CN107058857B - A kind of carburant absorptivity reaches 95% or more smelting scrap steel ductile iron process - Google Patents

Abstract

The invention discloses the smelting scrap steel ductile iron process that a kind of carburant absorptivity reaches 95% or more, divide in smelting furnace and furnace charge and carburant are added several times, furnace charge includes magnesium iron bits, foundry returns and steel scrap, when furnace charge all melts in smelting furnace, it starts to warm up, after all carburants have been completely melt, be added deslagging agent, then by slag with beat roll rod choose stove outside；After the sample examination qualification of stokehold, spheroidising, then late inoculation processing are proceeded by；Casting；The nodulizing grade of gained magnesium iron is 2~3 grades, and hardness is between 155HB-165HB；Mass percent meter based on magnesium iron, content of pearlite in alloy 5% ± 0.5%, S contents<0.02%, ferrite content > 85% are free of free cementite.The present invention creatively in process of production by processing to details and to the control of furnace charge, significantly improves the absorptivity of carburant.Product quality is improved, production cost is reduced.

Description

A kind of carburant absorptivity reaches 95% or more smelting scrap steel ductile iron process

Technical field

The invention belongs to metal material fields, are related to a kind of smelting scrap steel ductile iron process, and in particular to a kind of carburant suction Yield reaches 95% or more smelting scrap steel ductile iron process.

Background technology

Spheroidal graphite cast-iron (abbreviation magnesium iron) is the globular graphite obtained by processing such as nodularizations, is effectively improved the machine of cast iron Tool performance, in particular improves plasticity and toughness, to obtain the intensity also higher than carbon steel.Spheroidal graphite cast-iron is to grow up recently A kind of high-strength cast iron material, comprehensive performance is close to steel, and the elevated temperature strength and oxidative resistance of spheroidal graphite cast-iron are excellent, exactly Based on its excellent performance, spheroidal graphite cast-iron rapidly developed for be only second to gray cast iron, using very extensive cast iron materials.

The production of magnesium iron is typically using carrying out spheroidising, this spheroidal graphite cast-iron again after the pig iron and foundry returns high temperature melting Production method need to be up to 80% with pig iron amount, since pig iron cost of material is high, cause the production cost of spheroidal graphite cast-iron high.It is former Year, high-quality base iron growing tension at home, and client requires to be increasingly stringenter to magnesium iron product material.

There is extensive application in recent decades using producing nodular iron castings melting technique in the prior art.

Such as CN200910019239.2《It is a kind of to utilize producing nodular iron castings smelting technology》, including：Step 1. exists Steel is added in stove, and carburant is added on steel, then heating makes steel fusing and abundant carburizing；Steel is added in step 2. again, and Foundry returns is added；Nodulizer is added in step 3., inovulant carries out nodularization, inoculation；Step 4. is cast.The present invention uses The method of smelting of existing spheroidal graphite cast-iron electric furnace smelting is not existed together mainly phosphorus content using steel and iron, to steel carburetting to centainly Dimension is just at iron.The present invention is at low cost, high-quality；In the case where tensile strength is constant, elongation percentage is doubled.

For another example CN201010225659.9《The preparation method and pouring device of spheroidal graphite cast-iron》, first by following ingredients：It is low Carbon steel scrap 60~70%, give up spheroidal graphite cast-iron 15~25%, in the electric frequency electric induction furnace of 1/3 input of the pig iron 10~20%, then by 1.6 ~2.1% low-phosphorous sulphur carburant is added in electric frequency electric induction furnace, then by remaining low-carbon waste steel, useless spheroidal graphite cast-iron, life Melting is carried out in the electric frequency electric induction furnace of iron input, finally pours into the molten iron after melting in the backpack body in pouring device.

