cast iron HT300 are 2.9-3.3% of carbon, 0.9-1.3% of silicon, 0.9-1.2% of manganese, less than or equal to 0.06% of phosphorus, less than or equal to 0.06% of sulfur, 0.6-1.0% of copper, 0.2-0.4% of chromium and 0-0.6% of molybdenum; the chemical components of the nodular cast iron QT400-18 are 3.7-4.0% of carbon, 1.0-1.4% of silicon, 0.1-0.4% of manganese, less than or equal to 0.06% of phosphorus and less than or equal to 0.06% of sulfur; the chemical components of the nodular cast iron QT500-7 are 3.6-3.9% of carbon, 0.9-1.3% of silicon, 0.2-0.5% of manganese, less than or equal to 0.06% of phosphorus and less than or equal to 0.06% of sulfur; the chemical components of the nodular cast iron QT600-3 are 3.5-3.8% of carbon, 0.8-1.2% of silicon, 0.3-0.6% of manganese, less than or equal to 0.05% of phosphorus, less than or equal to 0.06% of sulfur, 0.5-1.0% of copper, 0-0.2% of chromium and 0-0.6% of molybdenum; the chemical components of the vermicular cast iron RuT260 are 3.7-3.9% of carbon, 1.7-2.0% of silicon, 0.2-0.5% of manganese, less than or equal to 0.06% of phosphorus and less than or equal to 0.06% of sulfur; the chemical components of the vermicular cast iron RuT300 are 3.6-3.8% of carbon, 1.6-1.9% of silicon, 0.3-0.5% of manganese, less than or equal to 0.06% of phosphorus and less than or equal to 0.06% of sulfur; the chemical components of the vermicular cast iron RuT340 are 3.5 to 3.7 percent of carbon, 1.4 to 1.8 percent of silicon, 0.4 to 0.6 percent of manganese, less than or equal to 0.05 percent of phosphorus and less than or equal to 0.06 percent of sulfur.

5. The same-furnace smelting and processing technical method of the heterogeneous cast iron intermediate frequency electric furnace according to claim 1, characterized in that: the iron casting has a single melting proportioning process, and common grey iron castings, nodular iron castings and vermicular iron castings comprise: HT200, HT250, HT300, QT400-18, QT500-7, RuT260, RuT300, RuT 340; the melting and proportioning proportion of various iron castings is as follows: the melting proportion of the grey cast iron HT200 is 15-45% of pig iron, 5-15% of scrap steel, 40-80% of scrap returns, 0.20-0.50% of ferromanganese, 0.20-0.50% of ferrosilicon and 0.5-0.7% of inoculant; the molten ingredients of the grey cast iron HT250 comprise 20 to 45 percent of pig iron, 10 to 20 percent of scrap steel, 35 to 70 percent of scrap returns, 0.30 to 0.60 percent of ferromanganese, 0.15 to 0.40 percent of ferrosilicon and 0.55 to 0.70 percent of inoculant; the molten ingredients of the grey cast iron HT300 comprise 30-50 percent of pig iron, 15-25 percent of scrap steel, 25-55 percent of scrap returns, 0.40-0.70 percent of ferromanganese, 0.10-0.35 percent of ferrosilicon, 0.30-0.50 percent of soldering iron, 0.70-1.00 percent of electrolytic copper and 0.60-0.75 percent of inoculant; the molten proportioning proportion of the nodular cast iron QT400-18 is 60-80% of pig iron, 10-15% of scrap steel, 5-30% of foundry returns, less than or equal to 0.30% of ferromanganese, 1.40-1.60% of nodulizer and 1.50-1.70% of inoculant; the melting proportion of the nodular cast iron QT500-7 is 60-75% of pig iron, 15-20% of scrap steel, 5-25% of foundry returns, less than or equal to 0.40% of ferromanganese, 1.30-1.50% of nodulizer and 1.40-1.60% of inoculant; the molten proportioning proportion of the nodular cast iron QT600-3 is 60-70% of pig iron, 15-20% of scrap steel, 10-25% of scrap returns, less than or equal to 0.50% of ferromanganese, 1.30-1.50% of nodulizer, 0.70-1.10% of electrolytic copper and 1.40-1.60% of inoculant; the melting proportion of the vermicular cast iron RuT260 is 60-75 percent of pig iron, 10-20 percent of scrap steel, 5-30 percent of scrap returns, less than or equal to 0.40 percent of ferromanganese, 1.00-1.20 percent of vermiculizer and 0.50-0.90 percent of inoculant; the melting proportion of the vermicular cast iron RuT300 is 60 to 75 percent of pig iron, 10 to 20 percent of scrap steel, 5 to 30 percent of scrap returns, less than or equal to 0.50 percent of ferromanganese, 1.00 to 1.30 percent of vermiculizer and 0.50 to 1.00 percent of inoculant; the melting proportion of the vermicular cast iron RuT340 is 60 to 70 percent of pig iron, 15 to 20 percent of scrap steel, 10 to 25 percent of scrap returns, less than or equal to 0.60 percent of ferromanganese, 1.10 to 1.30 percent of vermiculizer and 0.60 to 1.00 percent of inoculant.

