CN117265368A - Preparation method of as-cast pearlite ductile iron casting - Google Patents
Preparation method of as-cast pearlite ductile iron casting Download PDFInfo
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- 238000005266 casting Methods 0.000 title claims abstract description 222
- 229910001141 Ductile iron Inorganic materials 0.000 title claims abstract description 100
- 229910001562 pearlite Inorganic materials 0.000 title claims abstract description 82
- 238000002360 preparation method Methods 0.000 title claims abstract description 14
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 226
- 238000000034 method Methods 0.000 claims abstract description 130
- 229910052742 iron Inorganic materials 0.000 claims abstract description 113
- 239000000126 substance Substances 0.000 claims abstract description 85
- 230000008569 process Effects 0.000 claims abstract description 69
- 239000000203 mixture Substances 0.000 claims abstract description 53
- 238000001816 cooling Methods 0.000 claims abstract description 48
- 238000004519 manufacturing process Methods 0.000 claims abstract description 39
- 239000000956 alloy Substances 0.000 claims abstract description 14
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 13
- 238000010309 melting process Methods 0.000 claims abstract description 12
- 238000010438 heat treatment Methods 0.000 claims abstract description 11
- 238000007599 discharging Methods 0.000 claims abstract description 8
- 239000011159 matrix material Substances 0.000 claims abstract description 8
- 239000000463 material Substances 0.000 claims description 43
- 238000002844 melting Methods 0.000 claims description 43
- 230000008018 melting Effects 0.000 claims description 43
- 238000010079 rubber tapping Methods 0.000 claims description 27
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 24
- 239000004576 sand Substances 0.000 claims description 22
- 239000007788 liquid Substances 0.000 claims description 21
- 238000005070 sampling Methods 0.000 claims description 20
- 239000003795 chemical substances by application Substances 0.000 claims description 18
- 238000005507 spraying Methods 0.000 claims description 17
- 238000004458 analytical method Methods 0.000 claims description 16
- 238000001514 detection method Methods 0.000 claims description 16
- 238000011081 inoculation Methods 0.000 claims description 16
- 238000006243 chemical reaction Methods 0.000 claims description 15
- 238000007664 blowing Methods 0.000 claims description 13
- 239000002054 inoculum Substances 0.000 claims description 13
- 238000003756 stirring Methods 0.000 claims description 13
- 229910001018 Cast iron Inorganic materials 0.000 claims description 12
- 229910000805 Pig iron Inorganic materials 0.000 claims description 11
- 229910000831 Steel Inorganic materials 0.000 claims description 11
- 239000010959 steel Substances 0.000 claims description 11
- 239000002893 slag Substances 0.000 claims description 10
- 229910052729 chemical element Inorganic materials 0.000 claims description 8
- 238000003723 Smelting Methods 0.000 claims description 7
- 238000007689 inspection Methods 0.000 claims description 7
- 239000007921 spray Substances 0.000 claims description 7
- 244000035744 Hura crepitans Species 0.000 claims description 5
- 230000003647 oxidation Effects 0.000 claims description 5
- 238000007254 oxidation reaction Methods 0.000 claims description 5
- 238000005275 alloying Methods 0.000 claims description 4
- 230000009286 beneficial effect Effects 0.000 claims description 4
- 230000003111 delayed effect Effects 0.000 claims description 4
- -1 furnace returns Substances 0.000 claims description 4
- 239000008399 tap water Substances 0.000 claims description 4
- 235000020679 tap water Nutrition 0.000 claims description 4
- 229910001021 Ferroalloy Inorganic materials 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- 239000002245 particle Substances 0.000 claims description 3
- 238000005192 partition Methods 0.000 claims description 3
- 239000010451 perlite Substances 0.000 claims description 3
- 235000019362 perlite Nutrition 0.000 claims description 3
- 230000035484 reaction time Effects 0.000 claims description 3
- 238000005303 weighing Methods 0.000 claims description 3
- 238000004140 cleaning Methods 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 230000010485 coping Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- 229910000640 Fe alloy Inorganic materials 0.000 description 1
- 229910000616 Ferromanganese Inorganic materials 0.000 description 1
- 229910000519 Ferrosilicon Inorganic materials 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 238000010009 beating Methods 0.000 description 1
- 238000005422 blasting Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000007849 furan resin Substances 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- DALUDRGQOYMVLD-UHFFFAOYSA-N iron manganese Chemical compound [Mn].[Fe] DALUDRGQOYMVLD-UHFFFAOYSA-N 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/08—Making cast-iron alloys
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/02—Sand moulds or like moulds for shaped castings
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
- B22D27/04—Influencing the temperature of the metal, e.g. by heating or cooling the mould
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D37/00—Controlling or regulating the pouring of molten metal from a casting melt-holding vessel
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D46/00—Controlling, supervising, not restricted to casting covered by a single main group, e.g. for safety reasons
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C1/00—Refining of pig-iron; Cast iron
- C21C1/10—Making spheroidal graphite cast-iron
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
- C22C33/06—Making ferrous alloys by melting using master alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C37/00—Cast-iron alloys
- C22C37/04—Cast-iron alloys containing spheroidal graphite
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C37/00—Cast-iron alloys
- C22C37/10—Cast-iron alloys containing aluminium or silicon
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
Abstract
The invention discloses a preparation method of as-cast pearlite ductile iron castings, which comprises the following steps: (1) burden, equipment and technical file preparation-2) determining the chemical composition range of the cast pearlite ductile iron casting-3) determining the melting process specification of the cast pearlite ductile iron casting-4) determining the pouring and cooling process specification of the cast pearlite ductile iron casting-5, controlling the molten iron melting process according to the process specification requirement-6, discharging molten iron and spheroidizing-inoculating-7, controlling the casting pouring and cooling process-8, and checking the casting quality; the method does not need a heat treatment step and does not add alloy elements, and the method directly obtains nearly 100% of as-cast pearlite matrix structure without heat treatment or addition of alloy elements, thereby reducing the production period and the production cost and improving the production efficiency.
