Method for improving interface composite quality of stainless steel carbon steel composite plate and steel strip

Abstract

A method for improving the interface composite quality of stainless steel and carbon steel clad plate and a steel strip, comprising the following steps: 1) fixing the steel strip around the edges of carbon steel or stainless steel to be assembled, the steel strip having the following composition by weight percentage: C: 0.01-0.05%, Si: 0.10-0.20%, Mn: 0.20-0.80%, Al: 0.3-3%, Ti: 0.05-3%, P≤0.015%, S≤0.01%, the balance comprising Fe and other unavoidable impurities, and simultaneously satisfying: CE IIW<0.2%; 2) after matching the stainless steel and the carbon steel, assembling and welding, the steel strip being distributed on the interface of the stainless steel and the carbon steel of the assembly. After welding the assembly, nitrogen and oxygen in the air on the interface are solidified at the root of the weld during the heating process by using the high adsorption of titanium and aluminum to nitrogen and oxygen, preventing the formation of oxide aggregation on the interface, thereby improving the composite quality.

Description

Technical Field

[0001] This invention relates to the field of composite plate rolling technology, and in particular to a method and steel strip for improving the interfacial bonding quality of stainless steel and carbon steel composite plates. Background Technology

[0002] Rolled composite plates, as a new type of composite material in the steel industry, have formed an important application market due to their combination of the advantages of two or three materials. Their main production processes include surface treatment of the bonding surfaces (usually grinding), assembly of two or more materials into a blank, vacuum treatment, heating, rolling, and finally, finishing of the finished product.

[0003] For example, Chinese Patent Application No. 202211391663.1 discloses a method for manufacturing a carbon steel ferritic stainless steel rolled composite plate. The method uses a carbon steel billet as the base material of the composite plate and a stainless steel medium plate as the cladding material. The method includes: grinding the surfaces to be bonded on the carbon steel billet and the stainless steel medium plate respectively to achieve a roughness Ra of 0.8–1.5 μm; beveling the carbon steel billet to create a single V-shaped bevel; then stacking the carbon steel billet and the stainless steel medium plate together, making them adjacent to each other, to obtain a composite billet; welding the composite billet and then vacuuming it to obtain a composite plate blank; sequentially heating, rolling, cooling, and coiling the composite plate blank to obtain a composite steel coil; and annealing the composite steel coil after leveling it into a steel plate to obtain the composite plate.

[0004] Before metallurgical bonding, the composite surface of the composite billet is a vacuum cavity. Vacuum treatment requires a very high degree of vacuum, which is often impossible to guarantee during production due to factors such as insufficient vacuum equipment capacity or weld cracks leading to vacuum failure. Insufficient or failed vacuum means air is present in the cavity. During billet heating, the air oxidizes the surfaces of the steel plate to be bonded, and these oxide particles hinder the formation of the bonding interface, resulting in poor bonding. If too much air enters the bonding cavity, bonding cannot be completed; if too little air is present, the bonding quality will be affected, and the presence of oxide particles at the bonding interface will reduce the bonding force. Summary of the Invention

[0005] The purpose of this invention is to provide a method and steel strip for improving the interfacial bonding quality of stainless steel and carbon steel composite plates, which can effectively prevent poor bonding caused by weld failure during heating and rolling, and significantly improve the stability of the bonding quality of the composite plate.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for improving the interfacial bonding quality of stainless steel and carbon steel composite plates includes the following steps:

[0008] 1) Fix the steel strip around the perimeter of the carbon steel or stainless steel billet to be assembled. The steel strip has the following composition by weight percentage: C: 0.01-0.05%, Si: 0.10-0.20%, Mn: 0.20-0.80%, Al: 0.3-3%, Ti: 0.05-3%, P≤0.015%, S≤0.01%, with the balance including Fe and other unavoidable impurities. Furthermore, it must simultaneously satisfy: CE IIW<0.2%, CE IIW

[0009] =C+Mn / 6+Ni / 15+Cu / 15+Cr / 5+Mo / 5+V / 5;

[0010] 2) After the stainless steel and carbon steel are matched, they are assembled and welded, with the steel strip distributed at the interface between the stainless steel and carbon steel in the assembled billet. After welding, the assembled billet is ready for subsequent processes (including vacuum treatment, heating, and rolling).

