阅读说明：本技术 一种消除球墨铸铁反白口现象的熔炼工艺方法 (Smelting process method for eliminating reverse white cast phenomenon of nodular cast iron ) 是由 王军 章桂林 韩虎 于 2020-04-16 设计创作，主要内容包括：本发明公开了一种消除球墨铸铁反白口现象的熔炼工艺方法,严格要求原材料选择生铁,废钢,增碳剂,碳化硅,球化剂,孕育剂,随流孕育剂,熔炼工艺方法的步骤包括：加料熔炼,调质,铁水预处理,球化孕育处理,浇注孕育,铸件开箱。本发明从原材料的选择,确保c、s的含量,提高稀土的溶解度,和孕育处理三个方面解决了铸件反白口现象,提高了产品合格率,提升了企业的经济效益。(The invention discloses a smelting process method for eliminating the phenomenon of the white cast iron, which strictly requires raw materials of pig iron, scrap steel, carburant, silicon carbide, nodulizer, inoculant and stream inoculant, and comprises the following steps: charging and smelting, quenching and tempering, molten iron pretreatment, spheroidizing inoculation, pouring inoculation and casting unpacking. The method ensures the contents of c and s, improves the solubility of rare earth and inoculates the casting from the selection of raw materials, solves the phenomenon of white cast, improves the product percent of pass and improves the economic benefit of enterprises.)

1. A smelting process method for eliminating the reverse white cast phenomenon of nodular cast iron is characterized by comprising the following steps: the raw materials are selected as follows:

pig iron, chemical components (by mass percent): c-4.45%, Si-0.85%, Mn-0.016%, P-0.023%, S-0.006%, Cr-0.033%, Ti-0.010%, V-0.040% and the balance of Fe;

scrap steel, chemical components (by mass percent): c-0.018%, Si-0.08%, Mn-0.09%, P-0.02%, S-0.014%, Cr-0.05%, Ti-0.036%, V-0.038%, and the balance of Fe;

carburant, chemical components (by mass percent): the nitrogen content of the low-nitrogen carburant is less than or equal to 0.02 percent, the carbon content is more than or equal to 98 percent, the S content is less than or equal to 0.03 percent, and the granularity is 1-5 MM;

silicon carbide, chemical components (by mass percent): 89-92% of silicon carbide, 60-63% of silicon, 27% of carbon, 1-5MM of granularity and the balance of impurities;

the nodulizer comprises the following chemical components: mg: 5.15-5.3%, Al: 0.21-0.25%, Si: 42-46%, Ca: 1-2%, Re: 0.3-0.6%, particle size: 5-30 mm;

inoculant and chemical components: si: > 68%, Ca: 2.0-3.0%, Ba: 1.5-2.8%, particle size: 3-8MM, and the balance Fe;

stream inoculant, and chemical components: si: 48-50%, Sr:0.6-1.2, Ca: not more than 0.1, not more than 0.4 of Al, granularity: 0.2-0.7 mm.

The smelting process comprises the following steps:

s1, charging and smelting: according to the mass percentage, 20 percent of pig iron is firstly added into an electric furnace, 19 percent of scrap steel and 1 percent of carburant are simultaneously added into the electric furnace, and then 30 percent of foundry returns and 30 percent of pig iron are sequentially added;

s2, hardening and tempering: smelting the molten iron in the furnace to 1400 ℃ and 1450 ℃, adjusting the chemical components of the molten iron to the chemical component requirements of corresponding marks, and simultaneously enabling the S content in the molten iron to be 0.015-0.025%;

s3, molten iron pretreatment: pouring 1/3 molten iron from the electric furnace into a ladle, adding 0.2% SiC into the electric furnace, simultaneously heating the electric furnace with the maximum power to ensure that the molten iron in the furnace forms a hump phenomenon and fully absorbs SiC, finally returning the poured 1/3 molten iron into the electric furnace to ensure that the molten iron in the furnace is heated to 1500-.

S4. spheroidizing inoculation treatment

A. Adding a nodulizer into a nodulizing chamber of a nodulizing reaction package, wherein the nodulizer accounts for 0.9-1.0% of the weight of the cast iron,

B. covering an inoculant on the nodulizer, wherein the inoculant accounts for 0.25-0.34% of the weight of the discharged iron,

C. covering a silicon steel sheet on the inoculant, wherein the silicon steel sheet accounts for 0.55 to 0.6 percent of the weight of cast iron,

D. covering SiC on the silicon steel sheet, wherein the SiC is 0.1 percent of the weight of the cast iron,

E. tapping from an electric furnace to a balling ladle, controlling the tapping temperature at 1460-1480 ℃, directly flushing molten iron onto a nodulizer during tapping, directly throwing an inoculant into the balling ladle in one third of tapping, wherein the inoculant is a high-calcium barium inoculant which is 0.2 percent of the tapping weight, and meanwhile, measuring the balling explosion time by using a stopwatch, the balling explosion time is 60-100 seconds, the balling reaction is qualified,

s5, pouring inoculation: pouring at 1330-1350 ℃, adding a stream-following inoculant during pouring, wherein the stream-following inoculant is a silicon-strontium inoculant which is 0.1-0.15 percent of the weight of the discharged iron, feeding the stream-following inoculant into a casting mold cavity along with molten iron by using a stream-following inoculation device,

s6, unpacking a casting: and opening the box when the temperature of the casting is less than or equal to 300 ℃.

Technical Field

The invention relates to the field of casting of castings, in particular to a smelting process method for eliminating the phenomenon of reverse white cast of nodular cast iron.

Background

In the production process of the ductile iron, a phenomenon that white structures appear in the center of a section of a casting due to structural reasons is called reversed white, the reversed white can reduce the impact strength of materials and can cause difficulty in drilling, and therefore the reversed white is a defect of the casting and should be prevented.