For another example CN201310251955.X《The smelting technology of alloy nodular cast iron roll》, include the following steps：First by A foundry returns is placed in fusing in intermediate frequency furnace；It adds first part of high-quality steel scrap and carries out melting；Wait for foundry returns and high-quality useless After steel dissolves, it is warming up to 1360-1380 DEG C, first part of carburant (graphite carburant) is added, iron filings are added while stirring；It is fusion After change, second part of high-quality steel scrap is added；It is warming up to 1360-1380 DEG C after dissolving, second part of carburant is added；Add again after dissolving Enter second part of foundry returns；It is warming up to 1380-1400 DEG C after dissolving and keeps the temperature 2.5-5 minutes；First part of foundry returns：Second part Foundry returns is 1:4, first part of high-quality steel scrap：Second part of high-quality steel scrap is 2:3, first part of carburant：Second part of increasing Carbon agent is 4:1.By the above-mentioned means, the present invention can improve the mechanical property of roll, and prolong the service life, reduces cost.

However, in the prior art carburant absorptivity generally under 90%, even if can reach 95% it is very advanced Melting technique.Production cost can effectively be reduced by improving the absorptivity of carburant, and enterprise is made to be on a good wicket in competition.Also It can make the graphite nodule more rounding of magnesium iron, increase the number of graphite.

Although disclosing five big influence factors of carburant absorptivity in the prior art, such as：

1. the influence of carburant granularity；

Carburetting process using carburant includes dissolving diffusion process and oxidation loss process.The granule size of carburant is not Together, it is also just different to dissolve diffusion velocity and oxidation loss speed.And the height of carburant absorptivity is dependent on carburant dissolving The comprehensive function of diffusion velocity and oxidation loss speed：Under normal circumstances, carburant particle is small, and solution rate is fast, loss speed Degree is big；Carburant particle is big, and solution rate is slow, and loss rate is small.The selection of carburant granule size and furnace diameter and capacity It is related.Under normal circumstances, the diameter of burner hearth and capacity are big, and the granularity of carburant wants larger；Conversely, the granularity of carburant wants small Some.For 0.5~2.5mm of 1t or less electro-smelting crystalline graphite granularity requirements；1t~3t electro-smelting crystalline graphite granularities It is required that 2.5~5mm；5.0~20mm of 3t~10t electro-smelting crystalline graphite granularity requirements；It is covered in crystalline graphite grain in casting ladle Degree requires 0.5~1mm.

2. the influence of carburant addition；

Certain temperature and chemical composition under the same conditions, the saturated concentration of carbon is certain in iron liquid.Carbon in cast iron Solubility limit is ([C%]=1.3+0.0257T-0.31 [Si%] -0.33 [P%] -0.45 [S%]+0.028 [Mn%] (T is bonded hard ferrite magnet).Under certain saturation degree, carburant addition is more, longer the time required to dissolving diffusion, corresponding to be lost Amount is bigger, and absorptivity will reduce.

3. influence of the temperature to carburant absorptivity；

From dynamics and thermodynamic (al) viewpoint analysis, the oxidisability of iron liquid is related with the equilibrium temperature of C-Si-O systems, i.e. iron O in liquid can react with C, Si.And equilibrium temperature is different with target C, Si content and changes, iron liquid is in equilibrium temperature When above, the preferential oxidation that carbon occurs, C and O generate CO and CO2.In this way, the oxidation of coal loss in iron liquid increases.Therefore, flat When more than the temperature that weighs, carburant absorptivity reduces；When carburetting temperature is below equilibrium temperature, since temperature is relatively low, carbon is satisfied It is reduced with solubility, while the dissolving diffusion velocity of carbon declines, thus recovery rate is relatively low；Carburetting temperature in equilibrium temperature, Carburant absorptivity highest.

