KR100377364B1 - Manufacturing method of clad steel - Google Patents

Abstract

An object of the present invention is to provide a method for producing a clad steel sheet, which has no difference in quality, is excellent in economy, and has a short manufacturing period by eliminating the plating process of nickel which is uneconomical in manufacturing the clad steel sheet.

According to the present invention, by weight%, C 0.01-0.15%, Si 0.50% or less, Mn 2.0% or less, P 0.030% or less, S 0.010% or less as a base component, Cu, Ni, A method for producing a clad steel sheet using a steel ingot containing at least one of the alloy components containing Cr and Mo of 1.0% or less, Nb, Ti and V of 0.10% or less and Ca of 0.0050% or less, respectively. Is provided. In the method of manufacturing a clad steel sheet of the present invention, the steel ingot is hot rolled to be manufactured as a slab, the surface of the manufactured slab is blasted, and the nickel is coated on the blasted slab with a thickness of 0.01. Thermal spraying is carried out to mm-0.5 mm. In the present invention, the nickel-sprayed slab is attached to any one of the stainless steel sheet and titanium plate to produce a pack, and after inserting the separation material between the pack, the circumference of the pack is welded, The inside is made of a slab pack vacuumed. In the present invention, the slab pack is heated to a temperature of 900 ℃ to 1100 ℃, and then hot rolled second, hot rolled at a temperature of 800 ℃ or more, and then post-heat treatment at a temperature of 400 ℃ to 700 ℃, composite Re-separation into plates completes the clad steel sheet.

Description

Method of manufacturing clad steel sheet

The present invention relates to a method for manufacturing a clad steel sheet, and more particularly, to a method for manufacturing a clad steel sheet having improved manufacturing process to lower the manufacturing cost of a clad strip, which is a composite steel sheet having lowered corrosion resistance.

In general, stainless clad steel sheet has been manufactured by attaching a nickel plating on the surface of the stainless steel sheet and then attached to the low alloy steel sheet.

In the conventional method of manufacturing a clad steel sheet, a nickel insertion layer is formed between a stainless steel sheet and a low alloy steel sheet. At this time, the nickel insertion layer is formed on the surface of the stainless steel plate by a plating operation in which nickel metal is coated with a surface coating by using a general electroplating method.

In the conventional method of manufacturing a clad steel sheet, a pack is made of a stainless steel plate and a low alloy steel plate plated with a nickel plating layer. Attach the packs so that they are sandwiched. At this time, a separator such as alumina powder is put between the pair of packs, and the nickel layers of the packs face each other. Then, after sealing the outer circumference overlapped in the sandwich shape as described above, the inside of the vacuum treatment to produce a slab pack. The slab pack thus made is hot rolled and made of clad steel sheet.

However, the conventional method of manufacturing a clad steel sheet is a non-economical method because a large plating bath is required first because the electroplating process on the stainless steel plate and then the nickel metal layer is coated.

In addition, the manufacturing method of the conventional clad steel sheet is very economical because the manufacturing cost is very high, mass demand was almost impossible.

The present invention has been made to solve the problems of the prior art as described above, by eliminating the plating process of nickel, which is uneconomical in the manufacture of clad steel sheet, there is no difference in quality, excellent economic efficiency, short production period of clad steel sheet It is an object of the present invention to provide a method for producing the same.

1 is a block diagram illustrating a method of manufacturing a clad steel sheet according to an embodiment of the present invention.

According to the present invention for achieving the object as described above, by weight%, C 0.01-0.15%, Si 0.50% or less, Mn 2.0% or less, P 0.030% or less, S 0.010% or less as a basic component Clad steel sheet using a steel ingot containing at least one of alloy components of Cu, Ni, Cr, Mo of 1.0% or less, Nb, Ti, V of 0.10% or less and Ca of 0.0050% or less of the basic components, respectively. Provided is a method of manufacturing a clad steel sheet for producing the same. In the method of manufacturing such clad steel sheet, the steel ingot is first hot-rolled into a slab, the surface of the manufactured slab is blasted, and nickel (Ni) is 0.01 mm thick in the blasted slab. A first step of thermally spraying to 0.5 mm, a second step of attaching the nickel-sprayed slab to a plate member of a stainless steel plate or a titanium plate to form a pack, and the second step A third step of manufacturing a pair of packs prepared in the step, inserting separators between the packs, welding the outer circumference of the pack, and manufacturing the inside of the pack into a vacuum slab pack; A fourth step of heating the slab pack of three stages to a temperature of 900 ° C to 1100 ° C, followed by hot rolling to a secondary temperature, hot rolling at a temperature of 800 ° C or higher, and then post-heat treatment at a temperature of 400 ° C to 700 ° C, Heat location in the fourth step Preparing a slab packs into a composite plate to complete the clad sheet.

