KR20090113280A - Steel material for heat cutting using oxygen - Google Patents

Abstract

A steel material which has been rid of surface scale and which contains Si: 0.08 to 0.20%, Al: more than 0.03% to 0.08%, and one or more of P, Ti and V and satisfies the relationships: [Al/Si<=0.45] and [262×(Al/Si)+197×(P/Si)+225×(Ti/Si) +50×(V/Si)>123] wherein each symbol of element represents the content of the element. The steel material permits high-speed stable thermal cutting and is usable as the material for laser beam cutting, plasma arc cutting, and gas cutting. The steel material may have an inorganic zinc primer coat on the surface.

Description

Steel cutting material using oxygen {STEEL MATERIAL FOR HEAT CUTTING USING OXYGEN}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel material for thermal cutting using oxygen, and more particularly to a steel material for thermal cutting using deoxygenated surface that can be cut at high speed with a laser, plasma, gas or the like. In particular, the so-called "Zink primer", which is a primary waterproofing coating containing zinc powder, and even an inorganic zinc primer, even when coated with an inorganic zinc primer, also relates to a steel for thermal cutting using oxygen capable of high-speed cutting with a laser, plasma, or gas. will be.

In recent years, the technological progress of the laser cutting machine is remarkable, and the laser cutting machine can be applied not only to the thin plate with the plate thickness of 3.2 mm or less, but also to the cutting of the thick plate up to 30 mm, and the laser cutting machine is spreading also for cutting the thick plate. .

The laser cutting machine has an advantage that cannot be seen in a gas cutting machine because there are few safety problems and the unmanned driving at night is possible.

In addition, in order to perform the night-time unattended operation by a laser cutting machine, it is preferable to set it as the operation using large steel materials (Hereinafter, steel materials may be represented by a "steel plate.") So that sufficient work can be ensured. .

However, in the case of unattended operation at night, when there is no worker who handles the trouble when the cutting trouble occurs, there is a problem that the trouble is left unattended or the trouble product is mass produced. Among these troubles, the larger ones are said to be cut off and the smaller ones are to be distorted.However, in particular, the disturbances of the cutting planes may be a factor that impairs the product value of the product. This will adversely affect the next process, for example welding. For this reason, an increase in cost is caused to correct the cut surface, and in some cases, scrap processing may be required as a defective product, which cannot be overlooked.

The trouble is largely divided into two types, ones having a cause on the cutter side and ones having a cause on the steel plate side.

Various causes are considered in the trouble which causes the cutter side, and there exist a defect by the change of the laser output by voltage fluctuations at night, and the vibration of a cutter, the small wave of a large steel plate, a wound, etc., for example. Various studies have been made to solve such a trouble factor, but it is impossible to solve completely.

For this reason, even in recent years, even if the problem of the laser output fluctuation | variation and vibration generate | occur | produced to the cutter side a large amount of margins to the fluctuation | variation of cutting conditions is large, and the big steel plate which enables unattended operation at night is requested | required, It is required to be of high quality throughout.

In addition, it is pointed out that the influence of the surface property of a steel plate is large in laser cutting property conventionally. In particular, laser cutting of steel sheets coated with zinc primer containing zinc powder has been known to have various problems. Among them, a particularly big problem is that if the cutting speed is increased, scratches or dross sticks easily on the cut surface, so that the cutting speed cannot be increased, workability is lowered, and the cutting work is interrupted due to cutting failure. In particular, if the cutting operation is interrupted during the night unattended operation, it has a great influence on the post-process, and the productivity is remarkably lowered. Moreover, not only can a cutting speed not be raised, there is a limit also to the plate | board thickness which can be cut | disconnected by laser cutting, and the steel plate with too large plate | board thickness may not be able to cut | disconnect.

Regarding the improvement of the laser cutting speed, the examination by the improvement of the primer of the surface mainly mainly has been performed conventionally.

For example, Patent Document 1 discloses a "laser cutting steel" in which the amount of Zn and SiO ₂ (silica) in the zinc primer coated on the steel is limited, and in particular, the amount of SiO ₂ is extremely reduced to improve the laser cutting property. Is disclosed. In Patent Document 1, SiO ₂ is a component contained in the primer from the viewpoint of improving the fire resistance and strength of the primer layer, but since SiO ₂ is stabilized to a high temperature, it prevents the conduction of laser energy to the steel sheet, and thus the cutting speed. It has been described that the adverse effect on the e is very large.

In addition, Patent Document 2 discloses a "primary laser cutting property" containing a silicate condensate, zinc powder, and pigments having a lower melting point than iron such as talc, mica, red oxide, ferro alloy, and fluorite. Antirust coating composition "(primer) is disclosed.

In addition, Patent Document 3 discloses a "steel plate pretreatment method" formed by coating a composition containing a silicon-based inorganic binder and a fine zinc powder having an average particle diameter of 5 µm or less as a main component.

On the other hand, technological progress is remarkable also in plasma cutting, and a rapid improvement in the quality and cutting ratio of the cutting surface is seen. In addition, the plasma cutting machine has an advantage that does not require the maintenance of the laser cutting machine. However, in plasma cutting, there is a problem that the life of the consumable used for the cutting machine is short, and in particular, when cutting the thick steel plate, it is necessary to generate plasma at a high output, so that the life of the consumable becomes extremely short. Therefore, when performing plasma cutting, it is required to cut at high speed without largely increasing an output.

Patent Document 4 discloses a "steel sheet excellent in meltability" which is very suitable for applying thermal cutting methods such as laser cutting and plasma cutting.

[Patent Document 1: Japanese Patent Application Laid-Open No. 10-226846]

[Patent Document 2: Japanese Patent Application Laid-Open No. 2002-114944]

[Patent Document 3: Japanese Patent Application Laid-Open No. 2001-295071]

[Patent Document 4: Japanese Patent Application Laid-Open No. 11-199984]

The primers proposed in the above-mentioned patent document 1 and the coating composition proposed in the patent document 2 are also insufficient in laser cutting using a recent high-power laser cutting machine, and cutting or fast cutting of thick steel sheets larger than 16 mm Cannot cope with enough. Moreover, since the countermeasure against the generation | occurrence | production of a cutting | disconnection defect is not considered, interruption | disconnection will become easy to generate | occur | produce especially in unattended operation at night.