[0011] Preferably, the steel strip is distributed continuously or intermittently in the root of the weld seam during the assembly welding.

[0012] Preferably, the thickness of the steel strip is ≥0.1mm. If the thickness is too thin, the adsorption capacity will be insufficient, resulting in an insignificant effect.

[0013] Preferably, the width of the steel strip is ≥ 0.2% of the width of the composite plate. If the width is too narrow, the adsorption capacity will be insufficient, resulting in an insignificant effect.

[0014] Preferably, the steel strip is fixed to the edge of carbon steel or stainless steel by welding, mechanical means, or bonding. If the steel strip is not fixed, it will slip during the assembly process, resulting in excessive concentration of steel strip in some areas and insufficient steel strip in others, thus reducing the effective adsorption area in the deficient areas. In addition, fixing the steel strip can also ensure that the interface inside the composite plate is not contaminated.

[0015] Furthermore, the steel strip composition contains Fe and other unavoidable impurities.

[0016] Furthermore, the steel strip composition also includes one or more of the following components: B≤0.002%, Ni≤0.05%, and Cr≤0.05%.

[0017] This invention designs a steel strip containing aluminum and titanium, which is placed at the root of the weld seam during the assembly of the billet. After the assembly is welded, during the heating process (even if the vacuum is not completely removed), the high adsorption properties of titanium and aluminum for nitrogen and oxygen are used to solidify the nitrogen and oxygen in the air at the composite interface at the root of the weld seam, preventing the formation of oxides on the composite interface and thus improving the composite quality.

[0018] In addition, the steel strip is distributed in strip shape at the root of the weld at the edge of the billet, which can play the role of high-temperature adsorption of oxygen and nitrogen without causing component contamination to the interface inside the composite plate.

[0019] The steel strip can be trimmed normally after being rolled into a composite plate, without the need for additional trimming.

[0020] The present invention also provides a steel strip for the composite interface of stainless steel and carbon steel composite plates, the composition by weight percentage being: C: 0.01-0.05%, Si: 0.10-0.20%, Mn: 0.20-0.80%, Al: 0.3-3%, Ti: 0.05-3%, P≤0.015%, S≤0.01%, the balance being Fe and other unavoidable impurities, and simultaneously satisfying: CE IIW < 0.2%, CE IIW = C + Mn / 6 + Ni / 15 + Cu / 15 + Cr / 5 + Mo / 5 + V / 5.

[0021] Furthermore, the balance consists of Fe and other unavoidable impurities.

[0022] Furthermore, it also contains one or more of the following components: B≤0.002%, Ni≤0.05%, and Cr≤0.05%.

[0023] The microstructure of the steel strip described in this invention is ferrite + martensite + a small amount of pearlite.

[0024] The steel strip of the present invention has a yield strength of 400-800 MPa, a tensile strength of 500-1200 MPa, and an elongation of 12-40%.

[0025] In the composition design of the steel strip described in this invention:

[0026] C plays a role in solid solution strengthening in steel, but too high a C content is detrimental to weldability and toughness. Therefore, the carbon content of steel strip is controlled at 0.01-0.05%.

[0027] Silicon (Si): Adding silicon to steel can improve its purity and deoxidation properties. However, silicon is detrimental to weldability. This invention controls the silicon content to 0.10–0.20% to ensure that the steel strip has good weldability.

[0028] Mn can delay the pearlite transformation and also has a solid solution strengthening effect on steel, making it a major solid solution strengthening element in steel. However, excessively high manganese content is detrimental to weldability. The Mn content of the steel strip described in this invention is controlled at 0.20–0.80%.

[0029] Al: A strong deoxidizing element, it is the main oxygen adsorption element of the steel strip mentioned above in this invention. The content of aluminum is controlled at 0.3% to 3%. At high temperature, aluminum and air mainly form Al2O3 and AlN, which improves strength and can refine the elemental austenite grain size of steel during heat treatment.

