WO2014191783A1

WO2014191783A1 - Production process of ultra high purity microalloyed steel containing sulphure, affecting metallurgical resulphurization processes

Info

Publication number: WO2014191783A1
Application number: PCT/HU2014/000045
Authority: WO
Inventors: László KISS; Oszkár GREGA
Original assignee: Astra Mining Hungary Kft.
Priority date: 2013-05-27
Filing date: 2014-05-15
Publication date: 2014-12-04
Also published as: HUP1300336A2

Abstract

The invention is a process for the manufacturing of high purity, sulphur microalloyed steel. By the invention, following effective deoxidation the sulphur content of the steel is first reduced under S < 0.005 % then the sulphur quantity adequate to prescribed concentration is added to the pure steel by cored sulphur wire.

Description

PRODUCTION PROCESS OF ULTRA HIGH PURITY MICROALLOYED STEEL CONTAINING SULPHURE, AFFECTING METALLURGICAL RESULPHURIZA- TION PROCESSES

[001]

The technological process as defined in the invention is suitable for the production of high purity microalloyed steel containing sulphur with better machinability. With the new technological process first we produce an ultra-high purity (free from gas, inclusion and sulphur) liquid steel, and in this steel bath prepared as above the operations of resulphurization providing good cutting performance, which is further refined by laser melting on the surface, in order to obtain surface precision machining.

[002]

The widest range of application of quality and hardened steel is the engineering and automotive industry. Beyond the strict requirements of chemical composition and mechanical values, these kinds of steel should have good hardenability, resistance to fatigue and dynamic load, homogeneous material structure free of enrichment, fine-grained structure and high macro and micro inclusion purity.

[003]

In recent years, the processing industry requires the production of steels different from the traditional standard, matching more strict requirements, such as narrowing the Jominy band hardenability almost to a line, and the industrial solution of microalloying technology with sulphur and metallurgical technologies to improve castability.

[004]

As it is known, the special characteristic of traditional steels for automatic machining is the broken chip generation at cutting instead of continuous chip. Previously continuous chip was obtained by alloying the steel with lead. However, because of the harmfulness of lead for health and the environment, the lead alloy was replaced by sulphur alloy steel. [005]

As known, the sulphur content is an inevitable, generally harmful accompanying element of iron metallurgy products. But sulphur has a very favourable effect: thanks to the low melting point of MnS generated on crystal the cutting performance of steel becomes better, and through the sublimation property of sulphur supports the self-lubrication during usage of the manufactured product.

[006]

By recognizing the advantages of alloying later, this solution has been expanded to steels for semi-automatic machining, and subsequently to many other quality types of steel.

007}

The theoretical basis for the production of steel for automatic machining alloyed with sulphur has been developed, and the effect mechanism of single elements has been determined. On this basis, several recommended compositions have been elaborated and other requirements have been formulated, some of which are representative:

[008]

The patent specification no. US-4.719.079 mentions that with a sulphur content of S = 0,15-0,4% the following values are important: the distribution of MnS inclusions with an optimal value of 30pm²/mm², and the proportion of complex MnS compounds respect to total MnS, which is practically MnScompiex/MnS_totai≤ 20%.

[009]

The patent specification no. S-2004/0.223.867 besides the recommendation of a narrow range for sulphur content, namely S = 0.02-0.3% considers determining also the shape of MnS inclusions. Accordingly, their major axis could be 0.5 - 20.0 pm. At the same time, the acceptable proportion of MnS respect to total sulphide is max. 30%. [010]

The standard n. US-2007/0.044.867 has defined the favourable range of comparative proportion of Mn and S: Mn[%]*S[%] = 0,4-1 ,2, Mn[%]/S[%] > 3,0.

[011]

Patent specification no. US-4.784.828, besides the sulphur content of S = 0.1- 0.45% deals with the joint quantity of O and N. According to this solution, the joint value of O+N = 0,065% is favourable. The patent specification no. US- 2009/0.169.414 also considers important the presence of soluble N, and the C/Mn/N proportion. According to the instructions the sulphur content shall be in the range of S = 0.35-1.0% because a lower level of S does not improve the cutting performance, whilst the higher level of S impairs the hot workability. An O > 0.008% is necessary for the creation of MnO-MnS rounded complex inclusions forming tension concentrating cores, but above the level of O = 0.03% starts the CO formation.

