JP7323425B2 - Method for removing oxide scale and method for manufacturing stainless steel strip - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for removing oxide scale and a method for manufacturing a stainless steel strip.

As a method for removing the oxide scale formed on the surface of the stainless steel strip after hot rolling and cold rolling, the stainless steel strip subjected to scale breaker treatment and shot blasting treatment is immersed in a pickling tank. is common. Hereinafter, removing the oxide scale formed on the surface of the stainless steel strip is referred to as "descaling".

However, in this oxide scale removal method, for example, when the stainless steel strip is made of difficult-to-pickle steel, the strip threading speed must be reduced more than usual. Alternatively, the stainless steel strip after being immersed in the pickling bath must be passed through a coil grinder line for surface grinding. Further, for example, even if the stainless steel strip is of a general-purpose steel grade, there is a limit to descaling the strip at a higher than normal threading speed. For these reasons, the above oxide scale removing method has problems in terms of increasing the strip threading speed and simplification of the manufacturing process, and there is room for improvement in terms of improving the production efficiency of the stainless steel strip. In the case of removing the oxide scale formed on the surface of the stainless steel plate, there is the same problem as in the case of the stainless steel strip in terms of improving production efficiency.

In order to improve the production efficiency of stainless steel strips and stainless steel sheets, various methods for removing oxide scale have been researched and implemented. For example, Patent Literature 1 discloses a method of removing a scale layer generated when a stainless steel plate is annealed by irradiating it with a laser beam. The scale layer is formed by layered oxide scale.

Japanese Patent Application Laid-Open No. 4-182020 (published on June 29, 1992)

However, even the oxide scale removing method disclosed in Patent Document 1 is not necessarily sufficient in terms of removing the scale layer in a short period of time.

SUMMARY OF THE INVENTION One aspect of the present invention has been made in view of the above problems, and an object of the present invention is to realize a method for removing oxide scale that can perform descaling in a short time and improve the production efficiency of a stainless steel strip. It is in.

As a result of intensive studies by the present inventors in order to solve the above-mentioned problems, the surface of the stainless steel strip after annealing is irradiated with a laser beam of a pulsed laser whose fluence has a value within a predetermined numerical range. It was found that the production efficiency of the steel strip was improved. Based on the results of this study, the inventors have completed the invention. The present invention specifically consists of the following configurations.

[1] An oxide scale removal method for removing oxide scale formed on the surface of a stainless steel strip after hot rolling or cold rolling, wherein a pulse width of The fluence F [J/cm ² ] when τ [ns] is α × (τ [ns] / 100) ^1/2 [J / cm ² ] or more β × (τ [ns] / 100) ^{1 /2} [J/cm ² ] or less (where α = 1, β = 15).

According to the above configuration, descaling can be performed without applying a scale breaker treatment, a shot blasting treatment, or the like. Therefore, the descaling time can be shortened, and the production efficiency of the stainless steel strip can be improved.

Further, according to the above configuration, the fluence F of the laser light of the pulse laser is α×(τ [ns]/100) ^1/2 [J/cm ² ] or more with respect to the pulse width τ, β×(τ [ns ]/100) ^1/2 [J/cm ² ] or less (where α=1 and β=15). As a result, descaling can be achieved in a shorter time than conventional pulsed laser beam irradiation, while keeping the reduction in the thickness of the stainless steel strip from the surface irradiated with the laser beam (hereinafter referred to as base material damage) within an allowable range. It can be carried out.

In the relational expression between the pulse width τ and the fluence F, preferably α≧4, more preferably α≧5, and even more preferably α≧6. If α≧4, even for a stainless steel strip of difficult-to-pickle steel containing 2.5 to 5.0 [%] Si, 18 to 20 [%] Cr, and 12 to 20 [%] Ni , can be effectively descaled. If α≧5, even for a stainless steel strip of difficult-to-pickle steel containing 2.5 to 5.0 [%] Si, 18 to 20 [%] Cr, and 12 to 20 [%] Ni , can be descaled more efficiently. When α≧6, descaling can be most efficiently performed regardless of the steel grade of the stainless steel strip.