6. The same-furnace smelting and processing technical method of the heterogeneous cast iron intermediate frequency electric furnace according to claim 1, characterized in that: the calculation formula of the chemical components before melting is as follows: x_i=（X_ti*G_t+X_fi*G_f+X_hi*G_h+X_ji*G_j）*（1-L_yi) G, wherein X_iIs the weight percentage content of chemical element i in the cast iron, X_tiThe weight percentage content of chemical element i in the pig iron, G_tThe amount of pig iron added in the ingredients for melting cast iron, X_fiIs the weight percentage content G of chemical element i in the scrap steel_fAdding amount of scrap steel in cast iron melting ingredients, X_hiIs the weight percentage content G of chemical element i in the foundry returns_hOf scrap returns in the batching for melting cast ironAmount of addition, X_jiThe weight percentage content G of chemical element i in the alloy furnace charge_jThe addition of the alloy charge in the melting burden of cast iron, L_yiThe oxidation burning loss rate of a chemical element i in the cast iron melting process, and G is the total weight of molten iron in each furnace in the cast iron melting production.

7. The same-furnace smelting and processing technical method of the heterogeneous cast iron intermediate frequency electric furnace according to claim 1, characterized in that: and (5) sampling in the step (5) to analyze chemical components before tapping, detecting chemical components of the iron liquid before tapping by using a direct-reading spectrometer, wherein the sampling temperature range is preferably 1370-1430 ℃, and adjusting the chemical components of the iron liquid before tapping by selecting one or more of a method for supplementing the same alloy, a method for supplementing pig iron or carburant, a method for supplementing scrap steel, a method for tapping and redistributing iron and a method for delaying burning loss.

8. The same-furnace smelting and processing technical method of the heterogeneous cast iron intermediate frequency electric furnace according to claim 1, characterized in that: and (5) before the molten iron is ready to be discharged from the furnace, performing molten iron furnace front treatment, wherein the molten iron treatment method comprises the steps of high-temperature standing of the molten iron, purification and deslagging of the molten iron, and deoxidation and desulfurization of the molten iron.

Technical Field

The invention belongs to the field of cast iron smelting, and particularly relates to a method for smelting heterogeneous cast iron in a same medium-frequency electric furnace, which is used for smelting different material types or different grades of iron castings by using molten iron in the same medium-frequency electric furnace.

Background

In the aspect of the existing intermediate frequency electric furnace cast iron smelting technology, each furnace molten iron can only be smelted to produce cast iron pieces with the same material grade, and in the production process of multiple-variety and small-batch casting blanks, because the number of casting pieces and the weight of the molten iron required by production are smaller, the problems that the batch of the casting pieces with the same grade and the consumption of the molten iron are not enough to melt the whole furnace molten iron often occur, and the smelting space in the furnace is wasted; the smelting technology for producing iron castings of different material types or different brands by simultaneously smelting the same molten iron in the same furnace is rare, comprehensive research of a system is lacked, and cast iron smelting personnel generally only depend on production practice experience to grope and control, so that the accurate, quick and low-cost control of the cast iron smelting production process and the internal quality of the castings cannot be guaranteed.