[012]

Patent specification no. JP-5-345.951 defines the S content in S = 0,16-0,5%, because at least this level is needed to ensure machinability, but above this level the quantity of surface defects increases and the hardness and workability of steel decrease. The distribution of MnS inclusions may be in the range of 10- δΟμΐΓ^/ιτιηι², because above that level the quantity of surface defects increases. The free O content can be O = 00-300ppm, below this level the MnS grain size decreases, the machinability impairs, whilst above this level the oxide formation causing more surface and internal defects increases. Patent specification no. JP- 9-031.522 determines the range of free O content positively affecting the formation of sulphides more rigorously in 100-200ppm, favourably in 120- 180ppm. Patent specification no. JP-2005-023.342 reveals that the free O content shall be O > 0.008% while in the molten steel before casting this level shall be O = 0.004%. Finally, patent specification no. JP-2007-239.015 determines the proportion of O, S and Mn using another approach, accordingly O/S = 0.01-0.18, whilst Mn/(S+O) = 2.5-4.0. [013]

Based on the overview that is far from being complete it is clear that the various solutions consider important different factors for the production of good quality steel with relative higher sulphur content. The sulphur concentration for qualities defined by general standards is 0.025 - 0.035 %, whilst in special cases a 0.035 - 0.075 % value is required. In steels for automatic machining, magnitude higher sulphur content can also occur.

[014]

The sulphur is freely soluble in steel while it considerably does not dissolve in solid iron. In liquid steel FeS and MnS are present. The melting point of FeS is 1193 °C, whilst that of MnS is 1620 °C. The problem is caused by the fact that the FeS forms an eutectic with iron with a melting point of 988 °C. Since the FeS essentially does not dissolve in iron crystals, at cooling the FeS concentrates in the melt among the iron crystals. This melt will chill when temperature reaches the temperature of eutectic crystallisation and occurs in the form of so called intercrystalline sulphide net. Given that this net is extremely rigid it causes the steel to be fragile. In a non-deoxidized bath the problem is intensified by the presence of various oxide inclusions which form different complex oxisulphide inclusions with sulphides. The presence of these inclusions impairs the continuous casting, hot workability and ductility. It causes anisotropy, which decreases the persistency of steel and increases its cold break.

[015]

On the contrary, as it is evident based on the above patent specifications, the MnS forms rounded inclusions, which slightly affect the strength characteristic of steel, but in adequate quantity it is able to render the steel chips frangible.

[016]

At resulphurization no FeS but MnS will be created. Therefore the FeS content shall be reduced by desulphurization as much as technologically possible. Then, the sulphur content can be safely increased, in the extent exceeding general standards.

[017]

The resulphurization process applied for traditional steel production is performed directly in kettle at steel tapping when micro alloying the sulphur by adding 99% purity sulphur powder.

[018]

A serious disadvantage of the microalloying technology described above is the fact showed by also the above mentioned patent specifications, that these are not able to meet the very serious quality requirements provided by nuclear, pneumatic engineering and space technology, i.e. the steel purity of ∑0 < 12 ppm; S < 5 ppm. Thus, the direct or indirect dosage of sulphur powder in a not adequately clear steel bath, the melting loss, the environmental pollution that is approx. 50%, and the process has a moderate alloying precision.

[019]

The aim of the invention is to elaborate a sulphur microalloying method, which improves the cutting performance of high purity steel suitable for production meanwhile eliminating the above mentioned disadvantages.

[020]

According to the technology described in the invention, the aim is to ensure a composition of∑0 < 12 ppm and S < 5 ppm with an effective staged deoxidation (carbon before, after and under vacuum), and for the purpose to be able to perform the resulphurization of steel in pure steel with a recovery of sulphur of over 95%.

[021]

Another aim of the process is to reduce the quantity of inclusions worsening the castability of steel with a technology obtaining high purity of steel to the extent to fully replace the Ca-inclusion modification technology inevitably applied by all the other patents, beside the considerable improvement of the quality properties of steel.

[022]

According to the recognition leading to the invention we intend to produce the steel alloyed with sulphur as follows:

[023]

It is obliged to perform deoxidation and desulphurization operations before steel alloying, namely a very effective deoxidation and desulphurization shall be achieved. The values S < 0,005 % and ΣΟ <12 ppm shall be achieved in the steel bath, and the sulphur shall be realloyed in the perfectly deoxidated bath, and the sulphur can be added only subsequently, applying cored wire.

[024]

Finally, during the entire production process, including steel casting, a reoxidation protection shall be provided.

