CN103146882A - Method for controlling class B inclusions of steel rail for high-speed railway - Google Patents

Abstract

The invention relates to the technical field of steel-making, in particular to a method for controlling class B inclusions of a steel rail for high-speed railway. The method is characterized by being started with changing alloy adding variety after converter steel tapping, post-furnace deoxidization system, LF (Ladle Furnace) furnace refining slagging system and VD (Vacuum Degassing) vacuum treatment and by comprising the following steps of: (1) adding SiCaBa powder after converter steel tapping and reducing oxygen content in furnace slag; (2) controlling the addition quantity of a SiCaBa powder desoxidant under the condition guaranteeing total oxygen in steel; (3) adding lime and bauxite and employing a secondary slag practice; and (4) adding a magnesian covering agent for covering tank at the argon blowing point after vacuum breaking of VD furnace. Compared with the prior art, the method provided by the invention has the advantages that the grade of the class B inclusions in liquid steel is reduced below 0.5, steel modification due to unaccepted total aluminum is avoided, and the total aluminum content in steel is lower than the standard by 0.0010%; therefore, the heavy rail tempering rate is improved and huge economic benefit is created for steel and iron enterprises.

Description

A kind of control rail for high-speed railway category-B inclusion method

Technical field

The present invention relates to steelmaking technical field, relate in particular to a kind of method of controlling rail for high-speed railway category-B inclusion.

Background technology

At present along with the development of railway of passengers' private line, to the high speed heavy rail steel, particularly 350, the Properties of Heavy Rail Steel By demand of 380km/h is more and more higher, but the requirement of steel has also been improved, be mainly the requirement of Cleanliness of Molten Steel." rail for high-speed railway " TB/T 3276～2011 that the Ministry of Railways newly issues, the category-B inclusion of regulation 250km/h and above Rail for railway requires≤1.0 grades.

It is mainly to take without the aluminium explained hereafter using on starting material that traditional technology adopts, but owing to all containing certain residual aluminium in alloy, starting material, and the residual aluminium of this part enters into molten steel fully and can't get rid of, and forms Al ₂O ₃Inclusion, cause category-B inclusion (aluminum oxide) increase in Properties of Heavy Rail Steel By, when category-B inclusion content in the high speed heavy rail steel is above standard upper limit requirement, can only be forced to make into other low rail kinds that requires, both affect the normal production program, increased again production cost.

Summary of the invention

The purpose of this invention is to provide a kind of method of controlling rail for high-speed railway category-B inclusion, by taking alloy after converter tapping to add the change of deoxidation system and refining slagging regime after kind, stove, and the top slag is processed, realize the production of low basicity slag, improve Cleanliness of Molten Steel.

For solving the problems of the technologies described above, technical scheme of the present invention is:

A kind of method of controlling rail for high-speed railway category-B inclusion adds deoxidation system after kind, stove, LF stove refining slagging regime and VD vacuum-treat to start with from changing alloy after converter tapping, and its concrete operation step is as follows:

1) add the SiCaBa powder of 0.5～0.7kg/ ton steel after converter tapping, reduce oxygen level in slag, when the lower slag of steel-making, every tank adds the SiCaBa powder of 1.0～1.4kg/ ton steel again, in slag, target oxygen content is 18～22%, adopts simultaneously to add the Si-Ca-Ba iron of 2～3kg/ ton steel to carry out deoxidation of molten steel;

2) the LF stove is processed early stage, adds the SiCaBa powder of 0.7～0.8kg/ ton steel before heating, is guaranteeing under the entire oxygen content in the steel condition, controls SiCaBa powder add-on and is not more than 1.0kg/ ton steel, requires the LF treatment time to be not less than 28min;

3) add fritting synthetic slag 1.5～1.8kg/ ton steel before the heating of LF stove, cancelling fluorite adds, the lime and 0.4～0.5kg/ ton steel and the bauxitic clay that add 1.5～2.0kg/ ton steel, lime and bauxitic clay add-on ratio are (3.5～4.0): 1, adopt the secondary slag practice;

4) the VD vacuum between hold period argon pressure be not less than 0.15Mpa, pressurize total time is no less than 18min, argon flow amount 300～500NL/min, adopt the operation of 180～220NL/min low discharge argon gas after between hold period in 3～5min time, require the Argon effect to guarantee that liquid level stirs diameter and is not less than 150～200mm, add the magnesia insulating covering agent lid of 1.0～1.2kg/ ton tank at the Argon point after broken sky, to promote Al in steel ₂O ₃Inclusion floating.

Compared with prior art, the invention has the beneficial effects as follows: B in molten type impurity grade is reduced to below 0.5 grade, stopped to occur because full aluminium does not conform to the situation that changes steel, and in steel Holo-Al content than standard low 0.0010%, improve heavy rail and be smelt rate, can create huge economic benefit for iron and steel enterprise.

