JPH0531663A - Treating method for belt-like metallic substance - Google Patents

Abstract

PURPOSE:To increase the efficiency of a work to process a belt-like metallic substance by effecting heat treatment, wherein a surface scale is modified, in the atmosphere oxygen concentration of which is a specified value, subsequently effecting cooling treatment wherein a crack or peel of the scale is caused to occur, and grinding and removing a surface part containing a ground so as to finish the coarseness of a finish surface to a specified value. CONSTITUTION:A belt-like metallic substance 2 is unwound from a a pay-off reel 1 and heated in a heating furnace 6. Owing to a strain generated during rapid cooling of the metallic substance in a cooling zone 7, a crack and peel occur in a scale. The crack and peel in the scale oxide are promoted through shot blast 8, and a shape is remedied by means of a tension leveler 10 while a tension is exerted on the belt-like metallic substance by means of a bridle roll 9. A surface part containing scale oxide is ground by means of the resilient grinding wheel roll 11a of a heavy grinding device 11 to effect descale simultaneously with removal of a flaw. In this case, oxygen concentration in the atmosphere in the heating furnace 6 is set to 2-18vol% and surface coarseness after heavy grinding is set to Rmay< total 30mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a surface scale and a surface flaw of a strip-shaped metal body produced in a hot rolling process or a thin cast continuous casting process in stainless steel, ordinary steel, titanium and its alloys, high alloys and the like. The present invention relates to a method for treating a strip-shaped metal body, which enables improvement of the surface quality of the strip-shaped metal body, pickling treatment, and simplification of the surface flaw removal step in a separate line.

[0002]

2. Description of the Related Art In a manufacturing process of a strip-shaped metal body, an oxide scale or a surface flaw is generated on the surface of the strip-shaped metal body due to heating of the slab and subsequent hot rolling or continuous casting of thin slabs. And a process for finishing the surface is required. Here, the strip-shaped metal body is a hot-rolled coil of stainless steel, ordinary steel, titanium and its alloys, high alloys or the like, or a coil continuously cast and wound into a thin wall. As a conventional typical method, a steel ball having a diameter of 0.2 to 0.6 mm is projected on the surface of a strip-shaped metal body to perform shot blasting for surface cleaning to cause cracks or peeling of the scale, and then, Descale by pickling with nitric hydrofluoric acid, sulfuric acid, hydrochloric acid, etc., then perform cold rolling to correct the shape of the strip metal body, and then remove the surface flaws of the strip metal body by belt grinding on another line. Is the way.

However, in the conventional manufacturing process, the pickling process is a continuous line with the annealing process, and the grinding line and the rolling line or the dummy plate welding line are arranged separately, so that the oxide scale and the surface of the strip-shaped metal body are arranged. In order to remove the flaw, it is necessary to pass 2 to 4 lines, and there is a problem that the efficiency is extremely low. The annealing pickling line
Since descaling is performed by pickling, it is inefficient, and there are various problems in terms of productivity, cost, and labor saving such as generation of a large amount of waste liquid accompanying pickling.
Also, in order to uniformly remove surface flaws by belt grinding in the plate width direction, it is necessary to straighten the shape of the coil by cold working, but this is often done using a normal cold rolling mill. In addition to the original gauge down (thickness reduction) work, extra shape correction work is required, which not only does not improve efficiency, but also raises costs.
Further, in the grinding line, the method of grinding the surface of the strip-shaped metal body with a rotary endless belt is mainly used, but since the belt life is short and frequent belt replacement is required, workability is poor and the strip running speed is low, Moreover, there is a problem that uniform grinding cannot be performed unless the plate shape before grinding is flat.

Therefore, for the purpose of improving the efficiency of descaling and improving the surface quality of the hot-rolled steel strip, a plurality of pickling treatment steps are provided after the pretreatment step of the tension leveler, and between the plurality of pickling treatment steps. Japanese Unexamined Patent Publication No. 59-41482 discloses a descaling line mainly combined with a grinding process for removing metal residues and smut. However, although the surface quality of the steel strip is improved to some extent in the descaling line, its effect is limited, and since a large amount of descaling is performed by pickling treatment, a considerably large-scale pickling treatment facility is required. Therefore, the initial investment is large. Moreover, it is necessary to treat a large amount of waste liquid accompanying pickling. Further, since the grinding process provided between each pickling treatment process is not for actively removing the surface flaws of the steel strip, the steel strip passed through the descaling line is used for removing the surface flaws. There is a problem that it has to be passed to another grinding line.