[2] The oxide scale removing method according to [1], wherein the pulse width τ [ns] of the laser light is 10 [ns] or more and 1000 [ns] or less.

According to the above configuration, the pulse width τ of the laser light of the pulse laser is 10 [ns] or more and 1000 [ns] or less, so that the production efficiency of the stainless steel strip is further improved while keeping the base material damage within the allowable range. can be improved.

Further, by setting the upper limit of the pulse width τ to 1000 [ns], the thermal effect of the laser light on the stainless steel strip and the fluence F can be reduced, and the size of the laser oscillator can be reduced. Furthermore, by setting the lower limit of the pulse width τ to 10 [ns], the cost of the laser oscillator can be kept within the allowable range. Therefore, it becomes easy to apply the oxide scale removing method according to one aspect of the present invention to a mass production line. The pulse width τ is preferably set in the range of 30 [ns] to 500 [ns], more preferably in the range of 50 [ns] to 300 [ns].

[3] The scale removal according to [1] or [2], further comprising a pickling treatment step of subjecting the surface of the stainless steel strip to a pickling treatment after the laser beam irradiation step. Method.

According to the above configuration, since the stainless steel strip after annealing is subjected to the pickling treatment after being irradiated with the laser beam of the pulse laser, more oxide scale can be removed. Therefore, the quality of the stainless steel strip can be further improved.

[4] A method for producing a stainless steel strip, comprising an oxide scale removing step of removing the oxide scale using the oxide scale removing method according to any one of [1] to [3]. According to the above configuration, it is possible to realize a method for manufacturing a stainless steel strip with improved production efficiency.

ADVANTAGE OF THE INVENTION According to one aspect of the present invention, it is possible to realize an oxide scale removal method capable of performing descaling in a short time and improving the production efficiency of a stainless steel strip.

BRIEF DESCRIPTION OF THE DRAWINGS It is a flowchart which shows an example of the flow of each process about the manufacturing method of the stainless steel strip which concerns on one Embodiment of this invention. 1 is a flow chart showing an example of the flow of each step in a method for removing oxide scale according to an embodiment of the present invention. It is a schematic diagram of the equipment which implements the said oxide scale removal method. FIG. 4 is a view showing optical micrographs of oxidized scale of a stainless steel strip of SUS304 when a pulsed laser is irradiated at different fluences. FIG. 4 is a diagram showing optical micrographs of oxidized scale of a stainless steel strip of SUS430 when a pulsed laser is irradiated at different fluences. FIG. 4 is a view showing optical micrographs when oxidized scale of a stainless steel strip of SUSXM15J1 is irradiated with a pulsed laser at different fluences. It is a graph which shows the relationship between a fluence and a scale removal rate. 4 is a graph showing the relationship between fluence and base metal damage rate.

[Outline of manufacturing method of stainless steel strip]
An outline of a method for manufacturing a stainless steel strip according to one embodiment of the present invention will be described below with reference to FIG. As shown in FIG. 1, the manufacturing method according to the present embodiment includes a steelmaking process (S1), a continuous casting process (S2), a hot rolling process (S3), a continuous annealing process (S4), an oxide scale removing process (S5 ). Note that the manufacturing method according to the present embodiment may include a cold rolling step and a refinement step, if necessary. Moreover, there is no restriction on the type of stainless steel that is used as the material for the stainless steel strip. For example, in terms of mass %, it contains 2.5 to 5.0 [%] Si, 18 to 20 [%] Cr, and 12 to 20 [%] Ni. and various stainless steels can be used as the material.