In addition, in the case of the technique proposed in Patent Literature 1, the amount of SiO ₂ in the paint is significantly reduced, and in the case of the technique proposed in Patent Literature 2, the coating does not contain SiO ₂ at all. For this reason, it is difficult to avoid insufficient fire resistance and strength of a coating film. When the intensity | strength fall of a coating film has arisen, since peeling of a coating film and a damage | wound may occur easily, it also leads to deterioration of rust prevention property.

In Patent Document 3, although the meltability by laser cutting is evaluated about the steel plate processed by the above-mentioned method, the test is considered to have been performed by adjusting (ie, optimizing) the focus of the laser. The evaluation was not considered. The laser cutting test (melt test) is performed at a speed of 1 m / min (1000 mm / min), and the laser cutting property at a higher speed than that is not evaluated.

Although patent document 4 has description regarding plasma cutting, a plasma cutting test is performed at the speed of 0.1 m / min, and it cannot endure practically at this speed.

Accordingly, an object of the present invention is to provide a steel cutting steel that uses oxygen capable of cutting steel at high speed, and in particular, it is difficult to cause cutting trouble even when a laser cutting machine as a thermal cutting machine is used for unattended operation at night, In particular, the present invention provides a laser cutting steel material capable of remarkably improving the laser cutting property of a coated steel material and further preventing the occurrence of cutting interruption when an unattended operation is performed by a large power laser cutting machine at night.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, the inventors performed various irradiation about the laser cutting property of steel materials using the laser cutter of a large output for the first time. As a result, the knowledge of the following (a) and (b) was obtained first.

(a) Cutting defects seen in cutting operations of high-power laser cutters of steels with conventional scales and steels coated with zinc primers, especially steels coated with inorganic zinc primers, especially at night, unmanned automatic The major cause of interruption of cutting at the time of operation is the so-called "focal misalignment" in which the position of the steel fluctuates with respect to the laser focus due to the wavy state of the steel or the wound. Therefore, when the descaled steel and the coated steel are insensitive to laser defocus, in other words, when the fluctuation range from the laser cut position to the steel is large, the cutting speed can be increased stably. Moreover, cutting is also possible in the case of a steel plate with a large thickness.

(b) The laser cutting property of the steel is closely related to the process point of Fe ₂ SiO ₄ (firelight) generated by oxidation of the steel during laser cutting. Then, when the process point of Fe ₂ SiO ₄ is lowered, Fe (or iron oxide) melted at the time of cutting is easily discharged from the cut portion, so that laser cutting property is improved.

So then, Fe ₂ performs a review of the technique make the eutectic point of the SiO _4, as a result, to (c) ~ obtain a knowledge of the (f).

(c) As an element that lowers the process point of Fe ₂ SiO ₄ , the effects of Al, P, Ti, and V are large.

(d) Only by including Al, P, Ti, and V in the steel will change the mechanical properties and weldability of the steel, but the content of Al, P, Ti, and V in terms of the Si content in the steel When appropriate, the laser cutting speed of the steel which has been descaled and the steel coated with the zinc primer, especially the steel coated with the inorganic zinc primer can be significantly improved, without adversely affecting the performance of the steel. .

(e) In order to raise the laser cutting speed, when the heat input of cutting is increased, so-called "burning" phenomenon, which is a defect due to abnormal combustion, occurs and cannot be cut, but Al, P, Ti in a ratio with the Si content of the above (d) And in the case of the steel material which optimized the content of V, the burning phenomenon hardly occurs, and therefore it is possible to cut at an extremely high speed.

(f) In addition, in the case of the steel material in which the Al, P, Ti, and V content is optimized in the ratio with the Si content described above, the variation range from the laser focus position that can be cut is increased, and the insensitivity to the focus shift in the cutting process is insensitive. As a result, the cutting failure due to the positional change of the steel and the interruption of cutting during automatic night operation can be easily prevented.

The present inventors also conducted an examination focusing on the surface of the steel material to which the laser first arrives. As a result, the following knowledge (g) was obtained.

(g) The surface properties of the steel affect the laser cutting properties. When the surface roughness is small, the reflection of the laser light becomes remarkable, and energy is not sufficiently transmitted to the steel material surface, and the cutting property is lowered. Moreover, when apply | coating a zinc primer, since sufficient adhesive durability of a coating film cannot be obtained, it is not preferable. On the other hand, when the surface roughness is large, the laser is diffusely reflected on the surface of the steel material, and the laser cutting property is lowered.

Based on the above investigation regarding the laser cutting property, the present inventors considered application to a thermal cutting method other than laser cutting next. As a result, the following (h) knowledge was obtained.

(h) The knowledge obtained by irradiation of laser cutting property can be applied to thermal cutting other than laser cutting, specifically, cutting such as plasma cutting and gas cutting. However, in cutting | disconnection, in order to improve cutting property by controlling the oxide produced | generated during cutting | disconnection, it is necessary to use oxygen.

This invention is completed based on said knowledge, The summary is the steel material for thermal cutting which uses oxygen shown to following (1)-(8), and the steel material for laser cutting shown to (9)-(16). Is in.

(1) The steel which has been descaled from the surface, containing at least one of P, Ti, and V, in mass%, containing more than 0.08% and more than Si: 0.08 to 0.20% and Al: 0.03%, In addition, the steel for thermal cutting using oxygen characterized by satisfying the following formulas (1) and (2).

Al / Si ≦ 0.45... … (One)

262 x (Al / Si) + 197 x (P / Si) + 225 x (Ti / Si) + 50 x (V / Si)> 123. … (2)

In addition, the element symbol in Formula (1) and Formula (2) shows content in the mass% of the element.

(2) A steel material for thermal cutting using oxygen according to (1), wherein an inorganic zinc primer is applied to the surface.

(3) The steel material for thermal cutting using oxygen as described in said (1) or (2) characterized by surface roughness of 15-85 micrometers in ten-point average roughness RzJIS.

(4) In mass%, C: 0.02 to 0.17%, Si: 0.08 to 0.20%, Mn: 0.20 to 1.60%, Cu: less than 0.03%, Ni: 0.05% or less, S: 0.015% or less, Al: 0.03% Steel containing 0.08% or less and N: 0.009% or less and containing at least one of P: 0.04% or less, Ti: 0.08% or less, and V: 0.08% or less, with the balance being Fe and impurities The steel material for thermal cutting which uses the oxygen in any one of said (1)-(2) which has a composition.

