Background technology
Roll is the main consumption spare part during steel rolling is produced, and roll quality directly influences stocking surface quality, operating rate of rolling mill and stocking production cost, improves roll quality, and reduce the roll production cost is the problem that roll manufacturing enterprise constantly pays close attention to always.Centrifugal casting has been widely used in especially being applied in the production of high alloy composite roll in the roll production because of having characteristics such as production efficiency height, cast(ing) surface dense structure and allowance are few.Hot roll material commonly used at present has high nickel chromium triangle infinitely chilled ductile cast iron, half steel, high-chromium white cast iron and high carbon high-speed steel etc., and the former is continuous net-shaped distribution because of carbide by high nickel chromium triangle infinitely chilled ductile cast iron roll, and roll fragility is big; And ferrosteel roll is low because of hardness, and wearability is relatively poor; The high carbon high-speed steel roll has good wearability and higher intensity and toughness, but contains alloying elements such as more expensive vanadium, molybdenum, niobium, cobalt, and the roll production cost is high.The chrome content of high-chromium white cast iron is between 12-28%, and phosphorus content is between 2.4-3.6%, and its wearability depends on kind and the form distribution etc. of content, matrix and the carbide of carbon and alloying element.The microscopic structure of rich chromium cast iron is made up of primary austenite or its transmutation product and eutectic structure.Its eutectic carbide is the M of the shaft-like and lath-shaped of hexagon
7C
3The type carbide is the suspension shape and distributes, and microhardness is up to Hv1300-1800.Rich chromium cast iron is as roll, has on the harder matrix of certain toughness through can obtaining after the heat treatment, is evenly distributed with the proeutectoid carbide tissue that isolated lump shape primary carbide and a certain amount of disperse distribute, and has wear-resistant preferably grinding abrasion performance.The adding of alloying element and corresponding casting and Technology for Heating Processing all are to add a certain amount of retained austenite for alloy carbide and the martensite that obtains this form distribution.Rich chromium cast iron has been widely used in the roll production at present.
Japan Patent JP2006070350-A discloses a kind of high-chromium iron-cast roller, concrete chemical composition as follows (mass fraction, %): 2.5-3.5C, 0.2-1.0Si; 0.6-2.0Mn, 11-22Cr, 1-3Mo; 0.01-0.15N, balance iron and unavoidable impurities, and 4.5≤Cr/C≤6.5.It is that high chromium nihard, intermediate layer are that half steel and core are the composite roll of magnesium iron that Japan patent of invention JP1005609-A and JP96023060-B2 also disclose a kind of skin, and the chemical composition (mass fraction) of outer floor height chromium nihard is: 2.4-3.4%C, 2.0-4.5%Ni; 2.0-3.4%Si, 5-10%Cr, 0.5-1.5%Mn; 0.4-2.0%Mo ,≤0.1%P ,≤0.08%S; In addition, also contain 0.5-4.0%Cu with (or) Sn, surplus Fe; The chemical composition of intermediate layer half steel (mass fraction) is: 1.0-2.5%C, and≤1.5%Ni, 0.5-1.5%Si, 2-5%Cr, 0.5-1.5%Mn ,≤0.5%Mo ,≤0.1%P ,≤0.1%S,, surplus Fe; The chemical composition of core magnesium iron (mass fraction) is: 3.0-3.8%C ,≤2.0%Ni, 1.8-3.0%Si ,≤1.0%Cr ,≤1.0%Mo, 0.3-1.0%Mn ,≤0.1%P, 0.02-0.10%Mg ,≤0.02%S, surplus Fe.