First, in a steelmaking step (S1), scrap containing Fe, Cr, Ni, etc. as main components is melted in an electric furnace (not shown), and then components are adjusted in a refining furnace (not shown) to produce molten steel. Next, in the continuous casting step (S2), the molten steel produced in the refining furnace is taken out into a ladle (not shown) and then continuously poured from the ladle into a mold (not shown) for cooling. Then, the cooled and hardened stainless steel is cut into predetermined lengths to produce a plurality of slabs.

Next, in the hot rolling step (S3), the slab produced in the continuous casting step (S2) is heated to a predetermined temperature, and the slab that has reached the predetermined temperature is hot rolled by a hot rolling mill (not shown). do. Specifically, the slab is subjected to rough rolling and finish rolling in multiple stages, and is hot rolled until the slab has a predetermined thickness. A strip of stainless steel (hereinafter referred to as stainless steel strip 1) is produced by hot rolling.

Next, in the continuous annealing step (S4), the stainless steel strip 1 produced in the hot rolling step (S3) is continuously annealed in an annealing furnace (not shown). Continuous annealing of the stainless steel strip 1 softens the stainless steel strip 1 whose ductility has been reduced due to hardening, thereby restoring the ductility of the stainless steel strip 1 . Next, in the oxide scale removal step (S5), the oxide scale (not shown) formed on the surface of the stainless steel strip 1 after continuous annealing is irradiated with laser light 3 of a pulse laser (see FIG. 3), Descaling is performed by subjecting the stainless steel strip 1 to a pickling treatment. Details of the oxide scale removal step (S5) will be described later.

The method for manufacturing a stainless steel strip according to the present embodiment is merely an example, and is not limited to the contents and order of the above-described steps, equipment to be used, and the like. For example, the stainless steel strip 1 may be further cold rolled. Alternatively, the stainless steel strip 1 after cold rolling may be continuously annealed and then subjected to the oxide scale removing step (S5). In these cases, the oxide scale removal step (S5) may be performed both after hot rolling and after cold rolling, or may be performed either.

[Method for removing oxide scale]
Next, a method for removing oxide scale according to an embodiment of the present invention will be described with reference to FIGS. 2 and 3. FIG. The oxide scale removal method according to the present embodiment is carried out in the oxide scale removal step (S5) shown in FIG. there is

<Laser light irradiation process>
First, in the laser beam irradiation step (S51) shown in FIG. 2, the oxide scale formed on the surface of the stainless steel strip 1 after continuous annealing is irradiated with the laser beam 3 of the pulse laser (see FIG. 3). Perform descaling by Descaling with a pulsed laser is a technique using laser ablation. Laser ablation is to vaporize a substance to be irradiated by laser light irradiation. Specifically, by scanning a pulsed laser pulsed from a laser oscillator 21 described later with a laser head 22 described later, the oxide scale is irradiated with the laser light 3 of the pulsed laser, and the oxide scale is vaporized.

In the laser beam irradiation step (S51), the laser beam of the pulse laser is irradiated using the laser beam irradiation device 2 shown in FIG. The laser beam irradiation device 2 includes a laser oscillator 21, a laser head 22, a driving section (not shown), and a control section (not shown).

(laser oscillator and laser head)
The laser oscillator 21 generates and pulse-oscillates the laser light 3 shown in FIG. The type of the laser oscillator 21 is not particularly limited, but from the viewpoint of shortening the descaling time, a solid-state laser having a larger laser output per unit area than other laser oscillators is preferable.

The laser head 22 collects the laser light 3 of the pulsed laser pulsed from the laser oscillator 21 and irradiates the oxide scale formed on the surface of the stainless steel strip 1 after continuous annealing. When the pulse width τ is 100 [ns], the pulse laser beam 3 irradiated from the laser head 22 to the oxide scale has a lower limit α of the fluence F of 1 [J/cm ² ] and an upper limit β of 15 [J/cm 2 ]. J/cm ² ]. Preferably, the lower limit value α of the fluence F is 4 [J/cm ² ], a more preferred lower limit value α is 5 [J/cm ² ], and a further preferred lower limit value α is 6 [J/cm ² ]. be. The pulse width τ can be set within a range of 10 [ns] to 1000 [ns]. It is preferably set in the range of 30 [ns] to 500 [ns], more preferably in the range of 50 [ns] to 300 [ns].