[0005]

SUMMARY OF THE INVENTION The present invention is directed to a surface scale of a strip-shaped metal body produced in a hot rolling process or a thin cast continuous casting process in stainless steel, ordinary steel, titanium and its alloys, high alloys, and the like. When removing surface flaws, mechanical descaling and surface conditioning methods that improve the surface quality of the strip-shaped metal body and simplify the pickling treatment and surface flaw removal process, etc., make the strip-shaped metal body treatment work more efficient. At the same time, the manufacturing cost is reduced by simplifying the treatment of acid and waste liquid, the investment for pollution control is reduced, the working environment is improved, and the continuous treatment makes unnecessary the scratching work on another line. Has an aim.

[0006]

The present invention has been completed as a result of various studies on mechanical descaling and surface conditioning methods and combinations of the methods for this purpose, and the gist thereof is as follows. Is. 1. The strip-shaped metal body is rewound from the payoff reel and supplied, followed by heat treatment for modifying the surface scale in an atmosphere with an oxygen concentration of 2 to 18 vol.%, And subsequently cracking or peeling of the scale. Cooling, then mechanically grinding and removing the surface layer part including the base material to perform heavy grinding to finish the surface roughness to R _max ≦ 30 μm, and then mechanically polishing and removing the base material having a depth of 35 μm or less. A method for treating a strip-shaped metal body, which comprises performing a surface conditioning treatment, a cleaning treatment, and a winding with a tension reel. 2. A method for treating a strip-shaped metal body, which comprises performing trimming processing or grinding treatment on a strip-shaped metal body edge after unwinding the strip-shaped metal body. 3. A method for treating a strip-shaped metal body, which is characterized in that, following the cooling treatment, a pretreatment for promoting cracks or peeling of the surface scale is promoted by mechanical means. 4. A method for treating a strip-shaped metal body, which comprises performing shape correction treatment after the cooling treatment. 5. A method for treating a strip-shaped metal body, which comprises performing a shape correction treatment subsequent to the above-mentioned pretreatment. 6. A method for treating a strip-shaped metal body, which comprises pickling after the surface conditioning treatment and polishing.

[0007]

The method for treating a strip-shaped metal body according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic explanatory view showing one embodiment of a process line for carrying out the method of the present invention. In FIG. 1, 1 is a pay-off reel for rewinding and feeding a strip-shaped metal body, 2 is a strip-shaped metal body that is hot-rolled or is continuously cast into a thin-walled slab, and 3 is a dummy plate for the strip-shaped metal body (hereinafter referred to as a leader) ) Welding or welding between leaders, and for example, a submerged arc welding machine, a TIG welding machine, a plasma welding machine, a spot welding machine or the like is used. 4 is a trimmer for cutting and removing edge flaws and hot cracks generated in hot rolling or continuous casting of thin cast slabs, and 5 is an edge for grinding and removing relatively minute ones of such flaws and cracks. It's a grinder. 6 is a heating furnace for heating the metal strip, which is usually a heating furnace for burning heavy oil or gas.
An electric heating furnace such as induction heating or direct current heating may be used.

Reference numeral 7 is a cooling zone for cooling the strip-shaped metal body after heating, such as gas cooling, spray cooling, water spray cooling and roll cooling. Reference numeral 8 is a dry or wet shot blast for projecting a steel ball on the surface of the strip-shaped metal body. 9
Is a bridle roll that applies the tension required to grind a metal strip. Reference numeral 10 is a tension leveler for bending or tensioning the strip-shaped metal body. 11
Is, for example, an elastic whetstone roll 11a and a backup roll 1
It is a heavy grinding device which forms a pair with 1b and grinds both front and back surfaces of the strip-shaped metal body. 12 is, for example, an elastic grindstone roll or a brush roll 12a and a backup roll 12b.
It is a surface conditioning device that mechanically conditions both the front and back surfaces of a strip-shaped metal body by pairing with and.