Chinese invention patent CN101015836A discloses high ferrochrome of casting or the casting high chromium steel roller on a kind of milling train that is applied to rolling welded still pipe, can be used on the rolling mill for welded steel pipe of different shapes such as straight seam welded steel pipe milling train, spiral welded steel pipe milling train, rectangle rolling mill for welded steel pipe; Its composition of casting high ferrochrome roll is by weight percentage: C:1.8~2.8%, and Si :≤1.0%, Mn :≤1.0%, P :≤0.05%; S :≤0.05%, Cr:12~22%, Ni:0.5~3.0%; Mo:0.8~3.0%, Ti:0~0.3%, V:0~1.0%; Cu:0~1.0%, RE:0.01~0.5%, all the other are Fe; This invention is adopted high ferrochrome or high chrome and is adopted casting technique production; Its roll product material tissue is evenly about, and wearability and toughness improve a lot, and be 2-5 times of forging roller product service life; Owing to adopt casting; Shortened manufacturing procedure, reduced processing capacity, stock utilization can reach 70% even can reach 80%.Chinese invention patent CN1951606A discloses high chromium cast iron composite cold roller production process, and its roll comprises roller core and roll wearing layer, and roller core adopts low-alloy steel or medium carbon steel to make; The roll wearing layer adopts high-chromium white cast iron to make, and roller core and roll wearing layer are through eddy-current heating, its thermoforming process: casting mold is put into induction heating equipment; Again prefabricated low-alloy steel or medium carbon steel roller core are put into casting mold; Open induction heating equipment heating roller core, when being heated to 1200~1400 ℃, pour into the rich chromium cast iron liquation; Continue the small-power heating again and stop heating after 5~15 minutes, finish until solidifying through recirculated water.This invention exists production efficiency low, and the body of roll and roller core combine deficiencies such as difference.Chinese invention patent CN1854328A also discloses the composite high-chromium iron-cast roller of improvement, it is characterized in that roll working lining composition is C2.5-3.0%, Si0.5-1.2%, Mn0.6-1.2%; Ni1.0-1.5%, Cr12-20%, Mo0.5-3.5%, V0.05-0.5%; W0.2-1.5%, Al0.03-0.3%, N0.03-0.1%; P≤0.04%, S≤0.04%, all the other are iron and impurity.The more original roll rich chromium cast iron of this invention roll working lining working lining, wearability improves more than 50%.But above-mentioned high-chromium iron-cast roller all need add expensive nickel, molybdenum alloy element in producing, and causes the roll production cost to increase.
Summary of the invention
The object of the invention is to provide a kind of cheap composite roll for centrifugally casting high-chromium cast iron of roll mechanical property and thermal fatigue property and price and preparation method thereof that helps significantly to improve; Last alloy iron filings and carbon ferrochrome to process high nickel chromium triangle infinitely chilled ductile cast iron roll are main alloy raw material; In addition; In order to improve roll quenching degree; Also add an amount of mid-carbon fe-mn and ferro-boron,, also added materials such as calsibar alloy, aluminium, ferrotianium, rare earth ferrosilicon, zinc, magnesium in order to purify and thinning solidification structure.
The objective of the invention is to reach like this, a kind of composite roll for centrifugally casting high-chromium cast iron comprises skin of the roll and roll roller core; The chemical component weight % of the material of described skin of the roll is: the alloy iron filings of 25~28% high nickel chromium triangle infinitely chilled ductile cast iron roll, 28~30% carbon ferrochrome, 1.5~2.5% mid-carbon fe-mn; 2.5~3.5% ferro-boron, 0.5~0.8% calsibar alloy, 0.2~0.4% aluminium; 0.3~0.5% ferrotianium, 0.2~0.4% rare earth ferrosilicon, 0.10~0.15% zinc; 0.15~0.18% magnesium, surplus are the low-carbon waste steel sheet; Said roll roller core is high-strength alloy cast iron or low-alloy spheroidal graphite cast-iron, and described skin of the roll and roller core two parts form through centrifugal composite casting.
The chemical component weight % of the alloy iron filings of high nickel chromium triangle infinitely chilled ductile cast iron roll of the present invention is: 3.01~4.80% Ni, 1.00~2.00% Cr, 2.90~3.60% C; 0.60~1.50% Si; 0.40~1.20% Mn, 0.20~1.00% Mo, surplus is Fe; The chemical component weight % of described carbon ferrochrome is: 62.0~68.0% Cr, and 7.0~8.5% C, 2.0~3.5% Si, surplus is Fe; The chemical component weight % of described mid-carbon fe-mn is: 75.0~82.0% Mn, and 1.0~1.8% C ,≤1.5% Si ,≤0.20% P ,≤0.03% S, surplus is Fe; The chemical component weight % of described ferro-boron is: 17.0~19.0% B, and<0.5% C,<3.5% Si, surplus is Fe; The chemical component weight % of described calsibar alloy is: 40~45% Si, 10~12% Ca, 10~12% Ba ,≤0.8% C ,≤0.04% P ,≤0.06% S, surplus is Fe.