(5) The steel for thermal cutting using oxygen as described in said (4) characterized by further containing Cr: 0.2% or less by mass%.

(6) Heat using oxygen as described in said (4) or (5) which further contains at least 1 sort (s) of Mo: 0.4% or less, W: 0.4% or less, and Nb: 0.04% or less by mass%. Steel for cutting.

(7) The steel for thermal cutting using oxygen as described in any one of said (4)-(6) characterized by further containing B: 0.003% or less by mass%.

(8) The mass% further contains at least one of Ca: 0.005% or less, Mg: 0.005% or less and REM: 0.005% or less, according to any one of (4) to (7) above. Steel for thermal cutting using oxygen.

(9) Descaled steel material, which contains at least one of P, Ti, and V, in mass%, exceeding Si: 0.08 to 0.20% and Al: 0.03% and not more than 0.08%, In addition, the steel materials for laser cutting, characterized by satisfying the following formulas (1) and (2).

Al / Si ≦ 0.45... … (One)

262 x (Al / Si) + 197 x (P / Si) + 225 x (Ti / Si) + 50 x (V / Si)> 123. … (2)

In addition, the element symbol in Formula (1) and Formula (2) shows content in the mass% of the element.

(10) The steel material for laser cutting according to (9), wherein an inorganic zinc primer is applied to the surface.

(11) The steel material for laser cutting according to (9) or (10), wherein the surface roughness is 15 to 85 µm in ten point average roughness RzJIS.

(12) At mass%, C: 0.02 to 0.17%, Si: 0.08 to 0.20%, Mn: 0.20 to 1.60%, Cu: less than 0.03%, Ni: 0.05% or less, S: 0.015% or less, Al: 0.03% Steel containing more than 0.08% and less than N: 0.009% and containing at least one of P: 0.04% or less, Ti: 0.08% or less and V: 0.08% or less, with the balance being Fe and impurities The steel material for laser cutting as described in any one of said (9)-(11) which has a composition.

(13) The steel material for laser cutting according to the above (12), further containing Cr: 0.2% or less by mass%.

(14) The steel material for laser cutting according to (12) or (13), further comprising at least one of Mo: 0.4% or less, W: 0.4% or less, and Nb: 0.04% or less by mass%. .

(15) The steel material for laser cutting according to any one of the above (12) to (14), further containing B: 0.003% or less by mass%.

(16) The mass% further contains at least one of Ca: 0.005% or less, Mg: 0.005% or less and REM: 0.005% or less, according to any one of (12) to (15) above. Steel for laser cutting.

In addition, "REM" is a general term of 17 elements in total of Sc, Y, and a lanthanoid, and content of REM points out the total content of 1 type, or 2 or more types of elements in REM.

Hereinafter, invention which concerns on the steel material for thermal cutting which uses oxygen shown to said (1)-(8), and the steel material for laser cutting shown to (9)-(16), respectively is "this invention (1)"-" This invention (16) "is called. In addition, it may collectively be called "this invention."

(Effects of the Invention)

The thermal cutting steel using oxygen of the present invention (that is, the steel containing oxygen as an assist gas, in other words, the thermal cutting steel using an oxidation reaction) can perform stable thermal cutting at a high speed, and can perform laser cutting and plasma. It can be used for cutting and gas cutting. In particular, since the laser cutting steel of the present invention is insensitive to the focal shift of the laser due to a wavy state or a wound, the range of variation from the laser focus position that can be cut is increased, and the burning heat is increased even when the cutting heat input is increased. It has extremely good laser cutting property that this is hard to occur. Therefore, when the steel material of this invention is used, even when the zinc primer layer which is a primary rustproof coating film is formed, cutting at a very high speed using a high-power laser cutting machine is possible, and since it is difficult to generate | occur | produce a cutting defect, it is night Cutting interruption in unattended operation can be prevented. In particular, a stable laser cutting operation is performed at a high speed of 1050 mm / min for a 16 mm thick steel and 800 mm / min for a 23 mm thick steel. can do.

Hereinafter, each requirement of this invention is demonstrated in detail. In addition, "%" of content of each element means the "mass%."

(A) Basic chemical composition of steel:

Si: 0.08 to 0.20%

Si is an element which oxidizes during thermal cutting using oxygen to form Fe ₂ SiO ₄ (firelight) in the scale layer, and largely dominates thermal cutting property. In addition, below, "thermal cutting using oxygen" may be represented by "laser cutting."

When the content of Si is less than 0.08%, a sufficient amount of Fe ₂ SiO ₄ is not generated at the time of cleavage and the cleavage property is reduced. That is, the process temperature of Fe ₂ SiO ₄ is 1173 ° C., which is much lower than the melting point of FeO (1369 ° C.). Therefore, when Fe ₂ SiO ₄ is present in the iron oxide produced at the time of laser cutting, the liquid phase is maintained up to 1173 ° C., so that the molten Fe or iron oxide can be easily discharged in the low temperature region. However, when the Si content in the base material is less than 0.08%, the amount of Fe ₂ SiO ₄ generated decreases, and it becomes difficult to discharge molten Fe or iron oxide, so that the melting of the cut surface proceeds, and a phenomenon called "depression" occurs. Occurs.

On the other hand, when the content of Si exceeds 0.20%, a sufficient amount of Fe ₂ SiO ₄ is produced, but it is necessary to contain a large amount of Al, P, Ti and V which will be described later. The property will fall.

Therefore, content of Si was made into 0.08 to 0.20%. The upper limit with preferable Si content is 0.18%. Moreover, a preferable minimum is 0.10%.

Al: more than 0.03% and less than 0.08%

Al reduces the process temperature of Fe ₂ SiO ₄ present in the iron oxide produced during the laser cutting for deoxidation and facilitates the discharge of the molten Fe or iron oxide in the low temperature region, thereby improving the laser cutting property. It is a necessary element and needs to contain an amount exceeding 0.03%. However, when Al content increases, especially when it exceeds 0.08%, hard island martensite will be produced in a weld part, and toughness will deteriorate. Therefore, content of Al was made into 0.08% or less exceeding 0.03%. Moreover, since many ones of content of Al are preferable in the said range, it is preferable that the minimum of Al content shall be 0.035%.