Description
Technical Field
The invention relates to a preparation method of as-cast pearlite ductile iron castings, and belongs to the field of casting.
Background
The pearlite nodular cast iron is nodular cast iron (spheroidal graphite cast iron for short) with the pearlite content of more than 80 percent in a matrix structure, and the three brands of nodular cast iron, namely QT600-3, QT700-2 and QT800-2 in the national standard, belong to the type. The pearlite nodular cast iron has relatively high strength and hardness, and good fatigue resistance and wear resistance. In the prior art, heat treatment or alloying methods are generally used to produce pearlitic ductile iron castings. However, the heat treatment of the castings consumes a certain energy source and time, so that the manufacturing period of the cast products is prolonged, and the production efficiency is reduced; because some alloy elements are needed to be added in the cast iron alloying, and the price of alloy materials is relatively high, the production cost of the ductile iron casting is obviously increased.
Disclosure of Invention
The invention aims to solve the technical problems of providing a preparation method of cast pearlite ductile iron castings, which does not need heat treatment or adding alloy elements, directly obtains nearly 100% of cast pearlite matrix structure, reduces the production period and the production cost, and improves the production efficiency; meanwhile, the method has important guiding significance for keeping the quality of castings stable and improving, and reducing waste and loss.
In order to solve the technical problems, the invention adopts the following technical scheme:
the preparation method of the as-cast pearlite ductile iron casting comprises the following steps:
(1) burden, equipment and technical file preparation-2) determining the chemical composition range of the cast pearlite ductile iron casting-3) determining the melting process specification of the cast pearlite ductile iron casting-4) determining the pouring and cooling process specification of the cast pearlite ductile iron casting-5, controlling the molten iron melting process according to the process specification requirement-6, discharging molten iron and spheroidizing-inoculating-7, controlling the casting pouring and cooling process-8, and checking the casting quality; there is no heat treatment step in the steps, and no alloying elements are added.
The technical scheme of the invention is further improved as follows: the specific operation of the step (1) is as follows: checking various furnace charges including pig iron, scrap steel, furnace returns, alloy furnace charges and auxiliary materials required by the prepared cast iron melting production; checking and preparing various equipment required by smelting including a medium-frequency electric furnace, a molten iron ladle, a crown block, tools and detection equipment; various technical files containing standards, manuals, technical regulations, operation instructions and batching process sheets required by cast iron smelting operation are prepared.
The technical scheme of the invention is further improved as follows: the range of the chemical composition of the as-cast pearlite ductile iron casting in the step (2) is as follows in table 1:
the technical scheme of the invention is further improved as follows: the casting pearlite ductile iron casting melting process in the step (3) comprises the following steps:
(3.1) determining the melting and proportioning ratio of the as-cast pearlite ductile iron castings according to the material and chemical composition requirements of the castings and combining the chemical composition ratios in table 1;
(3.2) determining an as-cast pearlite ductile iron melting and batching process recipe, wherein the as-cast pearlite ductile iron melting and batching process recipe specifically comprises the following steps: preparing the material marks, product names and codes of the produced castings; preparing the specification and model of the melting equipment and the total weight of molten iron; the specification and the model of various furnace charges and the addition amount; controlling the chemical composition of the molten iron in the front of the furnace; the sequence of various charges added into the furnace; the process bill is compiled on a date and the expiration date;
the melting batch ratios of the specific as-cast pearlitic ductile iron castings are shown in table 2 below:
the technical scheme of the invention is further improved as follows: the pouring and cooling process in the step (4) comprises the following steps:
(4.1) determining casting process parameters of the as-cast pearlite ductile iron casting: tapping temperature of molten iron is 1510+/-15 ℃, initial casting temperature is 1410+/-10 ℃, final casting temperature is 1370+/-10 ℃, single casting time is 5-20s, and total casting time of each ladle of molten iron is 10-13min;
(4.2) determining a cooling process of the as-cast pearlite ductile iron casting: usually is
After each casting is poured, tap water is immediately sprayed to the periphery of the sand box and the upper surface of the casting mould for cooling, and the concrete method comprises the following steps: adopting DN25 water pipe to install DN15 spray head to spray, controlling water pressure at 0.35-0.40MPa; the water spraying and cooling time is as follows: spraying water for 3-5 min when the sand mould size is below 500X500mm, spraying water for 5-8 min when the sand mould size is above 500X500-1000X1000mm, and spraying water for 8-12 min when the sand mould size is above 1000X1000 mm.
The technical scheme of the invention is further improved as follows: in the production period, when the temperature of the casting mold is reduced in 5-8 months in summer, the air cooling method is adopted to promote the cooling of the casting mold, and the specific method is as follows: adopting a 1.5m movable floor type industrial fan to blow air against the surface of the casting mould, wherein the air blowing and cooling time is as follows: blowing for 5-10 min when the sand mould size is below 500X500mm, blowing for 10-15 min when the sand mould size is above 500X500-1000X1000mm, and blowing for 15-20 min when the sand mould size is above 1000X1000 mm.