[0030] Ti: Ti is a strong carbide-forming element. Adding more than 0.025% Ti to steel allows it to function as an alloy. When the temperature exceeds 600℃, the nitrogen absorption rate of titanium increases rapidly. It has a strong adsorption capacity for N, forming TiN, and also adsorbs O, forming TiO2. Therefore, the steel strip described in this invention has a high Ti content, controlled between 0.05% and 3%.

[0031] S and P: Sulfur combines with manganese and other compounds in steel to form manganese sulfide, a plastic inclusion that is particularly detrimental to the steel's lateral plasticity and toughness. Therefore, the sulfur content should be as low as possible. Phosphorus is also a harmful element in steel, severely impairing the plasticity and toughness of the steel plate. For the purposes of this invention, both sulfur and phosphorus are unavoidable impurity elements and should be as low as possible. Considering the actual steelmaking level of steel mills, this invention requires P ≤ 0.015% and S ≤ 0.010%.

[0032] B: Boron can greatly improve the hardenability of steel and has some benefit to weldability. Therefore, this invention requires the upper limit of boron content to be 0.002%.

[0033] Ni: An element that stabilizes austenite and plays a role in improving strength. Adding nickel to steel, especially to quenched and tempered steel, can significantly improve the low-temperature impact toughness of the steel. Appropriate amounts of nickel can be added. This invention allows the addition of no more than 0.05% nickel.

[0034] Cr: Adding chromium to carbon steel also helps to inhibit the diffusion of chromium from the welding material into the steel strip. This invention allows for the addition of no more than 0.05% chromium.

[0035] In summary, this invention designs a steel strip containing aluminum and titanium. The Al element has a very strong adsorption effect on oxygen atoms, and the Ti element can effectively adsorb nitrogen atoms at high temperatures. The nitrogen and oxygen in the air at the composite interface are solidified at the root of the weld, preventing the formation of oxides on the composite interface and thus improving the composite quality. Moreover, the welding carbon equivalent is very low, ensuring that the weld strength is not affected.

[0036] Compared with the prior art, the advantages of the present invention are as follows:

[0037] In the existing assembly process, under poor vacuum conditions, the Cr element in the stainless steel reacts more easily with oxygen to form CrO at the composite interface between carbon steel and stainless steel. CrO is dense and deformable, and can easily form an isolation layer at the composite interface between carbon steel and stainless steel, affecting the composite quality.

[0038] This invention optimizes the billet assembly process of stainless steel and carbon steel rolled composite plates. An aluminum- and titanium-containing steel strip is added to the edge region between the stainless steel and carbon steel sections, achieving this optimization without altering the billet assembly process or weld structure. After the steel strip enters the cavity formed by the stainless steel and carbon steel billet, in the presence of air during heating, the steel strip can adsorb nitrogen and oxygen from the air at a high temperature of 600–1000°C, significantly reducing oxidation particles at the carbon steel and stainless steel composite interface. This process optimization greatly improves the stability of the composite quality of the rolled carbon steel and stainless steel composite plate.

[0039] In addition, steel strips containing aluminum and titanium are added to the edge area between stainless steel and carbon steel. The process is simple to implement and the cost is very low, which can bring quality improvement and considerable economic benefits to composite panel manufacturers.

[0040] This invention is applicable to improving the interfacial composite quality of rolled composite plates of most types of stainless steel and carbon steel. The types of stainless steel include austenitic stainless steel, ferritic stainless steel, duplex stainless steel, etc.; the types of carbon steel include shipbuilding steel, structural steel, bridge steel, etc. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the structure of the composite plate described in this invention;

[0042] Figure 2 This is a scanning electron microscope (SEM) image of the steel strip region at the edge of the composite plate described in this invention.

[0043] Figures 3-6 This is a schematic diagram illustrating the analysis of the particle chemical composition (Ti, N, Al, O) of the strip steel region described in this invention.

[0044] Figure 7 This is a photograph of the carbon steel and stainless steel composite interface of the composite plate described in this invention. Detailed Implementation

[0045] The present invention will be described in more detail below with reference to examples. These examples are merely descriptions of the best mode of implementation of the invention and do not limit the scope of the invention in any way.

[0046] See Figure 1 The composite plate of the present invention comprises carbon steel 1, stainless steel 2, and steel strip 3.