In the following, with reference to the accompanying drawings a preferred embodiment of a method for manufacturing a clad steel sheet according to the present invention will be described in detail.

1 is a block diagram illustrating a method of manufacturing a clad steel sheet according to an embodiment of the present invention.

In the manufacturing method of the clad steel sheet of the present invention, by weight%, containing 0.01% to 0.15% of carbon (C) as a basic component, copper (Cu), nickel (Ni), chromium (Cr), molybdenum (Mo), Low alloy ingots containing at least one of niobium (Nb), titanium (Ti), vanadium (V) and calcium (Ca) are used.

Such low alloyed steel ingots contain carbon (C) of 0.01% to 0.15%, and basically 0.50% or less of silicon (Si) and manganese (Mn) so as to minimize carbide formation at the bonding interface and maintain a good interface state. ) It contains 2.0% or less, phosphorus (P) 0.030% or less and sulfur (S) 0.010% or less as basic ingredients.

In addition, the low alloy ingot is added to the copper (Cu), nickel (Ni), chromium (Cr), molybdenum (Mo) of 1.0% or less to increase the strength and corrosion resistance of the low alloy steel matrix, Niobium (Nb), titanium (Ti), and vanadium (V) each contain 0.10% or less for the purpose of miniaturization. In addition, the low alloy ingot contains less than 0.0050% of calcium (Ca) to control the non-metallic inclusions of the steel to increase the cleanliness of the steel.

Here, the reason for limiting the numerical value of the chemical component of the said low alloyed steel ingot is as follows.

Although carbon (C) is an element that improves the strength, increasing the carbon (C) content to 0.15% or more leads to an increase in the amount of pearlite and carbide at the boundary portion, and there is a fear of promoting the peeling of the interface. In addition, the carbon (C) content is not less than 0.01% in the production of steel, not only decreases the strength, but also takes a long smelting time and economical, the carbon (C) content in the manufacturing method of the clad steel sheet of the present invention is 0.01 It was limited to%-0.15%.

Silicon (Si) deoxidizes in steel and improves corrosion resistance. However, when it is added to 0.50% or more, silicon (Si) acts as a non-metallic inclusion in steel and lowers interfacial adhesion, so it is limited to 0.50% or less.

Manganese (Mn) is an effective element that deoxidizes in steel and improves weldability, hot workability, and strength, but when 2.0% or more is added, it can form sulfides or oxides by forming non-metallic inclusions such as manganese sulfur (MnS). Therefore, it was limited to 2.0% or less.

The presence of a large amount of phosphorus (P) is better because the segregation at the center or grain boundaries of the steel sheet deteriorates the interface quality, and if more than 0.030%, it is extremely harmful to the above quality characteristics, it was limited to 0.030% or less.

Sulfur (S) is an element that impairs interfacial adhesion, so the smaller the content, the more effective it is, but it is impossible to remove it completely. By damaging the sex, it was limited to 0.010% or less.

Copper (Cu) is an element which improves the corrosion resistance in the welded portion and the base metal portion, and is less than 0.10%, so the corrosion resistance is less than 0.10%. When the copper (Cu) content is more than 0.50%, surface defects are easily generated during hot rolling, so it is limited to 0.50% or less.

Nickel (Ni) has the effect of suppressing the high temperature cracking of the steel sheet due to the addition of copper (Cu) in the steel, and does not significantly increase the strength and hardness of the welded part and the base material after hot rolling, and interfacial adhesion and low temperature Since it is an effective element which greatly improves toughness, the effect is excellent as it is added, but since addition of 1.0% or more is expensive, it is preferable to limit it to 1.0% or less from an economic point of view.

Since chromium (Cr) is an effective element for improving the corrosion resistance and strength, the effect is excellent as it is added.In addition, up to 1.0%, the corrosion resistance and strength are continuously increased, but the effect is more than 1.0%. It is limited to 1.0% or less because it causes an increase in manufacturing cost economically.

Molybdenum (Mo) is an effective element to improve the strength and corrosion resistance of the matrix structure, but the addition of up to 1.0% continuously increases the strength and corrosion resistance, but when it is added more than 1.0%, the production cost increases economically. Therefore, it was limited to 1.0% or less.