The technical scheme of the invention is further improved as follows: the specific operation of the step (5) is as follows:
(5.1) preparing materials, charging materials and heating and melting according to the requirements of an as-cast pearlite ductile iron melting and batching process bill:
according to the requirements of an as-cast pearlite nodular cast iron melting and batching process bill, various furnace charges required by melting operation are accurately weighed, positioned and orderly arranged in a partition manner, and marks are made to prevent misuse or confusion; then various furnace charges such as pig iron, scrap steel, returned furnace materials, ferroalloy and the like are sequentially added into the furnace according to a production operation plan and process requirements, and the furnace charges are fed and heated, so that the furnace charges are sequentially melted;
(5.2) sampling for stokehold chemical composition analysis
After the furnace burden is completely melted and homogenized, sampling and detecting molten iron components in the furnace, wherein the sampling temperature range is 1350-1450 ℃;
according to the requirements of the process file, a direct-reading spectrometer is adopted to rapidly and accurately detect the chemical components of the stokehole molten iron and send out a stokehole chemical component analysis report;
according to the requirements of the process file, checking whether the analysis result of the chemical components in front of the furnace meets the requirements of various process parameters, and judging whether the detection result of the chemical components in the molten iron is qualified;
(5.3) adjusting the iron liquid chemical composition in the furnace front
If the detection result of the chemical composition of the molten iron does not meet the process requirement, the chemical composition adjustment in front of the furnace is needed, and the chemical composition adjustment method in front of the furnace comprises the methods of adding similar alloy methods, adding pig iron or carburant methods, adding scrap steel methods, tapping and re-proportioning methods and a delayed burning loss method, and one or more proper adjustment methods are selected according to the specific condition that the chemical composition in front of the furnace exceeds the standard;
after an adjustment method is selected, the weight of the furnace burden to be added is calculated, and the furnace burden is weighed and prepared; weighing various furnace charges to be added, and after the preparation of the materials, adding all the various furnace charges to be added into the furnace according to the method and the sequence of the process requirements;
after the charging material is added, the molten iron is continuously heated, so that after the charging material is fully melted and homogenized, secondary sampling is performed, and the chemical composition of the molten iron is detected; and comparing the content of various chemical elements in the measured molten iron with the process requirements according to the chemical component detection result, if the content of each chemical element is within the range of the process parameter requirements, judging that the chemical component analysis result meets the process requirements, and carrying out subsequent operation if the chemical component analysis result is not qualified, and continuing to carry out chemical component adjustment.
The technical scheme of the invention is further improved as follows: the tapping of molten iron and the spheroidization-inoculation treatment in the step (6) are carried out simultaneously, and the specific operation is as follows:
firstly, putting all the baked nodulizer into a pit at the bottom of a casting ladle, tamping, putting 2/3 of the total amount of the baked inoculant, tamping, tightly covering with a covering agent, and tightly covering the upper surface with a ductile iron plate with the thickness of 2.5-4.5 mm, wherein the periphery and the upper part of the ductile iron plate are tightly covered with the covering agent; wherein the covering agent is perlite particles;
the first tapping amount is 2/3 of the ladle capacity, and after the spheroidization reaction is finished, the inoculation and tapping are continued until Bao Natie liquid is filled; the tapping flow should be stable and uniform, the flow is moderate, and the current interruption or splashing is prevented;
the spheroidizing reaction time of each ladle of molten iron is 1-2 min; in the spheroidizing reaction process, the upper part of the ladle opening is covered by a ladle cover so as to be beneficial to relieving the oxidation and loss of molten iron; after the spheroidizing reaction is finished, removing a ladle cover in time, fully stirring Bao Natie liquid by using a stirring rod, removing slag on the surface of the molten iron, then adding the rest 1/3 inoculant to perform secondary inoculation, discharging the molten iron in the ladle, and stirring and deslagging again;
immediately sampling a test block in front of a casting furnace after the spheroidizing-inoculating process is finished, breaking and observing the fracture morphology of the test block after chilling, judging the spheroidizing quality of molten iron, and casting a casting if the molten iron is qualified; if the spheroidization of the molten iron is poor or not, casting cannot be poured, and Bao Natie liquid is subjected to ingot mixing or furnace return adjustment.
The technical scheme of the invention is further improved as follows: the specific operation of the step (8) is as follows:
casting a standard single casting sample while casting the casting, and dissecting the casting according to the requirement of a product graph to prepare a body sample; according to the requirements of casting acceptance technical documents, the material performance items of the castings, including chemical components, metallographic structures, tensile strength, yield strength, elongation and hardness, are detected, and the inspection results are ensured to meet the technical requirements.
The technical scheme of the invention is further improved as follows: nearly 100% of as-cast pearlitic matrix structure can be obtained.
By adopting the technical scheme, the invention has the following technical progress:
the invention adopts a set of system, complete technology of determining chemical components of the cast pearlite ductile iron castings, melting ingredients, spheroidizing and inoculating molten iron, and a casting pouring and cooling operation control method, so that heat treatment is not needed, alloy elements are not needed to be added, nearly 100% of cast pearlite matrix structure can be directly obtained, the production period and production cost are reduced, and the production efficiency is improved; meanwhile, the method has important guiding significance for keeping the quality of castings stable and improving, and reducing waste and loss.
Drawings
FIG. 1 is a graphite morphology diagram (100X) of an embodiment of the present invention;
FIG. 2 is a matrix organization chart (100X) of an embodiment of the invention.
Detailed Description
The invention is further illustrated by the following examples:
the preparation method of the as-cast pearlite ductile iron casting comprises the following steps:
(1) burden, equipment and technical documentation preparation-2) determination of the chemical composition range of the cast pearlite ductile iron casting-3) determination of the melting process specification of the cast pearlite ductile iron casting-4) determination of the pouring and cooling process specification of the cast pearlite ductile iron casting-5, molten iron melting process control-6, molten iron tapping and spheroidization-inoculation treatment-7, casting pouring and cooling process control-8, and casting quality inspection.
(1) Burden, installation and technical document preparation
Preparing various furnace charges such as pig iron, scrap steel, furnace returns, alloy furnace charges, auxiliary materials and the like required by cast iron melting production; checking and preparing various equipment required by smelting of a medium-frequency electric furnace, a molten iron ladle, a crown block, tools, detection equipment and the like; preparing various technical files such as standard, manual, technical rules, operation instruction book, batching process list and the like required by cast iron smelting operation.
The furnace returns-refer to the metal furnace returns into the furnace and remelts for use, and generally comprises casting heads of castings with the same materials, scrapped castings, ingot blocks of residual molten iron in the previous furnace and the like;
alloy furnace charge-metal furnace charge with less addition, which is used for adjusting chemical components of molten iron or treating molten iron, such as ferromanganese, ferrosilicon, nodulizer, inoculant and the like;
auxiliary materials, namely nonmetallic auxiliary materials such as carburant, refining agent, covering agent, slag conglomeration agent and the like which are used in a small amount in cast iron melting operation.