Disclosure of Invention

The invention provides a method for smelting heterogeneous cast iron in a medium-frequency electric furnace in the same furnace, which realizes the smelting of molten iron in the medium-frequency electric furnace in the same furnace to obtain cast iron pieces of different material types or different brands.

The technical scheme adopted for solving the problems is as follows:

the method for smelting heterogeneous cast iron in the same medium-frequency electric furnace is characterized by comprising the following steps of:

(1) preparing furnace burden and equipment;

(2) determining the melting operation sequence of different material types or different brands of molten iron of the iron casting;

(3) determining a melting process of the iron casting and establishing a process list of a melting proportion of the iron casting;

(4) calculating chemical components of molten iron of the iron casting to be produced;

(5) comparing the calculation result of the chemical composition of the molten iron with the standard range value, preparing materials, charging, heating and melting after confirming that the liquefied iron composition is within an allowable error range, sampling for analyzing the chemical composition of the molten iron before tapping, adjusting the chemical composition of the molten iron before tapping according to the analysis result, and then carrying out molten iron treatment and tapping pouring;

(6) and (5) determining the melting process of the next iron casting, making a next iron casting melting batching process list, and repeating the steps (4) and (5) to finish the melting of the next iron casting.

The technical scheme of the invention is further improved as follows: the furnace charge comprises pig iron, scrap steel, scrap returns, ferroalloy and auxiliary materials required by the melting production of the cast iron; the device comprises an intermediate frequency electric furnace, an iron liquid treatment bag, a crown block and detection equipment.

The technical scheme of the invention is further improved as follows: the types of the materials of the iron casting are as follows: common grey cast iron, alloy grey cast iron, nodular cast iron and vermicular cast iron; the cast iron part has the following brands: HT200, HT250, HT300, QT400-18, QT500-7, QT600-3, RuT260, RuT300, RuT 340; the smelting sequence of molten iron of different material types is as follows: common grey cast iron, vermicular cast iron, nodular cast iron and alloy grey cast iron; the smelting sequence of molten iron with the same material and different grades is as follows: gray cast iron: HT200, HT250, HT 300; nodular cast iron: QT400-18, QT500-7 and QT 600-3; vermicular cast iron: RuT260, RuT300, RuT 340.

The technical scheme of the invention is further improved as follows: the grey iron casting, the nodular iron casting and the vermicular iron casting comprise: HT200, HT250, HT300, QT400-18, QT500-7, RuT260, RuT300, RuT 340; the qualified content range of the chemical components of the molten iron before the various iron castings are taken out of the furnace is as follows: the chemical components of the grey cast iron HT200 are 3.2-3.5% of carbon, 1.2-1.6% of silicon, 0.8-1.0% of manganese, less than or equal to 0.10% of phosphorus and less than or equal to 0.10% of sulfur; the chemical components of the grey cast iron HT250 are 3.0-3.4% of carbon, 1.1-1.5% of silicon, 0.8-1.1% of manganese, less than or equal to 0.08% of phosphorus and less than or equal to 0.08% of sulfur; the chemical components of the grey cast iron HT300 are 2.9-3.3% of carbon, 0.9-1.3% of silicon, 0.9-1.2% of manganese, less than or equal to 0.06% of phosphorus, less than or equal to 0.06% of sulfur, 0.6-1.0% of copper, 0.2-0.4% of chromium and 0-0.6% of molybdenum; the chemical components of the nodular cast iron QT400-18 are 3.7-4.0% of carbon, 1.0-1.4% of silicon, 0.1-0.4% of manganese, less than or equal to 0.06% of phosphorus and less than or equal to 0.06% of sulfur; the chemical components of the nodular cast iron QT500-7 are 3.6-3.9% of carbon, 0.9-1.3% of silicon, 0.2-0.5% of manganese, less than or equal to 0.06% of phosphorus and less than or equal to 0.06% of sulfur; the chemical components of the nodular cast iron QT600-3 are 3.5-3.8% of carbon, 0.8-1.2% of silicon, 0.3-0.6% of manganese, less than or equal to 0.05% of phosphorus, less than or equal to 0.06% of sulfur, 0.5-1.0% of copper, 0-0.2% of chromium and 0-0.6% of molybdenum; the chemical components of the vermicular cast iron RuT260 are 3.7-3.9% of carbon, 1.7-2.0% of silicon, 0.2-0.5% of manganese, less than or equal to 0.06% of phosphorus and less than or equal to 0.06% of sulfur; the chemical components of the vermicular cast iron RuT300 are 3.6-3.8% of carbon, 1.6-1.9% of silicon, 0.3-0.5% of manganese, less than or equal to 0.06% of phosphorus and less than or equal to 0.06% of sulfur; the chemical components of the vermicular cast iron RuT340 are 3.5 to 3.7 percent of carbon, 1.4 to 1.8 percent of silicon, 0.4 to 0.6 percent of manganese, less than or equal to 0.05 percent of phosphorus and less than or equal to 0.06 percent of sulfur.

