JPH02284777A - Manufacture of stainless steel cladded plate having excellent corrosion resistance and toughness - Google Patents

Abstract

PURPOSE:To improve corrosion resistance and toughness by using stainless steel as cladding material and steel material containing C, Si, Mn, Al as a base material, rapidly heating the cladding material side at higher temp. than that of the base material side and controlling the finishing temp. of rolling to the specific temp. at the base material side. CONSTITUTION:The stainless steel as the cladding material 1 and the steel material composed of 0.01-0.2wt.% C, 0.05-0.8% Si, 0.3-2.2% Mn, 0.001-0.07% Al and the balance of iron as the base material 2, are used. At the time of clad-rolling, by rapidly heating the cladding material side, the temp. of the cladding material side is higher than that of the base material side and the finish temp. of the rolling is controlled to 650-850 deg.C at the base material side. By this method, the generation of crack in the cladding material is prevented and the sensibility is suppressed and the generation of peeling at interface is prevented and further, the stainless steel cladded steel improving the strength and the toughness of the base material and having excellent corrosion resistance can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a method of manufacturing a stainless clad steel plate by rolling.

(Conventional technology) The main uses of stainless steel clad steel with low temperature toughness include linezumib used in oil fields in low-temperature areas containing a lot of hydrogen sulfide and carbon dioxide, offshore structures in icy areas, and icebreakers. can be mentioned. These applications naturally require corrosion resistance from the laminate and excellent strength and low-temperature toughness from the base material.

The main manufacturing methods for clad steel include rolling joining, and other methods such as explosion bonding, overlaying, and casting, but rolling joining is the most superior in terms of productivity and cost, and is widely used. be hired (to be)

Normally, rolling craft assembly methods include the sandwich type (a), oven type (b), and double-sided clad type (e), as shown in Figure 3. If there is a concern about deterioration of the corrosion resistance of stainless steel, a method of inserting an intermediate material such as Ni foil between the stainless steel composite material and the base material and rolling it is also adopted. 1 in the figure is a laminated material,
2 represents the base material, and 3 represents the release agent.

The rolled clad material that has been assembled in the above-mentioned manner is charged into a heating furnace, heated to a temperature of usually 1150° C. or higher, and joined by hot rolling to be finished to a prescribed thickness. Incidentally, in order to obtain high bondability, a rolling reduction ratio of 1050°C or higher and 2 to 3 or higher is usually adopted.

In addition, the laminating material is SUS 316 (L), 5US304
(L) etc., the finishing temperature of rolling is 750°C or higher, 5US containing 25% or more Cr, 3% or more Mo.
When using 329J2L, the rolling temperature is 95
0°C or higher, and similarly for 5US444 etc., the rolling finishing temperature is required to be 950°C or higher.

(Problem B to be solved by the invention) As mentioned above, maintaining the finishing temperature of rolling at a high temperature is, for example, using 5US316 (L), 5tJS3
In the case of 04(L), when rolling at low temperature, there is a risk that the laminate will break due to work hardening or peel off at the cladding interface, so the finishing temperature of rolling should be set to 75.
0°C or higher, Mo: 3% or higher, Cr: 25
When using 5O3329J2L etc. containing 50% or more as a laminate, there is a risk that the σ phase will precipitate during the rolling process and cause cracks, so rolling must be completed at 950°C or higher. It is. SUS 444, S U
Even when 5310S is used as a laminate, there is a risk that Cr carbides will precipitate during the rolling process and cause sensitization, so the rolling finishing temperature needs to be 950°C or higher as described above. ℃ to 10℃
The reality is that it is difficult to completely suppress sensitization unless accelerated cooling beyond /S is performed.

In this way, in conventional rolling of stainless steel crat steel, the rolling temperature is largely regulated by the properties of the laminated material, and finishing rolling is optimal from the perspective of maximizing the strength and toughness of the base material. Not done under the conditions. For example, when carbon steel is rolled at 950° C. or higher, its toughness is low and the fracture surface transition temperature νTs in the glossy Ruby impact test rises to near room temperature. Therefore 5tJS3
It is extremely difficult to manufacture a low-temperature stainless clad steel plate using laminate materials such as 29J2L and SUS 444.5tJS310S by rolling.

The present invention was devised in view of the current situation, and is intended to suppress the sensitization of the laminate during clad rolling, prevent cracking and breakage of the laminate, and peeling at the cladding interface, and to The purpose of the present invention is to provide a method for manufacturing stainless clad steel with excellent corrosion resistance using rolling conditions that maximize low-temperature toughness.

