The smelting process of austenite steel for engine air valve
Technical field
The invention belongs to smelting iron and steel technical field, particularly relating to the trade mark is 53Cr21Mn9Ni4N(21-4N), 5Cr20Mn8Ni2N(21-2N), a kind of smelting process of 33Cr23Ni8Mn3N (23-8N) Austenitic engine air valve steel.
Background technology
Valve Steel be manufacture petrol engine and diesel motor must use material, engine is the power of automobile, tractor, diesel locomotive, ships, engineering machinery, tank, mobile power station, air valve is then the vital part of engine, Valve Steel is also the critical material in whole engine, very large in the importance of traffic field of power machinery.The production of Valve Steel is a professional very strong field in special steel, although quantity is not very large, but its working conditions is severe, usually all wash away at high temperature, high pressure, height and work under high condition of denuding, thus higher to the performance requriements of Valve Steel, substantially will reach hot strength high, thermohardening is good, fatigue strength is high, wear resistance and anticorrosive good.---multiple developmental stage such as silicochromium type stainless steel---alpha alloy---Austenitic high temperature steel that make a general survey of the development course of air valve material, Valve Steel experienced by carbon steel and low alloy steel.At present, using both at home and abroad maximum is Austenitic high temperature steel, wherein based on 53Cr21Mn9Ni4N(21-4N), 5Cr20Mn8Ni2N(21-2N), 33Cr23Ni8Mn3N (23-8N).
The valve austenaging steel of austenite Valve Steel to be the fifties in last century be joint nickel exploitation, the at present domestic and international grade of steel most widely used for the manufacture of automobile, motorcycle engine vent valve.It take austenite as matrix, to obtain enough hot strengths, toughness, higher hardness, wear resistance and at the stability of alternating hot and cold condition undertissue and anti-oxidant, corrosion resistance nature preferably, at working temperature 600 ~ 700 DEG C, there is good mechanical property and high-temperature behavior as precipitation hardening phase Dispersed precipitate using carbon, nitrogen compound.In austenite Valve Steel, nitrogen content is 0.20 ~ 0.50%, be austenitic steel nitrogen content >=0.4% according to regulation matrix on metallurgy be high nitrogen steel, austenite Valve Steel can be considered middle high nitrogen steel, its smelting process mainly adopts induction furnace melting nitrogen-containing alloy to carry out esr more both at home and abroad, because production cost is higher, major part is small-scale production just, the main dependence on import of high-quality product.Existing smelting equipment: intermediate frequency furnace smelting steel iron charge, yield of alloy are high, high, the bad dephosphorization of power consumption; Electric arc furnace smelting dephosphorization is fast, quick heating, and steel technology is high.Austenite Valve Steel is high quality steel, wherein alloy content is up to about 30%, smelting technology makes every effort to reduce alloying element as the scaling loss of Cr, Ni, Mn, to ensure that the content of N is within standard range simultaneously, general smelting process adopts induction furnace melting nitrogen-containing alloy, as chromium nitride, ferronickel etc. are cast for steel ingot again.Chinese patent application CN201110186100.4 discloses a kind of intermediate frequency furnace electric arc furnace duplex smelting process, comprise: iron and steel stock loads in intermediate frequency furnace by (1), to come out of the stove to obtain 1520-1530 DEG C of molten steel, wherein prepare burden and to carry out according to electric arc furnace non-oxidizing process burden calculation method, allocate into according to 8-12% cast iron, end point carbon is 0.40%-0.60%; (2) in electric arc furnace, add lime, then add above-mentioned molten steel, heat up, dephosphorization, decarburization, finally tapping enters refining procedures.The smelting process of the high nitrogen steel of Chinese patent application CN200810300678.6 mono-kind; its step comprises: (1) is with electric arc furnace or induction furnace melting molten steel; (2) adopt another electric arc furnace or induction furnace melting nitrogen-containing alloy simultaneously; by the summation of the molten steel composition in above-mentioned (1), (2) step and steel grade adaptation; (3) molten steel of melting is joined in nitrogen-containing alloy liquid; and refining under nitrogen protection, obtain high nitrogen steel.
