CN101956122A

CN101956122A - Smelting process for manufacturing gray cast iron

Info

Publication number: CN101956122A
Application number: CN2010105270348A
Authority: CN
Inventors: 欧阳代云; 罗雪峰; 苏建勇
Original assignee: GUANGDONG SHAOZHU GROUP CO Ltd
Current assignee: GUANGDONG SHAOZHU GROUP CO Ltd
Priority date: 2010-11-01
Filing date: 2010-11-01
Publication date: 2011-01-26

Abstract

The invention relates to a smelting process for manufacturing gray cast iron, which comprises the following steps: adding raw materials composed of 60-70% of scrap steel and 40-30% of scrap returns into an intermediate frequency furnace; after the raw materials are molten into molten iron, controlling the temperature in the range of 1550-1590 DEG C; standing the molten iron at high temperature for removing high-melting point impurities or slag in the molten iron to improve the purity of the molten iron and damage the structure of the protogenic crystal nucleus in the original molten iron; and then, skimming the slag, carrying out sampling analysis, and carburizing once in the furnace according to a target value by taking asphaltene of which the granularity is 5-10mm as a carburant to obtain the gray cast iron raw material. Compared with the traditional common gray cast iron, the tensile strength is increased by 30MPa, and the hardness is increased by 10HB; the gray cast iron has small section sensitivity, moderate hardness, small chilling tendency, compact structure and good processing performance and service performance; the cost of the molten iron per ton is reduced by about ***, and the cost of the castings per ton can be saved by ***-***; and the quality of the produced castings is good.

Description

A kind of melting technology of making graphitic cast iron

Technical field

The invention belongs to the novel proportioning process technical field of intermediate frequency furnace melting molten iron, relate to a kind of employing steel scrap, adopt carburelant carburetting and ferrosilicon to increase the melting technology that measure such as silicon guarantees the manufacturing graphitic cast iron of ironcasting chemical ingredients as raw material.

Background technology

Homemade DISA does not have case extrusion moduling line, and supporting have three 1.5t intermediate frequency furnaces, produces ironcasting.The traditional technology of intermediate frequency furnace melting molten iron charge composition adopts foundry iron to add the melting technology that foundry returns adds steel scrap always.Along with the continuous growth of foundry iron price, adopt foundry iron to add melting technology that foundry returns adds steel scrap in the traditional technology and produce the cost of ironcasting and significantly increase, therefore reduce the problem that molten iron cost just becomes many castings colleagues producer.

Summary of the invention

In order to overcome the above-mentioned shortcoming of prior art, the invention provides and a kind ofly can reduce casting cost, guarantee the melting technology of the manufacturing graphitic cast iron of casting quality.

The present invention solves the technological method that its technical problem adopts: a kind of melting technology of making graphitic cast iron, adopting weight proportion is that 60-70% steel scrap and 40-30% foundry returns join in the intermediate frequency furnace as raw material, after raw material is fused into iron liquid, controlled temperature is in 1550-1590 ℃ scope, iron liquid carries out quiescence in high temperature, remove high-melting-point impurity or slag in the iron liquid, improve the purity of iron liquid, and the structure of primary nucleus in the destruction original iron melt, skim then, sampling analysis, according to target value is carried out carburetting, adopt during carburetting granularity be the bituminous matter of 5-10mm as carburelant carburetting in stove, make the graphitic cast iron raw material.

Described carburetting adopts the mode of adjusting iron liquid composition after the first carburetting to carry out.

Add ferrosilicon in the iron liquid after described carburetting and increase silicon.

Described raw material steel scrap should lack the few rust of oil, and one-tenth is distinguished one from the other, or adopts the steel scrap of the tailing of general carbon steel.

Described foundry returns will be cleaned out through ball blast or rolling barrel, and foundry returns requires no-sundries, and few rust is dry.

The invention has the beneficial effects as follows: the graphitic cast iron that makes through the present invention is in close condition (carbon equivalent, the cooling situation) under, the tensile strength ratio is the high 30MPa of common grey iron in the past, and hardness ratio (was beaten hardness, about wall thickness 30mm) about high 10HB in the past on the same foundry goods, the graphitic cast iron sensitivity profile is little, hardness is moderate, and chilling tendency is little, dense structure, embody good processing properties and use properties, the ton molten iron cost descends about 200 yuan; Guaranteeing that logistics equilibrated in workshop simultaneously, can reduce molten iron cost to greatest extent, formulate rational charge composition scheme, substitute the pig iron with steel scrap and carburetant, according to the difference of the condition of production, foundry goods per ton approximately can be saved 100-400 unit, and the foundry goods of producing is also than also good in the past.

Embodiment

The present invention is further described below in conjunction with embodiment.

A kind of melting technology of making graphitic cast iron, adopting weight proportion is that 60-70% steel scrap and 40-30% foundry returns join in the intermediate frequency furnace as raw material, fully phases out the adding of foundry iron, adopts carburelant carburetting, ferrosilicon increases the composition of measure assurance molten iron such as silicon.