An also purpose of the present invention reaches like this, a kind of preparation method of composite roll for centrifugally casting high-chromium cast iron, and it may further comprise the steps:
The first step: the melting of outer rich chromium cast iron:
1. elder generation is mixed in one with alloy iron filings, calsibar alloy and the low-carbon waste steel sheet of high nickel chromium triangle infinitely chilled ductile cast iron roll, and on forcing press, is compacted into bulk, puts into the electric induction furnace heat fused then, adds carbon ferrochrome and mid-carbon fe-mn more successively,
2. after molten iron melts clearly, when molten iron temperature reaches 1500~1520 ℃, add aluminium, add ferrotianium, ferro-boron then successively, when molten iron temperature reaches 1520~1560 ℃, come out of the stove,
3. in the process of tapping a blast furnace, when tapping a blast furnace 40~60% the time, metallic zinc is coated tight with the stalloy of thickness 0.10~0.25mm, throws away into casting ladle with stream then,
4. rare earth ferrosilicon is crushed to fritter, after oven dry, places the casting ladle bottom; The passivation particle magnesium that will apply passivation layer simultaneously also places the casting ladle bottom, and cylinder iron bits cover, and with the method that pours in the bag molten iron is carried out composite inoculating and handles; Add slag former simultaneously, molten iron is to be cast after skimming;
Second step: the melting of roller core cast iron:
With electric furnace or cupola melting roller core molten iron, roller core is selected high-strength alloy cast iron or low-alloy spheroidal graphite cast-iron for use, 1480~1520 ℃ of roller core molten iron tapping temperatures;
The 3rd step: the roll composite casting is shaped:
1. earlier the rich chromium cast iron molten iron is poured in the casting mold that on centrifuge, rotates, molten steel pouring temperature is 1420~1460 ℃, and the casting mold material is a casting pig; Wall thickness 120mm~240mm; Preheat temperature is greater than 150 ℃, and under this temperature stenciling coating, mold temperature is not less than 100 ℃ during cast; Paint thickness is less than 3.5mm,
2. the casting mold rotation speed n is pressed following formula and is confirmed:
Formula (1)
In the formula: n-casting mold revolution, r/min, γ-rich chromium cast iron liquation density, g/cm
3, r-skin of the roll inside radius, cm, β-adjustment coefficient, rich chromium cast iron are 1.3~1.5,
3. behind skin cast finishing 6~15min, measure skin of the roll (being the body of roll) internal surface temperature with the contactless temperature-measuring appearance, when temperature is 1240 ℃~1300 ℃, pour into the roller core molten iron, molten steel pouring temperature is 1300~1350 ℃,
4. after the roller core molten iron pouring finishes 12~24h, take out the rich chromium cast iron composite roll and advance holding furnace or burial pit;
The 4th step: rich chromium cast iron composite roll heat treatment:
The rich chromium cast iron composite roll is directly carried out roughing under as cast condition, in heating furnace, be heated to 520~580 ℃ then, heat temperature raising speed is 15~25 ℃/h; Air-cooled behind insulation 6~10h, the programming rate with 25~35 ℃/h is heated to 450~500 ℃ again, behind insulation 12~15h; Stove is chilled to below 150 ℃; Air cooling is refined to given size and precision with roll at last, obtains composite roll for centrifugally casting high-chromium cast iron.
In another concrete embodiment of the present invention, being compacted into bulk on the described forcing press and being the length and width and the Gao Ge that are compacted into physical dimension is the bulk of 150~250mm.
In also concrete embodiment of the present invention, describedly rare earth ferrosilicon is crushed to fritter is meant the fritter that is crushed to granularity<18mm.
In another concrete embodiment of the present invention, the bake out temperature of described oven dry is<220 ℃.
In another concrete embodiment of the present invention, the particle size of described passivation particle magnesium is that the thickness of 1.0~2.5mm, passivation layer is 0.10~0.15mm.
In of the present invention and then concrete embodiment, described passivation layer is to constitute sodium chloride by following raw material by weight percentage: 30~40%, and potassium chloride: 25~35%, magnesium chloride: 20~30%, barium chloride: 5~10%.