P, Ti and V

P, Ti, and V are all elements that lower the process point of Fe ₂ SiO ₄ , and have an effect of facilitating the discharge of molten Fe or iron oxide in a low temperature region, thereby improving laser cutting property. For this reason, 1 or more types of P, Ti, and V shall be included. In addition, content of P, Ti, and V must satisfy said formula (2) at least as mentioned later.

Here, as a steel material containing the chemical composition exceeding Si: 0.08-0.20% and Al: 0.03% and containing 0.08% or less, and containing at least one of P, Ti, and V. The laser cutting property may be inadequate only by lowering the process temperature of Fe ₂ SiO ₄ present in the iron oxide. Therefore, it is necessary to satisfy following formula (1) and formula (2).

Al / Si ≦ 0.45... … (One)

262 x (Al / Si) + 197 x (P / Si) + 225 x (Ti / Si) + 50 x (V / Si)> 123. … (2)

In addition, the element symbol in Formula (1) and Formula (2) shows content in the mass% of the element.

This is considered to be due to the formation of high melting point Al ₂ O ₃ (alumina) in addition to Fe ₂ SiO ₄ during laser cutting when the value of "Al / Si" exceeds 0.45. Therefore, the above formula (1), that is, [Al / Si ≦ 0.45] was also satisfied.

In addition, Al, P, Ti, and V have the effect of lowering the process point of Fe ₂ SiO ₄ , in other words, the effect of lowering the temperature at which Fe ₂ SiO ₄ exists as a liquid phase, but the process point of Fe ₂ SiO ₄ includes these elements. And the ratio of Si content. Since the effect is different for each element, the above equation (2) is necessary in consideration of the dependence of each element. Here, when (2) is not satisfied, that is, when the value of "262 x (Al / Si) + 197 x (P / Si) + 225 x (Ti / Si) + 50 x (V / Si)" is 123 or less The laser cutting property cannot be stably and reliably increased. Therefore, it is assumed that the formula (2), that is, [262 × (Al / Si) + 197 × (P / Si) + 225 × (Ti / Si) + 50 × (V / Si)> 123) is also satisfied. When this condition is satisfied, laser cutting property can be raised stably and reliably.

For the above reasons, the steel for thermal cutting using oxygen according to the present invention (1) and the laser cutting steel according to the present invention (9) exceed 0.08% and Si: 0.08% to 0.20% and Al: 0.03%. In addition to including the following, at least one of P, Ti, and V was contained, and the above formulas (1) and (2) were defined to be satisfied.

(B) About the surface condition of the steel:

The steel material which has the chemical composition of said (A) shows the outstanding outstanding cutting property even with the scale after rolling as a surface situation. However, in the case where the scale after rolling is attached, the scale property may change due to heat treatment conditions and the like, which may greatly affect the cutting property.

For this reason, the steel material for thermal cutting which concerns on this invention (1) prescribed | regulated that the surface scale was removed in order to raise the thermal cutting property using oxygen more stably and reliably. Similarly, the steel material for laser cutting which concerns on this invention (9) also prescribed | regulated that the surface scale was removed in order to raise laser cutting property more stably and reliably.

In addition, the method of descaling after rolling does not need to be specifically defined, For example, what is necessary is just to carry out by well-known processing methods, such as a pickling process and a shot blasting process.

The heat cutting steel material according to the present invention (1) and the laser cutting steel material according to the present invention (9) exhibit an effect even if an inorganic zinc primer is applied to the surface after removing the scale from the surface. That is, since the temperature at which the Fe ₂ SiO ₄ is present as the liquid phase decreases, as described above, even in the inorganic zinc primer coated state on the steel material surface, has a laser-cutting and Heat Insulation barrier property with good oxygen respectively.

Therefore, the steel for thermal cutting which uses oxygen which concerns on this invention (2), and the steel for laser cutting which concerns on this invention (10) are respectively the steel for thermal cutting which uses oxygen of this invention (1), and this invention. In the steel material for laser cutting of (9), it prescribed | regulated that the inorganic zinc primer was apply | coated to the surface.

In addition, the method of apply | coating an inorganic zinc primer to the steel surface does not need to specifically define, For example, what is necessary is just to carry out by well-known processing methods, such as an air spraying process and a brushing process.

As the inorganic zinc primer, a known commercially available inorganic zinc primer can be used. That is, the coating material containing Zn powder can be used which has alkylsilicate type resin as a main component. In addition, when the inorganic zinc primer is a pigment which is Fe ₂ SiO ₄ containing an element of, Al, P, Ti, and V lower the temperature that exists as a liquid the addition of the primer, but also by the effect of the process temperature is lowered, and laser Thermal cutting property using oxygen including cutting property is improved.

It is preferable to make the film thickness of the dry coating film of the inorganic zinc primer to apply | coat into the range of 9-25 micrometers. Even if a coating film is thinner than 9 micrometers or thicker than 25 micrometers on the contrary, the thermal cutting property using oxygen including laser cutting property may fall. When a coating film is thinner than 9 micrometers, corrosion resistance may also deteriorate. In addition, said film thickness means an average film thickness, The film thickness of the coating film in the surface of steel materials using an electronic film thickness meter, for example, the "CRT-2000II electronic digital film thickness meter by Sanko Electronics Research Institute." Can be obtained as an average value of 10 or more points.

The steel for thermal cutting using the oxygen which concerns on this invention (3), and the steel for laser cutting which concerns on this invention (11) are 15- to 10-point average roughness RzJIS whose surface roughness prescribed | regulated to JIS B 0601 (2001). In the case of 85 micrometers, thermal cutting property and laser cutting property using oxygen are improved, respectively. When surface roughness is less than 15 micrometers, energy may not be sufficiently transmitted to a steel material surface, and cutting property may fall. This is because, for example, in the case of laser cutting, the reflection of the laser light becomes remarkable. Moreover, when surface roughness is less than 15 micrometers, the adhesion durability of the coating film at the time of zinc primer application may not be obtained. On the other hand, even when surface roughness exceeds 85 micrometers, energy may not be sufficiently transmitted to a steel material surface, and cutting property may fall. This is because, for example, in the case of laser cutting, the laser is diffusely reflected on the steel surface.