Select for use the main raw steel scrap should lack the few rust of oil, one-tenth is distinguished one from the other, and the tailing of general carbon steel is the most desirable, and the tailing of steel alloy should not use; Foundry returns will be cleaned out through ball blast or rolling barrel, no-sundries, and the drying of becoming rusty less is advisable; Because batching adopts steel scrap and foundry returns, carbon in the original iron melt, silicon are lower, should adopt first low-carbon (LC) and silicon, back high-carbon and silicon (steel scrap, the foundry returns) principle of feeding in raw material, and purpose is protected furnace lining.

Select rational order of addition(of ingredients), the tailing collocation that size differs adds, and " scaffolding " phenomenon in the process of avoiding feeding in raw material improves melting efficiency, thereby reduces the stove molten iron is melting time, the furnace lining storing time.

Select suitable particle size for use and plant carburant, improve the method for carburetting: because batching is based on the steel scrap foundry returns, original iron melt carbon, silicon are lower, and key is the carburetting technology, and it is as follows to influence the principal element of carburetting effect:

The one, the granularity of carburelant and kind are to the influence of carburetting effect: granularity is excessive, the real contact area of itself and iron liquid reduces, the carburelant specific absorption is low, undersized, its density is little, floats over iron liquid surface, less contact and fly upward with iron liquid spill, reduce specific absorption, desired particle size 5-10mm, the carburelant kind has three kinds of clay matter, jet matter and bituminous matters, clay matter fusing point height, unfavorable dissolving absorbs, the little fusing point height of its density of jet matter, and also unfavorable dissolving absorbs, the bituminous matter fusing point is low, density is moderate, and dissolving is fast, the specific absorption height.

The 2nd, the original iron melt composition is to the influence of carburetting effect: C is high in the iron liquid can reduce carburetting speed, the high combination reaction that promotes silicon carbide of Si content, reduce specific absorption, the high absorption that promotes carbon of Mn content, O content increases, carbon depletion strengthens, so correct carburetion method is to adjust alloying constituent after the first carburetting, has so not only helped improving the specific absorption of carbon but also has reduced the scaling loss of alloy after melting.

The 3rd, the method for carburetting is to the influence of carburetting effect: the method for carburetting has two kinds, and the one, batch of material input method, but have the excessive burning phenomenon that exists of carbon in the iron charge melting process, high-carbon iron liquid is serious to lining erosion, should not adopt; The 2nd, iron liquid melts good back carburetting in stove, and this moment, iron liquid heated up in stove, and furnace power strengthens, and stirring capacity improves, and the specific absorption of carbon improves.

Be warmed up to more than 1550 and skim, sampling analysis, according to target value is carried out carburetting, must emphasize, the batch of material carburetion method, in the iron charge melting process, the carburelant scaling loss is serious, should adopt a carburetting of high temperature to be advisable, must adjust composition after the first carburetting, the alloy scaling loss is few, accuracy rate height, production practice prove that temperature is high more, carbon absorbs high more, and the method technological operation of this kind carburetting is simple, easily grasps, stable, carbon absorbs more than 85%, meets the principle of economical and efficient carburetting; The key takeaway that improves this proportioning process gray cast iron smelting quality is, will be raised to 1550-1590 to molten iron temperature, carry out quiescence in high temperature, main purpose is to remove high-melting-point impurity or slag, improving the purity of iron liquid, secondly is the structure of destroying primary nucleus in the original iron melt.

The graphitic cast iron that adopts proportioning process of the present invention is in close condition (carbon equivalent, the cooling situation) descends the tensile strength ratio high 30MPa of common grey iron in the past, hardness ratio (was beaten hardness on the same foundry goods in the past, about wall thickness 30mm) about high 10HB, the graphitic cast iron sensitivity profile is little, and hardness is moderate, and chilling tendency is little, good processing properties and use properties embody in dense structure; The ton molten iron cost descends about 200 yuan.

Claims

1. melting technology of making graphitic cast iron, it is characterized in that: adopting weight proportion is that 60-70% steel scrap and 40-30% foundry returns join in the intermediate frequency furnace as raw material, after raw material is fused into iron liquid, controlled temperature is in 1550-1590 ℃ scope, iron liquid carries out quiescence in high temperature, remove high-melting-point impurity or slag in the iron liquid, improve the purity of iron liquid, and the structure of primary nucleus in the destruction original iron melt, skim then, sampling analysis, according to target value is carried out carburetting, adopt during carburetting granularity be the bituminous matter of 5-10mm as carburelant carburetting in stove, make the graphitic cast iron raw material.

2. the melting technology of manufacturing graphitic cast iron as claimed in claim 1 is characterized in that: described carburetting adopts the mode of adjusting iron liquid composition after the first carburetting to carry out.

3. the melting technology of manufacturing graphitic cast iron as claimed in claim 1 or 2 is characterized in that: add ferrosilicon in the iron liquid after described carburetting and increase silicon.

4. the melting technology of manufacturing graphitic cast iron as claimed in claim 1 is characterized in that: described raw material steel scrap should lack the few rust of oil, and one-tenth is distinguished one from the other, or adopts the steel scrap of the tailing of general carbon steel.

5. the melting technology of manufacturing graphitic cast iron as claimed in claim 1 is characterized in that: described foundry returns will be cleaned out through ball blast or rolling barrel, and foundry returns requires no-sundries, and few rust is dry.