Summary of the invention
The object of the invention is to overcome above-mentioned deficiency, provide and can ensure that alloying element burn out rate is low, utilize a kind of method of producing austenite Valve Steel of AOD inflated with nitrogen alloying.
The present invention is achieved by the following technical solution:
The smelting process of austenite steel for engine air valve, comprises the following steps:
(1) induction furnace melting obtains aluminium alloy, electric arc furnace smelting molten steel containing chromium, nickel-containing alloys material;
(2) be blended in ladle by gained aluminium alloy in step (1) and gained molten steel, enter in AOD furnace and blow, require coarse adjustment alloying constituent according to Valve Steel chemical composition, carry out the operation of inflated with nitrogen alloying, N content reaches GB;
(3) step (2) gained is entered LF stove, carry out deoxidation, desulfurization and the operation of fine setting alloy;
(4) poured into a mould by step (3) gained, after cooling, the demoulding obtains steel ingot.
In described step (1), chrome-bearing alloy comprises: high carbon ferro-chrome, low carbon ferrochromium; Nickel-containing alloys comprises: nickel plate, ferronickel; Tap when fine melt, temperature T >=1560 DEG C.
In described step (1) can adding portion returns as alloy amount.
In described step (1), control P content during arc melting steel scrap, meets P content after converting steel with induction furnace molten steel and is less than GB range lower limit.
Following requirement is had: the mass percent entering C in AOD furnace molten steel is: 1.5 ~ 3.0%, Si≤0.8% in described step (2); When C >=0.60, restoring operation is carried out in temperature >=1670 DEG C, and reduction period takes inflated with nitrogen alloying, tapping temperature >=1480 DEG C.
The present invention utilizes induction furnace melting alloy, and alloy recovery is high, effectively solves the problem that the scaling loss of metallic element is high; Arc melting steel scrap; Carry out the two converting steel process again to enter in AOD furnace and blow, utilize cheap nitrogen to carry out filling nitrogen alloying.Molten steel also can be blended into induction furnace and go out in aluminium alloy ladle or aluminium alloy is blended in arc furnace tapping ladle by the present invention.
The present invention compared with prior art has following beneficial effect:
1) do not add nitrogen-containing alloy in smelting process, utilize cheap nitrogen to carry out filling nitrogen alloying, utilize induction furnace melting chromium, nickelalloy at initial smelting period simultaneously, greatly reduce the scaling loss of alloying element, thus reduce costs;
2) have employed ladle refining technique, improve Cleanliness of Molten Steel, ensure that quality product.
Present invention incorporates high and argon oxygen decarburizing furnace (AOD furnace) decarburization and cr yield of induction furnace melting alloy recovery, fill the feature of nitrogen alloying, a kind of austenite Valve Steel smelting process developed under the condition that other smelting equipments coordinate, the method has that production cost is low, alloy recovery is high, replaces nitrogen alloy with cheap nitrogen, the feature of suitable for mass production.
Accompanying drawing explanation
Fig. 1 is the process flow sheet of the embodiment of the present invention.
Embodiment
Below in conjunction with specific embodiment, the invention will be further described.
Embodiment one:
Austenite Valve Steel 53Cr21Mn9Ni4N(21-4N) smelt example:
1,53Cr21Mn9Ni4N(21-4N) chemical composition is in table 1.
Table 153Cr21Mn9Ni4N chemical composition
2, technical process
(1), induction furnace: feed stock for blast furnace through overbaking, need ensure dry anhydrous, become to be dispensed into induction furnace raw materials for metallurgy as follows according to target chemical:
High carbon chromium: 5200kg ferronickel: 2000kg
53Cr21Mn9Ni4N returns: 3050kg
Remove the gred during DEG C alloy material fine melt in T >=1540, skim 80%, add insulating covering agent.T >=1560 DEG C, the mixed tapping of slag is directly with by intermediate frequency furnace, tap 10t, and its chemical composition is as table 2:
Table 2 induction furnace tapping ladle chemistry
C |
Si |
Mn |
P |
S |
Ni |
Cr |
N |
V |
Nb |
Cu |
2.99 |
1.08 |
3.78 |
0.036 |
0.042 |
3.14 |
27.23 |
0.19 |
|
|
|
Owing to having allocated part returns into, containing part N in steel, alloy mainly allocated into by above induction furnace has been Cr and Ni.