The technical scheme of the invention is further improved as follows: according to the process list of the melting and batching proportion of the iron castings, the melting and batching proportion of various iron castings is as follows: the melting proportion of the grey cast iron HT200 is 15-45% of pig iron, 5-15% of scrap steel, 40-80% of scrap returns, 0.20-0.50% of ferromanganese, 0.20-0.50% of ferrosilicon and 0.5-0.7% of inoculant; the molten ingredients of the grey cast iron HT250 comprise 20 to 45 percent of pig iron, 10 to 20 percent of scrap steel, 35 to 70 percent of scrap returns, 0.30 to 0.60 percent of ferromanganese, 0.15 to 0.40 percent of ferrosilicon and 0.55 to 0.70 percent of inoculant; the molten ingredients of the grey cast iron HT300 comprise 30-50 percent of pig iron, 15-25 percent of scrap steel, 25-55 percent of scrap returns, 0.40-0.70 percent of ferromanganese, 0.10-0.35 percent of ferrosilicon, 0.30-0.50 percent of soldering iron, 0.70-1.00 percent of electrolytic copper and 0.60-0.75 percent of inoculant; the molten proportioning proportion of the nodular cast iron QT400-18 is 60-80% of pig iron, 10-15% of scrap steel, 5-30% of foundry returns, less than or equal to 0.30% of ferromanganese, 1.40-1.60% of nodulizer and 1.50-1.70% of inoculant; the melting proportion of the nodular cast iron QT500-7 is 60-75% of pig iron, 15-20% of scrap steel, 5-25% of foundry returns, less than or equal to 0.40% of ferromanganese, 1.30-1.50% of nodulizer and 1.40-1.60% of inoculant; the molten proportioning proportion of the nodular cast iron QT600-3 is 60-70% of pig iron, 15-20% of scrap steel, 10-25% of scrap returns, less than or equal to 0.50% of ferromanganese, 1.30-1.50% of nodulizer, 0.70-1.10% of electrolytic copper and 1.40-1.60% of inoculant; the melting proportion of the vermicular cast iron RuT260 is 60-75 percent of pig iron, 10-20 percent of scrap steel, 5-30 percent of scrap returns, less than or equal to 0.40 percent of ferromanganese, 1.00-1.20 percent of vermiculizer and 0.50-0.90 percent of inoculant; the melting proportion of the vermicular cast iron RuT300 is 60 to 75 percent of pig iron, 10 to 20 percent of scrap steel, 5 to 30 percent of scrap returns, less than or equal to 0.50 percent of ferromanganese, 1.00 to 1.30 percent of vermiculizer and 0.50 to 1.00 percent of inoculant; the melting proportion of the vermicular cast iron RuT340 is 60 to 70 percent of pig iron, 15 to 20 percent of scrap steel, 10 to 25 percent of scrap returns, less than or equal to 0.60 percent of ferromanganese, 1.10 to 1.30 percent of vermiculizer and 0.60 to 1.00 percent of inoculant.