(2) Determining the chemical composition range of as-cast pearlite ductile iron casting
The chemical elements in the as-cast pearlite ductile iron casting comprise five elements of carbon, silicon, manganese, phosphorus and sulfur.
In order to ensure that the material and performance of the pearlite ductile iron castings meet the technical requirements, the chemical composition range of the pearlite ductile iron should be reasonably determined. For the as-cast pearlite ductile iron castings, according to the technical requirements of the materials of the castings, the factors of the thickness, the weight, the size and the like of the castings are comprehensively considered to determine the proper chemical composition control range of various castings. The chemical composition control range of the as-cast pearlite ductile iron castings of the present invention is shown in the following table 1:
TABLE 1 control ranges of as-cast pearlite ductile iron casting liquid iron and casting chemical composition
(3) Determining the melting technological procedure of as-cast pearlite ductile iron casting
After the control range of the chemical composition of the as-cast pearlite ductile iron casting is determined, the next step is to compile a cast iron melting technological specification, and the main content of the cast iron melting technological specification comprises:
(3.1) determining the melting and proportioning ratio of the as-cast pearlite ductile iron castings according to the material and chemical composition requirements of the castings and combining the chemical composition ratios in table 1;
the melting batch ratios of the specific as-cast pearlitic ductile iron castings are shown in table 2 below:
(3.2) determining an as-cast pearlite ductile iron melting and batching process recipe, wherein the as-cast pearlite ductile iron melting and batching process recipe specifically comprises the following steps: preparing the material marks, product names and codes of the produced castings; preparing the specification and model of the melting equipment and the total weight of molten iron; the specification and the model of various furnace charges and the addition amount; controlling the chemical composition of the molten iron in the front of the furnace; the sequence of various charges added into the furnace; the date and expiration date of the bill.
(4) Determining casting and cooling technological rules of as-cast pearlite ductile iron casting
(4.1) determining casting process parameters of the as-cast pearlite ductile iron casting: tapping temperature of molten iron is 1510+/-15 ℃, initial casting temperature is 1410+/-10 ℃, final casting temperature is 1370+/-10 ℃, single casting time is 5-20s, and total casting time of each ladle of molten iron is 10-13min;
(4.2) determining a cooling process of the as-cast pearlite ductile iron casting: (1) The casting pouring temperature, single piece pouring time, total pouring time of each ladle of molten iron and other technological parameters are strictly controlled according to technological specification requirements:
after each casting is poured, immediately spraying tap water to the periphery of the sand box and the upper surface of the casting mould to cool, wherein the concrete method comprises the following steps of: and a DN25 water pipe is adopted to install a DN15 spray head for spraying, and the water pressure is controlled to be 0.35-0.40MPa. The water spray cooling time is generally: spraying water for 3-5 min when the sand mould size is below 500X500mm, spraying water for 5-8 min when the sand mould size is above 500X500-1000X1000mm, and spraying water for 8-12 min when the sand mould size is above 1000X1000 mm.
If the production period is in summer (5-8 months), the casting mold is cooled by adopting an air cooling method while the casting mold is sprayed with water for cooling, and the concrete method comprises the following steps: adopting a 1.5m movable floor type industrial fan to blow air against the surface of the casting mould, wherein the air blowing and cooling time is generally as follows: blowing for 5-10 min when the sand mould size is below 500X500mm, blowing for 10-15 min when the sand mould size is above 500X500-1000X1000mm, and blowing for 15-20 min when the sand mould size is above 1000X1000 mm.
And after the cooling treatment is finished, opening the box and taking out the piece after the casting mold is cooled to room temperature.
(5) Controlling molten iron melting process according to technological specification
(5.1) preparing materials, charging materials and heating and melting according to the requirements of an as-cast pearlite ductile iron melting and batching process bill:
according to the requirements of an as-cast pearlite nodular cast iron melting and batching process bill, various furnace charges required by melting operation are accurately weighed, positioned and orderly arranged in a partition manner, and marks are made to prevent misuse or confusion; then various furnace charges such as pig iron, scrap steel, returned furnace materials, ferroalloy and the like are sequentially added into the furnace according to a production operation plan and process requirements, and the furnace charges are fed and heated, so that the furnace charges are sequentially melted;
(5.2) sampling for stokehold chemical composition analysis
After the furnace burden is completely melted and homogenized, sampling and detecting molten iron components in the furnace, wherein the sampling temperature range is 1350-1450 ℃;
according to the requirements of the process file, a direct-reading spectrometer is adopted to rapidly and accurately detect the chemical components of the stokehole molten iron and send out a stokehole chemical component analysis report;
according to the requirements of the process file, checking whether the analysis result of the chemical components in front of the furnace meets the requirements of various process parameters, and judging whether the detection result of the chemical components in the molten iron is qualified;
(5.3) adjusting the iron liquid chemical composition in the furnace front
If the detection result of the chemical composition of the molten iron does not meet the process requirement, the chemical composition adjustment in front of the furnace is needed, and the chemical composition adjustment method in front of the furnace comprises the methods of adding similar alloy methods, adding pig iron or carburant methods, adding scrap steel methods, tapping and re-proportioning methods and a delayed burning loss method, and one or more proper adjustment methods are selected according to the specific condition that the chemical composition in front of the furnace exceeds the standard;
after an adjustment method is selected, the weight of the furnace burden to be added is calculated, and the furnace burden is weighed and prepared; weighing various furnace charges to be added, and after the preparation of the materials, adding all the various furnace charges to be added into the furnace according to the method and the sequence of the process requirements;
after the charging material is added, the molten iron is continuously heated, so that after the charging material is fully melted and homogenized, secondary sampling is performed, and the chemical composition of the molten iron is detected; and comparing the content of various chemical elements in the measured molten iron with the process requirements according to the chemical component detection result, if the content of each chemical element is within the range of the process parameter requirements, judging that the chemical component analysis result meets the process requirements, and carrying out subsequent operation if the chemical component analysis result is not qualified, and continuing to carry out chemical component adjustment.