The pulse width τ is the time per pulse during which the laser light 3 of the pulse laser heats the object to be irradiated. The fluence F is the energy density per unit area in the laser light 3 of the pulse laser. The fluence F in this embodiment is a value obtained by dividing the energy per pulse of the laser light 3 of the pulse laser by the irradiation area of the laser light 3 . Therefore, if the other conditions are the same, the fluence F of the laser light 3 increases as the pulse width τ of the laser light 3 increases.

Here, the ablation threshold when the pulse width τ is different will be described. The appropriate range of fluence F varies depending on the pulse width τ. The ablation threshold is the fluence required for transpiration of oxide scale. The ablation threshold F _th is proportional to the square root of the pulse width _τL . The relationship between the pulse width _τL and the ablation threshold _Fth is represented by the following equation (1).

F _th ≈ρ×Ω×D ^1/2 ×(τ _L ) ^1/2 Equation (1)
ρ: Density of oxide [g/cm ³ ], Ω: Energy required for transpiration [J], D: Cooling time of outermost electrons [ps]
If the ablation threshold when the pulse width τ _L1 of the laser beam 3 is τ L1 is F _th1 , and the ablation threshold when the pulse width τ _L2 is τ L2 is F _th2 , the relationship between the pulse width τ _L1 and the ablation threshold F _th1 is expressed by the following equation. (2). Also, the relationship between the pulse width τ _L2 and the ablation threshold F _th2 is represented by the following equation (3).

F _th1 ≈ρ×Ω×D ^1/2 ×(τ _L1 ) ^1/2 Equation (2)
F _th2 ≈ρ×Ω×D ^1/2 ×(τ _L2 ) ^1/2 Equation (3)
Eliminating ρ, Ω, and D using the above equations (2) and (3), and rearranging the above equations (2) and (3), the following equation (4) can be derived.

F _th1 =F _th2 ×(τ _L1 /τ _L2 ) ^1/2 Equation (4)
From the above equation (4), when the lower limit of the fluence F (ablation threshold F _th2 ) when the pulse width τ _L2 is 100 [ns] is α [J/cm ² ], the pulse width τ _L1 = τ [ns] The lower limit value (ablation threshold F _th1 ) of the fluence F for is α(τ/100) ^1/2 . On the other hand, when the upper limit of the fluence F (ablation threshold F _th2 ) is β [J/cm ² ], the upper limit of the fluence F (ablation threshold F _th1 ) for the pulse width τ _L1 =τ [ns] is β(τ /100) becomes ^1/2 .

That is, depending on the pulse width τ _L1 = τ [ns], the appropriate range (lower limit and upper limit) of the fluence F of the laser light 3 changes, and the range of the fluence F for this pulse width τ is given by the following equation (5). expressed.

α×(τ/100) ^1/2 ≦F≦β×(τ/100) ^1/2 Expression (5)
Regarding the density ρ of oxides, the densities of main oxides are the density ρ of Fe ₂ O ₃ = 5.24 [g/cm 3 ] and the density ρ of Cr ₂ O ₃ = 5.22 [g/cm ³ ]. cm ³ ] and the density of SiO ₂ ρ=2.196 [g/cm ³ ].