4. iron liquid stirs the influence to carburant absorptivity；

Stirring is conducive to the dissolving and diffusion of carbon, avoids carburant from floating on iron liquid surface and is burnt.It is incomplete in carburant Before dissolving, mixing time is long, and absorptivity is high.Stirring can also reduce carburetting soaking time, so that the production cycle is shortened, avoid iron liquid Middle alloying element scaling loss.But mixing time is long, not only has a significant impact to the service life of stove, but also is dissolved in carburant Afterwards, stirring can aggravate the loss of carbon in iron liquid.Therefore, it is suitable that suitable iron liquid mixing time should be completely dissolved with ensureing carburant Preferably.

5. influence of the iron liquid chemical composition to carburant absorptivity；

When initial carbon content is high in iron liquid, under certain solubility limit, the infiltration rate of carburant is slow, uptake Few, scaling loss is relatively more, and carburant absorptivity is low.When iron liquid initial carbon content is relatively low, situation is opposite.In addition, silicon in iron liquid The absorption that carbon is hindered with sulphur, reduces the absorptivity of carburant；And manganese element contributes to the absorption of carbon, improves carburant absorptivity. For influence degree, silicon is maximum, and manganese takes second place, and carbon, sulphur influence smaller.Therefore, in actual production process, manganese should first be increased, then increase Carbon increases silicon afterwards.

But due to product cost and technology etc., need carburant absorptivity 95% or more, and in the prior art On the basis of combine above-mentioned five big influence factors, carburant absorptivity that can reach 95% or more smelting scrap steel ductile iron process also not Can be satisfactory, or be difficult to stablize or complex process or high expensive.

Invention content

In order to improve the quality of magnesium iron, the present invention is mainly to the absorptivity factor of influence carburant：1, carburant model It selects；2, the selection of carburant granularity；3, the addition time control of carburant；4, after carburant is added, in molten iron fusion process Control；Total system technological development is carried out, to provide the smelting scrap steel ball that a kind of carburant absorptivity reaches 95% or more Iron process.

The technical solution adopted by the present invention is：

A kind of carburant absorptivity reaches 95% or more smelting scrap steel ductile iron process, includes the following steps：

(1) divide in smelting furnace and furnace charge is added several times, furnace charge includes magnesium iron bits, foundry returns and steel scrap, first in furnace bottom A furnace charge is added and is initially added into carburant after starting to dissolve molten iron under stove；After carburant is added every time, furnace charge is used It pushes down, the addition number of furnace charge is often more primary than carburant addition；Wherein, foundry returns will reserve 10 ± 2%；

(2) divide after all adding furnace charge several times, when furnace charge all melts in smelting furnace, start to warm up to molten iron temperature and reach 1550 ± 5 DEG C, 3 ± 0.5 minutes are kept the temperature, when heat preservation, stirs evenly, and after all carburants have been completely melt, deslagging agent is added, After slag all concentrates in together, slag is rolled rod and chosen outside stove with beating；

(3) the reserved foundry returns of step (1) is added after the stokehold major element of chemical examination reaches requirement in stokehold sample examination, It being warming up to 1620 ± 5 DEG C, carries out spheroidising, nodularization is to use dam-type nodularization packet, the addition of nodulizer is 1.5 ± 0.1%, it is placed on the other side that molten iron liquidates, 1 ± 0.1% magnesium iron bits and 0.5 ± 0.2% ferrosilicon is pressed to breed on nodulizer Agent；

(4) late inoculation is handled；

When big packet turns parcel, late inoculation is carried out；Inoculation method is the silicon barium powder with 0.5mm specifications, by breeding Funnel, it is 0.2 ± 0.05% that incubation dose, which is added, in each parcel molten iron；

(5) it casts；

The nodulizing grade of gained magnesium iron is 2~3 grades, and hardness is between 155HB-165HB；Mass percent based on magnesium iron Meter, content of pearlite in alloy 5% ± 0.5%, S contents<0.02%, ferrite content > 85% are free of free cementite, the above percentage Than for mass percent.

Further, in step (1), the ratio of ratio >=65% shared by steel scrap, carburant is 2.5% ± 0.2%；It melts down Material and magnesium iron bits are according to 1:1 ratio collocation uses.