(6) Carrying out tapping and spheroidization-inoculation treatment on molten iron
The tapping of the molten iron and the spheroidization-inoculation are carried out simultaneously.
The spheroidizing-inoculating treatment is usually carried out by adopting an in-ladle pouring method and is carried out simultaneously with tapping of molten iron, and the baked spheroidizing agent and inoculant (the dosage is shown as a burdening sheet) are added into a casting ladle according to the technological requirements, and the specific operation method and the technical requirements are as follows:
firstly, putting all the baked nodulizer into a pit at the bottom of a casting ladle, tamping, putting 2/3 of the total amount of the baked inoculant, tamping, tightly covering with a covering agent, and tightly covering the upper surface with a ductile iron plate with the thickness of 2.5-4.5 mm, wherein the periphery and the upper part of the ductile iron plate are tightly covered with the covering agent; wherein the covering agent is perlite particles;
the first tapping amount is 2/3 of the ladle capacity, and after the spheroidization reaction is finished, the inoculation and tapping are continued until Bao Natie liquid is filled; the tapping flow should be stable and uniform, the flow is moderate, and the current interruption or splashing is prevented;
the spheroidizing reaction time of each ladle of molten iron is 1-2 min; in the spheroidizing reaction process, the upper part of the ladle opening is covered by a ladle cover so as to be beneficial to relieving the oxidation and loss of molten iron; after the spheroidizing reaction is finished, removing a ladle cover in time, fully stirring Bao Natie liquid by using a stirring rod, removing slag on the surface of the molten iron, then adding the rest 1/3 inoculant to perform secondary inoculation, discharging the molten iron in the ladle, and stirring and deslagging again;
immediately sampling a test block in front of a casting furnace after the spheroidizing-inoculating process is finished, breaking and observing the fracture morphology of the test block after chilling, judging the spheroidizing quality of molten iron, and casting a casting if the molten iron is qualified; if the spheroidization of the molten iron is poor or not, casting cannot be poured, and Bao Natie liquid is subjected to ingot mixing or furnace return adjustment.
(7) Casting pouring and cooling rate control
Before tapping and pouring molten iron, preparing a special ladle for ductile iron according to the technological requirements, performing daily maintenance on the ladle, cleaning slag on the ladle port and the inner cavity surface, drying, and baking until the slag is dark red. And (3) taking the molten iron out of the furnace and performing spheroidization-inoculation treatment, pouring the casting after the spheroidization-inoculation treatment is finished, and controlling casting pouring and cooling technological parameters according to technological requirements. The specific procedures and technical requirements are shown in Table 3 below.
TABLE 3 casting and cooling specifications for as-cast pearlitic ductile iron castings
(8) Performing casting quality inspection
And when casting, casting a standard single casting sample, and if required, dissecting the casting according to the requirements of a product graph to prepare a body sample. According to the requirements of casting acceptance technical documents, the chemical components, metallographic structure, tensile strength, yield strength, elongation, hardness and other material performance items of the castings are detected, and the inspection result is ensured to meet the technical requirements.
Examples: production of castings Using as an example an as-cast pearlitic ductile iron casting No. 1 bearing cap on a Diesel Engine
The casting material of the No. 1 bearing cap is QT700-2, belongs to flat-plate thick-wall as-cast pearlite ductile iron castings, has a main wall thickness of about 43mm, has an outline dimension of about 200 multiplied by 150mm, and has a casting weight of about 7Kg. The mechanical property requirements of the casting are as follows: the tensile strength is not lower than 700Mpa, the yield strength is not lower than 400Mpa, the elongation is not lower than 2%, and the hardness is required to be 220-320HB. Castings are not allowed to have casting defects that affect the strength and appearance quality of the castings.
A1.2 furnace burden and Equipment selection and preparation
Smelting equipment for producing No. 1 bearing cap as-cast pearlite ductile iron castings selects a 0.5t medium frequency electric furnace. The furnace burden for cast iron melting comprises: the Wu An Q10 pig iron is selected, the scrap steel is selected from the low-carbon steel offcuts of steel mills, and various iron alloys are purchased according to the international standard requirements. According to the technical requirements of casting acceptance and the combination of production practice, the production processes of the castings are compiled, and various casting molds are manufactured. And (3) manually molding and core making by adopting furan resin self-hardening sand.
A2 determining the chemical composition of the as-cast pearlite ductile iron casting
According to the technical requirements of iron casting materials, various factors such as casting wall thickness, weight, size and the like are comprehensively considered, and the chemical composition control range of the as-cast pearlite ductile iron casting is referred to in table 1 to determine the chemical composition of the as-cast pearlite ductile iron casting bearing cap, wherein the control ranges of the bearing cap molten iron and the casting chemical composition (%) are as follows:
c:3.6-3.8; si:0.8-1.0 (molten iron) and 2.0-2.3 (casting); mn:0.4-0.5;
P：≤0.05；S：≤0.05。
a3 determining the melting technological procedure of the as-cast pearlite ductile iron casting
A3.1 determining the iron liquid chemical composition in the bearing cap furnace of the as-cast pearlite ductile iron casting
C：3.6-3.8；Si：0.8-1.0；Mn：0.4-0.5；P：≤0.05；
S：≤0.05。
A3.2 determining the molten iron melting and proportioning proportion of the bearing cap of the as-cast pearlite nodular cast iron
According to the technical requirements of iron casting materials, the chemical components and reserve of the existing furnace burden, the characteristics of melting equipment, the oxidation burning loss rate of various metal elements and other factors are comprehensively considered, and the molten iron melting proportioning proportion of the cast pearlite nodular cast iron is referred to in the table 2 to determine the molten iron proportioning proportion of the bearing cover of the cast pearlite nodular cast iron, wherein the molten iron melting proportioning process of the bearing cover is as follows:
cast iron melting and batching process sheet
No. 1 bearing cap (0.5 t furnace) brand: QT700-2 xxx year, month, and date
A4 determining casting and cooling technological rules of as-cast pearlite ductile iron casting bearing cap
The size of the sand mould (sand box) for producing the bearing cover casting is 750X750mm, the weight of each molten iron is about 80Kg, the main wall thickness of the casting is more than or equal to 40mm, and the casting ladle specification can be 500Kg ductile iron ladle. The tapping temperature of the bearing cover molten iron is preferably as follows: 1500-1520 ℃, and the initial casting temperature is: 1420 ℃, the end casting temperature is: 1370 ℃, and the single casting time is as follows: 10-15s.