Technical scheme provided by the present invention compared with prior art has the following advantages:
1) roll of the present invention is main alloy raw material with alloy iron filings, carbon ferrochrome and the low-carbon waste steel sheet of processing high nickel chromium triangle infinitely chilled ductile cast iron roll, does not add alloying elements such as expensive nickel plate, molybdenum-iron, copper coin and vanadium iron, so the roll low production cost;
2) roll of the present invention adds ferromanganese and calsibar alloy pre-deoxidation, adds the aluminium final deoxidizing, so field trash is few in the roll, organizes high purity;
3) in the roll of the present invention, add ferro-boronization, can improve roll quenching degree and hardenability, the roll depth of hardening zone is greater than 50mm, and roll surface hardness reaches 78~81HSD;
4) roll of the present invention is after zinc, magnesium, ferrotianium and rare earth ferrosilicon are handled, and solidified structure is tiny, and carbide is suspension and distributes with isolated, helps increasing substantially of roll mechanical property and thermal fatigue property, and this roll barrel fracture toughness is greater than 30MPa.m
1/2, tensile strength is greater than 700Mpa.
5) roll of the present invention is applied on hot strip rolling mill, the bar mill, and improve 50~70% than high nickel chromium triangle infinitely chilled ductile cast iron roll service life, and production cost reduces by 15~20%.
The specific embodiment
The performance of roll material is by the metallographic structure decision, and the tissue of roll depends on chemical composition and Technology for Heating Processing, and composite roll of the present invention is formed through centrifugal composite casting by outer and roller core two parts, and its outer chemical composition is to confirm like this:
The outer field main raw material(s) of the present invention is alloy iron filings, carbon ferrochrome and the low-carbon waste steel sheet of high nickel chromium triangle infinitely chilled ductile cast iron roll, contains elements such as nickel, chromium in the alloy iron filings of high nickel chromium triangle infinitely chilled ductile cast iron roll, and adding in the roll to increase constituent content such as nickel, chromium in the roll; Also increase simultaneously the carbon content in the roll; But addition is too many, and field trash increases in the roll, damages the mechanical property of roll on the contrary; Therefore, its addition is controlled at 25~28%.Add carbon ferrochrome and mainly be in order to replenish the chromium content in the roll, make that chromium content is controlled at more than 16% in the roll, help obtaining the M of high rigidity
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3The type carbide, thus the wearability of roll improved, and addition is too much, can cause in the roll carbon content too high, be prone to cracking during roll uses and peel off, so the carbon ferrochrome addition is controlled at 28~30%.Add 1.5~2.5% mid-carbon fe-mns in addition, except playing deoxidation, also can improve roll quenching degree.In roll, add ferro-boron, part of boron can get into carbide, helps improving carbide hardness and heat endurance; Part of boron gets into matrix; Can improve matrix quenching degree and hardenability, thereby can improve the roll wearability, but the ferro-boron addition is too much; Reduce roll toughness on the contrary, so the ferro-boron addition is controlled at 2.5~3.5%.Add calsibar alloy in the roll; Mainly play deoxidation and improve inclusion morphology and distribution, thereby improve roll strength and toughness, though the solubility of barium in iron liquid is lower; But the adding of barium improves the solubility of calcium in iron liquid; Thereby improved the utilization rate of calcium, and make the deoxidation of calcium and the effect that makes inclusion modification obtain performance, impel the oxygen content in the iron liquid comparatively fast to reach balance; On the other hand, barium is participated in deoxygenation, its product BaO collide with other product and the probability that combines very big; Can from iron liquid, float rapidly, get rid of; The amount of inclusions reduces in the iron thereby make, and has correspondingly reduced the oxygen content of iron liquid, and suitable calsibar alloy addition is 0.5~0.8%.Add 0.2~0.4% aluminium, except playing deoxidation, also can improve carbide morphology and distribution, improve the comprehensive mechanical property of roll.Add 0.3~0.5% ferrotianium, but refinement roll solidified structure improves the roll comprehensive mechanical property.Add 0.2~0.4% rare earth ferrosilicon, 0.10~0.15% zinc, 0.15~0.18% magnesium; Can play deoxidation, desulfurization, purify metal liquid, thinning solidification structure; Promote carbide morphology to be suspension and the isolated effect that distributes; Thereby can improve the mechanical property of roll, and improve the thermal fatigue property of roll, help the roll prolongation in service life.