[025]

The cutting performance of steel provided by the technology defined in the invention can be further improved by introducing iron sulphide on the steel surface. The most favourable method of application is to lay a sulphide net on the surface of steel profiles and to melt the surface with laser.

[026]

Accordingly, the invention is suitable for the production of high purity microalloyed steel containing sulphur, during which following an effective deoxidation the sulphur content of steel is first reduced below S < 0.005 %, then the sulphur content adequate to the prescribed concentration will be added to the pure steel by sulphur cored wire. At one of the advantageous application methods of the process described in the invention, a melt shall be made in the steel manufacturing machine, in accordance with the chemical composition of steel and slag, the necessary metal alloying is performed during tapping with slag restraining, while subject to the carbon and active oxygen content, the liquid steel shall be pre-deoxidized with 0.7 - 1.1 kg/t Al and aluminate slag of a grain size of 2.0 - 2.5 kg/t, 10 mm.

[028]

Another advantageous application method of the process described in the invention is when in order to obtain an extra high purity, during the ladle metallurgical treatment referred to a steel ladle with a volumetric capacity of 80- 100 tons of steel, a clearing argon rinse with an intensity of 50 - 100 l/min or inductive mixing is performed.

[029]

At the third advantageous application method of the process described in the invention, during the ladle metallurgical treatment for the purpose of diffusion deoxidation a synthetic slag will be created by a CaO + AI2O3 + Al_meai mixture of proportion 88:19:1 and a pre-deoxidation with aggregation is performed.

[030]

The fourth advantageous application method of the process described in the invention is when during the ladle metallurgical treatment applying an aggregation and diffusion deoxidation by the dosage of Al-wire, the active oxygen level of steel is reduced below ~ 2 ppm and its sulphur content is reduced below 0.005%, and subject to the quality of steel to be produced an argon gas and/or inductive mixing and at a pressure lower than 3 torr, at least for 10 minutes under vacuum, carbon-deoxidation and gas elimination is performed.

[031]

The fifth advantageous application method of the process described in the invention is when the application of sulphur with a cored wire is performed right before issuing for casting, with a concentration adequate to the quality of steel. [032]

During the sixth advantageous application method of the process described in the invention after having performed the above mentioned resulphurization technology, a clogging or continuous casting is performed, and the melted steel is treated with protective tube, protective argon gas or casting powder.

[033]

At the seventh advantageous application method of the process described in the invention, after adding the sulphur content adequate to the prescribed concentration, the continuous casting is performed at an initial temperature 25°C higher than the liquidus temperature adequate to the composition of the produced steel, meanwhile the liquid steel is inducted in the crystal growth device in a closed system provided by protective tube, applying inductive mixing and casting powder.

[034]

The eighth advantageous application method of the process described in the invention is when the produced profiles are coated with a net made of steel wire with high sulphur content, and the surface is melted by laser.

[035]

Finally, the seventh advantageous application method of the process described in the invention is also when a net is applied with a gap width of 0.3 - 3 mm and a diagonal rate of 1.5 made of rhombus shaped gaps.

[036]

The process described in the invention can be learned in detail by a possible example. Understanding the examples is supported by the tables attached where:

Figure 1 shows the graph of severed (middle) band of Jominy hardenability provided for the quality 42 CrMoS4B,

Figure 2 shows the requirements listed in the supplementary booklet n.

MERCEDES DBL 4028 in relation to the aforementioned steel [037]

Example 1

The process defined in the invention can be known through the production of a tempered, premium quality, sulphur (and boron) microalloyed steel with a severed band of Jominy hardenability.

Quality requirements for steel:

Symbol of steel quality: 42DrMoS4BHH

Standard No. DIN EN 10083-1

Client's supplementary booklets aggravating quality requirements:

USA: EATON, MERITOR

GERMAN: HAY, ZF,

OTHER: DAIMLER-BENZ MERCEDES DBL 4028,

INA-Norm N011133,

MAN M 3418,

SCANNIA STD 4153

Purpose of application: Forging, jumping, stage prepared for inductive heating.

Further application, transmission devices of crafts? E.g. drive shaft of helicopter

(Further requirements are listed in Figure 1).

[038]

As mentioned above, the matter of microalloying with sulphur is to perform an effective deoxidation and desulphurization before alloying. The values S < 0,005 % and∑[O] <12 ppm shall be reached in the steel bath.