Here, the elastic grindstone roll is a roll-shaped grindstone having a certain degree of elasticity in order to easily fit to the shape of the plate, and, for example, discs coated with abrasive grains are laminated to form a roll. There are those (laminated type), those in which flap wheels are laminated and formed into a roll shape (flap type), and those in which nylon resin containing abrasive grains is integrally formed into a roll shape (integrated type). The brush roll includes, for example, a roll made of a brush made of nylon fiber containing abrasive grains.

Reference numeral 13 is a brush cleaning device for removing metal residues, scale powder, etc. adhering to the surface of the band-shaped metal body subjected to heavy grinding and surface conditioning. Reference numeral 14 is a flaw detector for inspecting the presence or absence of surface flaw remaining, and its method includes, for example, a CCD camera method and a laser light method. Reference numeral 15 is a switching machine for sending the strip-shaped metal body to a tension reel or a rolling mill. Reference numeral 16 is a tension reel for winding up the washed strip-shaped metal body. 17 is 1
It is a bridle roll which gives a tension necessary for continuously rolling the strip-shaped metal body that has been washed without winding up the strip-shaped metal body in 6. Denoted at 18 is a rolling mill for rolling the descaled or flawed strip-shaped metal body. Reference numeral 19 is a tension reel for winding up the rolled strip-shaped metal body.

In the processing step of the strip-shaped metal body having such a structure, the strip-shaped metal body 2 is rewound from the pay-off reel, first the welder 3 welds the leader, and then the leader of the preceding material is welded. Subsequently, after the flaws and cracks in the edge portion are removed by the trimmer 4 or the edge grinder 5, the scale is heated in the heating furnace 6 to make the scale near the substrate hollow, and it occurs during the subsequent rapid cooling in the cooling zone 7. The resulting strain causes cracking or peeling of the scale. Moreover, the cracking or peeling of the oxide scale is promoted by the collision force of the steel balls projected on the surface by the dry or wet shot blasting 8. Further, while the tension is applied to the strip-shaped metal body by the bridle roll 9, the crack and peeling are further promoted by the tension leveler 10, and the shape is corrected to facilitate uniform grinding and polishing. .

Next, the elastic grindstone roll 1 of the heavy grinding device 11
In 1a, the surface layer portion including the oxide scale is ground to perform descaling and flaw removal at the same time. Next, the elastic grindstone roll or brush roll 12a of the surface conditioning device 12 or the pickling treatment slightly grinds or abrades the base material and smoothes or smoothes the heavy-ground surface.
Blurred. Thereafter, the metal residue, scale powder, etc. adhering to the surface of the strip-shaped metal body are washed and removed to be finished, and after the flaw detector 14 confirms whether or not the surface flaw remains, it is wound up on the tension reel 16. After cleaning, the surface of the belt-shaped metal body is further smoothed by the rolling machine 18 while tension is applied to the belt-shaped metal body by the bridle roll 17, and the metal body is wound up on the tension reel 19.

[0013] The scale of the hot-rolled strip is repeatedly thinned during the hot-rolling and peeled off by rolling, and finally is extremely thin and strongly bonded to the base material. However, the scale increases in thickness or changes in composition due to heating, so that peeling or cracking is likely to occur. Such a reforming effect is extremely small when the oxygen concentration in the atmosphere in the heating furnace is less than 2 vol.%. Further, when the oxygen concentration exceeds 18 vol.%, The scale thickness is remarkably increased, the yield is extremely reduced, and the cost is increased. Therefore, the oxygen concentration in the atmosphere is set to 2 to 18 vol.%. The heating temperature is 70
The temperature is preferably 0 ° C or higher, more preferably 800 ° C or higher. In the scale by heating, peeling or cracking occurs due to strain generated during rapid cooling in the subsequent cooling process. For this effect, it is preferable to set the cooling rate to 5 ° C./sec or more, more preferably 10 ° C./sec or more.