Therefore, the steel for thermal cutting which uses oxygen which concerns on this invention (3), and the laser cutting steel which concerns on this invention (11) respectively cut | disconnect using oxygen of this invention (1) or (2), respectively. In the steel materials for steel and the laser cutting steel materials of the present invention (9) or (10), the surface roughness was defined to be 15 to 85 µm by the ten-point average roughness RzJIS.

(C) For a suitable chemical composition of the steel:

In addition to having the chemical composition as described in said (A), the steel material concerning this invention contains the element of the quantity demonstrated next.

C: 0.02 ~ 0.17%

Since C is an element which raises strength, it is preferable to contain 0.02% or more. However, if it exceeds 0.17%, the toughness of the steel sheet may be deteriorated. For this reason, it is preferable to make content of C into 0.02 to 0.17%. Moreover, C is an inexpensive element, and the improvement effect of cutting property by the heat of reaction of O (oxygen) and C in steel at the time of the cutting by a laser can also be expected. For this reason, it is more preferable that the minimum of C content shall be 0.05%. Moreover, as for the upper limit of C content, it is more preferable to set it as 0.16%.

Mn: 0.20-1.60%

Since Mn is an element effective for securing the strength of the steel, it is preferable to contain M0% or more. However, when the content of Mn exceeds 1.60%, deterioration of toughness and deterioration of laser cutting may be caused. Therefore, it is preferable to make content of Mn into 0.20 to 1.60%. Moreover, as for the minimum of Mn content, it is more preferable to set it as 0.30%.

Cu: less than 0.03%

Cu exists in steel as an impurity, and when there is much content, there exists a possibility of causing Cu checking. For this reason, it is preferable to suppress content of Cu to a fixed amount or less, and to set it as less than 0.03%.

Ni: 0.05% or less

Ni also exists in steel as an impurity, and when there is much content, there exists a possibility that it may adversely affect the grade of a casting piece. For this reason, it is good to suppress content of Ni to a fixed amount or less, and to set it as 0.05% or less.

S: 0.015% or less

S is present in steel as an impurity and hardly affects laser cutting property. However, when S is large in content, S may adversely affect mechanical properties such as toughness. Therefore, it is good to suppress content of S to below a fixed amount, and it is preferable to set it as 0.015% or less.

N: 0.009% or less

N exists in steel as an impurity, and when there is much content, there exists a possibility that it may adversely affect weldability and the quality of a casting piece. For this reason, it is good to suppress content of N to a fixed amount or less, and to set it as 0.009% or less.

P: 0.04% or less, Ti: 0.08% or less and V: 0.08% or less

As already described in section (A), P, Ti, and V are all elements that lower the process point of Fe ₂ SiO ₄ , which facilitates the discharge of molten Fe or iron oxide in the low temperature region, and thus the laser cutting property. Has the effect of raising. For this reason, under the conditions of containing Si and Al in the amount described in (A) and satisfying the above formulas (1) and (2), the higher the amount of P, Ti and V, the better the laser cutting. Although property can be obtained, when there are many of these contents, since there exists a possibility that it may adversely affect the various characteristics of steel materials, it is good to suppress content of these elements below a fixed amount. This will be described below.

P: 0.04% or less

Although P is an element that is inevitably included as an impurity, P has a function of lowering the process point of Fe ₂ SiO ₄ to increase laser cutting property, so that the higher the amount of P contained, the better laser cutting property can be obtained. However, when there is much content, there exists a possibility that it may adversely affect weldability and toughness. For this reason, it is good to suppress content of P to below a fixed amount, and it is desirable to set it as 0.04% or less. It is preferable to make the minimum of P content into 0.01%.

Ti: 0.08% or less

Ti is an element that lowers the process point of Fe ₂ SiO ₄ . Therefore, the higher the Ti content, the better the laser cutting property. However, when the content is large, there is a possibility that the toughness of the welded part may be adversely affected, and the cost is disadvantageous. For this reason, it is good to suppress content of Ti to a fixed amount or less, and to set it as 0.08% or less.

In addition, Ti also has the effect of increasing the strength of the steel sheet by precipitation strengthening, and in order to obtain this effect, it is preferable to contain Ti by 0.005% or more. Therefore, it is preferable that the minimum of Ti content shall be 0.005%.

V: 0.08% or less

V is also an element for lowering the process point of Fe ₂ SiO ₄ . For this reason, the higher the content of V, the better the laser cutting property. However, when the content is large, there is a possibility that the toughness of the welded part may be adversely affected, and the cost is disadvantageous. For this reason, it is good to suppress content of V to a fixed amount or less, and to set it as 0.08% or less.

In addition, V also has the effect of increasing the strength of the steel sheet by precipitation strengthening, and in order to obtain this effect, it is preferable to contain 0.02% or more. Therefore, it is preferable that the minimum of V content shall be 0.02%.

In addition, said P, Ti, and V should just contain 1 or more types of them.

From the above reason, the steel for steel cutting using oxygen which concerns on this invention (4), and the steel for laser cutting which concerns on this invention (12) are each in any one of this invention (1)-(3). In the steel for thermal cutting using oxygen and the steel for laser cutting according to any one of the present inventions (9) to (11), C: 0.02 to 0.17%, Si: 0.08 to 0.20%, Mn: 0.20 to 1.60%, Cu: Less than 0.03%, Ni: 0.05% or less, S: 0.015% or less, Al: Al: 0.03% or more, including 0.08% or less and N: 0.009% or less, P: 0.04% or less, Ti: 0.08% or less And V: 0.08% or less, and it is defined that the balance has a steel composition composed of Fe and impurities.

The steel material for thermal cutting using oxygen which concerns on this invention (4), and the laser cutting steel material which concerns on this invention (14) further, if necessary, 1 or more types chosen from the group of following (a)-(b). It can contain an element.

(A) Cr: 0.2% or less,

(B) one or more of Mo: 0.4% or less, W: 0.4% or less and Nb: 0.04% or less,

(C) B: 0.003% or less,

(D) at least one of Ca: 0.005% or less, Mg: 0.005% or less and REM: 0.005% or less.

That is, you may contain 1 or more types of elements in the said (A)-(D) group.

Hereinafter, the above elements will be described.

