Production method of stainless steel coil for molybdenum-containing welding strip

Abstract

The application provides a production method of stainless steel coil for molybdenum-containing welding strip, which comprises the following steps: (1) putting dephosphorized molten iron, pure nickel, molybdenum iron and low-P chromium iron into an induction furnace to smelt molybdenum-containing molten steel; (2) casting the molten steel into a slab; (3) continuously heating the slab twice; (4) hot-rolling the slab after the second heating to obtain a black coil with a thickness of 6.5 mm; and (5) cold-rolling the black coil through three rolling processes to obtain a steel strip coil with a thickness of 0.505 mm. The pure nickel, low-P chromium iron and dephosphorized molten iron are added into the molybdenum iron to smelt the molten steel, so that the low P content and Cu content of the stainless steel for welding strip are ensured; the cold rolling is carried out through three rolling processes, the reduction rate of each pass is reasonably distributed, and the tensile strength of the finished product is ensured to be between 1000-1100 MPa.

Description

Technical Field

[0001] This invention belongs to the field of stainless steel strip production technology, and relates to a method for producing stainless steel coils for molybdenum-containing welding strips. Background Technology

[0002] Molybdenum-containing stainless steel for welding strips is mainly used in new energy equipment such as polysilicon production furnaces. It is difficult to process and has high added value. Compared to other stainless steels for welding strips, molybdenum-containing stainless steel, with a molybdenum content of over 2.0%, experiences a higher hot-rolling load, more than 1.2 times that of ordinary stainless steel. Furthermore, the tensile strength requirement for hard-state cold-rolled coils of molybdenum-containing stainless steel for welding strips is 1000-1100 MPa, requiring special cold-rolling processes. Summary of the Invention

[0003] The purpose of this invention is to provide a method for producing stainless steel coils containing molybdenum welding strips, addressing the problems existing in the prior art.

[0004] Therefore, the present invention adopts the following technical solution:

[0005] A method for producing stainless steel coils for molybdenum-containing welding strips includes the following steps:

[0006] (1) Dephosphorized molten iron, pure nickel, ferromolybdenum and low-P ferrochrome are placed in an induction furnace for smelting, and then placed in an AOD converter and electrolytic manganese and low-aluminum ferrosilicon are added for smelting. The low-aluminum ferrosilicon has an Al content of 0.1%. Finally, it is placed in an LF refining furnace to smelt molten steel containing molybdenum.

[0007] (2) Cast the molten iron into slabs. During the casting process, control the temperature of the tundish to 1455℃~1470℃ and apply electromagnetic stirring. The current intensity of the electromagnetic stirring is 1350~1450A.

[0008] (3) The slab is heated twice in succession. The first heating temperature is 1160~1180℃ and the second heating temperature is 1190~1200℃.

[0009] (4) The slab after secondary heating is hot rolled into an intermediate slab with a thickness of 30 mm. Then the intermediate slab is rolled into a black coil with a thickness of 6.5 mm by a furnace coil mill.

[0010] (5) The black coil is cold rolled in three rolling passes. Each rolling pass is first hot annealed and pickled, and then rolled by a 20-roll mill to produce a steel strip coil with a thickness of 0.505 mm.

[0011] Further, the chemical composition of the molybdenum-containing molten steel in step (1) is as follows by mass percentage: C: ≤0.02%, Si: 0.30~0.40%, Mn: 1.85~1.95%, P ≤0.018%, S ≤0.002%, Cr: 21.05~21.20%, Ni: 13.83~13.93%, Mo: 2.0-2.1%, Cu: ≤0.05%, N: 0.060~0.070%, B: 0.0010~0.0020%, Al: ≤0.005%, Co: ≤0.05%, and the rest is Fe and unavoidable impurities.

[0012] Furthermore, the slab in step (2) has a size of 160mm×1240mm×10000mm.

[0013] Furthermore, the current intensity of the electromagnetic stirring in step (2) is 1380A.

[0014] Furthermore, in step (3), the first heating time is 200~230 min, and the second heating time is 220~250 min.

[0015] Furthermore, in step (4), the slab is rolled into an intermediate slab with a thickness of 30 mm by a 7-pass roughing mill, and the intermediate slab is rolled into a black coil with a thickness of 6.5 mm by a 5-pass hot rolling mill.

[0016] Furthermore, in step (5), the annealing temperature of the pickling and annealing in each rolling pass is controlled according to the material temperature, which is 1050~1070℃. The thickness of the first rolling pass is 3.0mm, the thickness of the second rolling pass is 0.71mm, and the thickness of the third rolling pass is 0.505mm.