Subsequently, descaling and flaw removal of the strip-shaped metal body are carried out by mechanical heavy grinding, but the thickness of the scale and the depth of surface flaws produced by hot rolling or subsequent annealing or thin cast slab continuous casting are performed. Has a thickness of at least about 5 to 10 μm, and therefore, in order to remove scales and surface defects, it is necessary to perform heavy grinding to remove the surface layer portion including the base material. The heavy grinding amount needs to exceed at least 10 μm. Desirably, it exceeds 20 μm. Further, the surface roughness after heavy grinding has a deep grinding mark such as a scratch when R _max exceeds 30 μm, and in order to sufficiently remove this, the load of the surface conditioning in the subsequent step increases. Therefore, the surface roughness after heavy grinding is set to R _max ≦ 30 μm from the viewpoint of reducing the load of surface conditioning. It is more desirable to set R _max ≦ 20 μm. Therefore, heavy grinding may be performed in two or more passes, and in the final pass, the abrasive grain count may be # 120 or more corresponding to R _max ≦ 20 μm.

Next, the surface conditioning after the heavy grinding is a process for smoothing the surface of the heavy grinding, but since an elastic grindstone roll or a brush roll having a finer grain size than that of the heavy grinding is used, If the removal thickness exceeds 35 μm, the treatment efficiency is poor and the yield is reduced. Therefore,
The thickness of the removed material for surface conditioning was set to 35 μm or less in terms of treatment efficiency and yield. The roughness R _max of the finished surface after surface conditioning is 10 μm
If it exceeds, the surface roughness R _max ≤ since the products after cold rolling and annealing do not have good surface quality due to residual grinds and surface irregularities.
10 μm is good. It is desirable to set R _max ≦ 5 μm, and for that purpose, it is desirable to perform the surface conditioning in at least two passes or more. Abrasive grain count is
It is preferable to use # 150 or higher, and to use a higher count than the previous pass in the subsequent pass. Further, in the case of a polishing tool having an abrasive grain count of # 150 or more, the load is 4.5 A
If it exceeds 1.0 cm / cm, the tool wear remarkably increases for a constant polishing amount, and therefore the tool life is significantly shortened. Therefore, it is desirable to set the load to 4.5 A / cm or less.

The welding between the leaders is for continuously processing the strip-shaped metal body, and spot welding with a short welding work time is desirable. In addition, the welding with a leader on the strip-shaped metal body is for directly connecting the two steps by omitting the welding work on another line, and the submerged arc welding, the TIG welding or the TIG welding, which has a high weld strength and can secure the tension in the rolling step. Plasma welding is preferred. The welding is performed after rewinding in terms of workability and work efficiency.

The trimming and edge grinding are for directly connecting the two steps by omitting the work of removing the flaws and cracks in the edge portion by another line, and relatively large flaws are taken in view of workability, work efficiency and yield. A round blade type trimmer is used for cracking, and a grindstone type edge grinder is used for minute ones. Furthermore, when shipping the hot-rolled and annealed coil as a product, the trimmer can be used as a tenter.

Mechanical means such as dry or wet shot blasting is used to promote cracking or peeling of the surface scale generated by the cooling treatment, if necessary. Further, a means such as a tension leveler corrects the defective shape of the strip-shaped metal body generated during heating and cooling, if necessary, and further promotes cracking or peeling of the surface scale.

If pickling is combined after surface conditioning, sharp grinding lines are rounded and the surface profile is improved, and the material containing a work-affected layer during grinding can be removed if necessary. The surface quality after rolling is further improved. For pickling, it is desirable to use sulfuric acid, nitric acid, and nitric hydrofluoric acid individually or in a plurality of treatments depending on the target material.

If rolling is combined after the surface conditioning, the surface can be made smoother and the rolling can be efficiently performed up to the intermediate plate thickness, so that the productivity can be greatly improved.
If the total rolling reduction is less than 20%, the residuals in the surface conditioning cannot be sufficiently eliminated. Therefore, the total rolling reduction is preferably 20% or more. Further, the type of rolling mill is preferably a 6-high rolling mill from the viewpoint of shape control. Further, the number of stands of the rolling mill is 3 to 3 because the rolling speed for heavy grinding and surface conditioning is one digit or more lower than the normal rolling speed.
Four stands are sufficient, and from the viewpoint of capital investment, three stands or less are preferable.