(2) electric arc furnace (EBT): feed stock for blast furnace is steel scrap+pig iron about 20t altogether, adopts double slag process to smelt.DEG C add reductive agent silicon carbide 1-1.5 ㎏/t in T >=1530 and make reducing slag, after slagging-off, make basicity R >=1.5 basic slag, controlling following parameter during tapping is: P≤0.05; Si≤0.6%; T >=1580 DEG C, slag free tapping, molten steel directly enters in above-mentioned induction furnace tapping ladle, and tap is about 15t, stays steel to be about 5t.
(3) AOD furnace: the aluminium alloy of molten steel in electric arc furnace and induction furnace is entered in AOD furnace, it enters furnace charge original chemical composition as table 3:
Table 3AOD enters furnace charge chemical composition
C | Si | Mn | P | S | Ni | Cr | N |
2.15 | 0.54 | 2.03 | 0.049 | 0.063 | 3.77 | 19.97 | 0.08 |
AOD furnace blowing gas oxidation period is oxygen and nitrogen, and gas flow ratio control is: O2:N2=26:4(M3/m), add lime, slag making basicity R is 1.5 ~ 2.2, adds alloy adjusting component, temperature reaches >=1660 DEG C time, sampling analysis C, when C reaches 0.60, during temperature >=1670 DEG C, start to enter reduction period, calculate add ferrosilicon amount, reduce >=3 minutes time add adjustment manganese alloy, nitrogen flow is 10 ~ 14M3/m, fill nitrogen 8-15 minute, sampling analysis, skim.Again slag making, control basicity R is 1.8-2.2, and according to analysis sample adjustment chemical composition, composition is qualified, and temperature T=1490 ± 20 DEG C tapping, furnace charge turns LF station.
(4) LF stove: above-mentioned furnace charge carries out ladle refining after entering LF station, mainly carries out alloy fine setting, deoxidization desulfuration to furnace charge, and removing is mingled with, and its furnace charge original chemical composition is as table 4:
Table 4LF stove enters stove chemical composition
C | Si | Mn | P | S | Ni | Cr | N |
0.52 | 0.34 | 8.59 | 0.033 | 0.006 | 3.31 | 20.05 | 0.41 |
Do not add alloy according to Initial Composition, adopt and make white slag deoxidization technique, in the uniform situation of alloy melting, T >=1460 DEG C, sampling analysis composition, the qualified rear stopping refining of composition, tapping, soft blow is bull ladle cast after 10 minutes.During cast, final finished composition is as table 5:
Table 5 final finished chemical composition
C | Si | Mn | P | S | Ni | Cr | N |
0.53 | 0.18 | 8.90 | 0.033 | 0.005 | 3.36 | 20.58 | 0.41 |
Embodiment two:
Austenite Valve Steel 33Cr23Ni8Mn3N (23-8N) smelts example:
1,33Cr23Ni8Mn3N (23-8N) chemical composition is in table 6.
Table 633Cr23Ni8Mn3N chemical composition
2, technical process
This steel grade smelting technology is as embodiment one, and only composition changes to some extent, and alloy addition adjusts accordingly according to steel grade chemical composition, due to this steel grade liquidus line comparatively 53Cr21Mn9Ni4N(21-4N) high, LF tapping temperature controls as >=1480 DEG C.
Embodiment is just for the ease of understanding technical scheme of the present invention; do not form limiting the scope of the invention; every do not depart from technical solution of the present invention interior perhaps above scheme is done according to technical spirit of the present invention any simple modification, equivalent variations and modification, all still belong within scope.