[039]

The process mentioned in the example is performed by the following technological method: UHP→Combined ladle metallurgy (heating + argon injection/evacuation + cored wire application) → Continuous (FA ) casting → Controlled re- cooling of semi-finished product.

[040]

In the primary phase, during the preparation of steel production, the carbonization material necessary for the production (calculated for 0,35% oxidation of carbon), the first rate of quicklime and the alloy metal FeMo calculated for the lower limit of prescription shall be added to the primary melting device, together with the waste charged into basket no I. Melted steel is made by argon agitation during melting.

[041]

At the end of melting the formation of milled slag is initiated with blowing in a mixture of argon + oxygen + coke-breeze through the door. In up-to-date UHP arc furnace this operation is performed with oxygen + coke-breeze blown through combined burners built in the lateral wall.

[042]

At the end of freshening process a steel and slag sample shall be tested in order to determine the chemical composition. We measure the active oxygen content and temperature of steel and then we adjust the prescribed temperature and final composition. Subject to the results, the liquid steel shall be pre-deoxidized with 0.7 - 1.1 kg/t Al and aluminate slag of a grain size of 2.0 - -2.5 kg/t, 10 mm.

[043]

The tapping is performed into a ladle suitable for lower argon treatment and evacuation, heated to a min. of 1000 °C. The tapping is performed with slag restraining. After a slag-free tapping a slag correction and staged deoxidation is applied.

[044] During the tapping the quantity calculated for the prescribed lower limit of FeCr, FeMnSi and/or FeMn, and other alloy material provided by the standard are added, and 1.1 kg/t of Al blocks of 8...16 kg/piece or 6...8 kg/piece Al cubes are applied for primary deoxidation, then on the clean steel surface a quantity of ~ 7 kg/t of CaO + AI2O3 (alumina) mixture of a "cherry" grain size is added.

[045]

In the secondary metallurgical phase the oxygen content of melted steel and slag is reduced by steel refining treatment with heat transfer. Steel treatment is performed in the heating unit by the following process. (The process scheme of the introduced technology subject to time and temperature is shown in table 1.)

[046]

In case the steel could not or only partially be tapped free of slag from primary melting device, after tapping the primary slag flooded into the ladle shall be eliminated and in the clear surface steel bath we perform eventually necessary carbonisation and correction alloying.

[047]

In order to restrain the reoxidation the new slag formation shall be started immediately by the dosage of fresh quicklime (CaO). The new slag is melted by starting arc heating and argon (+ inductive) mixing, than a slag reduction is performed for diffusion deoxidation, by forming a synthetic slag by the application of a CaO + AI₂O₃ + Almeai mixture of proportion 88: 19:1. This is followed by sample taking for the determination of slag composition, gas content and chemical characteristics.

048]

Then we measure the temperature, the active oxygen content of the steel bath and we initiate the deoxidation of the steel bath with aggregation and diffusion. For this latter purpose (coke-breeze + silicon powder) alumina + aluminium meal deoxidation materials are used. [049]

During the treatment the intensity of argon and/or inductive mixing is adjusted in a way that there will be no clean steel surface (the slag coverage shall be continuous). Applying deoxidation with aggregation and diffusion with the addition of Al wire, the oxygen level of steel is reduced below 2 ppm. The slag treatment shall be applied until the S content of the steel bath reaches the value of 0.005%.

[050]

Sample shall be taken in order to control the chemical composition and the active oxygen content of the steel shall be measured. Based on the result of the analysis, by adding the Al wire the final composition of Al = 0.02 - 0.04 % shall be adjusted.

051]

When all the analysis results are sufficient, a "soft argon rinse" for at least 15 minutes shall be performed, calculating for a steel ladle with a volumetric capacity of 80-100 tons of steel, with the intensity of 50 - 100 l/min for the adequate elimination of inclusions.

[052]

When based on the analysis results a correction alloy or post-deoxidation is to be performed, after adding the reducing substances the homogenization and inclusion eliminating operations shall be repeated that shall last for at least 15 minutes.

[053]

As a result of deoxidation and desulphurization operations a steel with very low sulphur content (S = max. 0.005 %) has been produced. As a result of diffusion deoxidation processes which take place in parallel with the desulphurization operations a premium quality steel with very low inclusion content has been produced, where the further reduction of inclusions is performed by synthetic slag treatment and argon rinse. [054]

As the consequence of the evacuation the [H], [N] content of the steel is reduced approx. by 30%, and as a result of carbon deoxidation using vacuum the total oxygen content of steel can be reduced to a very low value (max. 12 ppm). The time of evacuation is 10-15 minutes.