As described above, the laser light 3 emitted from the laser head 22 has a pulse width τ of 100 [ns]. In addition, the laser beam 3 has a fluence F of α=1 [J/cm ² ] or more and β=15 [J/cm ² ] or less. This pulse width τ can be set in the range of 10 [ns] to 1000 [ns], preferably 30 [ns] to 500 [ns], more preferably 50 [ns] to 300 [ns]. should be set within the range of

When the pulse width τ is set in each of the above ranges, the fluence F of the laser beam 3 with respect to the pulse width τ is α×(τ/100) ^1/2 or more and β×(τ/100) ^1/2 or less (however, , α=1, β=15). By setting the fluence F in this way, it is possible to greatly shorten the descaling time compared to laser light irradiation of a conventional pulsed laser while keeping base material damage within an allowable range (for details, see Examples below). ).

Although the type of the laser head 22 is not particularly limited, it is preferable to use a galvanometer scanner because it can irradiate the oxide scale with the laser light 3 with higher precision than other laser heads.

(drive unit and control unit)
The drive unit is connected to the laser head 22 and drives the laser head 22 to move the irradiation position of the laser light 3 of the pulse laser. The controller is connected to the laser oscillator 21 and the laser head 22, and controls irradiation conditions of the laser light 3 of the pulse laser. The irradiation conditions of the laser beam 3 include, for example, fluence F, pulse width τ, oscillation period, laser output, irradiation speed, irradiation width and beam diameter.

The oscillation period of the laser light 3 of the pulse laser is preferably 60 to 120 [kHz]. By setting the oscillation period of the laser light 3 within the above numerical range, when the laser light irradiation step (S51) is viewed as a whole, the fluence F with respect to the oxide scale formed on the surface of the stainless steel strip 1 can be irradiated with the laser light 3 optimized for

This is because, for example, if the oscillation period of the laser light 3 is less than 60 [kHz], the number of irradiation times per unit time to the stainless steel strip 1 is excessively reduced. Therefore, when the laser beam irradiation step (S51) is viewed as a whole, there is a possibility that the laser beam 3 having a sufficient fluence F for descaling cannot be irradiated. Further, when the oscillation period of the laser light 3 is greater than [120 kHz], the fluence F per pulse of the laser light 3 becomes small. Therefore, when looking at the laser light irradiation step (S51) as a whole, there is a possibility that the laser light 3 having a sufficient fluence F for descaling cannot be irradiated.

<Pickling treatment process>
Next, in the pickling treatment step (S52) shown in FIG. 2, the surface of the stainless steel strip 1 after the laser beam irradiation step (S51) is pickled. Specifically, the stainless steel strip 1 is immersed and passed through the pickling bath 41 in the pickling bath 4 shown in FIG. 3 to wash off the oxide scale that has not been completely removed in the laser light irradiation step (S51). The pickling bath liquid of the pickling bath 41 is, for example, HNO ₃ (nitric acid), H ₂ SO ₄ (sulfuric acid), FeCl ₃ (ferric chloride liquid), or a mixture of HNO ₃ and HF (hydrofluoric acid). Use

As a pretreatment for the pickling treatment, for example, between the laser beam irradiation step (S51) and the pickling treatment step (S52), the surface of the stainless steel strip 1 after undergoing the laser beam irradiation step (S51) may be subjected to a neutral salt electrolytic treatment. In the neutral salt electrolysis treatment, the stainless steel strip after hot rolling is immersed and threaded in a neutral salt solution containing a neutral salt such as Na ₂ SO ₄ , K ₂ SO ₄ or NaNO ₃ as a main component. is.

By performing this treatment, the stainless steel strip 1 after undergoing the laser beam irradiation step (S51) is electrolyzed in the neutral salt aqueous solution. Therefore, even if the oxide scale is an oxide such as a Cr-based oxide that has a dense structure and is chemically stable, the oxide scale can be reliably removed by the pickling treatment after the neutral salt electrolysis treatment. can.

Further, when cold rolling is performed, as a pretreatment, for example, between the laser light irradiation step (S51) and the pickling treatment step (S52), the stainless steel after the laser light irradiation step (S51) The surface of the belt 1 may be subjected to a molten salt immersion (salt bath) treatment. The salt bath treatment is a treatment in which the stainless steel strip 1 is immersed and threaded in a mixed alkaline molten salt bath containing caustic soda (NaOH) as a main agent and maintained at 400 to 500°C.

