JP2006206949A - METHOD FOR MANUFACTURING Ni ALLOY - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a Ni alloy superior in hot workability and surface properties at a high yield. <P>SOLUTION: The method for manufacturing the Ni alloy comprises producing a slab of the Ni alloy containing 30-50 mass% Ni by continuous casting; repairing only a side face of it; heating the slab; and hot-rolling it. It is preferable to repair the side face of the slab by grinding with a grinder. The Ni alloy preferably further includes, by mass%, 0.1% or less C, 0.01-0.3% Si, 0.01-0.8% Mn, 0.1% or less P, 0.1% or less N, 0.1% or less S, 0.1% or less Al, 0.1% or less O and the balance Fe with unavoidable impurities. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a Ni alloy with high yield.

  Fe-Ni alloy materials (hereinafter abbreviated as Ni alloys) have excellent characteristics in many respects. For example, invar alloys (Fe-36% Ni) are high-quality color televisions because of their low thermal expansion. It is used as a shadow mask material.

  This Ni alloy is usually manufactured through forging or continuous casting, followed by hot rolling and cold rolling.

  For example, in order to produce a Fe-Ni alloy sheet with high efficiency, after continuous casting, a continuous casting slab of Fe-Ni alloy is hot-rolled by a mill having a continuous hot rolling mill and hot-rolled steel sheet. Then, cold rolling and annealing are repeated on the hot-rolled steel sheet to obtain a final Fe-Ni alloy sheet.

  However, continuous cast slabs made of Fe-Ni alloy have poor hot workability, and impurities segregate to the grain boundaries of the cast structure, causing intergranular cracks, ear cracks, and in some cases fractures during hot rolling. However, the yield is greatly reduced.

  On the other hand, for slabs that are prone to cracking, the slab surface is generally cleaned and all scratches on the surface of the slab are removed, and then hot-rolled to eliminate the starting point of cracks, ear cracks and fractures. It is done to prevent.

  For example, in Patent Document 1, a method of hot rolling after shot blasting, or heating after shot blasting and performing breakdown rolling with a rolling reduction of 30 to 65%, the breakdown slab is heated in a furnace. The method of reheating and finish rolling is described. According to Patent Document 1, since hot rolling is performed after imparting processing strain by shot blasting, hot processing is performed after the crystals of the slab surface layer are recrystallized and refined, and hot workability is improved. Improved. Breakdown rolling is effective for breaking the cast structure.

For example, in Patent Document 2, a continuous cast slab is heated in a non-oxidizing atmosphere furnace, subjected to breakdown rolling with a rolling reduction of 30 to 65%, and then the breakdown slab is reheated in a non-oxidizing atmosphere furnace to finish rolling. How to do is described. According to Patent Document 2, grain boundary oxidation is prevented by heating in a non-oxidizing heating furnace.
JP 2000-5801 A JP 11-342403 A

  However, Patent Documents 1 and 2 have the following problems.

  -Performing full slab care will increase the care load and reduce the yield.

  ・ Implementation of shot blasting is effective, but its effect is small, and new shot blasting equipment is required for implementation.

  ・ Breakdown rolling requires high rolling costs, and the top and bottom of the slab are deformed due to rolling and must be cut off.

  -Non-oxidation heating is technically difficult to make completely non-oxidation in the case of large equipment such as slab heating, and the cost is very high.

  ・ Slabs that have been cleaned on their entire surface are prone to wrinkles on the surface during transportation and line movement. In the case of Ni alloy, the requirements for surface quality are extremely strict due to the application used, and this defect causes surface defects, so it is necessary to perform grinding again, such as rolling after removing surface defects by grinding. is there. And a yield falls by grinding. On the other hand, in order to prevent the surface of the slab that has been fully cleaned from being wrinkled, do not touch the ground or floor during slab transport or line movement, or thoroughly clean the ground or floor. It takes time and effort to use the means. This is because a slab is generally a heavy object of several tons, and when a slab is placed on a foreign object such as pebbles or grinding powder, the foreign object can easily sink into the slab surface due to its own weight. . As described above, there is a problem in that the yield of the surface flaws, or the handling and handling properties are reduced by cleaning the entire surface of the slab.

