KR102321290B1 - Manufacturing method of steel plate, steel plate, and use thereof - Google Patents

Abstract

The present invention relates to a method for manufacturing a steel sheet, particularly a steel sheet for a vehicle body seat, in which a steel alloy of a desired composition is melted, poured, and rolled into a sheet, wherein the steel alloy is an interstitial free steel (interstitial free steel). steel) (IF steel), and after rolling, the steel sheet is quenched and dressed and coated with an anti-corrosion metal coating by electrolytic process or vapor deposition. In order to achieve low Wsa values with the narrowest possible diffusion, a niobium content of greater than 0.01% by weight, preferably greater than 0.011% by weight, is added to the alloy of the sheet.

Description

Manufacturing method of steel plate, steel plate, and use thereof

The present invention relates to a method for manufacturing a steel sheet having improved appearance quality after formation.

In order to further improve the visual appearance of automobiles during painting, it has been found that it is indeed important, but not sufficient, to improve the paint appearance by adjusting the strip shape. Many parameters are important for good visual appearance in the manufacture of formed and painted sheets.

An essential indicator for good paintability and good paint appearance is the so-called fracture surface arithmetic (Wsa) value. Article published on www.blechnet.com on October 17, 2013, "New sheet galvanization provides a car paint mirror finish [ Neuartige Blechverzinkung bringt Automobile auf Hochglanz ] " states that a Wsa value of a sheet less than 0.35 μm ensures a good paint appearance. First of all, the article states that a low Wsa value indicates a good paint appearance. In this article, the Wsa value is Ra), it is said that it also affects the formability.According to this article, in the conventional sheet, Wsa actually exceeds 0.5 μm, and at the same time, it is successfully achieved by increasing the so-called peak count It has been shown empirically that it is important to lower the Wsa value of the sheet to less than 0.35 μm, while providing sufficient pockets of lubrication for forming.

In this case, the emphasis is on anticipating the subsequent shape of the sheet as a negative tolerance in a manner similar to that used in printing techniques using skin-pass rolls. In order to achieve the above-mentioned Wsa values, a new roll structure was created, and also the heat treatment in the furnace was improved.

A similar report was published by thyssenkrupp Steel Europe (www.besserlackieren.de), which likewise states that the surface finish of galvanized sheets can achieve this quality.

For example, EP 0 234 698 B1 discloses a method for producing a surface roughness with a defined raised area.

Apart from application zinc plating, electrolytic zinc plating or vapor deposition (PVD, CVD,...) is available to apply an anticorrosion coating based on cathode zinc to the steel sheet. Using hot-dip galvanizing, the strips are transported through a liquid zinc bath (about 450 °C), whereas the application of zinc by electrolytic galvanizing or vapor deposition is carried out at lower temperatures (100 °C and 300 °C respectively). lower) occurs.

The surface of electrolytic galvanizing or the surface of vapor-deposited zinc coating is clearly different compared to the surface prepared by hot-dip galvanizing. In particular, although electrolytic zinc plating has a high degree of flatness, it can be identified as a micro-roughness having a super magnification.

Basically, the production of galvanized steel sheet is in such a way that the sheet is produced from raw iron in a converter, cast in a continuous casting plant, and then rolled in a hot strip mill and cold rolled. is done With the electrolytic galvanizing process or with the application of zinc by vapor deposition, prior to applying the zinc coating, quenching and possibly dressing takes place, the application of zinc by electrolytic galvanizing or vapor deposition takes place, zinc application Afterwards, further coatings are possible, for example phosphating.

Austrian standard EN10152 continues to disclose products continuously electrolytically galvanized as low-alloy steels for cold forming.

All of the steels mentioned here are low alloy steels.

Especially in the automotive sector, IF and BH steels are used for body parts.

IF steel does not have interstitial embedded external atoms (small amounts of carbon and nitrogen are completely separated into carbides and nitrides by titanium and/or niobium), so it is an “interstitial” steel with excellent plastic deformability. free)" is understood as a river. These steels are used for deep-drawn components in automotive engineering.

Bake-hardening steel (BH steel) is characterized by a large increase in yield strength as part of the paint heat treatment (typically 20 minutes at 170°C) with very good deformability. These steels also have very good dent resistance, which is why they are often used in car body applications.