"Structure of the Invention" (Means for Solving the Problems) In order to achieve the above-mentioned object, the present inventors (1) used ferritic or austenitic stainless steel or duplex stainless steel as a mating material, and In weight%, C: 0.01-0.2%, Si: 0.05-0.8%
, Mr+: 0.3-2.2%, AJ: 0.001
Using a steel material containing ~0.07% and the balance consisting of iron and unavoidable impurities, the laminate side is heated rapidly during clad rolling to make the laminate side higher than the base metal side. , and the finishing temperature of rolling was set to 6 on the base metal side.
A method for producing a stainless clad steel sheet with excellent corrosion resistance and toughness, the method comprising controlling the temperature to 50 to 850°C.

(2) Ferritic or austenitic stainless steel or duplex stainless steel is used as the laminated material, and the base material is Coo in weight%. 01-0.2%, Si: 0, 0
5-0.8%, Mn: 0.3-2.2%, A6
: Contains 0.001 to 0.07%, and further contains Nb:0.
08% or less, Cu: 2.0% or less, Ni: 3.0% or less, Ti: 0.1% or less, Cr: 1.0% or less, Mo
: 1.0% or less, V: 0.1% or less, B: 0.00
4% or less, Ca: 0.008% or less, using a steel material consisting of one or more types of iron and inevitable impurities, and rapidly heating the laminate side in the middle of cra-7 rolling. The laminate side is made hotter than the base metal side, and the finishing temperature of rolling is set at 650 to 85 on the base metal side.
Controlled to 0℃? 1) A method for producing stainless clad steel material with excellent corrosion resistance and toughness.

(3) Ferritic or austenitic stainless steel or two-phase stainless steel is used as a laminated material, and the base material is C: 0.01 to 0.2%, Si: 0.
05-0.8%, Mn: 0.3-2.2%, 8N:
Using a steel material containing 0.001 to 0.07% and the balance consisting of iron and unavoidable impurities, the laminate side is heated more rapidly than the base material side during clad rolling. A method for manufacturing stainless steel craft steel having excellent corrosion resistance and toughness, in which the rolling finishing temperature is controlled at 650 to 850°C on the base metal side, and then the rolling temperature is reduced to 3 to 850°C.

(4) Ferritic or austenitic stainless steel or two-phase stainless steel is used as a laminated material, and as a base material, C: 0.01 to 0.2%, Si: 0, 0
5-0.8%, Mn: 0.3-2.2%, Af
f: Contains 0.001 to 0.07%, and further contains Nb
: 0.08% or less, Cu: 2.0% or less, Ni: 3.0
% or less, Ti: 0.1% or less, Cr: 1.0% or less, Mo: 1.0% or less, V: 0.1% or less, B: 0
．． 0.004% or less, Ca: 0. Using a steel material consisting of the balance iron containing one or more types of OO8% or less and unavoidable impurities, the laminate side is heated more rapidly than the base metal side during clad rolling. The finishing temperature of rolling is set to 6 on the base metal side.
A method for manufacturing a stainless clad steel sheet with excellent corrosion resistance and toughness is proposed, which is characterized by controlling the temperature to 50 to 850°C and then 3 to b. In the case of the method of the present invention, no cracking, breakage, or peeling at the cladding interface occurs in the cladding material during the cladding rolling process, and excellent toughness, especially excellent low-temperature toughness, is imparted to the base metal side. Stainless clad steel with excellent corrosion resistance can be manufactured.

(Function) As is clear from the claims, the features of the present invention are: (1) using ferritic or austenitic stainless steel or two-phase stainless steel as the bonding material; and (2) using the base material as the base material. (Details will be described later). ■ Rolling conditions must be such that both the laminate material and the base material can fully demonstrate their characteristics.
In order to adopt quality conditions, a temperature difference was created between the two during rolling.

First, considering the conditions on the base metal side, in order to improve strength and toughness, it is necessary to finish rolling in the austenite low temperature range or two-phase range. The purpose of rolling in the austenite low temperature range is to elongate the austenite grains and introduce deformation zones within the austenite grains. This is because the elongation of austenite grains and the introduction of deformation bands increase the number of nucleation sites for ferrite, which ultimately results in a finer structure and improved strength and toughness of the steel.

Rolling in the two-phase region achieves the same purpose as in the case described above, and in addition, the strength is improved by introducing strain within the ferrite grains, and at the same time, a deformed aggregated Mi weave is introduced. The aim is to also improve toughness. In the present invention, the finishing temperature of rolling is 650 to 850.
The reason for limiting the temperature to 850°C is that if the temperature exceeds 850°C, the austenite grains will become elongated grains due to recrystallization of the austenite grains.
This is because it is difficult to introduce a deformation band, and on the other hand, if the temperature is lower than 650°C, excessive strain is introduced into the ferrite grains, resulting in significant work hardening.

