JPS5930515B2 - Manufacturing method of highly corrosion-resistant alloy clad steel sheet without carburizing the composite material surface - Google Patents

Description

[Detailed Description of the Invention] The present invention is a combination of high corrosion-resistant alloy clad steel sheets made of stainless steel, nickel-based or iron-based superalloys, etc., and carbon steel or low alloy steel as the base material, and produced by a hot working method. The present invention relates to a method for preventing carburization that occurs on the surface of a composite material.

The conventional method of manufacturing clad steel plates by hot working of composite materials is to mechanically or chemically polish the adhesive surfaces of the composite material and the base material to make them clean, and if necessary, apply nickel or iron. , Copper or other metal is inserted between the adhesive surfaces as an insert metal, and a separating agent is applied to the upper surface of the stacked composite material in advance and dried, and another set of similar composite material-base material combination materials is made. Either as a sandwich-like combination material in which the separation agent coated surfaces of the composite materials face each other, or as a combination material in which a sacrificial plate having a hot deformation resistance similar to that of the base material is placed over the separation surface of the composite materials, After firmly seal-welding the four circumferences of the combined material, the combined material is heated to a predetermined temperature of about 1000°C or higher, hot rolled or forged, etc. to give sufficient plastic deformation to obtain a predetermined shape, and the composite material is... After completing the metallurgical bonding between the base metals, heat treatment is performed as necessary, and the four-circumference welds on the end faces are separated and cut to form two clad steel plates in the case of a sandwich-like combination, or clad steel plates in the case of a sacrificial plate. The process of obtaining a single steel plate has been adopted industrially.

One of the major drawbacks of this manufacturing method is that in the process of heating the composite material to high temperatures and subjecting it to hot processing, the chemistry between the air, carbon dioxide, and moisture contained within the composite and the carbon in the base material and separating agent is It is mentioned that carburization or decarburization phenomena often occur due to the reaction (particularly depending on the gas composition determined by the equilibrium relationship 2C0=CO2+C and the equilibrium carbon concentrations of the composite material and base material, respectively).

In particular, in highly corrosion-resistant alloys whose carbon concentration must be reduced as much as possible from the viewpoint of maintaining excellent corrosion resistance, a carburized layer is likely to form on the surface of the composite material coated with a separating agent. This carburized layer on the surface of the composite material is likely to be the main cause of accidents such as pitting and rusting during transportation and processing of clad steel sheets, deterioration of corrosion resistance during use, and corrosion cracking. After inspecting the material in advance, it must be completely removed by grinding or mechanical cutting. Such a carburized layer on the surface of the composite material of clad steel sheets makes it difficult to control the thickness of the composite material, and also causes a significant loss of productivity and economic efficiency, such as lowering yield and complicating the process. There is. Conventionally, when manufacturing clad steel sheets into a sandwich-like combination material using a hot working press bonding method, the performance that the separating agent should have is A. B. Not melting in the hot working temperature range. C. It is chemically stable even at high temperatures and does not cause chemical reactions with composite materials or generate large amounts of gas. D. Excellent separability after hot working; E. Can be easily removed by sandblasting or pickling after separation; The surface roughness after removal is excellent;F. It needs to be cheap and easy to obtain.

Therefore, as separation agents, Al2O3, SiO2, Cr
Experience has shown that inorganic oxide powder such as 2O3 is dissolved in an inorganic binder aqueous solution, such as water glass (Na2SiO3.XH2O), and then sprayed with a spray gun or dried after brushing. .

However, the separating agent layer on the surface of the composite material formed in this way is porous and has essentially no resistance to gas carburization on the surface of the composite material in the carburizing gas atmosphere inside the combination as described above. does not have. The carburized layer that forms on the surface of the composite material when manufacturing clad steel plates made of highly corrosion-resistant alloys such as stainless steel, nickel-based or iron-based superalloys using the hot bonding method is caused by weak carburizing gas that accumulates in the internal voids of the composite material. enters the composite material surface through the separating agent, and as a result, the corrosion resistance properties of the composite material, such as pitting corrosion resistance and intergranular corrosion resistance, deteriorate.