Roll of the present invention is before melting; Alloy iron filings, calsibar alloy, low-carbon waste steel sheet with high nickel chromium triangle infinitely chilled ductile cast iron roll is mixed in one earlier; And on forcing press, be compacted into and be of a size of: the square of long 150~250mm * wide 150~250mm * high 150~250mm, then the square of compacting is put into the electric induction furnace heat fused, can improve the melting rate of iron and cheet scrap like this; Reduce the scaling loss of metallic element, also can reduce The amount of inclusions in the metal liquid.
Roll of the present invention when tapping a blast furnace 40%~60% the time, coats metallic zinc tightly in the process of tapping a blast furnace with the stalloy of thickness 0.10~0.25mm, throw away into casting ladle with stream then, can reduce the oxidization burning loss of zinc, improves the recovery rate of zinc element;
The adding method of roll magnesium elements of the present invention is; With magnesium granules size 1.0~2.5mm, passivation layer thickness 0.10~0.15mm with contain the passivation particle magnesium that the passivation layer of 30~40% sodium chloride, 25~35% potassium chloride, 20~30% magnesium chlorides, 5~10% barium chlorides forms and also place the casting ladle bottom; And cylinder iron bits cover; With pouring method in the bag molten iron is handled, can be alleviated the oxidization burning loss of magnesium elements like this, also can control the reaction rate of magnesium elements and molten iron; Improve the recovery rate of magnesium elements, better bring into play the effect of magnesium elements.
Cast iron roll in as-cast roll neck intensity of the present invention is high, good toughness, and hardness has machining property preferably less than 50HSD.The body of roll adopts the centrifugal composite casting method to be shaped, and the body of roll is bright and clean, processing capacity is few, and the body of roll is organized as carbide, martensite, austenite and bainite, and hardness is between 72~75HSD, and available hard alloy cutter is directly processed, and need not carry out soft annealing and handle.Rich chromium cast iron composite roll of the present invention after the direct roughing, is heated to 520~580 ℃ then in heating furnace under as cast condition, heat temperature raising speed is 15~25 ℃/h; Air-cooled behind insulation 6~10h; Can make in the as-cast structure carbide precipitate in the retained austenite, reduce retained austenite stability, in process air cooler subsequently; Retained austenite is transformed into martensite; Separate out and the retained austenite of carbide are transformed into martensite, promote that roll hardness is increased to 78~81HSD, help the further raising of roll wearability.But separate out and the retained austenite of carbide are transformed into martensite, will increase the roll residual stress; Therefore, the programming rate with 25~35 ℃/h is heated to 450~500 ℃ again, behind insulation 12~15h; Stove is chilled to below 150 ℃, and air cooling can reduce the residual stress in the roll; Improve structure stability, at last roll is refined to given size and precision after, can satisfy the needs of steel rolling production.
The embodiment that provides below in conjunction with the inventor does further detailed description to the present invention.
Embodiment 1:
The rich chromium cast iron composite roll external diameter of present embodiment is φ 370mm; Skin of the roll thickness 60mm; The monolateral processing capacity 8mm of skin of the roll, skin of rich chromium cast iron composite roll (being the body of roll) and roller core are used 1000kg and the melting of 1500kg medium-frequency induction furnace respectively, and its manufacturing technology steps is:
The first step: the melting of outer rich chromium cast iron:
1. elder generation is mixed in one with alloy iron filings, calsibar alloy, the low-carbon waste steel sheet of high nickel chromium triangle infinitely chilled ductile cast iron roll; And be compacted on forcing press that to be of a size of (150~250) mm * (150~250) mm * (150~250) mm be that length and width and Gao Ge are the square of 150-250mm; Then the square of compacting is put into the electric induction furnace heat fused; Add carbon ferrochrome and mid-carbon fe-mn then successively
2. after molten iron melts clearly, when molten iron temperature reaches 1520 ℃, add aluminium, add ferrotianium, ferro-boron then successively, when molten iron temperature reaches 1558 ℃, come out of the stove,