Further, the steel scrap includes prompt industrial scrap；Foundry returns includes dead head.

Further, carburant be low-sulfur carburant, select calcined coke, in fixation C content >=98.5%, S content≤ 0.05%.

Further, the granularity of carburant is 5 ± 0.5mm granularities.

Further, in step (3), the C content of the base iron before spheroidising be 4.0% ± 1%, Si contents 1.2% ± 0.2%.

Further, smelting furnace uses intermediate frequency furnace melting.

Further, furnace charge is added in point 10 ± 2 equivalent in smelting furnace.

Advantageous effect of the present invention is apparent：

1. replacing base iron melting magnesium iron by using steel scrap, reduces impurity content, improve the degree of purity of base iron；

2. improving product quality, elongation percentage and tensile strength are obtained for raising；

3. various elements can be guaranteed, it is exceeded few that trace element is especially all kinds of tension-active elements；

4. there are more coarse graphite in base iron so that the casting made using base iron, it is genetic that there are graphite Harmful effect；All add carburant to make magnesium iron with steel scrap, foundry returns, is avoided that the negative effect that heredity is brought；

5. there are the heterogeneous crystallization nucleis of a large amount of Dispersed precipitates, graphite crystal nucleus significantly to increase after molten iron carburetting, promote stone Ink is formed, while reducing the degree of supercooling chilling tendency of molten iron；

6. reducing production cost, the space of profit is improved；

7. cast article material of the present invention can reach：QT450-10, nodulizing grade must not be less than three-level, < containing S 0.02%, ferrite content is higher than 85% or more, there is not allowed that free cementite.Hardness is between national standard 160-210HB It removes the limit, controls in 160HB or so.

The present invention in the case where not increasing any cost, creatively in process of production by processing to details and Control to furnace charge is more than 2/3 using steel scrap content in furnace charge, with the increased carbon content of carburant, is more than total phosphorus content half In the case of, the number of addition carburant from being increased to three times ten times, and steel scrap returns all in upper face pressure after being added every time The raw material of the heavier-weights such as furnace charge.Before molten iron discharging inside stove soak 3 minutes so that the phosphorus content of base iron has It and is obviously improved.The phosphorus content of base iron improves, and the phosphorus content of molten iron will also be promoted after corresponding nodularization, significantly be carried The high absorptivity of carburant.Product quality is improved, production cost is reduced.

Description of the drawings

Fig. 1 is the metallograph after the representative two block body strippings and slicings corrosion of 1 magnesium iron product of the embodiment of the present invention.

Fig. 2 is the metallograph after the representative two block body strippings and slicings corrosion of 2 magnesium iron product of comparative example of the present invention.

Specific implementation mode

Tie that the present invention is described further with specific embodiment below.

Embodiment 1：

Smelting equipment is intermediate frequency furnace, and the capacity at full capacity per stove is 1800KG.Raw material includes steel scrap, foundry returns and increasing Carbon agent, in terms of the mass percent of raw material, the ratio > 65% shared by steel scrap.Steel scrap is our factory's prompt industrial scrap, and foundry returns is The foundry returns of our factory.

The carburant granularity for selecting fair-sized, can guarantee the maximum absorbance of carburant.According to our factory's intermediate frequency furnace Size, select 5mm diameter particle sizes high-quality low-sulfur carburant.By percentage to the quality, the fixation C content > in carburant 98.5%, S content<0.05%, the addition total amount of carburant is 45KG；The carburant for selecting high-quality stable is to ensure carburant Use stable premise.

