JPS58132301A - Rolling method of making inclusion in casting ingot harmless - Google Patents

Abstract

PURPOSE:To disperse the inclusions in casting ingots finely and to make the same harmless by rolling the ingots under broadside rolling reduction under specific conditions then hot rolling the same under thickness rolling reduction. CONSTITUTION:A casting ingot is rolled under broadside rolling reduction under the conditions expressed by the equation e > axy, and is then hot rolled under thickness rolling reduction. Here, (e): the max. harmless diameter that forms no defects in products (mum), (x): width deformation ratio, (y): thickness deformation ratio, (a): the constant determined by the refining and casting stages of the casting ingot. After the rolling, the ingot is further subjected to cold rolling at >=75% draft. The inclusions in the ingot are finely dispersed by the rolling under the broadside and thickness rolling reduction, and the inclusions are made harmless without application of any special treatments in the stage of refining and casting.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rolling method for finely dispersing nonmetallic inclusions (hereinafter referred to as inclusions) and rendering them harmless by a combination of width reduction rolling and straight reduction rolling.

Conventional methods for rendering harmless inclusions that cause defects in products can be roughly divided into methods that reduce the amount of inclusions that are generated in molten metal, and methods that separate the inclusions that have been generated and remove the number of harmful inclusions. There are methods to reduce the amount of harmful inclusions and methods to change the form of harmful inclusions to make them harmless.

Methods for separating inclusions include: ■ Injection of gas such as argon, injection of powder, or reflux during vacuum processing, which causes inclusions of the main type to float in a ladle and cause defects in the product. A method to reduce the amount of operculum inclusions.

■ During casting, a weir is installed in the intermediate container between the shaped steel and the mold, a so-called tampsee, to allow inclusions to float to the surface.

(!ノ A method of stirring molten steel using electromagnetic force in a casting facility to make inclusions float.

(4) There is a method in which the entire vertical part of the mold straight F of the continuous pillow breast making machine is used to stop the inclusions.

As a method for rendering the form of long-term VC1 inclusions harmless, (5
) Applicable to ERW pipes and UO'iF from calcium addition method Vc! Il alumina cluster'kCaO-Aj203
A method of making it harmless by turning it into a system inclusion.

(Realuminium deoxidation T, 7 Recon deoxidation instead of '#L Sewing, U O [VC Nanban, Aluminum tax production, there is a method to eliminate alumina clusters 〇 However, these methods t1c is definitely a problem.

If this is the case, then the method of flotation of inclusions within the scope of (■) will generate inclusions from the re-acid 1C, and the result will be sufficient, even though the molten steel that has been cleaned once within the control line C is heated. I can buy one that is not.

・The power required to stir the inclusions in the inner bottle of the phantom tongue 7'4 is low and the effect is not sufficient.

(The l1ilL magnetic stirring method in J#Geki is effective in preventing inclusions from floating. However, the power consumption is large and the cost is high.

Similarly, even in the case of the continuous casting machine provided with the vertical section (2), the floating separation rate of inclusions is small and the effect is not sufficient.

Calcium addition method (2) tends to cause ladle-tundish connection υ and nozzle clogging between tundish and mold υ due to Ca0Aj203 inclusions, and the X structure tends to become unstable. In addition, when inclusions adhered to the inside of the nozzle come off, a huge inclusion may enter the nozzle and cause a defect.

■In silicon deoxidation, for alumina clusters,
Although it is effective, it is not effective against inclusions caused by contamination with converter slag.

The present inventors changed the viewpoint from the above conventional method, that is, the removal of inclusions at the 111 refining and casting stages, and investigated the detoxification of existing inclusions. found that not only can the inclusions be finely dispersed, but also that the inclusions can be finely dispersed and become substantially harmless by this rolling process.