3. in the process of tapping a blast furnace, when tapping a blast furnace 40% the time, metallic zinc is coated tight with the stalloy of thickness 0.10~0.25mm, throws away into casting ladle with stream then,
4. rare earth ferrosilicon is crushed to the fritter of granularity less than 18mm; After oven dry below 220 ℃; Place the casting ladle bottom; To apply simultaneously by mass percent is that the passivation particle magnesium of the passivation layer that constitutes of 30~40% sodium chloride, 25~35% potassium chloride, 20~30% magnesium chlorides and 5~10% barium chlorides and passivation layer thickness 0.10~0.15mm and magnesium granules size 1.0~2.5mm also places the casting ladle bottom, and cylinder iron bits cover, and with pouring method in the bag molten iron are carried out the composite inoculating processing.Add slag former simultaneously; Molten iron is to be cast after skimming; The addition of various raw materials (mass fraction) is in the skin of the roll: the alloy iron filings of 25% high nickel chromium triangle infinitely chilled ductile cast iron roll, 30% carbon ferrochrome, 1.5% mid-carbon fe-mn, 3.5% ferro-boron, 0.5% calsibar alloy, 0.4% aluminium, 0.3% ferrotianium, 0.4% rare earth ferrosilicon, 0.10% zinc, 0.18% magnesium, surplus are the low-carbon waste steel sheets;
Second step: the melting of roller core cast iron:
With electro-smelting roller core molten iron, roller core is selected high-strength alloy cast iron for use, 1518 ℃ of roller core molten iron tapping temperatures;
The 3rd step: the roll composite casting is shaped:
1. earlier the rich chromium cast iron molten iron is poured in the casting mold that on centrifuge, rotates, molten steel pouring temperature is 1459 ℃, and the casting mold material is a casting pig, wall thickness 120mm, preheat temperature is greater than 150 ℃, and under this temperature stenciling coating, mold temperature is not less than 100 ℃ during cast; Paint thickness is less than 3.5mm,
2. the casting mold rotation speed n is pressed following formula and is confirmed:
Formula (2)
In the formula: n-casting mold revolution, r/min, γ-rich chromium cast iron liquation density, g/cm
3, r-skin of the roll inside radius, cm, β-adjustment coefficient, rich chromium cast iron are 1.5,
3. behind skin cast the finishing 6min, measure skin of the roll (being the body of roll) internal surface temperature with the contactless temperature-measuring appearance, when temperature is 1240 ℃~1300 ℃, pour into the roller core molten iron, molten steel pouring temperature is 1312 ℃,
4. after the roller core molten iron pouring finishes 12h, take out the rich chromium cast iron composite roll and advance holding furnace;
The 4th step: rich chromium cast iron composite roll heat treatment:
The rich chromium cast iron composite roll is directly carried out roughing under as cast condition, in heating furnace, be heated to 520 ℃ then, heat temperature raising speed is 25 ℃/h; Air-cooled behind the insulation 10h; Programming rate with 35 ℃/h is heated to 500 ℃ again, and behind the insulation 12h, stove is chilled to below 150 ℃; Air cooling is refined to given size and precision with roll at last.The roll mechanical property is seen table 1.
Table 1 roll mechanical property
Hardness of roll body (HSD) |
Body of roll tensile strength (Mpa) |
Fracture toughness (MPa.m
1/2)
|
Roll neck hardness (HSD) |
Roll neck tensile strength (Mpa) |
80.5 |
785.7 |
31.4 |
42.2 |
384.6 |
Embodiment 2:
The present embodiment rich chromium cast iron composite roll body of roll is of a size of the skin (being the body of roll) and the roller core of
composite roll and uses 3t medium-frequency induction furnace and 5t/h cupola melting respectively, and its manufacturing technology steps is:
The first step: the melting of outer rich chromium cast iron:
1. elder generation is mixed in one with alloy iron filings, calsibar alloy, the low-carbon waste steel sheet of high nickel chromium triangle infinitely chilled ductile cast iron roll; And on forcing press, be compacted into the square that is of a size of (150~250) mm * (150~250) mm * (150~250) mm; Then the square of compacting is put into the electric induction furnace heat fused; Add carbon ferrochrome and mid-carbon fe-mn then successively
2. after molten iron melts clearly, when molten iron temperature reaches 1501 ℃, add aluminium, add ferrotianium, ferro-boron then successively, when molten iron temperature reaches 1526 ℃, come out of the stove,
3. in the process of tapping a blast furnace, when tapping a blast furnace 60% the time, metallic zinc is coated tight with the stalloy of thickness 0.10~0.25mm, throws away into casting ladle with stream then,