Cr: 0.2% or less

Cr has the effect | action which raises the strength of a steel plate. In order to acquire this effect, it is preferable to make content of Cr into 0.02% or more. More preferably, it is 0.03% or more. However, if the content exceeds 0.2%, Cr oxide having a high melting point is formed to deteriorate the flowability of the molten metal, leading to deterioration of the roughness of the laser cut surface and formation of cut notches. For this reason, content of Cr in the case of making it contain was made into 0.2% or less. In addition, the minimum of Cr content in the case of making it contain is preferable to set it as 0.02%, and it is still more preferable to set it as 0.03%.

At least one of Mo: 0.4% or less, W: 0.4% or less and Nb: 0.04% or less

Since Mo, W, and Nb have the effect of increasing the strength, the above-mentioned elements may be contained in order to obtain this effect. Hereinafter, it demonstrates in detail.

Mo has the effect | action which raises the strength of a steel plate by solid solution strengthening. In order to acquire this effect, it is preferable to contain Mo 0.1% or more. However, it is disadvantageous in terms of cost to contain Mo in excess of 0.4%, and there is a possibility that the weldability may be impaired. For this reason, content of Mo in the case of making it contain was made into 0.4% or less. In addition, it is preferable to make the minimum of Mo content in the case of making it into 0.1%.

W also has the effect of increasing the strength of the steel sheet by solid solution strengthening. In order to acquire this effect, it is preferable to contain W 0.05% or more. However, it is disadvantageous in terms of cost to contain W in a large amount exceeding 0.4%, and there is a possibility that the weldability may be impaired. For this reason, content of W in the case of making it contain was made into 0.4% or less. In addition, it is preferable to make the minimum of W content in the case of making it into 0.05%.

Nb has the effect | action which raises the strength of a steel plate by precipitation strengthening. In order to acquire this effect, it is preferable to make content of Nb into 0.005% or more. However, containing Nb in a large amount exceeding 0.04% is disadvantageous in terms of cost, and there is a fear of deteriorating the toughness of the welded portion. Therefore, content of Nb in the case of making it contain was made into 0.04% or less. In addition, it is preferable that the minimum of Nb content in the case of making it contain 0.005%.

Said Mo, W, and Nb can contain 1 or more types of them.

B: 0.0030% or less

B has the effect | action which raises hardenability. In order to acquire this effect, it is preferable to contain B 0.0005% or more. However, when B is contained exceeding 0.0030%, there exists a possibility that weldability may deteriorate. For this reason, content of B in the case of making it contain was made into 0.0030% or less. In addition, it is preferable to make the minimum of B content in the case of making it into 0.0005%.

At least one of Ca: 0.005% or less, Mg: 0.005% or less, and REM: 0.005% or less

Since Ca, Mg, and REM have the effect of improving the toughness of the weld heat affected zone (hereinafter referred to as "HAZ"), the above elements may be included in order to obtain this effect. Hereinafter, it demonstrates in detail.

Ca has the effect | action which improves HAZ toughness. In order to acquire this effect, it is preferable to contain Ca 0.001% or more. However, when Ca content exceeds 0.005%, there exists a possibility that a laser cutting property may be impaired. Therefore, content of Ca in the case of making it contain was made into 0.005% or less. In addition, it is preferable to make the minimum of Ca content in the case of making it into 0.001%.

Mg has the effect | action which improves HAZ toughness. In order to acquire this effect, it is preferable to contain Mg 0.001% or more. However, when the content of Mg exceeds 0.005%, there is a fear that the laser cutting property is impaired. For this reason, content of Mg in the case of making it contain was made into 0.005% or less. In addition, it is preferable to make the minimum of Mg content in the case of making it into 0.001%.

REM has the effect | action which improves HAZ toughness. In order to acquire this effect, it is preferable to contain REM 0.001% or more. However, when the content of REM exceeds 0.005%, there is a fear that the laser cutting property is impaired. Therefore, content of REM in the case of making it contain was made into 0.005% or less. In addition, the minimum of REM content in the case of making it contain is preferable to be 0.001%.

Said Ca, Mg, and REM can contain 1 or more types of them.

In addition, "REM" is a general term for 17 elements in total of Sc, Y, and a lanthanoid, and it is as having already demonstrated that content of REM points out the total content of 1 type, or 2 or more types of elements in REM.

For the reasons described above, the steel for thermal cutting using oxygen according to the present invention (5) and the laser cutting steel according to the present invention (13) are steel for thermal cutting using oxygen according to the present invention (4), respectively. And in the steel materials for laser cutting of this invention (12), it shall contain Cr: 0.2% or less.

In addition, the steel for thermal cutting which uses oxygen which concerns on this invention (6), and the steel for laser cutting which concerns on this invention (14), respectively for thermal cutting which uses oxygen of this invention (4) or (5), respectively. In the steel materials and the laser cutting steel materials of the present invention (12) or (13), one or more of Mo: 0.4% or less, W: 0.4% or less, and Nb: 0.04% or less were further contained.

In addition, the steel for thermal cutting which uses oxygen which concerns on this invention (7), and the laser cutting steel which concerns on this invention (15) use oxygen of any one of this invention (4)-(6), respectively. Among the steel for cutting steel and the laser cutting steel in any one of the present inventions (12) to (14), further, at least one of Mo: 0.4% or less, W: 0.4% or less, and Nb: 0.04% or less is contained. I did it.

Similarly, the steel for thermal cutting which uses oxygen which concerns on this invention (8), and the laser cutting steel which concerns on this invention (16) use oxygen of any one of this invention (4)-(7), respectively. Among the steel for heat cutting and the laser cutting steel in any one of the present inventions (12) to (15), further, at least one of Ca: 0.005% or less, Mg: 0.005% or less, and REM: 0.005% or less is contained. I did it.

In addition, the thickness of the heat cutting steel material and the laser cutting steel material using oxygen of the present invention is not particularly limited. Although it is naturally possible to cut a thin thing, even if it is 12 mm or more in thickness, it can fully cut. Therefore, the thickness of the steel is preferably 12 mm or more. However, the thickness of the steel which can be cut depends on the output characteristics of the cutter. For this reason, in the case of laser cutting, it is preferable that the upper limit of the thickness of steel materials shall be 30 mm. In the case of plasma cutting, the upper limit of the thickness of the steel is preferably 80 mm. In addition, when performing gas cutting, it is preferable that the upper limit of the thickness of steel materials shall be 4000 mm.

Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to these Examples.

(Example)

<Example 1>

After laboratory-solving the steels 1-19 which have the chemical composition shown in Table 1, it hot-rolled and produced two types of steel materials whose width is 250 mm, the length is 500 mm, and the thickness is 16 mm and 23 mm, respectively.

In addition, steels 1-16 in Table 1 are steels of the example of this invention in which a chemical composition exists in the range prescribed | regulated by this invention. In addition, steel 17-19 is the steel of the comparative example in which the chemical composition deviated from the conditions prescribed | regulated by this invention.

Next, the surface of the steel material after rolling was short-blasted and the rolling scale was removed. Moreover, also about any steel material after a shot blast, 10-point average roughness (RzJIS) in the surface was 49.6 micrometers.

Thereafter, an inorganic zinc primer (Cerabond 2000 Gray S, manufactured by China Paint Co., Ltd.) was applied to the surface of each steel except Test No. 1 in Table 2, that is, each steel of Test Nos. 2 to 20 by air spray. .

In addition, the application of the zinc primer is a small coating robot (PX-800 manufactured by Yaskawa Electric Co., Ltd., moving speed is 380 mm / s) and the coating gun (Devilvis T-AGHV, nozzle diameter 1.2 mm, cap No. 807). It was carried out under the condition that the atomizing air pressure was 0.128 MPa (1.3 kgf / cm 2), the pattern air pressure was 0.098 MPa (1.0 kgf / cm 2), the paint discharge amount was 132 g / min and the dry distance was 150 mm.

After the applied zinc primer coating film was naturally dried, the film thickness at any 81 points on the surface of the steel was measured using an electronic digital film thickness meter (CRT-2000II manufactured by Sanko Electronics Co., Ltd.), and the arithmetic mean The average film thickness for each test number was obtained. In addition, the average film thickness was in the range of 14-16 micrometers.

For the steel material (test number 1 in Table 2) with the above shot blasting treatment and the rolling scale removed, and the steel material (test numbers 2 to 19 in Table 2) coated with an inorganic zinc primer after the shot blasting treatment, The cleavage test was done.

The laser cutting machine used for cutting is a CO ₂ laser of 6KW output manufactured by Koike Sanso Kogyo Co., Ltd., and the cutting condition is 60% of duty (output time per hour of pulse oscillation), frequency is 1000 Hz, and oxygen gas pressure is The inner side was 0.05 MPa, and the outer side was 0.03 MPa.

After the piercing (penetration), a cut of 50 mm x 50 mm (the corner R is 3 mm) from each steel material, and the presence or absence of notch phenomenon at that time (that is, the presence or absence of a wound in the cut surface) In addition, the adhesion state of slag (that is, the adherend to the cutting back surface of molten steel containing an oxide) was observed. In addition, as shown in Table 2, the cutting speed was changed depending on the plate thickness.

In the evaluation of the laser cutting property, the laser focus is first determined on the steel surface, in other words, the position of the positioned nozzle tip is set to "0", and then the nozzle tip position is set at a pitch of 0.5 mm from the position of "0". The test was carried out on the conditions away from the steel surface and on the conditions near, and it was determined whether the notch phenomenon and the cutting defect of slag adhesion generate | occur | produce. And the deviation of the largest nozzle tip position where neither a notch phenomenon and slag is observed is measured, and the deviation | deviation from the cutable laser focus position, ie, the fluctuation range, was calculated | required. In addition, the cutting speed in this case was set to 600 mm / min when the steel thickness is 16 mm and 900 mm / min, and when the steel thickness is 23 mm.

In addition, evaluation of a limit cutting speed fixes a nozzle tip position to the said "0" position, in other words, fixes a laser focus on the surface of steel materials, and the said 900 mm / min (when steel thickness is 16 mm). Or the cutting speed of 600 mm / min (when steel thickness is 23 mm) was made 50 mm / min in pitch pitch, and it was determined whether the notch phenomenon, the slag adhesion, and the cutting defect of burning generate | occur | produced. And the maximum cutting speed in which none of notch development, slag adhesion, and burning were observed was made into the limit cutting speed.

In Table 2, the said irradiation result is put together and shown. In addition, in Table 2, the fluctuation range from the laser focus position which can be cut | disconnected was described as "the cuttable focus position."

From Table 2, in Test No. 1-17 of the example of this invention which satisfy | fills the conditions prescribed | regulated by this invention, when the thickness of steel materials is 16 mm, the variation range from the cut-off focus position is 3.5 mm or more, and steel materials Is 23 mm or more when the thickness of the steel is 23 mm, and any steel is insensitive to misalignment of the laser, and the limit cutting speed is 1050 mm / min or more when the thickness of the steel is 16 mm. In the case where the thickness of the film is 23 mm, it is obvious that the thickness is larger than 800 mm / min and excellent in laser cutting property.

In contrast, in Test Nos. 18 to 20 of the Comparative Example, the variation range from the cuttable focus position when the thickness of the steel was 16 mm was small at 2.0 to 2.5 mm, and the limit cutting speed remained at 900 mm / min. . In addition, in these test numbers, when the thickness of steel materials is 23 mm, the cutting speed of 600 mm / min is the limit of laser cutting, and the fluctuation range from the focus position which can be cut is 0.5 mm, and is small. It was a situation where cutting failure occurred due to the change.

<Example 2>

The test similar to the said Example 1 was performed by changing the surface roughness of steel materials in various ways. More specifically, using the steels 1 and 3 shown in Table 1, the size of the shot balls in the shot blast is changed in various ways to prepare test pieces having different surface roughness RzJIS, and laser cutting as shown in Example 1 Rated sex.

Table 3 shows the results of irradiation when the surface roughness is changed. In addition, in Table 3, the test materials of the test numbers 21-24 are steel materials with descaling, and the test materials of test numbers 25-28 apply a zinc primer like <Example 1> after descaling. In addition, test number 1 and test number 3 of <Example 1> were described as the test number 21 and the test number 25, respectively.

