CN103103443B - Bearing steel GCr15 production technology capable of preventing plugging of continuous casting water gap - Google Patents

Abstract

The invention relates to a bearing steel GCr15 production technology capable of preventing the plugging of a continuous casting water gap. The technology route comprises the steps of a top and bottom combined blow converter, an LF refining furnace, VD vacuum degassing and six-strand billet continuous casting of a Comcast six machine in sequence, the top and bottom combined blow converter conducts dephosphorization by adopting a double-slag method, the high catch carbon [C] at finishing point is more than or equal to 0.25%, final slag alkalinity before tapping is over 3.5, Als content in the molten steel in refining of the LF refining furnace is controlled to be over 0.05%, and Als/Alt is more than 95%; and argon blowing protection is conducted in the whole process of the continuous casting procedures, and low-pulling rate weak-cooling technology is adopted. Under the conditions of the technology, the cleanness of the molten steel can be improved, the non-metallic inclusion can be reduced, the plugging phenomenon of the continuous casting water gap can be prevented, the quality of the continuous casting blank can be improved, and the cost of the casting blank can be lowered, thereby finally improving the product quality.

Description

A kind of beating steel GCr15 production technique preventing continous casting sprue from blocking

Technical field

The invention belongs to metallurgical technology technical field, particularly a kind of beating steel GCr15 production technique preventing continous casting sprue from blocking.

Background technology

Bearing is " heart of industry ", and bearing steel is one of steel class that in special steel product, production difficulty is larger, and wherein the cleanliness factor of molten steel is the most important technical indicator affecting bearing steel performance.The bearing steel of high cleanliness, oxygen content in steel general control is 5 ~ 8 × 10 ^-6%, this just must control the content of oxygen in steel with aluminium deoxidation.

When production Aluminum steel kind, often can there is the phenomenon of nozzle clogging in continuous casting, especially for aluminium-deoxidized beating steel GCr15, finished product aluminium content about about 0.035%, often Submerged Nozzle Clogging Course phenomenon occurs in continuous casting is produced.When the blocking mouth of a river is serious, can cause that pulling rate reduces, mould liquid level fluctuation is large, to such an extent as to nozzle clogging, liquid steel temperature are low melts down, even can cause continuous caster stopping accident.Therefore, nozzle clogging both have impact on continuous casting billet quality, have impact on again normal Production Flow Chart, also limit many heats and even watered, add strand cost.

Generally the smelting technology of GCr15 is: converter procedure, the converter process of former smelting GCr15, terminal catch carbon >=0.09, finishing slag basicity > 3.0; LF refining procedure, originally LF refining procedure is when smelting GCr15, controls Alt content in molten steel and is greater than 0.050%, do not control for Als/Alt; VD operation, soft argon blowing time 5min; Continuous casting working procedure, M-EMS adopts electric current 400A, frequency 2.5Hz, adopts strong cold high pulling rate technique.

The major cause causing continuous casting to block the mouth of a river is Al in molten steel ₂o ₃inclusion is too high, or in casting process Al ₂o ₃further generation.

Summary of the invention

The present invention provides a kind of beating steel GCr15 production technique preventing continous casting sprue from blocking that can improve Cleanliness of Molten Steel, reduce non-metallic inclusion for solving in known technology the technical problem that exists.

The technical scheme that the present invention takes for the technical problem existed in solution known technology is:

A kind of beating steel GCr15 production technique preventing continous casting sprue from blocking, operational path comprises top and bottom combined blown converter → LF refining furnace → VD vacuum outgas → Comcast 6 machine 6 and flows billet continuous casting, it is characterized in that, described top and bottom combined blown converter adopts double slag dephosphorization, terminal highcasting speed [C] >=0.25%, and before tapping, finishing slag basicity is greater than 3.5, Tapping Temperature of Bof 1630 DEG C ~ 1650 DEG C, ladle temperature is higher than 800 DEG C, and strictly control converter slag, lower quantity of slag < 50mm is thick;

Described LF refining furnace refining time is greater than 50 minutes, control Als content > 0.05% in molten steel composition, Als/Alt > 95%, C:0.98 ~ 1.0%, Si:0.20 ~ 0.22%, Mn:0.34 ~ 0.36%, Cr:1.50 ~ 1.55%, P≤0.015%, S≤0.010%, Ti < 20ppm;

Adopt soft blow pattern in described VD vacuum outgas operation, soft blow argon 5 ~ 10min before VD departures, VD out-station temperature: open and water 1520 DEG C ± 3 DEG C, the first stove, connects and waters 1500 DEG C ± 3 DEG C, stove;

In described continuous casting working procedure, whole process carries out blowing argon, adopts the weak cold technique of low pulling rate, pulling rate 1.8m/min, cooling twice specific water 0.8L/kg;

M-EMS and end induction stirring is adopted in described continuous casting working procedure, described end induction stirring electric current 500A, frequency 12Hz, described M-EMS Current 350A, frequency 2Hz, during described M-EMS between mould liquid level undulated control ± 3%, do not comprise end points.

The advantage that the present invention has and positively effect are: the present invention is by the smelting of converter and LF refining furnace; control Als content > 0.05% in molten steel composition; Als/Alt > 95%; in continuous casting working procedure, whole process carries out blowing argon; avoid the secondary oxidation of molten steel; improve Cleanliness of Molten Steel; reduce non-metallic inclusion; continous casting sprue latch up phenomenon can be prevented; improve continuous casting billet quality; reduce strand cost, finally improve quality product.