It is an object of the present invention to provide a method for producing a steel sheet made of IF steel uncoated or after coating applied by further electrolytic coating or by CVD or DVD process, the steps of which are metals such as Zn, ZnNi, ZnCr Coatings or other metallic coatings that act as anticorrosive coatings in which in the deformed state the desired Wsa values can be better achieved and the range can be reliably maintained.

Said object is achieved by a method having the features of claim 1 .

Advantageous modifications are disclosed in the dependent claims.

Determination of Wsa values was performed in the rolling direction on Marciniak stretch-drawing specimens with 5% strain using SEP1941.

According to the present invention, it has been found that it is not possible to reliably and reliably maintain the Wsa value of a body component in a deformed state within a desired range (<0.35 μm) only by optimizing the long undulation in the non-deformed state.

According to the present invention, it has been found that the long undulation limit required in the deformed state can be explicitly taken into account by carrying out optional steps on the material.

In other words, in particular, by changing the alloy composition of the IF steel used, it is possible to reduce the long undulations in the deformed state to achieve a more stable manufacture of the body material.

Correspondingly, it has been found, according to the invention, that a guaranteed control of reduced long undulations in the deformed state can be achieved by adding niobium to the alloy in a percentage equal to or greater than 0.02% by weight, in particular in IF steels. In particular, for example, steel types DC04 to DC07 can be stabilized with a Wsa value of less than 0.30 μm.

When using IF steel, the Wsa level can be stabilized to an average of 0.29 μm by using the titanium-niobium concept instead of the typical titanium concept for body seats.

It has also been found advantageous that the addition of Nb to the steel allows the recrystallization annealing heating rate to be varied within a wide range without adversely affecting the Wsa value. According to the present invention, this heating rate is 5 to 30 K/s.