In the oxide scale removal step (S5), it is not essential to subject the surface of the stainless steel strip 1 after the laser beam irradiation step (S51) to a pickling treatment. Although it depends on the steel type of the stainless steel strip 1 to be treated and the conditions of the laser irradiation, if the oxide scale can be sufficiently removed only by the laser light irradiation step (S51), the pickling treatment step (S52) is omitted. You may That is, at least the laser light irradiation step (S51) should be performed in the oxide scale removal step (S5).

〔Example〕
An embodiment of the invention is described below. In this example, by performing the steelmaking process (S1), the continuous casting process (S2), the hot rolling process (S3) and the continuous annealing process (S4) described in the above embodiment, Stainless steel strips of the three chemical compositions shown were produced. This stainless steel strip corresponds to the "stainless steel strip 1 after continuous annealing" described in the above embodiment. Then, this stainless steel strip was subjected to a laser beam irradiation step (S51) while varying the fluence F within the range of 1.31 [J/cm ² ] to 6.55 [J/cm ² ]. In addition, each treatment performed in the steelmaking process (S1), the continuous casting process (S2), the hot rolling process (S3), and the continuous annealing process (S4) adopts a process that has been generally performed conventionally. bottom.

The sheet threading speed in the laser light irradiation step (S51) was set to 0.5 [m/min], and as the laser light irradiation device 2, Laser clear (Laserclear 50A manufactured by IHI Inspection and Measurement Co., Ltd.) was used in this example. Table 2 shows the irradiation conditions of the laser light 3 of the pulse laser in this example.

The surface of the stainless steel strip before the laser beam irradiation step (S51) and after the laser beam irradiation step (S51) was observed using an optical microscope. Observations were made on each of the stainless steel strips of each steel type in a range of 4.12 [mm ² ] on three surfaces at a magnification of 150 times. In the observed optical microscope photograph, the portion where the oxide scale remained and the portion where the oxide scale was removed were binarized using the difference in brightness, and the area of the portion where the oxide scale was removed was calculated as the observation range. The scale removal rate was calculated by dividing by the area.

4, 5 and 6 respectively show optical micrographs of stainless steel strips of SUS304, SUS430 and SUSXM15J1 and their binarized photographs. Moreover, FIG. 7 is a graph which shows the relationship between the fluence F and the scale removal rate. As shown in FIGS. 4 to 7, the surface of the stainless steel strip before the laser beam irradiation step (S51) was entirely covered with oxide scale. By irradiating the surface of the stainless steel strip with laser light 3 of a pulsed laser having a fluence F of 1.31 [J/cm ² ] or more and 6.55 [J/cm ² ] or less, the surface of the stainless steel strip It was found that the oxide scale of was effectively removed.

For example, in the stainless steel strip of the steel type SUS304 shown in FIG. 4, the scale removal rate was 62 [%] on average when irradiated with the laser beam 3 of the pulsed laser having a fluence F of 1.31 [J/cm ² ]. . Further, by irradiating the laser beam 3 of a pulsed laser with a fluence F of 3.93 [J/cm ² ], 5.24 [J/cm ² ] or 6.55 [J/cm ² ], scale removal is performed. The rate improved to an average of 71 [%], 85 [%] or 92 [%].

In the stainless steel strip of the steel type SUS430 shown in FIG. 5, the scale removal rate was 18 [%] on average when irradiated with the laser beam 3 of the pulse laser having a fluence F of 1.31 [J/cm ² ]. Further, by irradiating the laser beam 3 of a pulsed laser with a fluence F of 3.93 [J/cm ² ], 5.24 [J/cm ² ] or 6.55 [J/cm ² ], scale removal is performed. The rate improved to an average of 58[%], 74[%] or 88[%].