In addition, by accelerated cooling after rolling as described above, austenite-ferrite transformation occurs at low temperatures in carbon steel, and bainite transformation also occurs in some parts, resulting in even higher strength and toughness. Become. In the present invention, the accelerated cooling rate is limited to 3 to 60"C/s.
This is because the effect is not significant below .degree. C., and the effect is saturated when the temperature exceeds 60.degree. C./S.

The minimum rolling temperature in the company regulations is as stated above in the "Problem to be Solved by the Invention" section, so in order to maintain that temperature, high frequency or flame treatment is applied during the rolling process. Perform rapid heating, e.g.
In the case of US329J2L clad steel, the laminate side may be heated so that finish rolling is completed at 950°C or higher. Although high frequency or flame heating was used as the heating method in the examples, the heating method is not limited to these.

Since the method of the present invention cannot be carried out using the conventional sandwich type assembly, it is necessary to use the new sandwich type of the present invention shown in FIG. 1, the conventional oven type, or the double-sided clad type.

In the case of the new sandwich type and double-sided clad type, heating is performed from the top and bottom, while in the case of the oven type, only one side of the laminate is heated, resulting in half-warping. As a heating method for preventing warping, for example, as shown in FIG. 2, uniform heating in the longitudinal and width directions can be achieved by using a mechanism that allows a high frequency coil or a flame treatment header to follow the warping. In any case, heat treatment using high frequency, flame, etc. can be carried out freely during the rolling process, and it is quite possible to maintain the temperature near the contact interface between the laminate and the base material at 1050°C or higher, so there is no problem with bonding properties. .

FIG. 1 shows a cross section of the sandwich type assembly of the present invention, in which the mating +A' 1 is placed on the outside of the upper and lower surfaces, and the base material 2 is set with the release agent 3 in the center sandwiched therebetween. It is shown that there is. FIG. 2 is an explanatory diagram showing a heating device on the laminate side in a perspective view. It is shown in the figure that these are connected by a spring 6, and the cladding material side is heated.

Next, in order to achieve the object of the present invention, the chemical composition that the base material should have and the reason for limiting its numerical value will be described.

C: 0.01-0.2% C is an important reinforcing element, and if it is less than 0.01%, sufficient strength cannot be obtained for line pipe steel, shipbuilding steel, or marine structure steel, and 0. If it exceeds 0.2%, it will affect the weldability and the toughness of the welded part, so it should be 0.01 to 0.2%.
The range was set at 2%.

Si: 0.05 to 0.8% Si is a necessary element for deoxidizing in the manufacturing process, and is also a solid solution strengthening element. If it is less than 0.05%, the deoxidizing effect will not be sufficient, whereas if it exceeds 0.8%, the toughness and workability of the steel will deteriorate, so it is limited to a range of 0.05 to 0.8%.

Mn: 0.3 to 2.2% Mn is an extremely important element for controlling rolling. Since Mn lowers the Ar3 point, it facilitates rolling in the austenite low temperature range, and is an element that effectively works to improve strength L and toughness.

However, if it is less than 0.3%, the effect of lowering Ar3 points is small;
It is not possible to obtain a sufficient rolling reduction rate in the austenite low temperature range, and it is not possible to secure the strength and toughness required for line pipe steel, shipbuilding steel, and marine structure steel. on the other hand,
If it exceeds 2.2%, the deterioration for welding will be significant, so 0.3%
It was limited to ~2.2%.

8ff: 0.001 to 0.07% 746 is an important element as a deoxidizing element for steel manufacturing, and is also effective in improving the toughness of the weld heat affected zone.

However, if it is less than 0.001%, the deoxidizing effect is not sufficient,
On the other hand, since the effect on the weld heat affected zone is saturated even if it is added in excess of 0.07%, it is limited to a range of o, ooi to 0.07%.

The above are essential additive elements that fall into the first group.

Next, selectively added elements will be described.

Nb: 0.08% or less Nb has the effect of suppressing recrystallization of austenite and widening the recrystallization temperature range. This facilitates the elongation of austenite grains and the introduction of deformation bands, achieving significant grain refinement and improving toughness. Nb is also effective as a precipitation strengthening element.

However, if it exceeds 0.08%, the toughness of the weld will deteriorate significantly, so it is limited to 0.08% or less.