[0047] The chemical composition of the steel strip described in the embodiments of the present invention is shown in Table 1, the stainless steel and carbon steel composite pairing involved is shown in Table 2, the manufacturing process parameters of the embodiments are shown in Table 3, and the interface quality of the steel plates obtained in all embodiments is shown in Table 4.

[0048] See Figure 2The image shows a metallographic photograph (thickness-direction section) of the steel strip region in the rolled composite plate. Irregularly colored compound particles are clearly visible, distributed throughout the steel strip region. No oxide particles are found in the composite plate region outside the steel strip. This demonstrates the adsorption of oxygen and nitrogen by the special steel strip during the rolling composite process. Its compositional distribution is shown in [reference needed]. Figures 3-6 .

[0049] The adsorption effect of the aluminum and titanium-containing steel strip of this invention on oxygen and nitrogen is evident. Figures 3-6 .

[0050] Figures 3-6 To observe the characteristics of compound particles in the steel strip of the rolled composite plate using scanning electron microscopy (original billet vacuum degree 0.01 Pa), the figure shows that the local concentration of particles in the steel strip is Al-O combination and Ti-N combination. That is, O and N elements are concentrated in the dark color area, which is also the aggregation area of ​​Al and Ti. The light color area is Fe and Fe and Cr, indicating that O and N did not combine with Fe and therefore could not affect the composite quality.

[0051] Figure 7 The absence of any oxide particles on the interface between the stainless steel and carbon steel indicates that Al and Ti have a very good adsorption effect on insufficient vacuum.

[0052] In summary, this invention adds a steel strip containing aluminum and titanium between stainless steel and carbon steel. Without changing the billet assembly process and weld structure, the steel strip adsorbs nitrogen and oxygen in the air at a high temperature of 600-1000°C, which greatly reduces the oxidation particles on the composite interface of carbon steel and stainless steel, thereby significantly improving the stability of the composite quality of the rolled carbon steel and stainless steel composite plate.

[0053]

[0054] Table 2 Composite material types in embodiments of the present invention

[0055] 1 DH36 S22053 2 Q235B 304L 3 Q370R 316L 4 Q420qE 316L 5 FH40 317H 6 Q345B 410S 7 Q370qE 316L Comparative example Q370qE 316L

[0056] Table 3. Billet assembly and hot rolling process parameters of the present invention embodiments

[0057] 1 0.010 1150 980 19 2 0.004 1160 1000 100 3 0.04 1170 980 26 4 0.02 1140 990 17 5 0.03 1180 980 12 6 0.009 1150 960 20 7 0.09 1200 880 19 Comparative example 0.09 1200 880 19

[0058] Note: Vacuum level represents the amount of residual gas in the preform assembly cavity.

[0059] Table 3 Metallographic observation results of the steel strip described in this invention after rolling and composite processing.

[0060] Example 1 A small number of particles Non-oxidizing particles Example 2 No mass Non-oxidizing particles Example 3 More particles Non-oxidizing particles Example 4 A small number of particles Non-oxidizing particles Example 5 A small number of particles Non-oxidizing particles Example 6 A small number of particles Non-oxidizing particles Example 7 A large number of particles Non-oxidizing particles Comparative example — More oxidized particles

[0061] Note: The absence of oxidized particles indicates good composite properties.

Claims

1. A method for improving the interfacial bonding quality of stainless steel and carbon steel composite plates, characterized in that, Includes the following steps: 1) Fix the steel strip around the perimeter of the carbon steel or stainless steel billet to be assembled. The steel strip has the following composition by weight percentage: C: 0.01~0.05%, Si: 0.10~0.20%, Mn: 0.20~0.80%, Al: 0.3~3%, Ti: 0.05~3%, P≤0.015%, S≤0.01%, with the balance including Fe and other unavoidable impurities. It must also meet the following conditions: CE IIW<0.2%, CE IIW =C+Mn / 6+Ni / 15+Cu / 15+Cr / 5+Mo / 5+V / 5; 2) After stainless steel and carbon steel are matched, they are assembled and welded. The steel strip is distributed at the stainless steel and carbon steel composite interface of the assembled billet and at the root of the weld seam of the assembled billet.

2. The method as described in claim 1, characterized in that, The steel strip is distributed continuously or intermittently in the root of the weld seam during the assembly welding.