In the stainless steel strip of steel type SUSXM15J1 shown in FIG. 6, the scale removal rate was 4 [%] on average when irradiated with the laser beam 3 of the pulse laser having a fluence F of 1.31 [J/cm ² ]. In addition, by irradiating the laser beam 3 of a pulsed laser with a fluence F of 3.93 [J/cm ² ], 5.24 [J/cm ² ] or 6.55 [J/cm ² ], the scale is removed. The rate improved to an average of 39[%], 62[%] or 73[%].

Since the stainless steel strip of SUSXM15J1 is a stainless steel strip of difficult-to-pickle steel, it is difficult to remove the oxide scale even if only the pickling treatment is performed. However, according to the method for removing oxide scale according to one aspect of the present invention, oxide scale can be effectively removed even from a stainless steel strip of difficult-to-pickle steel.

Although not implemented in this example, if the fluence F is 4 [J/cm ² ], Si is 2.5 to 5.0 [%], Cr is 18 to 20 [%], and Ni is It is expected that descaling can be effectively performed even for stainless steel strips of difficult-to-pickle steel containing 12 to 20 [%]. In addition, if the fluence F is 5 [J/cm ² ], the hard pickling containing 2.5 to 5.0 [%] Si, 18 to 20 [%] Cr, and 12 to 20 [%] Ni It is expected that descaling can also be performed more effectively on stainless steel strips of steel. In particular, when the fluence F is 6 [J/cm ² ], it is expected that descaling can be most efficiently performed regardless of the steel type of the stainless steel strip. Furthermore, in any steel type, the scale removal rate is expected to be further improved by performing the pickling treatment step (S52) after the laser light irradiation step (S51).

FIG. 8 is a graph showing the relationship between fluence F and base material damage rate. The area of the surface discoloration (burned portion) after descaling was calculated by image analysis, and the ratio of the area of the surface discoloration portion to the total area was defined as the base material damage rate. When this base material damage rate exceeded 2%, it was determined that the base material was damaged. Discrimination between the surface discolored portion and the normal portion was performed by adjusting the threshold and binarizing the optical micrograph of the sample surface after laser irradiation.

In this embodiment, since three areas of 4.12 [mm ² ] are observed, if the area exceeds 2% of 12.36 [mm ² ], that is, the area of 0.25 [mm ² ], It was determined that there was material damage. From FIG. 8, the base metal damage rate was less than 2% at a fluence F of 15 [J/cm ² ] or less, and it was determined that there was no base metal damage in any steel type.

[Additional notes]
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims, and implementations obtained by appropriately combining a plurality of technical means disclosed in the above-described embodiments The form is also included in the technical scope of the present invention.

INDUSTRIAL APPLICABILITY The present invention can be suitably used for descaling stainless steel strips of difficult-to-pickle steels and general-purpose steels.

1 stainless steel strip 3 pulse laser beam S5 oxide scale removal step S51 laser beam irradiation step S52 pickling treatment step F fluence τ pulse width

Claims (4)

A method for removing oxide scale formed on the surface of a stainless steel strip after hot rolling or cold rolling, comprising:
With respect to the surface of the stainless steel strip after annealing, the fluence F [J/cm ² ] when the pulse width is τ [ns] is α×(τ [ns]/100) ^1/2 [J/ cm ² ] or more and β×(τ [ns]/100) ^1/2 [J/cm ² ] or less (where α= 5.24 , β=15). A method for removing oxide scale, comprising an irradiation step. 2. The oxide scale removing method according to claim 1, wherein the pulse width τ [ns] of the laser light is 10 [ns] or more and 1000 [ns] or less. 3. The method for removing oxide scale according to claim 1, further comprising a pickling treatment step of pickling the surface of said stainless steel strip after said laser beam irradiation step. A method for producing the stainless steel strip, comprising an oxide scale removing step of removing the oxide scale using the oxide scale removing method according to any one of claims 1 to 3.

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