The present invention has been made based on the above-mentioned knowledge, and is characterized by the following characteristics: Rolling that renders inclusions harmless by width reduction rolling and hot thickness reduction rolling as shown in the following formula. There is a method.

e, > az -1 but s(0,9 ν<1.O a"4X10~9XlO(pws-') where e:
#Maximum harmless diameter (μm) that does not result in product defects g: Smooth deformation ratio (
Slab width after width reduction / Slab width at width reduction −) C: Thickness deformation ratio (Slab thickness after width reduction / Slab thickness before thickness ratio F) a: *For n-wire/casting type of slab The determined constant JII20 characteristic lies in a rolling method characterized by performing width reduction rolling and hot thickness reduction rolling under the above conditions, and then cold rolling at a rolling ratio of 75% or more.

In other words, according to the experimental studies conducted by the present inventors, the deformation behavior of the rolled workpiece during rolling is as shown in FIG.

(%K) When width reduction rolling and thickness reduction rolling are performed successively, the effect of making the inclusions finer becomes even more remarkable.

■ Rolling is carried out in a temperature range where the plasticity of inclusions is insufficient (130
It is effective to carry out the process at a temperature of 0C or lower) without distracting the inclusions.

■ After performing the prescribed width reduction rolling and hot thickness reduction rolling, if cold rolling is performed at a rolling ratio of 75 or more, the hard inclusions that cause defects in cans 01, which will be described later, will also break and become fine. Decentralize.

I understand that.9.

At this time, by width reduction rolling and subsequent thickness reduction rolling,
The reason why the inclusions become finer is that, according to an investigation of the inclusions in the nine cast slabs, which were carried out after the width reduction rolling and then the thickness reduction-down rolling halfway, vertical and horizontal cracks were observed in the inclusions. This is thought to be due to the collapse of the inside of the inclusion due to the second wheel compression in the longitudinal and lateral directions. 19. It has been found that the rounding of the compression of the two wheels of this inclusion is effective if the frame width ratio F is 10 whispers or more.

Next, the inventors of the present invention generally found that when steel products are manufactured by rolling slabs, the inclusions that cause product defects include the product's bath corrosion, the diameter of the inclusions that may be harmful depending on the use, and the actual We investigated the harmless diameter of inclusions that can be considered harmless (hereinafter referred to as "harmless diameter") and the types of inclusions that cause internal defects and surface defects in products from the perspective of not obstructing the product. Ta.

The results of 7 are as shown in Table 1, which shows the ultrasonic tIiL! In the scratches and tables, no inclusions of 200 μm or less were considered defects, and no true letters were generated, and the UO tube was not defective.
Based on the wave standard, inclusions of ril 50 μm or less are not a problem, and slippers, which are surface defects on hot-rolled coils, are 30 μm or less.
It was found that defects caused by inclusions of 0μ or less grooves do not occur.

9. In cans for carbonated beverages (hereinafter referred to as DI cans) produced by cold rolling and superweave drawing after nine months, 7-lunge processing cracks occur during deep drawing. . We know that inclusions, which are considered to be the cause of this defect, are harmless if they are less than 50 μm in size.

In addition, these inclusions of type 11 are caused by powder used as a lubricant in aluminum-based nucsters, converter slag, or related mold circles.69 Inclusions that cause defects in DI cans are especially Among these, inclusions with a high melting point and hardness are preferred, and 90. Collectively, the present inventors determined the amount of reduction after thickness reduction rolling and the maximum particle size of inclusions. The relationship is shown in Figure 2.

The horizontal pattern is the product of the width deformation ratio and the thickness deformation ratio.

In this way, it is proportional to the product of the width deformation ratio and the thickness deformation ratio, and as the product of the width deformation ratio and the thickness deformation ratio becomes smaller, the inclusion diameter becomes smaller. ""&'! ') ...(x) Here, sld width deformation ratio (width after rolling/width before rolling) t is the liao deformation ratio (width after rolling/width before rolling) dfnaK is the width at the time of death under the deformation ratio of 3.7, The upper limit of the diameter of inclusions (μ disease) present in the subsequent steel plate is a coefficient obtained from Figure 2, and as will be described later, this is a coefficient of 1 for one slab manufacturing machine.Here, jr f Elmlll is rounded to be harmless against product defects - Br existence 40 upper limit (ir, ax are maximum harmless diameters.