A temper-rolling procedure or dressing after recrystallization annealing is used to control mechanical properties and selectively influence surface roughness. In the process, roughness and long undulations are transferred from roll to strip.
The present invention provides the following solutions.
(1) A method of manufacturing a steel sheet, wherein a steel alloy of a predetermined composition is melted, poured, and rolled into a sheet, and the steel alloy is A) interstitial free steel (IF steel) ), and after rolling, the steel sheet is B) quenched and dressed as a steel sheet,
In order to make the Wsa value less than 0.35 μm, a certain amount of niobium is added to the alloy of the steel,
IF steel is melted, analyzed as follows by weight percent,
C: 0.001 to 0.015
Si: 0.01 to 0.5
Mn: 0.02 to 0.5
P: max 0.1
S: up to 0.05
Al: 0.01 to 1.0
Nb: 0.011 to 0.15
Ti: 0.01 to 0.4
The following elements:
boron up to 100 ppm;
up to 0.4% by weight vanadium,
optionally comprising up to 0.4% by weight of one or more of zirconium,
the remainder consists of iron and melting-directing impurities,
The alloy is subject to the following conditions,
N*(Ti+Nb)*S*10 ⁶ ,
Product is more than 1,
How to make a steel plate.
(2) according to (1),
The IF steel to be melted is analyzed as follows by weight percent,
C: 0.001 to 0.010
Si: 0.01 to 0.4
Mn: 0.02 to 0.4
P: up to 0.05
S: 0.03 max
Al: 0.01 to 0.50
Nb: 0.011 to 0.10
Ti: 0.01 to 0.3
How to make a steel plate.
(3) A method of manufacturing a steel sheet, wherein a steel alloy of a predetermined composition is melted, poured, and rolled into a sheet form, wherein the steel alloy is A) interstitial free steel (IF steel) ), and after rolling, the steel sheet is B) quenched and dressed as a steel sheet,
In order to make the Wsa value less than 0.35 μm, a certain amount of niobium is added to the alloy of the steel,
IF steel is melted, analyzed as follows by weight percent,
C: 0.001 to 0.020
Si: 0.01 to 0.7
Mn: 0.02 to 1.5
P: 0.15 max
S: up to 0.05
Al: 0.015 to 1.0
Nb: 0.02 to 0.15
Ti: 0.01 to 0.2
The following elements:
boron up to 100 ppm;
up to 0.4% by weight vanadium,
up to 0.4% by weight zirconium,
hafnium up to 0.5% by weight;
up to 0.5% by weight of tungsten,
optionally comprising up to 0.5% by weight of one or more of tantalum,
the remainder consists of iron and melting-directing impurities,
The alloy is subject to the following conditions,
N*(Ti+Nb)*S*10 ⁶ ,
Product is more than 1,
How to make a steel plate.
(4) according to (1),
After dressing, the steel sheet is provided with a metal corrosion protection coating by an electrolytic process or vapor deposition,
How to make a steel plate.
(5) according to (4),
wherein the metal anticorrosion coating is applied electrolytically or by a CVD or PVD process, the metal coating consisting of or based on zinc.
How to make a steel plate.
(6) according to (1),
A skin-pass roll having a roughness (Ra) of 1.6 to 3.3 μm is used,
How to make a steel plate.
(7) according to (1),
the degree of dressing is between 0.5% and 0.75%,
How to make a steel plate.
(8) according to (1),
The heating rate in the quenching can be between 5K/s and 30K/s,
How to make a steel plate.
(9) The method according to (1),
The alloy is subject to the following conditions,
N*(Ti+Nb)*S*10 ⁶ ,
The product is 1.5 or more,
How to make a steel plate.
(10) The method according to (1),
The IF steel to be melted is analyzed as follows by weight percent,
C: 0.001 to 0.005
Si: 0.01 to 0.3
Mn: 0.02 to 0.3
P: up to 0.05
S: 0.03 max
Al: 0.01 to 0.1
Nb: 0.011 to 0.05
Ti: 0.01 to 0.20
How to make a steel plate.
(11) according to (5),
The metal coating is a zinc coating, a zinc-chromium coating, a zinc-nickel coating, or a zinc-magnesium coating,
How to make a steel plate.
(12) according to (3),
wherein the IF steel to be melted is analyzed as follows in weight percent,
C: 0.001 to 0.010
Si: 0.01 to 0.5
Mn: 0.02 to 1.0
P: max 0.1
S: 0.03 max
Al: 0.015 to 0.5
Nb: 0.021 to 0.10
Ti: 0.01 to 0.15
How to make a steel plate.
(13) The method according to (3),
wherein the IF steel to be melted is analyzed as follows in weight percent,
C: 0.001 to 0.006
Si: 0.01 to 0.4
Mn: 0.02 to 0.6
P: max 0.1
S: 0.03 max
Al: 0.015 to 0.10
Nb: 0.021 to 0.05
Ti: 0.01 to 0.12
How to make a steel plate.
(14) A steel sheet manufactured by the method according to any one of (1) to (13).
(15) A method of using the steel sheet according to (14) for a body component of a vehicle or for a building.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be described by way of example on the basis of several drawings. From the drawing:
1 shows a comparison of improved Wsa values according to the invention before and after deformation versus long undulations in uncoated, dressed IF steel according to the prior art (via Example 48) (starting from Example 49).
Figure 2 shows the relationship between the niobium content in the base material (dressed IF steel) and the measured Wsa value in the deformed uncoated state.
3 shows a comparison of the long undulations in dressed IF steel in the uncoated state and in the electrolytically galvanized state after deformation.
4 shows an alloy according to the invention in tabular form;
5 is a table showing preferred alloy ranges.
6 is a table showing particularly preferred alloy ranges.
7 is a table showing several preferred embodiments according to the present invention and comparative examples.

1 shows a conventional IF steel manufactured and machined according to the prior art (via Example 48). Significant spread of Wsa values readily appears in the course of transformation. Starting from example 49, examples are IF steels according to the invention with significantly improved Wsa values and clearly reduced diffusion. It is self-evident that according to the present invention, the values can be reliably kept to about 0.30 μm or less. In this case, the light color bar is the Wsa value in the undeformed state, and the black bar is the value in the deformed state.

Figure 2 clearly shows the relationship between the niobium content of the base material (IF steel) and the measured Wsa values of the uncoated steel in the strained state. As the Nb content increases, not only the Wsa value decreases, but also the diffusion significantly decreases.