The step of smelting scrap steel magnesium iron, is as follows：

(1) a points of 11 times equivalent are added furnace charges in intermediate frequency furnace melting, and furnace charge includes magnesium iron bits, foundry returns and steel scrap, The ratio of ratio >=65% wherein shared by steel scrap, carburant is 2.5% ± 0.2%；Foundry returns and magnesium iron bits are according to 1:1 ratio Example collocation uses, and the steel scrap includes prompt industrial scrap, and foundry returns includes dead head；A furnace charge is first added in furnace bottom, waits for Start under stove after dissolving molten iron, be initially added into carburant, carburant is low-sulfur carburant, calcined coke is selected, with quality hundred Point than meter, in fixation C content >=98.5%, S content≤0.05%, the granularity of carburant is 5mm granularities；It is added every time It after carburant, is pushed down with furnace charge, 10 equivalent of carburant point are added；Wherein, foundry returns will reserve 10 ± 2%；

The addition time of carburant will be grown as possible；After carburant is added with spade every time, with iron filings, dead head and steel scrap pressure Firmly, prevent carburant from floating to influence absorptivity.

(2) after dividing 11 wholes to add furnace charge, molten iron burn Medium frequency induction heat size ninety percent it is full when, i.e. stove in smelting furnace Material all fusing when, start to warm up to molten iron temperature up to 1550 DEG C, keep the temperature 3 minutes, when heat preservation stirs evenly, and waits for all carburants After being completely melt, be added deslagging agent, after slag all concentrates in together, by slag with beat roll rod choose stove outside；

It is stirred with slag hitting rod when heat preservation so that carburant can adequately melt decomposition in stove, reach maximum Absorptivity；After stirring evenly, the slag above molten iron is removed.

(3) stokehold sample examination, the stokehold major element of chemical examination reach after requirement, wherein the C content of molten iron is 4.0% ± 1%, Si content 1.2% ± 2%；The reserved foundry returns of step (1) is added, is warming up to after tapping temperature at molten iron discharging nodularization Reason；1620 DEG C are warming up to, spheroidising is carried out, nodularization is to use dam-type nodularization packet, and the addition of nodulizer is 1.5%, It is placed on the other side that molten iron liquidates, 1% magnesium iron bits and 5% silicon iron inoculator are pressed on nodulizer；

(4) late inoculation is handled；

When big packet turns parcel, late inoculation is carried out；Inoculation method is the silicon barium powder with 0.5mm specifications, by breeding Funnel, it is 0.2% that incubation dose, which is added, in each parcel molten iron；

The addition because of nodulizer is prevented so that the super cooling tendency of magnesium iron increases, to reduce the precipitation of carbide, promotion analysis Go out a large amount of tiny and rounding graphite nodules.

(5) it casts；

The nodulizing grade of gained magnesium iron is 2~3 grades, and hardness is between 155HB-165HB；Mass percent based on magnesium iron Meter, content of pearlite in alloy 5% ± 0.5%, S contents<0.02%, ferrite content > 85% are free of free cementite, the above percentage Than for mass percent.

Invention itself comparative example：

It is also to use intermediate frequency furnace for smelting equipment, the capacity at full capacity per stove is 1800KG.Due to product sulfur content There are strict requirements, carburant addition is generally bigger, and the addition of a stove molten iron carburant is 45KG.Therefore, carburant Select the low-sulfur carburant of high-quality, i.e. 98.5% > of fixed carbon content, the high-quality calcined coke of 0.05% < of sulfur content；It selects Be 3mm diameters granularity.Since addition is larger, the method for taking gradation number to be added is divided into three parts, adds in three times Enter.Portion is added in furnace bottom, covers magnesium iron bits, dead head above, then add steel scrap.Equal stoves, which melt, 1/3 molten iron again second part It is added, sequentially adds magnesium iron bits, dead head, steel scrap.Molten iron, which melts, half stove again the addition of remaining 1/3 carburant.Furnace charge adds 9 After, first not anxious slag hitting reaches 1500 DEG C or so in temperature and is rolled rod and stirred with beating, then removes the gred, stove after slagging-off Preceding sample examination after chemical examination is errorless, then the addition of remaining furnace charge, is warming up to assigned temperature, is discharged spheroidising.By stokehold Spectrum analysis detects, and the absorptivity of carburant only has between 85~90%.