And immediately spraying tap water to the periphery of the sand box and the upper surface of the casting mould for cooling after each casting is poured, and spraying by adopting a DN25 water pipe to install a DN15 spray head, wherein the water pressure is controlled to be 0.35-0.4MPa. The water spraying cooling time is generally 6-7 minutes.
If the production period is in summer, the water spraying and cooling of the casting mould are implemented, and meanwhile, an air cooling method is adopted to promote the cooling of the casting mould, and the specific method is as follows: adopting a 1.5m movable floor type industrial fan to blow air against the surface of the casting mould, wherein the air blowing and cooling time is generally as follows: 12-13 minutes. And after the cooling treatment is finished, opening the box and taking out the piece after the casting cavity is cooled to room temperature.
A5, controlling the molten iron melting process according to the technical specification requirement of the bearing cap
According to the requirements of technological regulations, all furnace charges are added into a furnace, completely melted and homogenized, and then the liquid chemical composition of the bearing cover iron is sampled and detected, and the sampling temperature is preferably 1350-1450 ℃.
After sampling, a direct-reading spectrometer is adopted to rapidly and accurately detect the chemical components of the molten iron in the front of the furnace, the analysis result is compared with the process requirement, and whether the content of the chemical elements of the molten iron in the bearing cover accords with the process technical requirement is checked.
A5.3 adjusting bearing Cap stokehole iron liquid chemical composition
If the detection result of the chemical composition of the molten iron does not meet the process requirement, the adjustment of the chemical composition in front of the furnace is needed, and the common adjustment methods of the chemical composition in front of the furnace include methods such as a similar alloy adding method, a pig iron adding or carburant adding method, a scrap adding method, a tapping reconfiguration method, a delayed burning loss method and the like, and one or more suitable adjustment methods can be selected according to the specific condition that the chemical composition in front of the furnace exceeds the standard.
A6 bearing cover molten iron discharging furnace and spheroidizing-inoculating treatment
The molten iron of the No. 1 bearing cover is discharged from the furnace and spheroidized and inoculated simultaneously, and the molten iron spheroidized and inoculated is carried out by adopting a ladle pouring method. The nodulizer is produced by using tin-free QRMg8RE7 or QRMg8RE3, the granularity is 5 mm-15 mm, the adding amount is 1.2-1.3% of the weight of the molten iron in the ladle, and the nodulizer is added into the ladle at one time. The inoculant adopts a tin-free product BS-I or BS-IA, the granularity is 3 mm-10 mm, the adding amount is 1.3% -1.4% of the weight of the iron liquid in the ladle, the inoculant is added into the ladle in two times, the total amount is 2/3 of the adding amount in the first time, and the adding amount is 1/3 of the adding amount in the second time.
The nodulizer and the inoculant can be used after being preheated and dried, the preheating temperature is 300-350 ℃, the heat preservation time is 1-2 h, and other materials such as covering agents and the like should be kept dry. The spheroidizing iron ladle adopts a special ladle for the ductile iron, a cylindrical pit is built in the middle of the ladle bottom by using refractory materials and is used as a spheroidizing-inoculation reaction chamber, the ladle is maintained in time, the ladle nozzle and the inner wall are kept dry and clean, and the ladle nozzle and the inner wall are baked and preheated before each shift use, so that the temperature reduction range of Bao Natie liquid is prevented from being too large in the spheroidizing reaction process.
The specific operation method of spheroidization-inoculation treatment is as follows:
firstly, putting the prepared nodulizer into a pit at the bottom of a casting ladle and tamping, then putting 2/3 of the total amount of inoculant into the pit and tamping, then tightly covering the pit with a proper amount of covering agent, and tightly covering the pit with a ductile iron plate with the thickness of 2.5-4.5 mm, wherein the periphery and the upper part of the ductile iron plate are tightly covered with the covering agent. The first tapping amount is about 2/3 of the ladle capacity, and after the spheroidization reaction is finished, tapping is continued until Bao Natie liquid is filled. The tapping flow should be stable and uniform, the flow is moderate, and the current interruption or splashing is prevented.
The spheroidizing temperature of each ladle is generally controlled to be 1-430 ℃, and the spheroidizing time is generally 1-2 min. In the spheroidizing reaction process, the upper part of the ladle opening is covered by a ladle cover so as to be beneficial to relieving the oxidation and loss of the molten iron. After the spheroidizing reaction is finished, removing the ladle cover in time, fully stirring Bao Natie liquid by using a stirring rod, removing slag on the surface of the molten iron, adding the rest 1/3 inoculant to perform secondary inoculation, discharging the molten iron in the ladle, and stirring and deslagging again.
After the spheroidizing-inoculating process is finished, sampling a test block in front of the casting furnace immediately, observing the fracture morphology of the test block, and judging the spheroidizing quality of the molten iron. If the casting is qualified, casting can be poured; if the spheroidization of the molten iron is poor or not, casting is not poured, and Bao Natie liquid ingot is closed or returned to the furnace for adjustment.
A7 casting bearing cap casting and cooling treatment
A7.1 bearing cap ladle selection
By combining the characteristics of the bearing cover castings and the quality and yield requirements, a special ladle with the specification of 500Kg of ductile iron can be selected, the quality of the ladle is checked by an operator before each shift, whether the shape and the size of a spheroidizing reaction chamber are proper or not is checked, all spheroidizing-inoculating materials can be contained, the bulge phenomenon cannot occur after loading, and cleaning and repairing can be performed in time if the spheroidizing quality is not met.