According to the present invention, a niobium content of 0.02% by weight (=200 ppm) is set in the alloy. According to the present invention, the niobium content is preferably set to 0.021 to 0.15% by weight, more preferably 0.021 to 0.10% by weight, even more preferably 0.021 to 0.05% by weight. Using this value, a very good Wsa value can be obtained.

3 shows that the change in Wsa value is hardly affected by the galvanizing process.

It is possible to reduce the undulation value of the metal coated strip in the unstrained state to a low level by using an appropriate skin-pass roll. However, this improvement no longer exists in the deformed state.

The degree of dressing is between 0.5% and 0.75%.

Through the addition of Nb, it was possible to achieve the fact that the Wsa value increased little or no due to the deformation.

Especially after deformation, the IF steel produced according to the invention exhibits significantly better properties than the conventional IF steel according to the prior art.

According to the invention, the IF steel may have an alloy composition according to FIG. 4 (all values are in weight percent).

Preferably, the IF steel has a composition according to FIG. 5 :

A particularly preferred range of the IF steel is shown in FIG. 6 . IF steel contains the following elements: boron up to 100 ppm, vanadium up to 0.4 wt %, zirconium up to 0.4 wt %, hafnium up to 0.5 wt %, tungsten up to 0.5 wt %, 0.5 wt % It may optionally include one or more of up to tantalum.

The remainder consists of iron and melt-indicating impurities, respectively.

Figure 2 shows the corresponding measured relationship of the IF steel, which shows the Wsa value after deformation for the niobium content. In this case, a stable improvement of the Wsa value is evident as the Nb content increases. This relationship may possibly exist with the addition of niobium to the alloy in excess of 0.03 wt %. However, the range according to the invention allows, on the one hand, a sufficient reduction of the Wsa value and, on the other hand, prevents undesirable hardening effects, which can reduce the deformability in the base material.

The roll roughness Ra for the dressing procedure is 1.6 μm and 3.3 μm in order to be able to maintain the customer required roughness values in the strip for low long undulations in the unstrained state and subsequently in the deformed state. set to a value between Reducing the roll roughness value can further reduce the Wsa value, but will require reducing the customer's roughness specification.

All existing metal coating materials according to the prior art can be used as coating materials in the electrolytic deposition process. These include, but are not limited to, zinc alloys in particular.

In the present invention, it is advantageous to be able to successfully set the Wsa value to a very low level in a very stable manner by taking steps within the alloying concept of the steel.

The following example should demonstrate the positive effect of the niobium content (measured on a 5% modified Marciniak specimen) on the formation of the Wsa value of the molded component and should be distinguished from the other effects.

In the examples for coating variant Z listed below, strip speed and deposition conditions are also indicated for completeness. They are all within the normal parameters according to the prior art, but do not significantly affect the Wsa value in the deformed state.

1 : Example of measured Wsa values on IF steel according to the prior art (via example 48) and according to the invention (starting from example 49)

It has been found advantageous to comply with the following conditions.

In the case of a pure zinc coating (Z), the product is 1 or more, and in the case of a zinc-magnesium coating (ZM), the product is 2 or more.

N*(Ti+Nb)*S*10^6

According to the present invention, it can be assured that a coarser deposition is formed. This results in better deformability without negatively affecting strength.

2 shows the relationship between the Wsa value after deformation and the niobium content in the steel.

3 shows Wsa values after uncoated steel and electrolytic galvanizing.

Claims (16)