It is better if it is smaller than . In other words, inclusions that meet the conditions of formula (2) cannot be considered as defects in the equipment.

e) A rolling method that satisfies the dmax - (2) C (I) condition is the following formula (3), which is a combination of formulas (1) and (2). 3) Now, the coefficient a appearing in the above equation is used, but this is determined by the actual performance of the manufacturing process.

The results shown in Fig. 112 are obtained by deoxidizing the steel at the time of tapping the steel in the converter, without installing a weir in the tanditji, and by casting the round slab in a continuous caster with a 91-circular arc without taking into account the cleaning of the remaining steel. This is the user result.

In this case... a=6.9X10 (am) and -) circle.

However, after the steel was tapped in a converter, a powder injection process was carried out using CaO-based 7 lacs, and after death, a tandige with a weir and a straight part were installed. In the case of rolling 9, a=4. I X 10 (fim), which is nine.

That is, in addition to cleaning the molten steel to eliminate large inclusions, even a small reduction can have a significant detoxification effect.

Generally speaking, the value of a is considered to vary depending on the measures taken to clean the molten steel and the skill mK of the refining skill and casting skill.

In addition, e used in equation (3) is 200 μs, U
Ultrasonic defects on O-tubes include surface flaws on 150 μm hot-rolled coils (
Sliver flaws) are 300 μm, but this value varies depending on the guarantee standards of each manufacturing process.

The values of these maximum harmless diameters (6) and the harmless range covered by the strip juice of equation (3) are shown in FIG.

Product 1 shown in Figure 42 is j & 1 with width reduction rolling and subsequent hot press! be left behind. However, with this rolling method, the harmless diameter was 5
It is very difficult to produce 0 μm DI can material.

However, if the steel plate prepared by width reduction and hot thickness reduction rolling is cold rolled at a reduction rate of 75 inches or more, inclusions can actually be rendered harmless. In other words, it is considered that the inclusions are further finely dispersed in the TL.

Next, the fruit of this invention? Let's talk about IJ.

In the example, a rolling reduction rate of 16 inches or more (3
Product defects are significantly reduced by width reduction of 00 mm or more and hot thickness reduction rolling of 91 mm.

Table 3 shows examples in which cold rolling was performed after width reduction and hot thickness reduction rolling, and product defects are significantly reduced by cold rolling with a reduction ratio of ti76- or higher.

As stated above, by the width and thickness reduction rolling of the present invention, inclusions are finely dispersed, and large inclusions that cause product defects are eliminated. This rolling method is used during refining and casting.
Even without special treatment, inclusions can be finely dispersed and rendered harmless, and molten steel processing and casting costs can be significantly reduced.

In addition, direct rolling, which has a significant energy-saving effect, can be achieved by directly linking continuous casting, and the goal is to improve quality and save energy.

It also represents a significant advance in steel manufacturing methods.

[Brief explanation of the drawing]

Figure 1 shows the change in particle size of inclusions due to width reduction and thickness ratio reduction, and Figure 2 shows the relationship between width and thickness deformation ratio and the upper limit value of inclusion diameter for width reduction and hot rolling. It is a figure shown about a case. Fig. 1 Interchangeable A 躬jf [color cμza] Fig. 2 1 Deformation ratio

Claims (1)

[Scope of Claims] 1. A rolling method that eliminates inclusions in a slab in a width reduction rolling warehouse and a heat-thickness reduction rolling warehouse where f is a % value as shown in the following formula. a,) azy illg (0,9 ν<1.0 a=4X10s~9X10' CAm), e: old large harmless diameter (μm) that does not cause defects in the product 2 knee rhombic ratio (casting after INi pressure F) Single width/in one piece before width reduction) y: Thickness deformation ratio (thickness of slab after thickness reduction/thickness of slab of Sonno Fill) ′ a: Constant 2 determined by slab scouring and casting process, export lower rolling A rolling method for making inclusions in a slab harmless as claimed in claim 1, characterized in that after hot rolling, cold rolling is carried out at a reduction rate of 75 seconds or more.