The depth of the carburized layer on the surface of the composite material varies depending on the heating conditions and processing ratio, but the maximum is 0.5 mT! Some of them reach a depth of L, and therefore a finishing process is often required to remove the surface carburized layer by grinding or mechanical cutting. The object of the present invention is to eliminate the drawbacks of the conventional clad steel sheet manufacturing method described above, and to produce a composite material made of a highly corrosion-resistant alloy such as stainless steel, nickel-based or iron-based superalloy, and a base material made of carbon steel or low alloy steel. In the method of manufacturing a clad steel plate by sandwiching the composite material inside and combining them into a sandwich-like structure, sealingly welding the four circumferences of this sandwich-like combined material, and hot-working after heating, Add 0.1 of a separating agent that has a decarburizing effect to the surface opposite to the surface to be bonded to the material.
After coating to a thickness of 1.5 mm and drying, the above-mentioned polymeric plates were assembled in the shape of a sandwich, and chromite [general formula (MgFe)O, (Cr
．． Fe. Provided is a novel method for producing a highly corrosion-resistant alloy clad steel sheet without surface carburization, characterized by using a mixture of one or two types of soda glass-based powder (Al) 203] or soda glass powder at a ratio of 1008007 r/l. It is in.

The present invention is based on the gas composition analysis inside the composite material heated to high temperature and the laboratory test, which shows that the surface carburization phenomenon of composite material of clad steel sheets manufactured by hot pressing method is mainly controlled by gas carburization as described above. It was created as a result of repeated simulation experiments to clarify the problem, and various on-site preventive measures.

Next, the present invention will be described by way of examples with reference to the drawings.

In FIG. 1, the sandwich-like combination material used in the present invention has a base material 1 at the bottom, and a composite material 2 to be joined to the base material 1 is superimposed on the upper surface of the base material 1. Composite material 2
A separating agent having anti-carburizing effect is applied to the upper surface of the plate to a thickness of 0.1 mm to 1.5 mm. After the separating agent 3 is applied and dried, the composite material 2'' and the base material 1'' are superimposed on it to form a sandwich-like combination material.
A backing plate 4 is fixed to the four circumferences of this combined material by welding portions 5, and the inside is sealed. Figure 2 shows another embodiment of the sandwich-like combination material, in which 1 base material 1 mixture 2 separation agent 3 mixture 2
The combination of ``one base material 1'' is the same as that in Fig. 1, but
In this figure, the four circumferences are sealed using only the overlay welded portion 5' without using the contact plate 4. Both types are used depending on the thickness and material of the steel plate used and other conditions. FIG. 3 shows a sandwich-like combination material using a sacrificial board different from the above-mentioned sandwich-like combination material. In this case, the base material 11 is at the bottom, and the base material 11 is bonded to the upper surface of the base material 11. The mixed materials 12 are overlapped.

On the upper surface of the composite material 12, a separating agent 13 having a carburizing prevention effect is applied to a thickness of 0.1 mm to 1.5 m as in the case of FIGS. 1 and 2.
After drying this separation agent 13, the sacrificial board 16 is placed on top of it, and the composite material 12 is sandwiched between the joints to form a sandwich-like combination structure. The backing plate 14 is fixed by the welded portion 15, and the inside is sealed.
Figure 4 shows a four-piece sandwich structure similar to Figure 3.
The circumference is sealed by an overlay welded part 15" without using a backing plate. 2 to 1
0V01% water glass aqueous solution (Na2O-NSiO2・N
H2O) to chromite [(Mg-Fe)O.(Cr, .
Fe. It is effective to apply a mixture of one or two soda glass-based glass powders at a ratio of 100 to 800 gr/l to a thickness of 0.1 to 1.57 nm.

The sandwich-shaped composite material is heated and rolled to produce a clad steel sheet.