A method for manufacturing a steel sheet, wherein a steel alloy of a predetermined composition is melted, poured, and rolled into a sheet form, the steel alloy being A) interstitial free steel (IF steel), After rolling, the steel plate is B) quenched and dressed,
In order to make the Wsa value less than 0.35 μm, a certain amount of niobium is added to the alloy of the steel,
IF steel is melted, analyzed as follows by weight percent,
C: 0.001 to 0.015
Si: 0.01 to 0.5
Mn: 0.02 to 0.5
P: max 0.1
S: up to 0.05
Al: 0.01 to 1.0
Nb: 0.011 to 0.15
Ti: 0.01 to 0.4
The following elements:
boron up to 100 ppm;
up to 0.4% by weight vanadium,
optionally comprising up to 0.4% by weight of one or more of zirconium,
the remainder consists of iron and melting-directing impurities,
The alloy is subject to the following conditions,
N*(Ti+Nb)*S*10 ⁶ ,
Product is more than 1,
How to make a steel plate. According to claim 1,
The IF steel to be melted is analyzed as follows by weight percent,
C: 0.001 to 0.010
Si: 0.01 to 0.4
Mn: 0.02 to 0.4
P: up to 0.05
S: 0.03 max
Al: 0.01 to 0.50
Nb: 0.011 to 0.10
Ti: 0.01 to 0.3
How to make a steel plate. A method for manufacturing a steel sheet, wherein a steel alloy of a predetermined composition is melted, poured, and rolled into a sheet form, the steel alloy being A) interstitial free steel (IF steel), After rolling, the steel plate is B) quenched and dressed,
In order to make the Wsa value less than 0.35 μm, a certain amount of niobium is added to the alloy of the steel,
IF steel is melted, analyzed as follows by weight percent,
C: 0.001 to 0.020
Si: 0.01 to 0.7
Mn: 0.02 to 1.5
P: 0.15 max
S: up to 0.05
Al: 0.015 to 1.0
Nb: 0.02 to 0.15
Ti: 0.01 to 0.2
The following elements:
boron up to 100 ppm;
up to 0.4% by weight vanadium,
up to 0.4% by weight zirconium,
hafnium up to 0.5% by weight;
up to 0.5% by weight of tungsten,
optionally comprising up to 0.5% by weight of one or more of tantalum,
the remainder consists of iron and melting-directing impurities,
The alloy is subject to the following conditions,
N*(Ti+Nb)*S*10 ⁶ ,
Product is more than 1,
How to make a steel plate. According to claim 1,
After dressing, the steel sheet is provided with a metal corrosion protection coating by an electrolytic process or vapor deposition,
How to make a steel plate. 5. The method of claim 4,
wherein the metal anticorrosion coating is applied electrolytically or by a CVD or PVD process, the metal coating consisting of or based on zinc.
How to make a steel plate. According to claim 1,
A skin-pass roll having a roughness (Ra) of 1.6 to 3.3 μm is used,
How to make a steel plate. According to claim 1,
the degree of dressing is between 0.5% and 0.75%,
How to make a steel plate. According to claim 1,
The heating rate in the quenching can be between 5K/s and 30K/s,
How to make a steel plate. According to claim 1,
The alloy is subject to the following conditions,
N*(Ti+Nb)*S*10 ⁶ ,
The product is 1.5 or more,
How to make a steel plate. According to claim 1,
The IF steel to be melted is analyzed as follows by weight percent,
C: 0.001 to 0.005
Si: 0.01 to 0.3
Mn: 0.02 to 0.3
P: up to 0.05
S: 0.03 max
Al: 0.01 to 0.1
Nb: 0.011 to 0.05
Ti: 0.01 to 0.20
How to make a steel plate. 6. The method of claim 5,
wherein the metal coating is a zinc coating, a zinc-chromium coating, a zinc-nickel coating, or a zinc-magnesium coating,
How to make a steel plate. 4. The method of claim 3,
wherein the IF steel being melted is analyzed as follows in weight percent,
C: 0.001 to 0.010
Si: 0.01 to 0.5
Mn: 0.02 to 1.0
P: max 0.1
S: 0.03 max
Al: 0.015 to 0.5
Nb: 0.021 to 0.10
Ti: 0.01 to 0.15
How to make a steel plate. 4. The method of claim 3,
wherein the IF steel being melted is analyzed as follows in weight percent,
C: 0.001 to 0.006
Si: 0.01 to 0.4
Mn: 0.02 to 0.6
P: max 0.1
S: 0.03 max
Al: 0.015 to 0.10
Nb: 0.021 to 0.05
Ti: 0.01 to 0.12
How to make a steel plate. A steel sheet manufactured by the method according to any one of claims 1 to 13. A method of using the steel sheet according to claim 14 for a body component of a vehicle or for a building.
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