A7.2 cleaning and baking of bearing cover ladle
Before production and use, thoroughly cleaning slag at the ladle mouth and the inner cavity of the bearing cover, repairing defective parts of the ladle lining, baking the bearing cover to dark red, and preserving heat for 20-30min at 600-650 ℃.
A7.3 preparation of bearing Cap casting auxiliary Material and tool
And auxiliary materials such as slag conglomeration agent, covering agent, refractory clay and the like required by the bearing cover melting and pouring operation are prepared before production, and tools such as a slag beating rod, a stirring rod, a sampling spoon, a temperature measuring tube, a coupling head and the like are prepared, so that the smooth production operation and detection are ensured.
A7.4 casting blank for casting bearing cover
And after confirming that the temperature of the molten iron of the bearing cover in the ladle meets the process requirements, starting to pour the casting blank of the bearing cover. The pouring operation should be smooth and continuous, and the molten iron is prevented from splashing, cutting off or overflowing. In the casting process, a group of operators should coordinate and pay attention to adjust and control factors such as the flow rate, the height of a pressure head and the like of molten iron at any time, and measures should be taken in time to properly treat the phenomena such as fire running, box expansion and the like.
A7.5 bearing cap casting Cooling and shakeout
And (3) according to the technical requirement of the A4 process, carrying out cooling control after casting of the bearing cover casting by adopting a water cooling and air cooling mode, naturally cooling in a subsequent sand mould, and opening the box and shakeout after the cooling time of the casting in the casting mould reaches the technical requirement, and taking out the casting.
A7.6 cleaning of bearing cap casting blank
And (3) performing shot blasting cleaning on the blank of the bearing cover according to the process requirements, removing sand on the surface of the casting, performing coping and finishing by adopting tools such as a grinder, an angle grinder and the like, removing burrs and burrs on the surface of the blank, and coping and flattening the residual root of the casting head to ensure that the surface of the casting is smooth and clean. The technical requirement of casting surface quality inspection and acceptance is met.
A8 detection of bearing cap casting material and performance
And when the bearing cover casting is poured, a group of standard single casting samples are poured, and according to the requirements of a bearing cover product diagram and acceptance technical conditions, a casting body is dissected for sampling, and the metallographic structure and the mechanical property of the casting body are checked. According to the requirements of casting acceptance technical documents, the quality performance items such as chemical components, tensile strength, hardness and the like of castings are detected, and the inspection result is ensured to meet the technical requirements.
A9 bearing cap casting production experiment effect
The bearing cover casting produced by the technical method has the advantages that after the quality of the casting is comprehensively checked, the tensile strength of the casting body can be stabilized to be more than 700MPa, the Brinell hardness is kept in the range of 220-280HB, the quality of the casting is stable, and each checking item of the metallographic structure and the mechanical property meets the technical requirements of acceptance. And on the basis of ensuring the quality, the production efficiency can be improved, the energy consumption can be reduced, and the production cost of castings can be reduced.
The specific casting mechanical property detection result is as follows: tensile strength 738MPa, yield strength 461MPa, elongation 3.5% and hardness 260-270HB.
Figures 1 and 2 are pictures of metallographic structure of bearing caps, grade 5 graphite size, grade 2 spheroidization, and fine lamellar pearlite as cast matrix structure.
Claims (10)
1. A preparation method of as-cast pearlite ductile iron casting is characterized by comprising the following steps: the method comprises the following steps:
(1) burden, equipment and technical file preparation-2) determining the chemical composition range of the cast pearlite ductile iron casting-3) determining the melting process specification of the cast pearlite ductile iron casting-4) determining the pouring and cooling process specification of the cast pearlite ductile iron casting-5, controlling the molten iron melting process according to the process specification requirement-6, discharging molten iron and spheroidizing-inoculating-7, controlling the casting pouring and cooling process-8, and checking the casting quality; there is no heat treatment step in the steps, and no alloying elements are added.
2. The method for producing an as-cast pearlite ductile iron casting according to claim 1, wherein: the specific operation of the step (1) is as follows: checking various furnace charges including pig iron, scrap steel, furnace returns, alloy furnace charges and auxiliary materials required by the prepared cast iron melting production; checking and preparing various equipment required by smelting including a medium-frequency electric furnace, a molten iron ladle, a crown block, tools and detection equipment; various technical files containing standards, manuals, technical regulations, operation instructions and batching process sheets required by cast iron smelting operation are prepared.
3. The method for producing an as-cast pearlite ductile iron casting according to claim 1, wherein: the range of the chemical composition of the as-cast pearlite ductile iron casting in the step (2) is as follows in table 1:
。
4. a method of producing as-cast pearlitic ductile iron according to claim 3 wherein: the casting pearlite ductile iron casting melting process in the step (3) comprises the following steps:
(3.1) determining the melting and proportioning ratio of the as-cast pearlite ductile iron castings according to the material and chemical composition requirements of the castings and combining the chemical composition ratios in table 1;
(3.2) determining an as-cast pearlite ductile iron melting and batching process recipe, wherein the as-cast pearlite ductile iron melting and batching process recipe specifically comprises the following steps: preparing the material marks, product names and codes of the produced castings; preparing the specification and model of the melting equipment and the total weight of molten iron; the specification and the model of various furnace charges and the addition amount; controlling the chemical composition of the molten iron in the front of the furnace; the sequence of various charges added into the furnace; the process bill is compiled on a date and the expiration date;
the melting batch ratios of the specific as-cast pearlitic ductile iron castings are shown in table 2 below:
。
5. the method for producing an as-cast pearlite ductile iron casting according to claim 1, wherein: the pouring and cooling process in the step (4) comprises the following steps:
(4.1) determining casting process parameters of the as-cast pearlite ductile iron casting: tapping temperature of molten iron is 1510+/-15 ℃, initial casting temperature is 1410+/-10 ℃, final casting temperature is 1370+/-10 ℃, single casting time is 5-20s, and total casting time of each ladle of molten iron is 10-13min;
(4.2) determining a cooling process of the as-cast pearlite ductile iron casting: usually is
After each casting is poured, tap water is immediately sprayed to the periphery of the sand box and the upper surface of the casting mould for cooling, and the concrete method comprises the following steps: adopting DN25 water pipe to install DN15 spray head to spray, controlling water pressure at 0.35-0.40MPa; the water spraying and cooling time is as follows: spraying water for 3-5 min when the sand mould size is below 500X500mm, spraying water for 5-8 min when the sand mould size is above 500X500-1000X1000mm, and spraying water for 8-12 min when the sand mould size is above 1000X1000 mm.