Embodiment

For summary of the invention of the present invention, Characteristic can be understood further, hereby exemplify following examples, and coordinate accompanying drawing to be described in detail as follows:

The beating steel GCr15 production technique preventing continous casting sprue from blocking, operational path comprises top and bottom combined blown converter → LF refining furnace → VD vacuum outgas → Comcast 6 machine 6 and flows billet continuous casting, produce 6 stoves altogether.

(1) converter procedure

Converter adopts double slag dephosphorization, terminal highcasting speed [C] >=0.25%; Before tapping, require that finishing slag basicity is greater than 3.5, tapping temperature 1630 DEG C ~ 1650 DEG C, ladle temperature is higher than 800 DEG C, and strict control converter slag, lower quantity of slag < 50mm is thick.

Heat (batch) number	End point carbon [C] %	Tapping temperature DEG C	Finishing slag basicity
				3106738	0.25	1635	3.62
3106740	0.27	1633	3.81
				2107267	0.31	1637	3.73
2107269	0.28	1643	3.65
				3106747	0.29	1639	3.58
3106746	0.27	1641	3.70

(2) LF refining procedure

Refining adopts diffusive deoxidation, makes foaming white slag, notes arc-covering slag operation, and omnidistance control aluminium, requires Als > 0.050%, and refining cycle more than half forbidding feeds aluminium; Molten steel departures Als/Alt > 95%; Molten steel departures subject component: C:0.98 ~ 1.0%, Si:0.20 ~ 0.22%, Mn:0.34 ~ 0.36%, Cr:1.50 ~ 1.55%, P≤0.015%, S≤0.010%, Ti < 20ppm; Refining time is greater than 50 minutes, to promote inclusion floating, improves molten steel purity.

Heat (batch) number	3106738	3106740	2107267	2107269	3106747	3106746
							C％	0.99	0.99	0.98	1.00	0.99	0.99
Si％	0.22	0.22	0.21	0.22	0.20	0.22
							Mn％	0.35	0.35	0.34	0.35	0.35	0.35
Cr％	1.52	1.53	1.51	1.53	1.54	1.52
							P％	0.009	0.009	0.010	0.008	0.010	0.010
S％	0.003	0.005	0.003	0.006	0.004	0.005
							Ti(ppm)	1	0	0	0	1	0
Als％	0.071	0.053	0.06	0.062	0.059	0.064
							Als/Alt	98.3％	99.1％	100.0％	99.7％	95.8％	98.0％

(3) VD vacuum outgas operation

Keep 67Pa high vacuum time 15min, in order to promote inclusion floating, improving Molten Steel Cleanliness, increasing Al in molten steel ₂o ₃floatation Rate, adopt soft blow pattern, soft blow argon 5 ~ 10min before VD departures, VD out-station temperature: open and water 1520 DEG C ± 3 DEG C, the first stove, 1500 DEG C ± 3 DEG C, stove waters in company.

(4) continuous casting working procedure

For avoiding the secondary oxidation of molten steel, whole process carries out blowing argon, tundish superheating temperature 30 DEG C; Use M-EMS (electric current 350A, frequency 2Hz), end induction stirring (electric current 500A, frequency 12Hz), between mould liquid level undulated control ± 3%, do not comprise end points, to reduce the impact of foreign impurity; Adopt the weak cold technique of low pulling rate, pulling rate 1.8m/min, cooling twice specific water 0.8L/kg.

The present invention is by adopting above production technique, process modifications under the appointed conditions such as arc square billet continuous casting machine and perfect is flowed using 120t top and bottom combined blown converter, 120tLF refining furnace, 120t vacuum refining furnace, Comcast 6 machine 6, finally determine the new production technique of GCr15, prevent the nozzle clogging phenomenon of GCr15 steel grade in casting cycle, improve Cleanliness of Molten Steel, reduce non-metallic inclusion, continous casting sprue latch up phenomenon can be prevented, improve continuous casting billet quality, reduce strand cost, finally improve quality product.

Claims (1)

1. the beating steel GCr15 production technique preventing continous casting sprue from blocking, operational path comprises top and bottom combined blown converter → LF refining furnace → VD vacuum outgas → Comcast 6 machine 6 and flows billet continuous casting, it is characterized in that, described top and bottom combined blown converter adopts double slag dephosphorization, terminal highcasting speed [C] >=0.25%, and before tapping, finishing slag basicity is greater than 3.5, Tapping Temperature of Bof 1630 DEG C ~ 1650 DEG C, ladle temperature is higher than 800 DEG C, and strictly control converter slag, lower quantity of slag < 50mm is thick;

Described LF refining furnace refining time is greater than 50 minutes, control Als content > 0.05% in molten steel composition, Als/Alt > 95%, C:0.98 ~ 1.0%, Si:0.20 ~ 0.22%, Mn:0.34 ~ 0.36%, Cr:1.50 ~ 1.55%, P≤0.015%, S≤0.010%, Ti < 20ppm;

Adopt soft blow pattern in described VD vacuum outgas operation, soft blow argon 5 ~ 10min before VD departures, VD out-station temperature: open and water 1520 DEG C ± 3 DEG C, the first stove, connects and waters 1500 DEG C ± 3 DEG C, stove;

In described continuous casting working procedure, whole process carries out blowing argon, adopts the weak cold technique of low pulling rate, pulling rate 1.8m/min, cooling twice specific water 0.8L/kg;

M-EMS and end induction stirring is adopted in described continuous casting working procedure, described end induction stirring electric current 500A, frequency 12Hz, described M-EMS Current 350A, frequency 2Hz, during described M-EMS between mould liquid level undulated control ± 3%, do not comprise end points.