Cu: 2. Cu is an element effective in improving strength, corrosion resistance, and weather resistance. By aging treatment, ε−
The Cu phase precipitates and a significant improvement in strength is achieved. But 2
．． If added in excess of 0%, surface cracking due to Cu tends to occur during heating, so it was limited to 2.0% or less.

Ni: 3.0% or less Ni is an effective element for improving toughness, but it is expensive and
Even if it is added in an amount exceeding 3.0%, the effect of improving toughness is not improved so much, so it is limited to 3.0% or less.

Ti: 0.1% or less Like Nb, Ti is an element effective in suppressing recrystallization of austenite and strengthening precipitation.

It is also effective in improving the toughness of the weld heat affected zone.

However, if it exceeds 0.1%, toughness will deteriorate due to TiC precipitation, so it is limited to 0.1% or less.

Cr: 1.0% or less, Mo: 1.0% or less, V: 0
．． 1% or less Cr, Mo, and ■ are all effective elements for improving hardenability and precipitation strengthening. However, if added in excess of the above-mentioned specified amounts, the toughness of the weld will deteriorate, so Cr was limited to 1.0% or less, Mo: 1.0% or less, and V: 0.1% or less. .

B: 0.004% or less Addition of a small amount of B significantly improves hardenability.

However, if it is added in excess of 0.004%, the toughness of the weld will be significantly impaired, so it is limited to 0.004% or less.

Ca: 0.008% or less Ca is an element effective in controlling the morphology of inclusions in steel.

HIC is suppressed by adding Ca. But 0.
If it is added in an amount exceeding 0.08%, clusters of Ca inclusions are likely to form, and HIC will deteriorate. Therefore, the amount of Ca added was limited to 0,008% or less.

The elements of the second group described above, Nb, Cu, Ni,
One or more of Ti, CrXMo, ■, B, and Ca are added in amounts within their respective specified ranges, depending on the purpose of the stainless clad steel being manufactured.

(Example) Table 1 shows the chemical compositions of the base materials and composite materials used in the examples of the present invention.

The clad assembly of these materials is a new sand inch type,
There are three types: open type and double-sided clad type, and details of the assembled thickness and finished thickness are shown in Table 2.

Furnace heating prior to rolling was 1200°C. (The example in Table 4 was 1050° C.) Rapid heating during the rolling process was performed using high frequency and flame on the exit side of the rolling mill. The high frequency frequency is 30KH2. In the case of the sandwich type and double-sided cladding, a spiral coil is used to heat from the top and bottom during rolling, and in the case of the oven type, a device that follows the warp of the rolled plate as shown in Figure 2 is used. Only the side of the laminate was heated. Flame heating used pressurized coke oven gas as fuel. The number of times of heating in the rolling process is 1 to 6 times.

The rolling temperature was measured and controlled by thermocouples inserted into the base material and the laminate.

During accelerated cooling after rolling, water was used as a refrigerant, and the cooling rate was controlled by the amount of water.

Investigation items include interfacial peeling, cracking of laminated materials, shear test (JIS G 0601), and corrosion resistance test (JIS G 0601).
G0573.65% nitric acid corrosion test), a tensile test of the base material, a V-notch Charpy impact test of the base material, etc. were conducted. Table 3 shows the results in comparison with the conventional stainless steel manufacturing method.

In Table 3, the conventional method (high) indicates a finish rolling process at a high temperature from the viewpoint of cracking and corrosion resistance of the laminated material, and the conventional method (low) indicates a low-temperature finishing process with emphasis on the toughness of the base material. It means what was done in the process. Further, as a matter of course, in the conventional method, rapid heating during the rolling process is not carried out in any case. The cooling method after rolling is as follows:
Both air cooling and heating/cooling were performed.

From the results in Table 3, in the case of the conventional method, in any combination of the laminate material and the base material, in the conventional method (high) process, the toughness of the base material is very low, such as for example 5US310 S/B steel. low. In addition, in the conventional (low) process, cracks occurred in the laminated material (SUS329JL2) and significant sensitization occurred (SUS310S, 5US44).
4) Interfacial peeling may occur (S U S 304.5U
S316L) Yes.

On the other hand, examples of the present invention (in the table, the numbers in parentheses such as present invention (1), present invention (3), etc. indicate the number of the claimed invention) are present inventions (]) to (4). In all cases, there was no cracking, sensitization, or interface separation seen in the conventional method, and it was found that the toughness of the base material was significantly improved compared to the conventional method.