[0021]

EXAMPLES In accordance with the process shown in FIG. 1, heating / cooling, heavy grinding, and surface conditioning were performed on the strip-shaped metal body under the conditions shown in Tables 1 and 2, and descale evaluation, surface roughness and grinding amount were investigated. . The results are also shown in Tables 1 and 2. In this table, as the grinding amount, the weight before and after the treatment was measured, and the removed thickness was calculated from the specific gravity. For the surface roughness, a sample was taken after each treatment and measured in the plate width direction with a roughness meter, and the maximum roughness R _max was used. The descale evaluation was performed as follows. ◯: No scale remains and no surface flaws. Δ: No scale remains, but surface flaws remain. X: Scale and surface flaws remain. In addition, the surface quality of cold-rolled and annealed products depends on the degree of gloss.
And ranks A to D were evaluated, and rank B or higher was regarded as a pass. The conditions for cold rolling annealing were normal conditions. As is clear from this table, the evaluation results of the strip-shaped metal bodies according to the method of the present invention are all good, no scale residue and surface flaws are observed, and the product after cold rolling annealing also has good surface properties.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

[Table 3]

[0025]

[Table 4]

[0026]

As is apparent from the above, when removing the surface scale and surface flaws, the metal strip is treated according to the method of the present invention to improve the surface quality of the metal strip and pickling treatment and surface flaws. High efficiency of descaling by mechanical heavy grinding and mechanical surface conditioning method that can simplify the removal process, etc., while reducing manufacturing cost and pollution control cost by simplifying acid and waste liquid treatment As a result, the working environment has been improved, and it has become possible to eliminate flaws on another line by continuous processing. Further, the method of the present invention in which a welding machine, a trimmer, and an edge grinder are used in combination on the same line, does not require leader welding on another line and scratches on the ends to significantly improve workability, and further in a hot rolled annealed coil product. A single process has made it possible to significantly shorten the delivery time.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an embodiment for carrying out the present invention.

[Explanation of symbols]

1 Payoff reel 2 strip metal 3 welding machine 4 trimmer 5 edge grinder 6 heating furnace 7 cooling zones 8 Dry or wet shot blast 9 bridle roll 10 Tension leveler 11 Heavy grinding machine 11a Elastic whetstone roll 11b backup roll 12 Surface conditioning equipment 12a brush roll 12b backup roll 13 Brush cleaning device 14 flaw detector 15 Switching machine 16 tension reel 17 Bridle Roll 18 rolling mill 19 Tension reel

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shuichi Inoue             No. 3434 Shimada, Hikari City, Yamaguchi Prefecture Nippon Steel             Hikari Steel Works Co., Ltd. (72) Inventor Takahiro Fujiwara             No. 3434 Shimada, Hikari City, Yamaguchi Prefecture Nippon Steel             Hikari Steel Works Co., Ltd.

Claims (6)

[Claims] 1. A strip-shaped metal body is rewound from a pay-off reel and supplied, followed by heat treatment for modifying the surface scale in an atmosphere having an oxygen concentration of 2 to 18 vol.%, And subsequently cracking of the scale. Alternatively, a cooling treatment for causing peeling is performed, and subsequently, a surface layer portion including the base material is mechanically ground and removed to perform a heavy grinding treatment for finishing the roughness of a finished surface to R _max ≦ 30 μm, and then a base material having a depth of 35 μm or less. A method for treating a strip-shaped metal body, which comprises mechanically polishing and removing the surface of the metal, followed by cleaning, and then winding the metal with a tension reel. 2. The method for treating a strip-shaped metal body according to claim 1, wherein trimming treatment or grinding treatment of a strip-shaped metal body edge is performed after unwinding the strip-shaped metal body. 3. A method for treating a strip-shaped metal body, which is characterized in that, following the cooling treatment according to claim 1 or 2, a pretreatment that promotes cracking or peeling of the surface scale is promoted by mechanical means. 4. A method for treating a strip-shaped metal body, which comprises performing a shape correction treatment subsequent to the cooling treatment according to any one of claims 1, 2, and 3. 5. A method for treating a strip-shaped metal body, which comprises performing a shape correction treatment subsequent to the pretreatment according to claim 3. 6. Any one of claims 1, 2, 3, 4, and 5.
The method for treating a strip-shaped metal body, which comprises performing surface conditioning treatment polishing and then pickling.