The technical scheme of the invention is further improved as follows: the given calculation formula of the chemical composition before melting is as follows: x_i＝(X_ti*G_t+X_fi*G_f+X_hi*G_h+X_ji*G_j)*(1-L_yi) G, wherein X_iIs the weight percentage content of chemical element i in the cast iron, X_tiThe weight percentage content of chemical element i in the pig iron, G_tThe amount of pig iron added in the ingredients for melting cast iron, X_fiIs the weight percentage content G of chemical element i in the scrap steel_fAdding amount of scrap steel in cast iron melting ingredients, X_hiIs the weight percentage content G of chemical element i in the foundry returns_hThe addition amount of the returned materials in the cast iron melting and proportioning, X_jiThe weight percentage content G of chemical element i in the alloy furnace charge_jThe addition of the alloy charge in the melting burden of cast iron, L_yiThe oxidation burning loss rate of a chemical element i in the cast iron melting process, and G is the total weight of molten iron in each furnace in the cast iron melting production.

The technical scheme of the invention is further improved as follows: sampling to analyze chemical components of the iron liquid before tapping, detecting the chemical components of the iron liquid before tapping by adopting a direct-reading spectrometer, wherein the sampling temperature range is preferably 1370-1430 ℃, and adjusting the chemical components of the iron liquid before tapping by adopting one or more of a method for supplementing the same alloy, a method for supplementing pig iron or carburant, a method for supplementing scrap steel, a tapping reassortment method and a delayed burning loss method.

The technical scheme of the invention is further improved as follows: before the preparation of the molten iron, the preparation of the molten iron is carried out, the treatment of the molten iron before tapping is carried out, and the treatment method of the molten iron comprises the steps of high-temperature standing of the molten iron, purification and deslagging of the molten iron, and deoxidation and desulfurization of the molten iron.

Due to the adoption of the technical scheme, the invention has the technical progress that:

the invention designs a standardized flow of cast iron smelting, combines a single batching process and flow detection, and facilitates production operation of production personnel in the cast iron smelting, thereby realizing the same-furnace smelting of various iron castings; the quality of iron castings of different material types or different brands produced by smelting the same furnace molten iron is effectively improved, and the smelting cost of the iron castings is reduced by recycling the residual molten iron of the previous castings.

The determination of the correct melting sequence of the molten iron of different material types or different grades is beneficial to stabilizing and improving the metallurgical index of the molten iron, ensuring the material quality of the iron casting, reducing the oxidation loss of metal elements, saving furnace burden and reducing the production cost.

The setting of the proportion of the melting ingredients of the casting can ensure that production personnel can accurately add furnace burden, avoid the waste of the ingredients of the casting, effectively reduce the times of repeated ingredients and increase the working efficiency of the casting melting.

The standard range of the chemical component content of the iron liquid of various iron castings before tapping is given, and the qualification rate of cast iron products can be stably improved by combining the component detection of a spectrometer.

Detailed Description

A method for smelting heterogeneous cast iron in a medium-frequency electric furnace in the same furnace comprises the following steps:

1. preparing a furnace charge and equipment:

preparing various furnace charges such as pig iron, scrap steel, foundry returns, ferroalloy, auxiliary materials and the like required by the melting production of cast iron; various equipment required by smelting such as an intermediate frequency electric furnace, an iron liquid treatment bag, a crown block, detection equipment and the like are checked and prepared; preparing various technical documents such as standards, manuals, process rules, operation instruction books, ingredient process lists and the like required by the cast iron smelting operation; the returned material is metal furnace material returned to the furnace for re-melting, and generally comprises a homogeneous casting head, a scrapped casting and an ingot combining block of residual molten iron in the last furnace; the ferroalloy refers to various metal furnace charges which are used for adjusting chemical components of stokehole iron liquid or treating the iron liquid and are added in a small amount, such as ferromanganese, ferrosilicon, an inoculant, a nodulizer and the like; the auxiliary materials refer to non-metallic auxiliary materials such as carburant, covering agent, slag conglomeration agent, refining agent and the like used in the melting production process of cast iron.