3. The method as described in claim 1 or 2, characterized in that, The thickness of the steel strip is ≥0.1mm.

4. The method as described in claim 1 or 2, characterized in that, The width of the steel strip is ≥ 0.2% of the width of the composite plate.

5. The method as described in claim 3, characterized in that, The width of the steel strip is ≥ 0.2% of the width of the composite plate.

6. The method as described in claim 1 or 2, characterized in that, The steel strip is fixed to the edge of carbon steel or stainless steel by welding, mechanical means or adhesive bonding.

7. The method as described in claim 3, characterized in that, The steel strip is fixed to the edge of carbon steel or stainless steel by welding, mechanical means or adhesive bonding.

8. The method as described in claim 4, characterized in that, The steel strip is fixed to the edge of carbon steel or stainless steel by welding, mechanical means or adhesive bonding.

9. The method as described in claim 5, characterized in that, The steel strip is fixed to the edge of carbon steel or stainless steel by welding, mechanical means or adhesive bonding.

10. The method as described in claim 1 or 2, characterized in that, The steel strip composition contains Fe and other unavoidable impurities.

11. The method as described in claim 3, characterized in that, The steel strip composition contains Fe and other unavoidable impurities.

12. The method of claim 4, characterized in that, The steel strip composition contains Fe and other unavoidable impurities.

13. The method of claim 5, characterized in that, The steel strip composition contains Fe and other unavoidable impurities.

14. The method of claim 6, characterized in that, The steel strip composition contains Fe and other unavoidable impurities.

15. The method of claim 7, characterized in that, The steel strip composition contains Fe and other unavoidable impurities.

16. The method of claim 8, characterized in that, The steel strip composition contains Fe and other unavoidable impurities.

17. The method of claim 9, characterized in that, The steel strip composition contains Fe and other unavoidable impurities.

18. The method as described in claim 1, characterized in that, The steel strip composition also includes one or more of the following components: B≤0.002%, Ni≤0.05%, and Cr≤0.05%.

19. The method of claim 10, characterized in that, The steel strip composition also includes one or more of the following components: B≤0.002%, Ni≤0.05%, and Cr≤0.05%.

20. A steel strip for use in the method according to any one of claims 1 to 9, characterized in that, The steel strip has the following composition by weight percentage: C: 0.01~0.05%, Si: 0.10~0.20%, Mn: 0.20~0.80%, Al: 0.3~3%, Ti: 0.05~3%, P≤0.015%, S≤0.01%, with the balance including Fe and other unavoidable impurities. Furthermore, it must simultaneously satisfy: CE IIW<0.2%, CEIIW =C+Mn / 6+Ni / 15+Cu / 15+Cr / 5+Mo / 5+V / 5.

21. The steel strip as described in claim 20, characterized in that, The balance consists of Fe and other unavoidable impurities.

22. The steel strip as described in claim 20 or 21, characterized in that, It also contains one or more of the following components: B≤0.002%, Ni≤0.05%, and Cr≤0.05%.

23. The steel strip as described in claim 20 or 21, characterized in that, The microstructure of the steel strip is ferrite + martensite + a small amount of pearlite.

24. The steel strip as described in claim 22, characterized in that, The microstructure of the steel strip is ferrite + martensite + a small amount of pearlite.

25. The steel strip as described in claim 20, characterized in that, The steel strip has a yield strength of 400~800MPa, a tensile strength of 500~1200MPa, and an elongation of 12~40%.

26. The steel strip as described in claim 21, characterized in that, The steel strip has a yield strength of 400~800MPa, a tensile strength of 500~1200MPa, and an elongation of 12~40%.

27. The steel strip as described in claim 22, characterized in that, The steel strip has a yield strength of 400~800MPa, a tensile strength of 500~1200MPa, and an elongation of 12~40%.

28. The steel strip as described in claim 23, characterized in that, The steel strip has a yield strength of 400~800MPa, a tensile strength of 500~1200MPa, and an elongation of 12~40%.

29. The steel strip as described in claim 24, characterized in that, The steel strip has a yield strength of 400~800MPa, a tensile strength of 500~1200MPa, and an elongation of 12~40%.

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