[0017] The beneficial effects of this invention are as follows:

[0018] (1) Pure nickel, low-P ferrochrome and dephosphorized molten iron are added to ferromolybdenum to smelt steel for production, which ensures that the stainless steel for welding strip has low P and Cu content.

[0019] (2) The molten steel has low aluminum content and high purity. By controlling the superheat of the tundish to 25~40℃ and applying electromagnetic stirring, the hot plasticity of the slab is improved. The hot plasticity is improved by heating the slab twice and the ferrite content in the microstructure is guaranteed.

[0020] (3) Using 160mm slabs, hot rolling is carried out in 7 passes, and the furnace coil mill is rolled in 5 passes to produce 6.5mm thick black coils, which solves the problem of high rolling load in hot rolling of stainless steel containing molybdenum welding strip.

[0021] (4) Cold rolling is carried out through three rolling passes, and the reduction rate of each pass is reasonably allocated to ensure that the tensile strength of the finished product is between 1000-1100MPa. Attached Figure Description

[0022] Figure 1 This is a photograph of the surface of the stainless steel coil used for molybdenum-containing welding strip in Example 1;

[0023] Figure 2 This is a photograph of the surface of the stainless steel coil used for molybdenum-containing welding strip in Example 2;

[0024] Figure 3 This is a photograph of the surface of the stainless steel coil used for molybdenum-containing welding strip in Example 3; Detailed Implementation

[0025] The present invention will be described in detail below with reference to embodiments:

[0026] Example 1

[0027] (1) Dephosphorized molten iron, pure nickel, ferromolybdenum and low-P ferrochrome are placed in an induction furnace for smelting, and then placed in an AOD converter and electrolytic manganese and low-aluminum ferrosilicon are added for smelting. The low-aluminum ferrosilicon has an Al content of 0.1%. Adding electrolytic manganese and low-aluminum ferrosilicon can improve the chromium yield. Finally, it is placed in an LF refining furnace to smelt molybdenum-containing stainless steel for welding strips. Pure nickel and low-P ferrochrome are placed in an induction furnace. The low-P ferrochrome has a P content of 0.02%, and the dephosphorized molten iron has a P content of 0.007%. When smelting in the AOD converter, electrolytic manganese and low-aluminum ferrosilicon are added to the AOD converter. The low-aluminum ferrosilicon has an Al content of 0.1%. The percentages of various chemical components in the molybdenum-containing molten steel are: C: 0.02%, Si: 0.30%, Mn: 0.02%. : 1.85%, P: 0.018%, S: 0.002%, Cr: 21.05%, Ni: 13.83%, Mo: 2.0%, Cu: 0.05%, N: 0.060%, B: 0.0010%, Al: 0.005%, Co: 0.05%, the rest being Fe and unavoidable impurities.

[0028] (2) Cast the molten iron into a slab with a specification of 160mm×1240mm×10000mm. During the casting process, control the temperature of the tundish at 1455℃ and apply electromagnetic stirring. The current intensity of the electromagnetic stirring is 1380A. Then, perform full grinding on the slab. The overall grinding depth of the upper small surface is 1.5mm, and the edge is ground within a range of 200mm with a grinding depth of 3.0mm.

[0029] (3) The slab is heated twice in succession. After heating, it is easy to hot roll the slab. The first heating temperature is 1160℃ and the heating time is 200min. The second heating temperature is 1190℃ and the heating time is 220min.

[0030] (4) The slab after secondary heating is hot rolled. First, it is rolled into an intermediate slab with a thickness of 30 mm by a 7-pass rough rolling mill. Then, the intermediate slab is rolled into a black coil with a thickness of 6.5 mm by a 5-pass hot rolling mill.

[0031] (5) The black coil was cold rolled in three passes. Each pass was first hot annealed and pickled, and then rolled using a 20-roll mill. Finally, it was cold rolled into a steel strip coil with a thickness of 0.505 mm. The annealing temperature of each pass was controlled according to the material temperature, which was 1050℃. The thickness of the first pass was 3.0 mm, the thickness of the second pass was 0.71 mm, and the thickness of the third pass was 0.505 mm. The stainless steel coil for molybdenum welding strip was produced through three passes. The mechanical properties of the stainless steel coil are shown in Table 1.