The separating agent used in the present invention prevents charring from forming on the surface of the composite material during hot rolling, does not interfere with the manufacturing process, and is economical.

The following items meet this condition. Namely, 1) a group that forms a fine film on the surface of the composite material that can completely protect carburizing gas from the surface of the composite material in a high temperature range, and 2) a group that forms a film on the surface of the composite material that is so fine that it can completely protect carburizing gas from the surface of the composite material in a high temperature range, and 2) a group that forms a film on the surface of the composite material that is so fine that it can completely protect carburizing gas from the surface of the composite material in a high temperature range. There are two members of the group that can supply this.

The former includes soda glass-based glass powder (SiO26O~75%, Na2O
lO~20%, CaO5~20%, Al2O3+MgO
+K2O+B2O3O~25%) is most suitable, and the latter is chromite (Mg.Fe)O.(Cr.Fe
．． Al)203 was the most effective.

Next, a simulation experiment related to the present invention will be explained.

Figure 5 shows a SUS3O4 test piece (220# hub polished finish)
was coated with various separating agents and heated in a strongly carburizing gas atmosphere furnace (electric resistance graphite furnace at 1 atm atmosphere of 1050°C with about 50% CO and C
A simulation experiment example in which the sample was heated with O2 containing about 20%) clearly shows the surface carburization prevention effect of chromite glass powder as a separating agent.

If the particle size of these powders is finer than 20 mesh, it will not interfere with mechanical spray coating using a spray gun, but if the particle size is coarser than that, it is necessary to consider applying with a brush.

The water glass aqueous solvent used as a binder has poor caking ability when the water glass is less than 2V01%, and the separating agent tends to de-dissolve after drying.
If it exceeds 10V01%, it tends to cause clogging during mechanical spraying, and there is no change in caking ability, so the upper limit should be set at 10V01.
%. Chromite or glass powder is added to this water glass aqueous solution, but if it is too small, the spraying or brushing efficiency will be poor and it will take a long time to dry, and if too much is added, the spray nozzle will The lower and upper limits are set at 100 to 800 gr-/f, respectively, because clogging is likely to occur and the brushing workability is also affected.
And so. The separating agent prepared in this way is applied to the separating surface of the composite material by mechanical spraying or by bald coating, but if the coating thickness is 0.1 mm or less, the processing rate (combination Thickness reduction rate due to hot processing of material)
If the separation agent is applied more than about 50%, the separation property becomes extremely poor, and if the coating thickness is 1.5 mm or more, it takes a long time to apply and dry the separation agent, and it tends to fall off when turning over after drying. Therefore, the lower and upper limits of the coating thickness were set to 01 and 1.5 mm, respectively. It is recommended that drying after application of the separation agent be maintained at 50 to 200'C for about 1 hour or more. Next, embodiments according to the present invention will be described. Example 1 18mm thick stainless steel plate (JISSUS
3O4L and 405), stainless clad steel plates were manufactured using a 100 mm thick mild steel plate (equivalent to SS4L) as the base material.

In this case, three types of separating agents were used: (1) alumina, (1) chromite, and (3) glass powder, and the weight percentages of their chemical components were as follows. The mixture was added at a rate of 400 to 500 gr/l. Next, the separation surface of the composite material is ground with a grinder to remove scale and surface flaws, and then preheated at 80 to 100℃, and the specified separation agent is sprayed to a thickness of 0.3 mm using a spray gun. 60
Dry at ~80°C for 1 hour. The combination is as shown in FIG. 1, in which the base material, composite material, composite material, and base material are stacked in this order from above.
In this case, the four circumferences of the separation surface contact portion of the upper and lower composite materials were not sealed-welded, but the four circumferences of the sandwich-like combination material were hermetically welded. After soaking at 1200°C for 3 hours, rolling was carried out at a rolling ratio of 6.0 to produce a clad steel plate. As a result, as shown in Figures 6 and 7, regardless of whether the composite material is SUS3O4L or 405, almost no surface carburized layer was observed in the case where chromite and glass powder-based separation agents were used.
It was demonstrated that this separating agent has a large carburization resistance effect.