2. Determining the melting operation sequence of molten iron of different material types or different brands:

the types of materials of the common iron casting are as follows: ordinary grey cast iron, alloy grey cast iron, nodular cast iron and vermicular graphite cast iron, and the grades of the iron castings are as follows: HT200, HT250, HT300, QT400-18, QT500-7, QT600-3, RuT260, RuT300, RuT 340; the smelting sequence of molten iron of different material types is as follows: common grey cast iron, vermicular cast iron, nodular cast iron and alloy grey cast iron; the smelting sequence of molten iron with the same material and different grades is as follows: gray cast iron: HT200, HT250, HT 300; nodular cast iron: QT400-18, QT500-7 and QT 600-3; vermicular cast iron: RuT260, RuT300, RuT 340; the determination of the melting sequence of molten iron of different material types or different brands is convenient for melting production operation, easy to adjust melting ingredients and control the chemical components of molten iron and castings, and favorable for eliminating the adverse effect of furnace burden inheritance on the subsequent molten iron melting quality.

3. Determining a melting process of molten iron and formulating a cast iron melting process list:

the process list comprises the following contents: the material grade, product name and code of the casting to be produced, various iron casting melting and batching lists, process list compiling date and validity period and the like are prepared.

The melting ingredient proportion ranges of various common iron castings are shown in the following table:

4. according to the single requirement of the cast iron melting and batching process and a chemical composition calculation formula before melting, the chemical composition content before melting of the cast iron is obtained, the chemical composition content before melting is compared with the qualified range of the chemical composition of each given cast iron before tapping, if the chemical composition content is within the allowable parameter error range, the materials are prepared, the materials are charged and heated to be melted, the chemical composition before tapping is sampled to be measured, and the chemical composition of the molten iron before tapping is adjusted according to the analysis result.

Wherein the chemical composition calculation formula before the iron casting is melted is as follows: x_i＝(X_ti*G_t+X_fi*G_f+X_hi*G_h+X_ji*G_j)*(1-L_yi) G, wherein X_iIs the weight percentage content of chemical element i in the cast iron, X_tiThe weight percentage content of chemical element i in the pig iron, G_tThe amount of pig iron added in the ingredients for melting cast iron, X_fiIs the weight percentage content G of chemical element i in the scrap steel_fAdding amount of scrap steel in cast iron melting ingredients, X_hiIs the weight percentage content G of chemical element i in the foundry returns_hThe addition amount of the returned materials in the cast iron melting and proportioning, X_jiThe weight percentage content G of chemical element i in the alloy furnace charge_jThe addition of the alloy charge in the melting burden of cast iron, L_yiThe oxidation burning loss rate of a chemical element i in the cast iron melting process, and G is the total weight of molten iron in each furnace in the cast iron melting production.

The percent qualified range of the chemical components of various iron casting melts is as follows:

the melting oxidation burnout rate of the common elements is as follows:

wherein the chemical composition measurement before tapping adopts a direct-reading spectrometer, the temperature range of the molten iron is 1370-1430 ℃ during sampling detection, one or more of a similar alloy supplementing method, a pig iron or carburant supplementing method, a scrap steel supplementing method, a tapping reassortment method and a time-delay burning loss method are selected as the method for adjusting the chemical composition of the molten iron before tapping, the weight of the furnace charge to be supplemented is calculated, the furnace charge is weighed and prepared, the various furnace charges to be supplemented are weighed, and after the preparation is finished, the various furnace charges to be supplemented are all added into the furnace according to the method and the sequence of the process requirements; continuing to heat the molten iron after the furnace burden is replenished, performing secondary sampling after ensuring that the replenished furnace burden is fully melted and homogenized, and detecting chemical components of the molten iron; and comparing the content of various chemical elements in the measured molten iron with the process requirements according to the detection result of the chemical components, if the content of various chemical elements is in the range of the process parameter requirements, judging that the analysis result of the chemical components meets the process requirements, performing subsequent operation, and if the content of various chemical elements is not qualified, continuing to adjust the chemical components.