Niobium (Nb), titanium (Ti), and vanadium (V) refine the grains of the low alloyed steel structure to increase strength and increase impact toughness. However, when niobium (Nb), titanium (Ti), and vanadium (V) were added in an amount of 0.10% or more, the amount of niobium (Nb), titanium (Ti), and vanadium (V) had a bad effect on the interface quality due to the excessive formation of hardened structures and precipitates.

Calcium (Ca) spheroidizes non-metallic inclusions elongated in the rolling direction, such as sulfur manganese (MnS), and serves to increase adhesion to the bonding interface between low alloy steel and stainless steel or titanium. Such calcium (Ca) is limited to 0.0050% or less because when added over 0.0050%, non-metallic inclusions are excessively formed and cleanliness is impaired.

In the following, the manufacturing method of the clad steel sheet of the present invention will be described in order by dividing each step.

As shown in Figure 1, the small slab produced by the primary hot rolling of the ingot blasting (blasting) process and step of thermal spraying nickel (S10).

Low alloy ingots with chemical components as shown in Table 1 below are prepared by dissolving a weight of 30 kg by a vacuum induction furnace.

In Table 1, in order to compare the low alloyed steel ingots used in the method of manufacturing the clad steel sheet of the present invention, the compositional components of the comparative steels were indicated and expressed in weight%.

The low alloy ingot having the components shown in Table 1 is heated in a nitrogen atmosphere for 2 hours at a temperature of 1200 ℃ in a heating furnace. Such low alloy ingots are first hot rolled in the temperature range of 1000 DEG C to 1250 DEG C, thereby producing a small slab for a sprayed steel sheet having a final thickness of 50 mm. Here, the reason for limiting the hot rolling temperature to 1000 ° C ~ 1250 ° C is that when the hot rolling start temperature of the slab pack in the heating furnace is 1000 ° C or less, the temperature drop during hot rolling is severe and there is a time margin for rolling. This is because the hot rolling start temperature is lowered to such an extent.

The surface of the small slab thus manufactured is blasted. Here, blasting can be roughly divided into sand blasting using sand and grit blasting using metal chips. The present invention uses sand blasting which is inexpensive, economical and free of relative quality differences.

Then, the sandblasted steel is thermally sprayed with nickel with a thickness of 0.01 mm to 0.5 mm under the spraying conditions as shown in Table 2 below. Herein, the wire was 1.6 mm in diameter, electro-arc sprayed, and the size of the specimen was 110 × 180 × 17 t (mm).

At this time, the reason why the thickness of the nickel thermal sprayed layer is 0.01 mm or more is because the thickness becomes thin after hot rolling, and thus the effect is not provided. The thicker the nickel thermal sprayed layer is, the better the thickness is. In the case of hot rolling, a strong reduction is taken into consideration and economical emphasis is given so that the thickness is not usually 0.5 mm or more.

For reference, examples of the thermal spraying methods include an electric arc spraying method and a gas frame spraying method. Electric arc spraying is twice as productive as gas frame spraying. This electric arc spraying method is composed of a spraying line having a diameter of 1.6 mm, compared to a gas frame spraying method which mainly uses a spraying line having a diameter of 3.2 mm, and thus has a fine particle size of the sprayed layer. In addition, the electric arc spraying method has an advantage that the operation is easy because there is no break point in supplying the raw material (electricity) as compared to the gas frame spraying method. In the gas frame spraying method, since the diameter of the sprayed wire is thicker than that of the electric arc spraying method, the arc is rough and the coated particles of the sprayed layer are coarse. In addition, due to the interruption of the acetylene gas or nitrogen gas during the operation, there is a possibility that the knot of the thermal spray layer is formed, the quality defect may occur. Therefore, in order to improve the productivity and high quality, the electric arc spraying method may be selected rather than the gas frame spraying method. In manufacturing, the electric arc spraying method should be selected in consideration of the cost of acetylene gas or electricity. In the method for manufacturing a clad steel sheet according to the present invention, a nickel thermal spray layer can be coated regardless of the type of thermal spraying method. Since the economical factors dominate the selection of the thermal spraying method, the selection of the thermal spraying method is not limited.

Step of manufacturing a pair of stainless steel sheet or titanium plate attached (S20).

The nickel-sprayed low alloyed steel ingot prepared as described above is manufactured in a pack by attaching a stainless steel plate or a titanium plate. Here, the pack means that the steel sheet is superimposed on the low alloy ingot having the nickel-sprayed surface layer. The stainless steel sheet used austenitic "STS 304 (L)" and "STS 316 (L)", it is possible to apply a stainless steel having a ferrite structure, martensite structure and duplex (duplex) structure. In addition, the titanium plate is defined as the content of titanium (Ti) is more than 99%. These overlapping packs are paired in two.