The reason for the formation of white spots:

1. rare earth segregation: the rare earth elements have low solubility in molten iron, excessive rare earth alloy is gathered in a final solidification region in the solidification process of the molten iron, and the rare earth is an element of strong stable carbide, so white spots are formed at the hot spot of the casting.

2. Spheroidizing inoculation fade: the last solidification part of the nodular iron casting generates inoculation recession, or the inoculation effect is poor, and the number of graphite balls is small to form white cast.

3. Chemical composition of molten iron (composition segregation): C. the content of S is low.

Disclosure of Invention

The invention aims to provide a smelting process method for eliminating the reverse white cast phenomenon of nodular cast iron, so as to solve the problems in the background technology.

In order to achieve the purpose, the invention provides the following technical scheme: a smelting process method for eliminating the reverse white cast phenomenon of nodular cast iron comprises the following raw materials:

pig iron, chemical components (by mass percent): c-4.45%, Si-0.85%, Mn-0.016%, P-0.023%, S-0.006%, Cr-0.033%, Ti-0.010%, V-0.040% and the balance of Fe;

scrap steel, chemical components (by mass percent): c-0.018%, Si-0.08%, Mn-0.09%, P-0.02%, S-0.014%, Cr-0.05%, Ti-0.036%, V-0.038%, and the balance of Fe;

carburant, chemical components (by mass percent): the nitrogen content of the low-nitrogen carburant is less than or equal to 0.02 percent, the carbon content is more than or equal to 98 percent, the S content is less than or equal to 0.03 percent, and the granularity is 1-5 MM;

silicon carbide, chemical components (by mass percent): 89-92% of silicon carbide, 60-63% of silicon, 27% of carbon, 1-5MM of granularity and the balance of impurities;

the nodulizer comprises the following chemical components: 5.15-5.3% of Mg, Al: 0.21-0.25%, Si: 42-46%, Ca: 1-2%, Re 0.3-0.6%, particle size: 5-30 mm;

inoculant and chemical components: si > 68%, Ca 2.0-3.0%, Ba: 1.5-2.8%, particle size: 3-8MM, and the balance Fe;

stream inoculant, and chemical components: 48 to 50 percent of Si, 0.6 to 1.2 percent of Sr, less than or equal to 0.1 percent of Ca, less than or equal to 0.4 percent of Al, and the granularity: 0.2-0.7 mm.

The smelting process comprises the following steps:

1. charging and smelting: according to the mass percentage, 20 percent of pig iron is firstly added into an electric furnace, 19 percent of scrap steel and 1 percent of carburant are simultaneously added into the electric furnace, and then 30 percent of foundry returns and 30 percent of pig iron are sequentially added;

2. tempering: smelting the molten iron in the furnace to 1400 ℃ and 1450 ℃, adjusting the chemical components of the molten iron to the chemical component requirements of corresponding marks, and simultaneously enabling the S content in the molten iron to be 0.015-0.025%;

3. pretreating molten iron: pouring 1/3 molten iron from the electric furnace into a ladle, adding 0.2% SiC into the electric furnace, simultaneously heating the electric furnace with the maximum power to ensure that the molten iron in the furnace forms a hump phenomenon and fully absorbs SiC, finally returning the poured 1/3 molten iron into the electric furnace to ensure that the molten iron in the furnace is heated to 1500-.

4. Spheroidizing inoculation treatment

A. Adding a nodulizer into a nodulizing chamber of a nodulizing reaction package, wherein the nodulizer accounts for 0.9-1.0% of the weight of the cast iron,

B. covering an inoculant on the nodulizer, wherein the inoculant accounts for 0.25-0.34% of the weight of the discharged iron,

C. covering a silicon steel sheet on the inoculant, wherein the silicon steel sheet accounts for 0.55 to 0.6 percent of the weight of cast iron,

D. covering SiC on the silicon steel sheet, wherein the SiC is 0.1 percent of the weight of the cast iron,

E. tapping from an electric furnace to a balling ladle, controlling the tapping temperature at 1460-1480 ℃, directly flushing molten iron onto a nodulizer during tapping, directly throwing an inoculant into the balling ladle in one third of tapping, wherein the inoculant is a high-calcium barium inoculant which is 0.2 percent of the tapping weight, and meanwhile, measuring the balling explosion time by using a stopwatch, the balling explosion time is 60-100 seconds, the balling reaction is qualified,

5. pouring inoculation: pouring at 1330-1350 ℃, adding a stream-following inoculant during pouring, wherein the stream-following inoculant is a silicon-strontium inoculant which is 0.1-0.15 percent of the weight of the discharged iron, feeding the stream-following inoculant into a casting mold cavity along with molten iron by using a stream-following inoculation device,

6. opening the casting: and opening the box when the temperature of the casting is less than or equal to 300 ℃.

The invention has the beneficial effects that: the invention strictly controls the selection requirement of raw materials, ensures that the content of C and S meets the requirement from the materials, ensures to control the content of C and S by quenching and tempering and pretreatment in the smelting process, and uses a low-magnesium low-rare earth nodulizer by multiple inoculation, wherein magnesium is a main nodulizing element, the absorption rate of molten iron to magnesium is 70-80%, the magnesium content of the nodulizer is most preferably 5-6%, trace aluminum can improve the nodulizing capability of the nodulizer, and pore defects are easily formed by a high casting. The calcium can alleviate the intensity of molten iron spheroidization, reduce the consumption of a spheroidizing agent and ensure that the autumn reaction is qualified, thereby achieving an efficient inoculation result, ensuring that no white cast phenomenon is generated during the final solidification of a casting, improving the product percent of pass and promoting the economic benefit of enterprises.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.