4. rare earth ferrosilicon is crushed to the fritter of granularity less than 18mm; After oven dry below 220 ℃; Place the casting ladle bottom; To apply simultaneously by mass percent is that the passivation particle magnesium of the passivation layer that constitutes of 30~40% sodium chloride, 25~35% potassium chloride, 20~30% magnesium chlorides and 5~10% barium chlorides and passivation layer thickness 0.10~0.15mm and magnesium granules size 1.0~2.5mm also places the casting ladle bottom, and cylinder iron bits cover, and with pouring method in the bag molten iron are carried out the composite inoculating processing.Add slag former simultaneously; Molten iron is to be cast after skimming; The addition of various raw materials (mass fraction) is in the skin of the roll: the alloy iron filings of 28% high nickel chromium triangle infinitely chilled ductile cast iron roll, 28% carbon ferrochrome, 2.5% mid-carbon fe-mn, 2.5% ferro-boron, 0.8% calsibar alloy, 0.2% aluminium, 0.5% ferrotianium, 0.2% rare earth ferrosilicon, 0.15% zinc, 0.15% magnesium, surplus are the low-carbon waste steel sheets;
Second step: the melting of roller core cast iron:
With cupola melting roller core molten iron, roller core is selected low-alloy spheroidal graphite cast-iron for use, 1483 ℃ of roller core molten iron tapping temperatures;
The 3rd step: the roll composite casting is shaped:
1. earlier the rich chromium cast iron molten iron is poured in the casting mold that on centrifuge, rotates, molten steel pouring temperature is 1425 ℃, and the casting mold material is a casting pig, wall thickness 240mm, preheat temperature is greater than 150 ℃, and under this temperature stenciling coating, mold temperature is not less than 100 ℃ during cast; Paint thickness is less than 3.5mm,
2. casting mold revolution n presses following formula and confirms:
Formula (3)
In the formula: n-casting mold revolution, r/min, γ-rich chromium cast iron liquation density, g/cm
3, r-skin of the roll inside radius, cm, β-adjustment coefficient, rich chromium cast iron are 1.3,
3. behind skin cast the finishing 15min, measure skin of the roll (being the body of roll) internal surface temperature with the contactless temperature-measuring appearance, when temperature is 1240 ℃~1300 ℃, pour into the roller core molten iron, molten steel pouring temperature is 1346 ℃,
4. after the roller core molten iron pouring finishes 24h, take out the rich chromium cast iron composite roll and advance burial pit;
The 4th step: rich chromium cast iron composite roll heat treatment:
The rich chromium cast iron composite roll is directly carried out roughing under as cast condition, in heating furnace, be heated to 580 ℃ then, heat temperature raising speed is 15 ℃/h; Air-cooled behind the insulation 8h; Programming rate with 25 ℃/h is heated to 480 ℃ again, and behind the insulation 15h, stove is chilled to below 150 ℃; Air cooling is refined to given size and precision with roll at last.The roll mechanical property is seen table 2.
Table 2 roll mechanical property
Hardness of roll body (HSD) |
Body of roll tensile strength (Mpa) |
Fracture toughness (MPa.m
1/2)
|
Roll neck hardness (HSD) |
Roll neck tensile strength (Mpa) |
80.2 |
813.2 |
31.7 |
41.7 |
423.0 |
Embodiment 3:
The rich chromium cast iron composite roll external diameter of present embodiment is φ 370mm; Skin of the roll thickness 60mm; The monolateral processing capacity 8mm of skin of the roll, skin of rich chromium cast iron composite roll (being the body of roll) and roller core are used 1000kg and the melting of 1500kg medium-frequency induction furnace respectively, and its manufacturing technology steps is:
The first step: the melting of outer rich chromium cast iron:
1. elder generation is mixed in one with alloy iron filings, calsibar alloy, the low-carbon waste steel sheet of high nickel chromium triangle infinitely chilled ductile cast iron roll; And on forcing press, be compacted into the square that is of a size of (150~250) mm * (150~250) mm * (150~250) mm; Then the square of compacting is put into the electric induction furnace heat fused; Add carbon ferrochrome and mid-carbon fe-mn then successively
2. after molten iron melts clearly, when molten iron temperature reaches 1511 ℃, add aluminium, add ferrotianium, ferro-boron then successively, when molten iron temperature reaches 1538 ℃, come out of the stove,