Inserting the separation material between the pair of packs and welding the outer circumference of the small slab pack manufacturing step (S30).

The same two packs are attached to each other in an interview, with a separator added between the two packs. As the separation material, alumina (Al ₂ O ₃ ) powder and colloidal silica (colloidal silica) are usually used in a mixture of 2: 1. The reason for adding the separator is because it sticks together during the heating and hot rolling of the pack. After the separator is dried, the outer perimeter between the two packs is welded to each other. The interior of the two packs thus welded is evacuated through an exhaust vent of about 2 to 10 torr. The packs with this vacuumed interior are small slab packs.

Step of heating and secondary hot rolling and post-heat treatment of the small slab pack at a temperature of 900 ℃ ~ 1100 ℃ (S40).

The small slab pack prepared as described above is heated at a low temperature in a temperature range of 900 ° C. to 1100 ° C. in a heating furnace, and is subsequently hot rolled into a secondary furnace. Hot rolling must end the hot rolling at a temperature above 800 ° C to prevent the occurrence of internal stress during hot deformation at the junction interface. Next, the post-heat treatment is performed in a temperature range of 400 ° C. to 700 ° C. to remove the internal stress of the interfacial phase by hot rolling, recover workability, and increase the adhesion of the joint. Here, the reason for limiting the temperature of the post-heat treatment is that the effects listed above are not below 400 ° C, and above 700 ° C, the adhesion of the interface is drastically lowered due to the coarsening of carbides.

In the step (S50) of separating the small slab pack into the composite plate, the post slab small slab pack is separated into two plates again.

And, in the step (S60) of the completion of the clad steel sheet is economical and relatively easy to finish the clad steel sheet through the above steps.

In the following, the adhesion test of the clad steel sheet made by the method for producing a clad steel sheet of the present invention as described above will be described.

Specimens used in the adhesion test are hot-rolled small slab packs processed by the method of manufacturing a clad steel sheet of the present invention to a thickness of 17 mm. The adhesion test can be easily judged by bending the specimens by 180 °, and whether or not cracks are formed on the adhesive portion. This adhesion test is compared with the clad steel sheet made by the conventional method in Table 3 below.

As shown in Table 3, it can be seen that the specimens produced by the method of manufacturing the clad steel sheet of the present invention did not generate cracks and have good adhesion.

The method of manufacturing the clad steel sheet of the present invention has no difference in quality compared to the clad steel sheet manufactured by conventional expensive nickel plating, and can be used in steel pipes (pipes) or welded structures having high corrosion resistance, and forming a nickel plated layer. Since it does not require a plating process for, there is an advantage that can significantly reduce the production manufacturing cost.

The method of manufacturing the clad steel sheet of the present invention has the advantage of short production period by spraying nickel on the spot immediately.

Although the technical idea of the method for manufacturing the clad steel sheet of the present invention has been described with the accompanying drawings, this is for illustrative purposes only and not for limiting the present invention. In addition, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Claims (1)

C 0.01-0.15 wt (%) by weight, Si 0.50 wt% or less, Mn 2.0 wt% or less, P 0.030 wt% or less, S 0.010 wt% or less, the basic five major elements, and Cu, Ni, Cr, and Mo are 1.0 A clad steel sheet for producing a clad steel sheet using a steel ingot containing at least one alloy element and other impurities among the alloy elements having a wt% or less, Nb, Ti, and V 0.10 wt% or less, or Ca of 0.0050 wt% or less, respectively. In the manufacturing method, The steel ingot is first hot rolled to make a slab, the surface of the manufactured slab is blasted, and nickel (Ni) is sprayed on the blasted slab with a thickness of 0.01 mm to 0.5 mm. A first step S10, A second step (S20) of attaching the nickel-sprayed slab to the plate member of a stainless steel plate and a titanium plate in the first step (S10) to manufacture a pack; A third step of manufacturing a pair of packs prepared in the second step (S20), separating separators between the packs, welding the circumference of the pack, and manufacturing the inside of the pack into a vacuum slab pack; (S30) and, After heating the slab pack of the third step (S30) to a temperature of 900 ℃ to 1100 ℃, hot rolling second, hot rolling at a temperature of 800 ℃ or more, and then post-heat treatment at a temperature of 400 ℃ to 700 ℃ The fourth step (S40), Method of manufacturing a clad steel sheet comprising a fifth step (S50, S60) of completing the clad steel sheet by producing a slab pack heat-treated in the fourth step (S40) to a composite plate.