  As described above, since the Ni alloy contains a large amount of expensive Ni, the yield is particularly important, and it is essential to improve the yield in order to reduce the cost. At present, Ni alloys cannot be produced with good yield due to problems with properties and handling properties.

  From the above, in order to improve the yield, it is important not only to have excellent hot workability, but also to satisfy both of excellent surface properties by preventing surface flaws during line movement and conveyance. An object of the present invention is to produce a Ni alloy that is excellent in hot workability and surface properties and has a high yield.

  In order to solve the above problems, the present inventors have conducted intensive research. As a result, it was found that grain boundary cracking, ear cracking, and fracture can be sufficiently prevented by carrying out only the side care of the continuously cast slab and then performing hot rolling. In addition, by leaving the surface of the slab other than the side surface without taking care of it, the occurrence of surface flaws during transfer and line movement after the hot rolling process is greatly reduced, resulting in a significant increase in product yield. I also found improvements.

The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] After mass casting and manufacturing Ni alloy containing Ni: 30-50% by hot rolling, after slabs manufactured by continuous casting are cared only on the side surfaces, A method for producing a Ni alloy, characterized by heating and hot rolling.
[2] The method for producing a Ni alloy according to [1], wherein the slab side surface is ground by a grinder process.
[3] In the above [1] or [2], the Ni alloy is further in mass%, C: 0.1% or less, Si: 0.01 to 0.3%, Mn: 0.01 to 0 8%, P: 0.1% or less, N: 0.1% or less, S: 0.1% or less, Al: 0.1% or less, O: 0.1% or less, the balance being Fe And a method for producing a Ni alloy, which is an inevitable impurity.

  Since the Ni alloy produced according to the present invention is excellent in hot workability, it is possible to prevent the occurrence of intergranular cracks, ear cracks and fractures during hot rolling. Also, surface wrinkles are greatly reduced compared to conventional products. Thus, since the Ni alloy of the present invention is excellent in hot workability and surface properties, the Ni alloy can be produced with high yield, which is industrially beneficial.

  In the present invention, when Ni is produced by hot rolling a Ni alloy containing 30 to 50%, a slab produced by continuous casting is treated only on its side surface and then heated and hot rolled. It is characterized by that. By making the slab maintenance before hot rolling only on the side surface in this way, hot rolling, especially ear cracking and breakage, can be prevented, and surface flaw adhesion during conveyance and line movement after hot rolling can be prevented. Ni alloy can be manufactured with good yield.

  Hereinafter, the present invention will be described in detail.

  First, the Ni alloy of the present invention preferably contains 30 to 50% of Ni and contains the following small amount of alloy elements.

C: 0.1% or less An element that is inevitably mixed, and it is preferable that the amount be as small as possible. However, excessive reduction is accompanied by an increase in manufacturing cost in the steel making process. Therefore, 0.1% or less is preferable.

Si: 0.01-0.3%
Si can be used as a deoxidizer. In this case, 0.01% or more is required. On the other hand, if it exceeds 0.3%, the etching perforation is impaired, so the upper limit is made 0.3%.

Mn: 0.01% to 0.8%
Mn is required to be 0.01% or more in order to improve hot workability. On the other hand, if it exceeds 0.8%, the thermal expansion is increased, so 0.8% or less.

P: 0.1% or less,
It is an element that is inevitably mixed, and it is preferable that the amount be as small as possible. Therefore, 0.1% or less is preferable.

N: 0.1% or less,
It is an element that is inevitably mixed, and it is preferable that the amount be as small as possible. However, excessive reduction is accompanied by an increase in manufacturing cost in the steel making process. From the above, 0.1% or less is preferable.

S: 0.1% or less It is an element that is inevitably mixed, and it is preferable that the amount is as small as possible. Therefore, 0.1% or less is preferable.

Al: 0.1% or less It is an element that is inevitably mixed, and it is preferable that the amount is as small as possible. Therefore, 0.1% or less is preferable.