Comparative analysis：

One, the Spectroscopic analysis results of 1 base iron of embodiment are as shown in table 1：

Table 1

	C	Si	Mn	P	S
						First group	4.02	1.18	0.191	0.011	0.016
Second group	4.03	1.18	0.188	0.012	0.015
						Third group	4.01	1.21	0.189	0.011	0.014
4th group	4.04	1.18	0.192	0.013	0.016

Spectroscopic analysis results after 1 spheroidising of embodiment are as shown in table 2：

Table 2

Two, the Spectroscopic analysis results of comparative example base iron are as shown in table 3：

Table 3

Spectroscopic analysis results after comparative example spheroidising are as shown in table 4：

Table 4

Table 1 improves base iron carbon content after absorptivity, base iron carbon content before 3 absorptivity of table improves；1 table 3 of contrast table It can find, be more than 2/3 using steel scrap content in furnace charge, with the increased carbon content of carburant, the case where more than total phosphorus content half Under, the number of addition carburant from being increased to three times ten times, and after being added every time all in upper face pressure steel scrap foundry returns etc. The raw material of heavier-weight.Before molten iron discharging inside stove soak 3 minutes so that the phosphorus content of base iron has significantly Promotion.The phosphorus content of base iron improves, and the phosphorus content of molten iron will also be promoted after corresponding nodularization, and 2 table of table 4 can be clear See.

Spectrum analysis testing result in stokehold shown in table 2, the absorptivity of carburant reach 95% or more.

The metallograph of magnesium iron as shown in Figure 1,2-3 grades of nodulizing grade, hardness is between 155HB-165HB；After testing, base In the mass percent meter of magnesium iron, content of pearlite in alloy is in 5% or so, S contents<0.02%, ferrite content > 85%, without trip From cementite.Base iron spoken parts in traditional operas and inverted chill tendency are smaller simultaneously；Graphite nodule size is small in the magnesium iron of production, and roundness is high, iron Ferritic content is more, and the toughness of magnesium iron improves.

Spectrum analysis testing result in stokehold shown in table 4, the absorptivity of carburant only have between 85~90%.

2-3 grades of nodulizing grade as shown in Figure 2, content of pearlite in alloy 20% or so, hardness is not inconsistent between 170HB-180HB Requirement of the client for hardness is closed, its processing performance is influenced.

Claims (5)

1. a kind of carburant absorptivity reaches 95% or more smelting scrap steel ductile iron process, it is characterised in that include the following steps：

（1）Furnace charge is added in point 10 ± 2 equivalent in smelting furnace, and furnace charge includes magnesium iron bits, foundry returns and steel scrap, first in furnace bottom A furnace charge is added and is initially added into carburant after starting to dissolve molten iron under stove；After carburant is added every time, furnace charge is used It pushes down, the addition number of furnace charge is often more primary than carburant addition；Wherein, foundry returns will reserve 10% ± 2%；Foundry returns and ball Iron filings are according to 1:1 ratio collocation uses, ratio >=65% shared by steel scrap, and the ratio of carburant is 2.5% ± 0.2%；Carburant Granularity for low-sulfur carburant, carburant is 5 ± 0.5mm granularities；

（2）After all adding furnace charge point several times, when furnace charge all melts in smelting furnace, start to warm up to molten iron temperature up to 1550 ± 5 DEG C, 3 ± 0.5 minutes are kept the temperature, when heat preservation stirs evenly, and after all carburants have been completely melt, deslagging agent is added, slag is complete After portion concentrates in together, slag slag hitting rod is chosen outside stove；

（3）Major element is chemically examined in stokehold sample examination, stokehold, and the C content for reaching the base iron before spheroidising is 4.0% ± 1%, After the requirement of Si contents 1.2% ± 0.2%, step is added（1）Reserved foundry returns is warming up to 1620 ± 5 DEG C, carries out at nodularization Reason, nodularization are to use dam-type nodularization packet, and the addition of nodulizer is 1.5% ± 0.1%, is placed on the other side that molten iron liquidates, The magnesium iron of pressure 1% ± 0.1% considers the silicon iron inoculator with 0.5% ± 0.2% to be worth doing on nodulizer；