[0032] Table 1

[0033]

[0034] Table 1 shows that the tensile strength meets the corresponding requirements.

[0035] Photographs of the surface of rolled stainless steel coils, as shown Figure 1 As shown, through Figure 1 It can be seen that the rolled stainless steel coil has a smooth surface and is of good quality.

[0036] Example 2

[0037] (1) Dephosphorized molten iron, pure nickel, and low-P ferrochrome were smelted in an induction furnace, an AOD converter, and an LF refining furnace to produce molybdenum-containing molten iron for welding strip stainless steel. The pure nickel and low-P ferrochrome were then placed in the induction furnace. The low-P ferrochrome had a P content of 0.018%, and the dephosphorized molten iron had a P content of 0.006%. During AOD converter smelting, electrolytic manganese and low-aluminum ferrosilicon were added to the AOD converter. The low-aluminum ferrosilicon had an Al content of 0.08%. The percentages of various chemical components in the molybdenum-containing molten iron were: C: 0.018%, Si: 0.40%, Mn: 1.95%, P: 0.015%, S: 0.001%, Cr: 21.20%, Ni: 13.93%, Mo: 2.1%, Cu: 0.04%, N: 0.070%, B: 0.0020%, Al: 0.004%, Co: 0.02%, the rest being Fe and unavoidable impurities.

[0038] (2) Cast the molten iron into a slab with a specification of 160mm×1240mm×10000mm. During the casting process, control the temperature of the tundish at 1470℃ and apply electromagnetic stirring. The current intensity of the electromagnetic stirring is 1380A. Then, perform full grinding on the slab. The overall grinding depth of the upper small surface is 1.5mm, and the edge is ground within a range of 200mm with a grinding depth of 3.0mm.

[0039] (3) The slab is heated twice in succession. After heating, it is easy to hot roll the slab. The first heating temperature is 1180℃ and the heating time is 230min. The second heating temperature is 1200℃ and the heating time is 250min.

[0040] (4) The slab after secondary heating is hot rolled. First, it is rolled into an intermediate slab with a thickness of 30 mm by a 7-pass rough rolling mill. Then, the intermediate slab is rolled into a black coil with a thickness of 6.5 mm by a 5-pass hot rolling mill.

[0041] (5) The black coil was cold rolled in three passes. Each pass was first hot annealed and pickled, and then rolled using a 20-roll mill. Finally, it was cold rolled into a steel strip coil with a thickness of 0.505 mm. The annealing temperature of each pass was controlled according to the material temperature, which was 1070℃. The thickness of the first pass was 3.0 mm, the thickness of the second pass was 0.71 mm, and the thickness of the third pass was 0.505 mm. The stainless steel coil for molybdenum welding strip was produced through three passes. The mechanical properties of the stainless steel coil are shown in Table 2.

[0042] Table 2

[0043]

[0044] Table 2 shows that the tensile strength meets the corresponding requirements.

[0045] Photographs of the surface of rolled stainless steel coils, as shown Figure 2 As shown, through Figure 2 It can be seen that the rolled stainless steel coil has a smooth surface and is of good quality.

[0046] Example 3

[0047] (1) Dephosphorized molten iron, pure nickel, and low-P ferrochrome were smelted in an induction furnace, an AOD converter, and an LF refining furnace to produce molybdenum-containing molten iron for welding strip stainless steel. The pure nickel and low-P ferrochrome were then placed in the induction furnace. The low-P ferrochrome had a P content of 0.019%, and the dephosphorized molten iron had a P content of 0.007%. During AOD converter smelting, electrolytic manganese and low-aluminum ferrosilicon were added to the AOD converter. The low-aluminum ferrosilicon had an Al content of 0.08%. The percentages of various chemical components in the molybdenum-containing molten iron were: C: 0.015%, Si: 0.33%, Mn: 1.88%, P: 0.014%, S: 0.0015%, Cr: 21.13%, Ni: 13.88%, Mo: 2.05%, Cu: 0.03%, N: 0.068%, B: 0.0015%, Al: 0.0045%, Co: 0.04%, the rest being Fe and unavoidable impurities.

[0048] (2) Cast the molten iron into a slab with a specification of 160mm×1240mm×10000mm. During the casting process, control the temperature of the tundish at 1470℃ and apply electromagnetic stirring. The current intensity of the electromagnetic stirring is 1380A. Then, perform full grinding on the slab. The overall grinding depth of the upper small surface is 1.5mm, and the edge is ground within a range of 200mm with a grinding depth of 3.0mm.