5. Carrying out molten iron treatment and tapping casting: the iron liquid treatment method comprises the steps of standing the iron liquid at a high temperature, purifying and deslagging the iron liquid, and deoxidizing and desulfurizing the iron liquid; wherein the high-temperature standing specific operation of the molten iron is as follows: after the molten iron in the whole furnace is melted and the chemical components of the molten iron are detected to be qualified, continuously heating to raise the temperature, raising the temperature of the molten iron to be higher than the upper limit of the tapping temperature by 15-30 ℃, uniformly spreading a layer of covering agent on the surface of the molten iron, then stopping power supply and standing for 3-8 minutes, so as to promote slag and impurities in the molten iron to float to the surface of the molten iron, and remove the slag by slag accumulation and slag removal, and simultaneously, the method is also beneficial to fully melting furnace burden, promotes the chemical components of the molten iron to be homogenized and improves the internal quality of a casting; the specific operations of molten iron purification and slag removal are as follows: after the whole furnace iron liquid is melted and the chemical components of the iron liquid are detected to be qualified, a layer of slag conglomeration agent is scattered on the surface of the iron liquid before the iron liquid is discharged, or a small amount of purifying agent is added into the furnace, and after slag and impurities in the iron liquid float up to the surface of the iron liquid, the slag conglomeration and slag removal are carried out; wherein, the iron liquid deoxidation and desulfurization are adopted under the condition that the iron casting has special requirements; after the molten iron is treated, discharging the molten iron when the temperature meets the discharging temperature requirement, injecting the molten iron into a prepared molten iron bag, and performing blank casting; in general, during tapping, an in-ladle pouring method is adopted for liquid iron inoculation and modification treatment, if nodular cast iron is required to be spheroidized and inoculated, and if vermicular cast iron is required to be vermicular cast iron, the process is specifically carried out according to process requirements in the actual production.

6. And (3) finishing the steps, finishing the smelting of the iron casting for the first time, if the next iron casting needs to be smelted, determining a smelting and proportioning process of the iron casting of the second type according to the chemical components and the residual amount of the previous iron liquid and the factors in the aspects of the material requirement of the casting to be produced, the structural characteristics of the casting, the technical quality difficulty and the like, taking the previous iron liquid remaining in the furnace as a scrap return, carrying out smelting and proportioning calculation, and providing a smelting and proportioning process list of the iron liquid of the second type of casting for the next operation.

7. And (5) repeating the steps 4 and 5 until the smelting of all material types or all brands of iron castings is completed.

The following takes iron castings of No. 2 flywheel shell, No. 5 flywheel, No. 1 bearing cap and the like on a diesel engine as an example:

the material of the casting of the No. 2 flywheel shell is HT250, the casting belongs to a shell type thin-wall gray iron casting, the main wall thickness is 8-10mm, the external dimension of the casting blank is phi 560x150mm, and the weight of the casting is 60 Kg. The mechanical property requirements of the casting are as follows: the tensile strength is not lower than 250MPa, and the hardness is required to be 180 HB and 230 HB. The casting does not allow for casting defects that affect the strength and appearance quality of the casting. The casting material of No. 5 flywheel is alloy gray cast iron, belongs to wheel disc type thick wall gray cast iron, the main wall thickness is 35-55mm, the external dimension of the casting blank is phi 500x130mm, and the casting weight is 80 Kg. The mechanical property requirements of the casting are as follows: the tensile strength is not lower than 320MPa, and the hardness is required to be 210-240 HB. The casting does not allow for casting defects that affect the strength and appearance quality of the casting. The material quality of a casting of the No. 1 bearing cover is QT500-7, the casting belongs to a flat plate type thick-wall nodular iron casting, the main wall thickness is 35-40mm, the external dimension of a casting blank is 200x140mm, and the weight of the casting is 9 Kg. The mechanical property requirements of the casting are as follows: the tensile strength is not lower than 500MPa, the elongation is not lower than 7 percent, the hardness requirement is 170 HB and 240HB, and casting defects influencing the strength and the appearance quality of the casting are not allowed. According to a certain casting production operation planning task, the No. 2 flywheel shell 12, the No. 5 flywheel 10 and the No. 1 bearing cover 60 are required to be produced.