O: 0.1% or less It is an element that is inevitably mixed, and it is preferable that the amount is as small as possible. Therefore, 0.1% or less is preferable.

  The remainder other than the above consists of Fe and inevitable impurities. In the present invention, Co may be contained in an amount of 10% or less as an element that does not impair the effects of the present invention.

  Next, the results of examining the ear cracks and the like during hot rolling will be described.

  Ni alloys have low hot ductility and are easily oxidized during heating. In particular, if there are fine cracks, the portion has a high diffusion rate, so that the oxidation is remarkable. From this point, it is known that cracks are likely to occur during hot rolling, and sometimes break. Then, when the state of the progress of the crack in the hot rolling was observed with the crack starting point as the center, it was found that the crack progressed from the side surface and the crack starting point was on the side. This is presumably because the fine cracks on the side surfaces are oxidized and become brittle, and tension is applied by rolling, so that the cracks are easily expanded. From this, it was thought that the progress of the crack could be prevented by eliminating the starting point of the crack present on the side surface, and the slab that had been carefully maintained by grinding only the side surface was hot-rolled and the state of the crack was observed. As a result, no cracks occurred. On the other hand, slabs whose entire surface was ground were similarly hot-rolled and observed for cracks. After all, no cracks occurred. Then, when the side surface was subjected to hot rolling and the whole surface was subjected to hot rolling and the whole surface was subjected to hot rolling, the state after the hot rolling did not change. This result shows, for example, that there is no particular influence on cracking during hot rolling even if the slab upper surface is not ground. That is, since the fine crack part of the surface is thinly extended by rolling, it does not become a starting point of a crack, and it can be said that a crack does not expand at the time of rolling.

  From the above, it is important to eliminate the starting point of cracks before hot rolling from the viewpoint of improving hot workability, and since the starting point of cracks exists on the side surface of the slab, only the side surface is maintained and hot rolling is performed. It was found that cracking can be sufficiently prevented. Therefore, in the present invention, only the side surface of the slab is cleaned, and then hot rolling is performed.

  In the present invention, the side surface of the slab is perpendicular to the line surface (bottom surface) and parallel to the rolling direction when the surface directly in contact with the line is the bottom surface as shown in 2 and 4 of FIG. Points to the other side. On the other hand, the entire surface includes all of the bottom surface, the top surface, and the side surfaces, and is 1, 2, 3, and 4 in FIG.

  Moreover, it does not specifically limit as a care method. For example, a method using a grinder (including a grindstone grinder), mechanical grinding (milling, etc.), and scarf (dissolution removal) can be raised. The care conditions at this time are not particularly limited. However, since “care” in the present invention aims to remove the crack starting point by grinding or the like, for example, when the slab thickness is 240 to 250, the surface is preferably ground around 5 mm. Desirably, cracks are reconfirmed, for example, by conducting a soot penetration test, and the parts with cracks are cleaned.

  In addition, as a result of repeated studies, only the side surfaces of the slab are cleaned, and the surfaces other than the side surfaces are not cleaned, and the surface is left as a protective film. It was found that it has the effect of preventing surface flaws.

  Conventionally, since the entire surface of the slab has been cared for, for example, the surface portion of the surface that comes into contact with the line at the time of conveyance and line movement is also scraped off. For this reason, the surface of the contact surface is in a state of low hardness because the metal surface is exposed, and as described above, the foreign matter gets into the surface of the slab and is easily wrinkled during conveyance and line movement. However, as described above, in the present invention, the surface portion of the contact surface of the slab that has been scraped before hot rolling is intentionally left without being scraped, and this is used as a protective film, so that the yield does not decrease. The surface can be protected. In addition, since the surface is hardened with an oxide film, it is difficult to cause wrinkles during conveyance and line movement. Furthermore, it is not necessary to newly apply a protective film on the contact surface, which is preferable in terms of equipment and cost.

  Based on the above, the Ni alloy of the present invention is manufactured.