[0049] (3) The slab is heated twice in succession. After heating, it is easier to hot roll the slab. The first heating temperature is 1170℃ and the heating time is 210min. The second heating temperature is 1195℃ and the heating time is 225min. The first heating of the slab can turn the network ferrite into dots and improve the hot plasticity of the slab. The second heating of the slab increases the temperature and can reduce the rolling load.

[0050] (4) The slab after secondary heating is hot rolled. First, it is rolled into an intermediate slab with a thickness of 30 mm by a 7-pass rough rolling mill. Then, the intermediate slab is rolled into a black coil with a thickness of 6.5 mm by a 5-pass hot rolling mill.

[0051] (5) The black coil was cold rolled in three passes. Each pass was first hot annealed and pickled, and then rolled using a 20-roll mill. Finally, it was cold rolled into a steel strip coil with a thickness of 0.505 mm. The annealing temperature of each pass was controlled according to the material temperature, which was 1060℃. The thickness of the first pass was 3.0 mm, the thickness of the second pass was 0.71 mm, and the thickness of the third pass was 0.505 mm. The stainless steel coil for molybdenum welding strip was produced through three passes. The mechanical properties of the stainless steel coil are shown in Table 2.

[0052] Table 3

[0053]

[0054] Table 3 shows that the tensile strength meets the corresponding requirements.

[0055] Photographs of the surface of rolled stainless steel coils, as shown Figure 3 As shown, through Figure 3 It can be seen that the rolled stainless steel coil has a smooth surface and is of good quality.

Claims

1. A method for producing stainless steel coils for molybdenum-containing welding strips, characterized in that, Includes the following steps: (1) Dephosphorized molten iron, pure nickel, ferromolybdenum, and low-P ferrochrome are smelted in an induction furnace, then placed in an AOD converter and smelted with electrolytic manganese and low-aluminum ferrosilicon. The low-aluminum ferrosilicon contains 0.1% Al. Finally, it is placed in an LF refining furnace to smelt molybdenum-containing molten steel. The chemical composition of the molybdenum-containing molten steel, by mass percentage, is as follows: C: ≤ 0.02%, Si: 0.30~0.40%, Mn: 1.85~1.95%, P ≤ 0.018%, S ≤ 0.002%, Cr: 21.05~21.20%, Ni: 13.83~13.93%, Mo: 2.0-2.1%, Cu: ≤ 0.05%, N: 0.060~0.070%, B: 0.0010~0.0020%, Al: ≤ 0.005%, Co: ≤0.05%, the rest is Fe and unavoidable impurities; (2) Cast the molten iron into a slab with a specification of 160mm×1240mm×10000mm. During the casting process, control the temperature of the tundish to 1455℃~1470℃ and apply electromagnetic stirring with a current intensity of 1350~1450A. (3) The slab is heated twice in succession. The first heating temperature is 1160~1180℃ and the second heating temperature is 1190~1200℃. (4) The slab after secondary heating is hot rolled into an intermediate slab with a thickness of 30 mm. Then the intermediate slab is rolled into a black coil with a thickness of 6.5 mm by a furnace coil mill. Specifically, the slab is rolled into an intermediate slab with a thickness of 30 mm by 7 passes of rough rolling and the intermediate slab is rolled into a black coil with a thickness of 6.5 mm by 5 passes of furnace coil mill. (5) The black coil is cold rolled in three rolling passes. Each rolling pass is first hot annealed and pickled, and then rolled by a 20-roll mill to cold roll into a steel strip coil with a thickness of 0.505mm. The annealing temperature of the pickling in each rolling pass is controlled according to the material temperature, which is 1050~1070℃. The thickness of the first rolling pass is 3.0mm, the thickness of the second rolling pass is 0.71mm, and the thickness of the third rolling pass is 0.505mm.

2. The method for producing stainless steel coils for molybdenum-containing welding strips according to claim 1, characterized in that, The percentage of P content in the dephosphorized molten iron in step (1) is: P ≤ 0.02%, and the percentage of P content in the low-P ferrochrome is: P ≤ 0.007%.

3. The method for producing stainless steel coils for molybdenum-containing welding strips according to claim 1, characterized in that, The current intensity of the electromagnetic stirring in step (2) is 1380A.

4. The method for producing stainless steel coils for molybdenum-containing welding strips according to claim 1, characterized in that, In step (3), the first heating time is 200-230 min, and the second heating time is 220-250 min.

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