[055]

The evacuation shall be controlled in a way that the pressure should remain under 3 Hgmm for at least 10 minutes. During the evacuation the melted steel is mixed with argon (and/or inductive agitator) at a very low intensity with continuously monitoring the movement of the bath and the slag, its surface Waving shall not exceed the amplitude of 200 mm.

[056]

After evacuation a cleaning argon rinse shall be made for 5-8 minutes, and a microalloy corresponding to the specification for composition (Ti, B, Nb, V, Bi, etc.), and then - except the quality of tool and ball bearing inclusion modification is applied by adding Ca cored wire. Then the cleaning rinse with argon is repeated.

[057]

In this manner high purity steel (ao≤ 2 ppm; [H] < 1.0 ppm; finishing slag FeO < 1.0 %) can be produced.

[058]

After the end of evacuation a sample shall be taken for the analysis of steel, slag, active oxygen and hydrogen, and temperature is controlled. The technological operations of resulphurization, i.e. the adjustment of sulphur content conform to requirements shall be initiated only if the results are sufficient and the technological parameters are reached. During the operations of resulphurization the quantity of sulphur adequate to the specified concentration is alloyed with the addition of cored wire. [059]

The steels produced with the resulphurization technology are manufactured in a closed system, applying magnetic agitator, through casting provided by protection against reoxidation, providing the following completions:

- protection between the casting ladle and the intermediate ladle with ceramic shield tube,

- protection between the intermediate ladle and the crystallizator with ceramic immersion tube,

- protection of the steel positioned in the intermediate ladle with dry, special covering powder against reoxidation,

- protection of the steel positioned in the crystallizator with dry, special casting powder against reoxidation.

[060]

The casting in closed system is performed on a way that initial temperature of the steel casting is 25 °C higher than the liquidus temperature adequate to the composition of the manufactured steel, casting powder application shall be continuous and shall completely cover the surface of the steel mirror.

[061]

On the dose offered to continuous casting device a soft argon rinse is performed through porous brick built into the steel ladle.

[062]

The dry casting powder prescribed for cast quality is applied continuously to the surface of the steel in the mould. In case of manual application care shall be taken with sprinkled casting powder so that it shall reach the space around the immersion tube and corners of the mould, also paying attention to the surface of the casting powder to always stay black. When it starts to glow, subsequent casting powder dose is immediately applied. Casting powder is always selected for the given quality, instead of the common "powder grain sized" casting powder we apply "meal grain sized" powder as its quality is more adequate. [063]

Adjustment of casting parameters (depending on section size: casting speed, magnetic mixing intensity, secondary cooling, etc.) is determined according to local circumstances. To avoid the pressure flakes of casted billets during cooling down a re-cooling with directed temperature shall be performed.

[064]

The inspection, qualification of the re-cooled billets consists of the followings:

- macro and micro level laboratory examination of cut discs,

- preparing Baumann (silver-sulphur) print,

- controlling the surface and profile deviation of the billet.

The conformity of the qualified billets is verified by Expert's Quality Certification.

[065]

In case of usage in nuclear, engineering and automotive industry and also at bearing steels the gas elimination is performed in all cases in evacuator device because of strict quality requirements. In case of general quality steels the preparation of the steel is performed by injecting argon gas and/or inductive treatment instead of evacuation.

[066]

Example 2. [067]

The procedure according to the invention can be also performed on the following technological route.

UHP→ Combined ladle metallurgy (heating + argon injection + cored wire treatment) → Continuous (FAM)→ Controlled semi-finished product re- cooling

[068] It is clear that there is a difference only at the ladle metallurgy (secondary) phase where the improvement in inclusion clarity of the steel is solved with argon gas rinsing or by argon + magnetic mixing instead of evacuation. The termination of ladle metallurgy process in case of the application of argon (+ magnetic) mixing - subject to time and temperature - is shown on Figure 2. Figure 2 - that relates to the manufacturing of a boron alloyed insert hardened steel quality - can be understood compared to Figure 1 without detailed explanation.

[069]

Certainly, primary phase can also be performed in devices different from UHP furnace (e.g. LD converter) if this meets the requirements regarding the composition of steel produced at tapping.