However, it has been clarified that when rapidly cooled after rolling, in addition to improving the physical properties of the base metal, there is also a significant improvement in corrosion resistance (SUS329JL2/D steel, present invention (4), 5U
S310S/E steel Present invention (4)).

Table 4 shows an example in which clad rolling was carried out with furnace heating at 1050° C., and rapid heating of the laminate material side was carried out in the rolling process. However, in this example, heating was performed for a slightly longer time every two baths so that the temperature near the interface was maintained at 1050° C. or higher until the plate thickness reached 801 m. It can be seen that by employing the method of the present invention, high shear strength can be obtained even when heated to 1050° C. before rolling.

"Effects of the Invention" As detailed above, the method of the present invention prevents the occurrence of cracks in the laminated material, suppresses its sensitization, completely prevents the occurrence of peeling at the interface, and improves the strength and strength of the base material. It has now become possible to produce stainless steel clad steel with excellent corrosion resistance and significantly improved toughness. Moreover, as a side effect of the present invention, low temperature heating of the cladding, direct solution treatment (direct ST
This invention has had a significant impact on the industry.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing the assembly of a sand inch clad according to an embodiment of the present invention, and Fig. 2 is a perspective view showing an example of a heating device for laminate material for carrying out the method of the present invention. FIG. 3 shows a conventional clad assembly diagram in cross section. 2: Base material 3: Release agent, 4: High frequency coil, 5: Trolley,
6; Spring.弗■ Laminated material No. 1 En Daien C mountain)

Claims (4)

[Claims] (1) Ferritic or austenitic stainless steel or two-phase stainless steel is used as the laminated material, and the base material is C: 0.01-0.2% and Si: 0.05-0.05% by weight.
0.8%, Mn: 0.3-2.2%, Al: 0.001
Using a steel material containing ~0.07% and the balance consisting of iron and unavoidable impurities, the laminate side is heated rapidly during clad rolling to make the laminate side higher than the base metal side. , and the finishing temperature of rolling was set to 6 on the base metal side.
A method for producing a stainless clad steel sheet with excellent corrosion resistance and toughness, the method comprising controlling the temperature to 50 to 850°C. (2) Ferritic or austenitic stainless steel or two-phase stainless steel is used as the laminated material, and the base material is C: 0.01 to 0.2%, Si: 0.05 to
0.8%, Mn: 0.3-2.2%, Al: 0.001
~0.07%, further Nb: 0.08% or less, C
u: 2.0% or less, Ni: 3.0% or less, Ti: 0.1
% or less, Cr: 1.0% or less, Mo: 1.0% or less, V
: 0.1% or less, B: 0.004% or less, Ca: 0.0
Using a steel material consisting of iron with the remainder containing one or more types of 0.08% or less and unavoidable impurities, the laminate side is heated more quickly than the base material side by rapidly heating the laminate side during clad rolling. A method for producing a stainless clad steel material having excellent corrosion resistance and toughness, characterized by controlling the rolling finishing temperature to 650 to 850°C on the base metal side. (3) Using ferritic or austenitic stainless steel or two-phase stainless steel as a laminated material, the base material is C: 0.01-0.2%, Si: 0.05-0.05% by weight.
0.8%, Mn: 0.3-2.2%, Al: 0.001
Using a steel material containing ~0.07% and the balance consisting of iron and unavoidable impurities, the laminate side is heated rapidly during clad rolling to make the laminate side higher than the base metal side. , and the finishing temperature of rolling was set to 6 on the base metal side.
A method for producing stainless clad steel having excellent corrosion resistance and toughness, which comprises controlling the temperature to 50 to 850°C and then rapidly cooling at 3 to 60°C/s. (4) Ferritic or austenitic stainless steel or two-phase stainless steel is used as a composite material, and the base material is C: 0.01 to 0.2% and Si: 0.05 to 0.05% by weight.
0.8%, Mn: 0.3-2.2%, Al: 0.001
~0.07%, further Nb: 0.08% or less, C
u: 2.0% or less, Ni: 3.0% or less, Ti: 0.1
% or less, Cr: 1.0% or less, Mo: 1.0% or less, V
: 0.1% or less, B: 0.004% or less, Ca: 0.0
Using a steel material consisting of iron with the remainder containing one or more types of 0.08% or less and unavoidable impurities, the laminate side is heated more quickly than the base material side by rapidly heating the laminate side during clad rolling. The finishing temperature of rolling was controlled at 650 to 850°C on the base metal side, and then 3
A method for producing a stainless clad steel sheet with excellent corrosion resistance and toughness, characterized by accelerated cooling at ~60°C/s.