Embodiment

The invention will be further described below in conjunction with embodiment:

A kind of method of controlling rail for high-speed railway category-B inclusion of the present invention for the production requirement of used for high-speed railway rail steel and generation category-B inclusion reason, reduces Al in molten steel ₂O ₃Content specifically adds deoxidation system after kind, stove, LF stove refining slagging regime and VD vacuum-treat to start with from changing alloy after converter tapping, and its concrete operation step is as follows:

1) adopt the mode of complex deoxidization after Converter, the SiCaBa powder that adds 0.5～0.7kg/ ton steel after converter tapping, reduce oxygen level in slag, when the lower slag of steel-making, every tank adds the SiCaBa powder of 1.0～1.4kg/ ton steel again, in slag, target oxygen content is 18～22%, adopts simultaneously to add the Si-Ca-Ba iron of 2～3kg/ ton steel to carry out deoxidation of molten steel;

2) the LF stove is processed early stage, the SiCaBa powder that adds 0.7～0.8kg/ ton steel before the every tank heating of LF stove, guaranteeing under the entire oxygen content in the steel condition, the add-on of controlling the SiCaBa powder is not more than 1.0kg/ ton steel, require the LF treatment time to be not less than 28min, to guarantee that the inclusion in molten steel fully floats, and forbids adopting aluminium matter reductor;

3) add fritting synthetic slag 1.5～1.8kg/ ton steel before the heating of LF stove, slagging speed is fast, guarantees the submerged arc effect, cancels fluorite and adds, unstable the causing slag of quality of stopping fluorite is bad, add the lime of 1.5～2.0kg/ ton steel and the bauxitic clay of 0.4～0.5kg/ ton steel, lime and bauxitic clay add-on ratio are (3.5～4.0): 1, adopt the secondary slag practice, guarantee under the condition of adjusting component, control the add-on of lime, namely reduced basicity of slag, to suppress Al in slag ₂O ₃Be dissolved in steel, and reach thus the purpose that reduces Holo-Al content in steel; For preventing secondary oxidation of steel, transfer the once success of the compositions such as C, Si, Mn, avoid repeatedly large argon gas to stir;

4) the VD vacuum between hold period argon pressure be not less than 0.15Mpa, pressurize total time is no less than 18min, argon flow amount 300～500NL/min, adopt the operation of 180～220NL/min low discharge argon gas after between hold period in 3～5min time, require the Argon effect to guarantee that liquid level stirs diameter and is not less than 150～200mm, add the magnesia insulating covering agent lid of 1.0～1.2kg/ ton tank at the Argon point after broken sky, to promote Al in steel ₂O ₃Inclusion floating.

The LF furnace refining slag is that final composition dreamboat scope sees the following form 1.

Table 1

FeO

CaO

SiO 2

MgO

MnO

Al 2O 3

R

≤1.1

48～52

16～20

4～5%

0.1～0.3%

12～16%

2.6～3.0

In addition, it is also to be noted that in production, before the high speed heavy rail steel is produced, should select the alloy of low residual aluminium content, reduce the aluminium content that alloy is brought into; Because containing aluminum steel, production cause aluminium content in steel to exceed the phenomenon of standard-required in order to reduce tank on large tank time in addition, according to practical situation, require that large tank is preferential selects upper tank not contain aluminium pot, take second place and select low aluminum steel, low canister, regulation high-aluminum steel and advance vacuum and contain aluminium pot and do not allow to use on the high speed heavy rail steel.

Claims (1)

1. a method of controlling rail for high-speed railway category-B inclusion, is characterized in that, adds deoxidation system after kind, stove, LF stove refining slagging regime and VD vacuum-treat to start with from changing alloy after converter tapping, and its concrete operation step is as follows:

1) add the SiCaBa powder of 0.5～0.7kg/ ton steel after converter tapping, reduce oxygen level in slag, when the lower slag of steel-making, every tank adds the SiCaBa powder of 1.0～1.4kg/ ton steel again, in slag, target oxygen content is 18～22%, adopts simultaneously to add the Si-Ca-Ba iron of 2～3kg/ ton steel to carry out deoxidation of molten steel;

2) the LF stove is processed early stage, adds the SiCaBa powder of 0.7～0.8kg/ ton steel before heating, is guaranteeing under the entire oxygen content in the steel condition, controls SiCaBa powder add-on and is not more than 1.0kg/ ton steel, requires the LF treatment time to be not less than 28min;

3) add fritting synthetic slag 1.5～1.8kg/ ton steel before the heating of LF stove, cancelling fluorite adds, the lime and 0.4～0.5kg/ ton steel and the bauxitic clay that add 1.5～2.0kg/ ton steel, lime and bauxitic clay add-on ratio are (3.5～4.0): 1, adopt the secondary slag practice;

4) the VD vacuum between hold period argon pressure be not less than 0.15Mpa, pressurize total time is no less than 18min, argon flow amount 300～500NL/min, adopt the operation of 180～220NL/min low discharge argon gas after between hold period in 3～5min time, require the Argon effect to guarantee that liquid level stirs diameter and is not less than 150～200mm, add the magnesia insulating covering agent lid of 1.0～1.2kg/ ton tank at the Argon point after broken sky, to promote Al in steel ₂O ₃Inclusion floating.