（4）Late inoculation processing；

When big packet turns parcel, late inoculation is carried out；Inoculation method is the silicon barium powder with 0.5mm specifications, by breeding funnel, It is 0.2% ± 0.05% that incubation dose, which is added, in each parcel molten iron；

（5）Casting；

The nodulizing grade of gained magnesium iron is 2~3 grades, and hardness is between 155HB-165HB；Mass percent meter based on magnesium iron, Content of pearlite in alloy 5% ± 0.5%, S contents<0.02%, ferrite content > 85%, are free of free cementite, and the above percentage is matter Measure percentage.

2. a kind of carburant absorptivity according to claim 1 reaches 95% or more smelting scrap steel ductile iron process, feature It is, the steel scrap includes prompt industrial scrap；Foundry returns includes dead head.

3. a kind of carburant absorptivity according to claim 1 reaches 95% or more smelting scrap steel ductile iron process, feature Be, low-sulfur carburant select calcined coke, in fixation C content >=98.5%, S content≤0.05%.

4. a kind of carburant absorptivity according to claim 1 reaches 95% or more smelting scrap steel ductile iron process, feature It is, smelting furnace uses intermediate frequency furnace melting.

5. a kind of carburant absorptivity reaches 95% or more smelting scrap steel ductile iron process, it is characterised in that include the following steps：

（1）A points of 11 times equivalent are added furnace charges in intermediate frequency furnace melting, and furnace charge includes magnesium iron bits, foundry returns and steel scrap, wherein The ratio of ratio >=65% shared by steel scrap, carburant is 2.5% ± 0.2%；Foundry returns and magnesium iron bits are according to 1:1 ratio collocation It uses, the steel scrap includes prompt industrial scrap, and foundry returns includes dead head；A furnace charge is first added in furnace bottom, waits for stove bottom Under start after dissolving molten iron, be initially added into carburant, carburant is low-sulfur carburant, selects calcined coke, by percentage to the quality, The granularity of fixation C content >=98.5%, S content≤0.05% in it, carburant is 5mm granularities；After carburant is added every time, use Furnace charge is pushed down, and 10 equivalent of carburant point are added；Wherein, foundry returns will reserve 10% ± 2%；

（2）After point 11 wholes add furnace charge, when furnace charge all melts in smelting furnace, start to warm up to molten iron temperature up to 1550 DEG C, 3 minutes are kept the temperature, when heat preservation stirs evenly, and after all carburants have been completely melt, deslagging agent is added, slag all concentrates on After together, slag slag hitting rod is chosen outside stove；

（3）Stokehold sample examination, the stokehold major element of chemical examination reach after requirement, wherein and the C content of molten iron is 4.0% ± 1%, Si contents 1.2% ± 0.2%；Step is added（1）Reserved foundry returns is warming up to 1620 DEG C, carries out spheroidising, and nodularization is to use The addition of dam-type nodularization packet, nodulizer is 1.5%, is placed on the other side that molten iron liquidates, and 1% magnesium iron bits are pressed on nodulizer With 0.5% silicon iron inoculator；

（4）Late inoculation processing；

When big packet turns parcel, late inoculation is carried out；Inoculation method is the silicon barium powder with 0.5mm specifications, by breeding funnel, It is 0.2% that incubation dose, which is added, in each parcel molten iron；

（5）Casting；

The nodulizing grade of gained magnesium iron is 2~3 grades, and hardness is between 155HB-165HB；Mass percent meter based on magnesium iron, Content of pearlite in alloy 5% ± 0.5%, S contents<0.02%, ferrite content > 85%, are free of free cementite, and the above percentage is matter Measure percentage.