a. The selected raw materials and smelting equipment are as follows: a1.5 t intermediate frequency electric furnace is selected as smelting equipment for producing castings such as a 2# flywheel shell, a 5# flywheel, a 1# bearing cover and the like. The furnace burden for melting the cast iron is as follows: wuan Z14 or Q10 pig iron is selected, low-carbon steel leftovers of a steel mill are selected as waste steel, and various ferroalloys are purchased according to the international standard requirements. According to the technical requirements of the acceptance of the castings and the combination of production practice, the production process lists of the various castings are compiled, and corresponding production molds are manufactured.

b. Determining the melting sequence of iron castings with different brands: 2# flywheel shell-1 # bearing cap-5 # flywheel; firstly producing a 2# flywheel shell of a gray iron casting, secondly producing a 1# bearing cover of a nodular iron casting, and finally producing a 5# flywheel of an alloy iron casting.

c. And determining a molten iron smelting process list of the No. 2 flywheel shell by combining a common iron casting melting ingredient table, wherein the specific ingredient addition amount is actually controlled by calculating chemical components before melting and comparing with a chemical component qualified range table of the iron casting.

No. 2 flywheel shell (1.5t furnace) brand: HT250 xxxx year xx month xx day

d. Detecting chemical components of the molten iron of the 2# flywheel shell iron casting before tapping: measuring the sampling components of the casting iron liquid by using a spectrometer, and adjusting the components of the iron liquid if the sampling components do not meet the process requirements; the specific adjustment method can refer to step 4.

e. After the chemical components and melting temperature of the molten iron of the No. 2 flywheel shell iron casting meet the process requirements, discharging the casting from the furnace; and (3) inoculating the molten iron when the molten iron is discharged, adopting a ladle flushing method, adopting BS-I or FeSi75 ferrosilicon as an inoculant, adding the prepared inoculant into a casting ladle along with the flow while discharging the molten iron, stirring after the molten iron in the casting ladle is fully discharged, facilitating the full melting of the inoculant, detecting the temperature of the molten iron in the casting ladle, and pouring the casting after the temperature meets the process requirements, wherein the specific mode can refer to step 5.

f. The smelting of the second iron casting 1# bearing cover and the third iron casting 5# flywheel is carried out according to the steps of the embodiment 1-4, and the following processes are respectively a 1# bearing cover and a 5# flywheel smelting batching process:

number 1 bearing cap (1.5t furnace): QT500-7 xxxx years xx month xx days

No. 5 flywheel (1.5t furnace) brand: alloy gray cast iron xxxx year xx month xx day

After the two casting iron liquids meet the tapping requirement, the treatment of the iron liquid before tapping is needed,

treating No. 1 bearing cap molten iron: when tapping the molten iron, spheroidizing-inoculating treatment is carried out, a ladle flushing method is adopted, an inoculant adopts BS-I or FeSi75 ferrosilicon alloy, a spheroidizing agent adopts FeSiMg8RE3 ferrosilicon alloy, the prepared spheroidizing agent and 2/3 inoculant are filled into a reaction chamber at the bottom of a casting ladle while tapping the molten iron, a cover plate is covered and sealed, the spheroidizing reaction is carried out on 2/3 casting ladle iron liquid firstly, the tapping is continued to be full after the spheroidizing reaction is finished, the rest 1/3 inoculant is added into the casting ladle along with the flow, the casting ladle is stirred after the casting ladle is full of the inoculant, the spheroidizing agent and the inoculant are promoted to be fully melted, then the temperature of the molten iron in the casting ladle is detected, a casting can be cast after meeting the process requirements, and the specific treatment mode refers to step 5.

Treating No. 5 flywheel iron liquid: and (3) carrying out inoculation when the molten iron is discharged, adopting a ladle flushing method, adopting a BS-I composite inoculant as an inoculant, adding the prepared inoculant into a casting ladle along with flow while discharging the molten iron, stirring after the molten iron in the casting ladle is fully discharged, facilitating full melting of the inoculant, then detecting the temperature of the molten iron in the casting ladle, pouring a casting after the temperature meets the process requirements, and referring to the step 5 in the specific treatment mode.