From Table 3, in the case of the test numbers 21-28, the fluctuation range from the focus position which can be cut | disconnected is 3.0 mm or more when the thickness of steel materials is 16 mm, and 1.5 mm or more when the thickness of steel materials is 23 mm. Any steel is insensitive to the focal shift of the laser, and the limit cutting speed is 1050 mm / min or more when the thickness of the steel is 16 mm, and 750 mm / min when the thickness of the steel is 23 mm. It is clear that it is large above and excellent in laser cutting property. Moreover, among the said test numbers, laser cutting property in the case of the test numbers 21, 22, 25, and 26 especially in the range whose surface roughness RzJIS is 15-85 micrometers is further excellent.

<Example 3>

Using the remainder of the steel material used in <Example 1>, the steel material of thickness 23mm was plasma-cut especially, and the plasma cutting property was evaluated.

The plasma cutting machine used for cutting was a plasma cutting machine (Super 400) manufactured by Koike Sanso Industrial Co., Ltd., and the cutting conditions used an output current of 137.8A and used oxygen as the plasma gas.

After piercing (penetration), cut out the square material of 50 mm x 50 mm from each steel material, and examine the presence or absence of the wound in the cut surface at that time, and also to the cutting back surface of slag (that is, oxide containing molten steel) Adherence) was observed. Evaluation of the limit cutting speed was carried out by raising the cutting speed of 1200 mm / min to a 120 mm / min pitch (10% pitch of the initial cutting speed), and judged whether or not the notch phenomenon, the slag attachment, and the cutting defect of burning occurred. . And the maximum cutting speed in which none of notch development, slag adhesion, and burning were observed was made into the limit cutting speed.

Table 4 summarizes the above findings.

From the plasma cutting test results of Table 4, in test Nos. 29 to 45 of the example of the present invention that satisfies the conditions specified in the present invention, it is clear that cutting is possible at 2000 mm / min or more and is excellent in plasma cutting property.

On the other hand, in the test numbers 46-48 of a comparative example, the limit cutting speed was only 1680 mm / min.

The steel material of this invention can perform the high speed and stable heat cutting operation | work, and can be used for laser cutting, plasma cutting, and gas cutting. In particular, since the laser cutting steel of the present invention is insensitive to the focal shift of the laser due to a wavy state or a wound, the range of variation from the focal position that can be cut is increased, and the cutting heat input is also increased. It has extremely good laser cutting property that a burning phenomenon is hard to occur. Therefore, when the steel material of this invention is used, even when the zinc primer layer which is a primary rustproof coating film is formed, cutting at a very high speed using a high-power laser cutting machine is possible, and since it is difficult to generate | occur | produce a defective cutting, it is night Cutting interruption in unattended operation can be prevented, and it can greatly contribute to the productivity of laser cutting.

Claims (16)

As a descaled steel material, at least% of Si, 0.08 to 0.20%, and Al: 0.03% and 0.08% or less, and at least one of P, Ti, and V, Steel for heat cutting using oxygen, characterized by satisfying Formulas (1) and (2). Al / Si ≦ 0.45... … (One) 262 x (Al / Si) + 197 x (P / Si) + 225 x (Ti / Si) + 50 x (V / Si)> 123. … (2) In addition, the element symbol in Formula (1) and Formula (2) shows content in the mass% of the element. The method according to claim 1, Steel for heat cutting using oxygen, characterized by coating an inorganic zinc primer on the surface. The method according to claim 1 or 2, Steel for thermal cutting using oxygen, wherein the surface roughness is 15 to 85 µm in terms of ten-point average roughness RzJIS. The method according to any one of claims 1 to 3, In mass%, C: 0.02 to 0.17%, Si: 0.08 to 0.20%, Mn: 0.20 to 1.60%, Cu: less than 0.03%, Ni: 0.05% or less, S: 0.015% or less, Al: 0.03% or more and more than 0.08 Containing at least one of P: 0.04% or less, Ti: 0.08% or less, and V: 0.08% or less, and the balance has a steel composition composed of Fe and impurities. Steel for heat cutting using oxygen characterized in that. The method according to claim 4, A steel material for thermal cutting using oxygen, which further contains Cr: 0.2% or less by mass%. The method according to claim 4 or 5, A steel material for thermal cutting using oxygen, characterized by further containing at least one of Mo: 0.4% or less, W: 0.4% or less, and Nb: 0.04% or less. The method according to any one of claims 4 to 6, A steel material for thermal cutting using oxygen, which further contains B: 0.003% or less by mass%. The method according to any one of claims 4 to 7, A steel material for thermal cutting using oxygen, characterized by further containing at least one of Ca: 0.005% or less, Mg: 0.005% or less, and REM: 0.005% or less. As a descaled steel material, at least% of Si, 0.08 to 0.20%, and Al: 0.03% and 0.08% or less, and at least one of P, Ti, and V, Steel material for laser cutting, characterized by satisfying the formulas (1) and (2). Al / Si ≦ 0.45... … (One) 262 x (Al / Si) + 197 x (P / Si) + 225 x (Ti / Si) + 50 x (V / Si)> 123. … (2) In addition, the element symbol in Formula (1) and Formula (2) shows content in the mass% of the element. The method according to claim 9, An laser cutting steel, characterized by coating an inorganic zinc primer on the surface. The method according to claim 9 or 10, A steel for laser cutting, characterized in that the surface roughness is 15 to 85 µm in terms of ten points average roughness RzJIS. The method according to any one of claims 9 to 11, In mass%, C: 0.02 to 0.17%, Si: 0.08 to 0.20%, Mn: 0.20 to 1.60%, Cu: less than 0.03%, Ni: 0.05% or less, S: 0.015% or less, Al: 0.03% or more and more than 0.08 At least one of P: 0.04%, Ti: 0.08%, and V: 0.08% or less, and the balance has a steel composition composed of Fe and impurities. A laser cutting steel material. The method according to claim 12, A steel material for laser cutting, further comprising Cr: 0.2% or less by mass%. The method according to claim 12 or 13, A steel material for laser cutting, characterized in that it further contains at least one of Mo: 0.4% or less, W: 0.4% or less, and Nb: 0.04% or less. The method according to any one of claims 12 to 14, The steel material for laser cutting of mass% further containing B: 0.003% or less. The method according to any one of claims 12 to 15, A steel material for laser cutting, characterized in that it further contains at least one of Ca: 0.005% or less, Mg: 0.005% or less and REM: 0.005% or less.