3. in the process of tapping a blast furnace, when tapping a blast furnace 50% the time, metallic zinc is coated tight with the stalloy of thickness 0.10~0.25mm, throws away into casting ladle with stream then,
4. rare earth ferrosilicon is crushed to the fritter of granularity less than 18mm; After oven dry below 220 ℃; Place the casting ladle bottom; To apply simultaneously by mass percent is that the passivation particle magnesium of the passivation layer that constitutes of 30~40% sodium chloride, 25~35% potassium chloride, 20~30% magnesium chlorides and 5~10% barium chlorides and passivation layer thickness 0.10~0.15mm and magnesium granules size 1.0~2.5mm also places the casting ladle bottom, and cylinder iron bits cover, and with pouring method in the bag molten iron are carried out the composite inoculating processing.Add slag former simultaneously; Molten iron is to be cast after skimming; The addition of various raw materials (mass fraction) is in the skin of the roll: the alloy iron filings of 26% high nickel chromium triangle infinitely chilled ductile cast iron roll, 29% carbon ferrochrome, 2.0% mid-carbon fe-mn, 3.0% ferro-boron, 0.6% calsibar alloy, 0.3% aluminium, 0.4% ferrotianium, 0.3% rare earth ferrosilicon, 0.12% zinc, 0.16% magnesium, surplus are the low-carbon waste steel sheets;
Second step: the melting of roller core cast iron:
With electro-smelting roller core molten iron, roller core is selected low-alloy spheroidal graphite cast-iron for use, 1503 ℃ of roller core molten iron tapping temperatures;
The 3rd step: the roll composite casting is shaped:
1. earlier the rich chromium cast iron molten iron is poured in the casting mold that on centrifuge, rotates, molten steel pouring temperature is 1440 ℃, and the casting mold material is a casting pig, wall thickness 150mm, preheat temperature is greater than 150 ℃, and under this temperature stenciling coating, mold temperature is not less than 100 ℃ during cast; Paint thickness is less than 3.5mm,
2. the casting mold rotation speed n is pressed following formula and is confirmed:
Formula (4)
In the formula: n-casting mold revolution, r/min, γ-rich chromium cast iron liquation density, g/cm
3, r-skin of the roll inside radius, cm, β-adjustment coefficient, rich chromium cast iron are 1.4,
3. behind skin cast the finishing 8min, measure skin of the roll (being the body of roll) internal surface temperature with the contactless temperature-measuring appearance, when temperature is 1240 ℃~1300 ℃, pour into the roller core molten iron, molten steel pouring temperature is 1332 ℃,
4. after the roller core molten iron pouring finishes 18h, take out the rich chromium cast iron composite roll and advance burial pit;
The 4th step: rich chromium cast iron composite roll heat treatment:
The rich chromium cast iron composite roll is directly carried out roughing under as cast condition, in heating furnace, be heated to 560 ℃ then, heat temperature raising speed is 20 ℃/h; Air-cooled behind the insulation 8h; Programming rate with 30 ℃/h is heated to 450 ℃ again, and behind the insulation 13h, stove is chilled to below 150 ℃; Air cooling is refined to given size and precision with roll at last.The roll mechanical property is seen table 3.
Table 3 roll mechanical property
Hardness of roll body (HSD) |
Body of roll tensile strength (Mpa) |
Fracture toughness (MPa.m
1/2)
|
Roll neck hardness (HSD) |
Roll neck tensile strength (Mpa) |
79.8 |
820.5 |
32.0 |
42.4 |
417.3 |
Composite roll for centrifugally casting high-chromium cast iron hardness of roll body of the present invention and intensity are high, good toughness; Roll neck also has higher intensity; Roll of the present invention is main alloy raw material with alloy iron filings, carbon ferrochrome and the low-carbon waste steel sheet of processing high nickel chromium triangle infinitely chilled ductile cast iron roll; Do not add alloying elements such as expensive nickel plate, molybdenum-iron, copper coin and vanadium iron, so the roll low production cost, reduce more than 10% than high-chromium iron-cast roller commonly used; Reduce by 15~20% than high nickel chromium triangle infinitely chilled ductile cast iron roll; On hot strip rolling mill, bar mill, use, its roller loss-rate high-chromium iron-cast roller commonly used reduces more than 20%, improves 50~70% than high nickel chromium triangle infinitely chilled ductile cast iron roll.Roll of the present invention is safe in utilization, does not have roll breakage, peeling phenomenon appearance in the use, uses roll of the present invention, can improve steel rolling output, reduces the steel rolling cost, has remarkable economical and social benefit.