  Specifically, first, a slab having the above-described components is obtained by continuous casting.

  Then, based on the above, only the side surface of the slab is cared for.

  Subsequently, it heats and performs hot rolling. The conditions for hot rolling are not particularly limited, and the production can be performed under the conditions usually performed. However, from the viewpoint of preventing ear cracks and improving hot workability, for example, it is preferable to raise the temperature slowly with as little oxygen as possible.

  Furthermore, the hot-rolled steel strip obtained in this way can be cold-rolled and annealed one or more times depending on the purpose to obtain a thin plate.

  Examples of the present invention will be described. After melting steel having the chemical composition shown in Table 1, a 200 mm slab was cast by a continuous casting method. Next, after cooling, only the side surface of the slab was cleaned under the conditions shown in Table 2. Next, hot rolling was performed under the conditions of heating temperature: 1200 ° C. and finish rolling temperature: 900 ° C. to obtain a Ni alloy.

  On the other hand, as a comparative example, hot rolling and cold rolling were performed without performing slab maintenance before hot rolling. All conditions are the same as in the example except that the slab is not cleaned.

  In addition, as a reference example, a product in which slab cleaning was performed not only on the side surface but also on the entire surface was manufactured. The slab care conditions are as shown in Table 2, and all the conditions except for the slab care are the same as in the example.

  The resulting Ni alloy was examined for maintenance yields due to care and cracking during hot rolling. The maintenance yield was calculated by the method of weight after maintenance / weight before maintenance × 100, and the crack was subjected to a full length inspection of the hot-rolled sheet, and was visually judged to be cracked and not cracked. The obtained results are also shown in Table 2.

  From Table 2, in the example of this invention, it is favorable without the crack at the time of hot rolling. In addition, because of the maintenance of only the side, the yield is high. Furthermore, a hot-rolled steel sheet with good quality was obtained, which is inferior to the reference example in which the entire surface was cared for.

  On the other hand, in the comparative example, cracks occur during hot rolling.

  The Ni alloy hot-rolled sheet obtained in Example 1 was subjected to coil grinding with a coil grinder in order to remove surface scale and surface flaws. A surface inspection was conducted every time coil grinding was performed, and if surface scale and surface flaws remained, regrinding was performed, and grinding was performed until there was no surface scale and surface flaws. Table 3 shows the number of grinding passes and the grinding yield. In addition, since the hot-rolled sheet which was not care was severely cracked, grinding with a coil grinder could not be performed, and the product could not be produced.

  As shown in Table 3, in the present invention, each of the two finishes was completed, whereas the reference example in which the entire surface was cleaned had a larger number of backside grinding passes. This is because the back surface has a lot of wrinkles in the reference example (the scale is removed in two passes). The back surface has a lot of wrinkles because it generates rubs during transport and handling, or drops foreign matter. It is because it is. On the other hand, in the present invention, the hard film on the surface of the slab prevented the surface flaws from being generated due to the prevention of scratches and foreign objects. From the above results, the coil grinding yield is as low as 87.1 to 90.0% in the reference example, and as high as 94.2% in the present invention.

For example, it is suitable for fields that require strict surface quality control, such as shadow mask parts.

It is a slab after continuous casting, and is a view showing a slab side surface.

Explanation of symbols

1 Slab top surface
2Slab side
3Slab bottom
4 Slab side

Claims (3)

  When a Ni alloy containing Ni: 30-50% at mass% is continuously cast and then hot rolled, the slab manufactured by continuous casting is treated only on its side, and then heated and heated. A method for producing a Ni alloy, characterized by performing hot rolling.   The method for producing a Ni alloy according to claim 1, wherein the slab side surface is ground by a grinder treatment.   The Ni alloy is further in mass%, C: 0.1% or less, Si: 0.01 to 0.3%, Mn: 0.01 to 0.8%, P: 0.1% or less, N : 0.1% or less, S: 0.1% or less, Al: 0.1% or less, O: 0.1% or less, with the balance being Fe and inevitable impurities Or the manufacturing method of Ni alloy of 2.

Images