6. The method for producing an as-cast pearlite ductile iron casting according to claim 5, wherein: in the production period, when the temperature of the casting mold is reduced in 5-8 months in summer, the air cooling method is adopted to promote the cooling of the casting mold, and the specific method is as follows: adopting a 1.5m movable floor type industrial fan to blow air against the surface of the casting mould, wherein the air blowing and cooling time is as follows: blowing for 5-10 min when the sand mould size is below 500X500mm, blowing for 10-15 min when the sand mould size is above 500X500-1000X1000mm, and blowing for 15-20 min when the sand mould size is above 1000X1000 mm.
7. The method for producing an as-cast pearlite ductile iron casting according to claim 4, wherein: the specific operation of the step (5) is as follows:
(5.1) preparing materials, charging materials and heating and melting according to the requirements of an as-cast pearlite ductile iron melting and batching process bill:
according to the requirements of an as-cast pearlite nodular cast iron melting and batching process bill, various furnace charges required by melting operation are accurately weighed, positioned and orderly arranged in a partition manner, and marks are made to prevent misuse or confusion; then various furnace charges such as pig iron, scrap steel, returned furnace materials, ferroalloy and the like are sequentially added into the furnace according to a production operation plan and process requirements, and the furnace charges are fed and heated, so that the furnace charges are sequentially melted;
(5.2) sampling for stokehold chemical composition analysis
After the furnace burden is completely melted and homogenized, sampling and detecting molten iron components in the furnace, wherein the sampling temperature range is 1350-1450 ℃;
according to the requirements of the process file, a direct-reading spectrometer is adopted to rapidly and accurately detect the chemical components of the stokehole molten iron and send out a stokehole chemical component analysis report;
according to the requirements of the process file, checking whether the analysis result of the chemical components in front of the furnace meets the requirements of various process parameters, and judging whether the detection result of the chemical components in the molten iron is qualified;
(5.3) adjusting the iron liquid chemical composition in the furnace front
If the detection result of the chemical composition of the molten iron does not meet the process requirement, the chemical composition adjustment in front of the furnace is needed, and the chemical composition adjustment method in front of the furnace comprises the methods of adding similar alloy methods, adding pig iron or carburant methods, adding scrap steel methods, tapping and re-proportioning methods and a delayed burning loss method, and one or more proper adjustment methods are selected according to the specific condition that the chemical composition in front of the furnace exceeds the standard;
after an adjustment method is selected, the weight of the furnace burden to be added is calculated, and the furnace burden is weighed and prepared; weighing various furnace charges to be added, and after the preparation of the materials, adding all the various furnace charges to be added into the furnace according to the method and the sequence of the process requirements;
after the charging material is added, the molten iron is continuously heated, so that after the charging material is fully melted and homogenized, secondary sampling is performed, and the chemical composition of the molten iron is detected; and comparing the content of various chemical elements in the measured molten iron with the process requirements according to the chemical component detection result, if the content of each chemical element is within the range of the process parameter requirements, judging that the chemical component analysis result meets the process requirements, and carrying out subsequent operation if the chemical component analysis result is not qualified, and continuing to carry out chemical component adjustment.
8. The method for producing an as-cast pearlite ductile iron casting according to claim 1, wherein: the tapping of molten iron and the spheroidization-inoculation treatment in the step (6) are carried out simultaneously, and the specific operation is as follows:
firstly, putting all the baked nodulizer into a pit at the bottom of a casting ladle, tamping, putting 2/3 of the total amount of the baked inoculant, tamping, tightly covering with a covering agent, and tightly covering the upper surface with a ductile iron plate with the thickness of 2.5-4.5 mm, wherein the periphery and the upper part of the ductile iron plate are tightly covered with the covering agent; wherein the covering agent is perlite particles;
the first tapping amount is 2/3 of the ladle capacity, and after the spheroidization reaction is finished, the inoculation and tapping are continued until Bao Natie liquid is filled; the tapping flow should be stable and uniform, the flow is moderate, and the current interruption or splashing is prevented;
the spheroidizing reaction time of each ladle of molten iron is 1-2 min; in the spheroidizing reaction process, the upper part of the ladle opening is covered by a ladle cover so as to be beneficial to relieving the oxidation and loss of molten iron; after the spheroidizing reaction is finished, removing a ladle cover in time, fully stirring Bao Natie liquid by using a stirring rod, removing slag on the surface of the molten iron, then adding the rest 1/3 inoculant to perform secondary inoculation, discharging the molten iron in the ladle, and stirring and deslagging again;
immediately sampling a test block in front of a casting furnace after the spheroidizing-inoculating process is finished, breaking and observing the fracture morphology of the test block after chilling, judging the spheroidizing quality of molten iron, and casting a casting if the molten iron is qualified; if the spheroidization of the molten iron is poor or not, casting cannot be poured, and Bao Natie liquid is subjected to ingot mixing or furnace return adjustment.
9. The method for producing an as-cast pearlite ductile iron casting according to claim 1, wherein: the specific operation of the step (8) is as follows:
casting a standard single casting sample while casting the casting, and dissecting the casting according to the requirement of a product graph to prepare a body sample; according to the requirements of casting acceptance technical documents, the material performance items of the castings, including chemical components, metallographic structures, tensile strength, yield strength, elongation and hardness, are detected, and the inspection results are ensured to meet the technical requirements.
10. The method for producing an as-cast pearlite ductile iron casting according to claim 1, wherein: nearly 100% of as-cast pearlitic matrix structure can be obtained.
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