Furthermore, the separation agent after separation could be easily removed by pickling or sandblasting, and the surface texture was also good. Example 2 25mm thick stainless steel plate (JISSUS32
l), the base material is a 200 mm thick low alloy steel plate (ASTM
A 50 mm thick mild steel plate (equivalent to SS4l) was used as the sacrificial plate to produce a combination material as shown in FIG. 3.

In this case, three types of separating agents, alumina, chromite, and glass powder, were used, but the same conditions as in Example 1 were used for the ingredients and coating method. After soaking at 1200° C. for 5 hours, rolling was performed at a rolling ratio of 3.0 to produce a clad steel plate.
As a result, as shown in FIG. 8, it was found that chromite and glass powder-based separation agents are effective in preventing carburization.

Chromite, which is used as a separating agent to prevent surface carburization of the composite material, provides stable sinterability in a high temperature range, and contains Fe2O3 as an oxygen supply source.

Furthermore, in the case of glass, it has the effect of coating the surface of the composite material by softening and melting in a high temperature range. These effects were demonstrated from the results of the examples described above. In this way, the present invention prevents surface carburization of the composite material, thereby achieving
This not only contributes to improved quality, but also productivity and economic efficiency, and makes it possible to manufacture highly corrosion-resistant alloy clad steel sheets industrially and at low cost.

[Brief explanation of the drawing]

Fig. 1 is an explanatory sectional view of a first embodiment of the combined material used in the present invention, Fig. 2 is an explanatory sectional view of the second embodiment of the combined material used in the present invention, and Fig. 3 is an explanatory sectional view of the second embodiment of the combined material used in the present invention. FIG. 4 is an explanatory sectional view of the fourth embodiment of the combination material used in the present invention, and FIG. 5 is a simulation test in a carburizing gas atmosphere. Figures 6 and 7 are diagrams comparing the carburization prevention effects of various separating agents, respectively, for the combined materials shown in Figure 1.
Figure 8 shows the influence of each separating agent on carburization when manufacturing US3O4L and 405 stainless clad steel plates.
FIG. 3 is a diagram showing the influence of each separating agent on the surface carburization of the composite material when a US32L stainless clad steel plate is manufactured. 1,1",11,1"...Base material, 2,2",1
2...Mixture material, 3,13...Separating agent, 4
, 14...Top plate, 5, 5'', 15, 15'...
...Welded part, 16...Sacrificial plate.

Claims (1)

[Claims] 1. A composite plate made of a composite material made of a highly corrosion-resistant alloy such as stainless steel, nickel-based or iron-based superalloy, and a base material made of carbon steel or low alloy steel, with the composite material sandwiched inside. 4 of this sandwich-like combination material
In a method of manufacturing a clad steel plate by sealingly welding the circumference, heating and then hot working, a separating agent having an anti-carburization effect is applied to the surface of the composite material opposite to the bonding surface with the base material. 1.5
A method for producing a highly corrosion-resistant alloy clad steel sheet without carburizing the surface of the composite material, which comprises coating the material to a thickness of mm, drying it, combining it into a sandwich shape, sealingly welding four circumferences of the combined material, and heat rolling. 2. The sandwich-like combination material is vertically symmetrically placed on the base material.
2. The method for producing a clad steel sheet according to claim 1, wherein the composite materials are stacked in the order of composite material, composite material, and base material, and a separating agent is interposed between the composite materials. 3. The sandwich-like combination materials are stacked in the order of base material, composite material, and sacrificial board from the bottom, and a separating agent is interposed between the composite material and the sacrificial board. method for producing clad steel plates. 4. The separating agent is a mixture of a 2-10 Vol% water glass aqueous solution with one or two of chromite powder or soda glass-based glass powder added at a ratio of 100-800 gr/l. Range 1
The method for manufacturing a clad steel plate according to any one of Items 1 to 3.