[070]

If not continuous but clog casting is performed, the moulds are placed on corrugated cardboard and a ceramic-magnetic plate with the clog serial number is placed on the inner wall of the moulds. During casting a heat resistant stocking reoxidative protection with argon ring is applied between the casting ladle and the shell. After the casting of a clog in case of upper casting or a "star" in lower casting samples are taken for chemical composition with paper probe or vacuum pipette method.

[071]

The casted clogs after their chilling are removed from the mould and to avoid tension ruptures are placed to the heating furnace of the rolling mill warmed to 800 - 850 °C. If it is not possible we leave the clogs to cool down in the mould.

[072]

In cases when only the surface of the steel profile needs to be machined by cutting or eventually in case of small parts the cutting performance of steel profiles manufactured from steel made by the previous method can be improved as follows. [073]

A net made of steel wire of high iron-sulphide content is laid on the surface of the steel profile. The iron-sulphide net has a gap width of 0.3 - 3 mm and is made with rhomboid holes with a diagonal rate of 1.5. The surface of steel profile covered on this way is then melted so that the net will melt into the surface of the steel profile. The rhomboid surface segments inside the net will become easy to cut while the solidity of the whole surface is held. Following the direction given by the shorter diagonals of the rhomboids of the net cutting will be easier while vertically to that direction the elasticity of the surface is only slightly decreased.

[074]

As it is foreseeable by the introduction the application of the technology can involve the manufacturing of all kinds of quality and hardened steel where extremely high cleanliness, cored wire micro alloying technology and resulphurization and good castability are the primary tasks.

[075]

Quality characteristics of the manufactured steel products (stability, yield point, impact, hardenability, inclusion content, etc.) beside related standards are providing the more strict requirements (narrowed chemical composition and/or narrowed Jominy region, total oxygen content of max. 12 ppm, hydrogen content of max. 0.2 ppm, etc.) requested by the clients.

[076]

By using a net made of high iron-sulphide content wire the sulphur content of the surface can be further increased so that it improves the cutting performance of the surface but does not influence the stability of the entire surface.

Claims

C l a i m s :

1. ) Process for the manufacturing of high purity, sulphur microalloyed steel with the characteristics that following effective deoxidation the sulphur content of the steel is first reduced under S < 0.005 % then the sulphur quantity adequate to prescribed concentration is added to the pure steel by cored sulphur wire.

2. ) Procedure according to Requirement Point 1 with the characteristics that a melt is produced in a primary steel manufacturing device, then during tapping with slag restraining the necessary metal alloying is performed in accordance with the chemical composition of the steel and the slag, while - subject to carbon and active oxygen content - the liquid steel is pre-deoxidated with 0,7 - 1, 1 kg/t Al metal and 2,0 - 2,5 kg/t of aluminate slag of 10 mm grain size.

3. ) The procedure according to Requirement Point 1 or 2 with the characteristics that in order to reach high purity during ladle metallurgical treatment an argon cleaning rinse or inductive mixing is performed with 50 - 100 l/min intensity referred to a steel ladle receiving 80 - 100 tonnes of steel.

4. ) The procedure according to any of the Requirement Points 1-3 with the characteristics that for the purpose of diffusion deoxidation a synthetic slag is produced with a 19:1 rate mixture of CaO + AI2O3 + Al_meai an aggregation pre- deoxidation is performed.

5. ) The procedure according to any of the Requirement Points 1-4 with the characteristics that by using aggregation and diffusion deoxidation during ladle metallurgical treatment the active oxygen level of the steel is decreased to below ~ 2 ppm and its sulphur content to below 0.007% and - subject to the steel quality to be manufactured - argon gas and/or induction mixing and/or vacuum gas elimination under a pressure of 3 torr for a min. of 10 minutes. the protection of ceramic protection tube, argon protection gas and casting powder.

8. ) The procedure according to any of the Requirement Points 1-7 with the characteristics that following the introduction of the sulphur quantity adequate to the prescribed concentration a continuous casting is performed with an initial temperature 25°C higher than the liquidus temperature according to the composition of manufactured steel, when the liquid steel is taken to the crystallizator in a closed system with protective tube, applying induction mixing and casting powder.

9. ) The procedure .according to any of the Requirement Points 1-8 with the char- acteristics that the profiles produced are covered with a net made of high iron- sulphide content and the surface is melted by laser.

10. ) The procedure according to any of the Requirement Points 1-9 with the characteristics that a net with a gap width of 0.3 - 3 mm made with rhomboid holes with a diagonal rate of 1.5 is used. This increases the cutting performance of the material to one direction while its stability will not differ significantly in vertical direction.