Martensitic stainless steel pickling-free direct rolling process

Abstract

The invention belongs to the technical field of ferrous metallurgy, and particularly relates to a martensitic stainless steel pickling-free direct rolling process which comprises the following specific steps: S1, smelting: molten steel alloy comprises the following chemical components in percentage by weight: 0.16-0.35% of C, less than or equal to 1.00% of Si, less than or equal to 1.00% of Mn, less than or equal to 0.040% of P, less than or equal to 0.030% of S, less than or equal to 0.60% of Ni, 12.00-14.00% of Cr and the balance of Fe and inevitable impurities, and smelting and continuous casting are performed to form a blank; s2, hot rolling is conducted, specifically, the continuous casting blank or the casting blank is heated to complete hot rolling, the furnace staying time is 9-12 mm / 10 min, the furnace staying temperature is 1200-1300 DEG C, the total rolling deformation is 92%-98%, and coiling and cooling are conducted after hot rolling; s3, bell-type furnace annealing is carried out, specifically, bell-type furnace annealing of the hot-rolled coil is completed at the temperature of 800-950 DEG C, the heat preservation time is 18-22 hours, furnace cooling and rapid cooling are carried out, and then air cooling is carried out; and S4, pickling-free pre-descaling rolling is conducted, specifically, shot blasting treatment and rolling are conducted, the shot blasting rotating speed is 1800-2200 rpm, the shot blasting current is 100-130 A, and the rolling pass is 2-3. According to the process, the pickling step is omitted, the pre-descaling process is optimized, the production cost is reduced, and the surface quality of the directly-rolled black leather is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and in particular relates to a direct rolling process for martensitic stainless steel without pickling. Background Art

[0002] The conventional martensitic stainless steel production process is steelmaking, hot rolling, bell furnace annealing, pickling, cold rolling, cold annealing and pickling; with the current surge in market competition, customers are increasingly demanding cost reduction and efficiency improvement, and the strength and surface requirements of martensitic stainless steel in the field of knives and scissors are increasing. The direct rolling process after bell furnace annealing commonly used in the market will cause the surface oxide scale to be rolled too deep into the matrix, making the user's subsequent processing difficult, and the iron oxide scale is difficult to remove completely, resulting in low efficiency; if cold rolling after pickling is used, the surface quality will be improved but the cost will increase and cause serious pollution to the environment. Summary of the invention

[0003] The purpose of the present invention is to provide a direct rolling process for martensitic stainless steel without pickling, and to solve the problem that the direct rolling process after bell furnace annealing commonly used in the market currently causes the surface oxide scale to be rolled too deeply into the substrate, making the subsequent processing process of the user difficult and the iron oxide scale difficult to remove completely through the surface pre-scaling process.

[0004] In order to achieve the above object, the present invention adopts the following technical scheme: A direct rolling process for martensitic stainless steel without pickling, the specific steps are as follows: S1: Smelting: The chemical composition of molten steel alloy is as follows: C: 0.16%-0.35%, Si: ≤1.00%, Mn: ≤1.00%, P: ≤0.040%, S: ≤0.030%, Ni: ≤0.60%, Cr: 12.00%-14.00%, and the rest is Fe and unavoidable impurities. The smelting process is molten iron pretreatment → oxygen bottom blowing converter → decarburization by argon blowing → LF refining → continuous casting into billets; S2: Hot rolling: The continuous casting billet or the cast billet is heated to complete hot rolling, the furnace dwelling time is 9-12mm / 10min, the furnace dwelling temperature is 1200-1300℃, the total rolling deformation is 92%-98%, and the coiling is cooled after hot rolling, and the coiling is not subjected to laminar cooling; S3: bell furnace annealing: the hot rolled coil is bell furnace annealed at 800℃~950℃, the holding time is 18-22 hours, the furnace is cooled, the rapid cooling is carried out, and then the air cooling is carried out; S4: Pickling-free pre-descaling rolling: After shot blasting and rolling, the shot blasting speed is 1800-2200rpm, the shot blasting current is 100-130A, and the rolling passes are 2-3 times.

[0005] Preferably, in step S3, after heat preservation, the mixture is cooled to 650° C. in the furnace and then rapidly cooled to 300° C.

[0006] Preferably, in step S4, the shot blasting size is mixed in a ratio of 0.2-0.5 mm, and the sanding rate is 2%-4%.

[0007] Preferably, the rolling reduction rate in step S4 is 20-40%.

[0008] Compared with the prior art, the present invention has the following beneficial effects: (1) Adopt non-throw laminar cooling to simplify the process flow, improve efficiency and reduce the maintenance and replacement frequency of equipment; (2) Temperature and cooling are controlled by cooling with the furnace to avoid work hardening caused by excessive cooling. Rapid cooling to a fixed temperature makes the martensite structure fine and improves the hardness and wear resistance of the workpiece. (3) From the process flow, it is proposed to carry out surface pre-descaling after bell-type furnace annealing, and to ensure the removal of surface oxide scale by shot blasting, reduce the pickling process steps, and avoid the pressure of iron scale in the subsequent rolling process; by optimizing the pre-descaling process, the environmental pressure and production cost of the factory can be reduced, the surface quality of black skin after direct rolling can be improved, and the processing cost of users can be reduced during use. DETAILED DESCRIPTION

[0009] The technical solution of the present invention is described clearly and completely below in conjunction with the embodiments. Example 1

[0010] A direct rolling process for martensitic stainless steel without pickling, the specific steps are as follows: S1: Smelting: The chemical composition of the molten steel alloy is as follows: C: 0.23%, Si: 0.37%, Mn: 0.56%, P: 0.019%, S: 0.0027%, Ni: 0.06%, Cr: 13.19%, and the rest is Fe and unavoidable impurities. The smelting process is molten iron pretreatment → oxygen bottom blowing converter → decarburization by argon blowing → LF refining → continuous casting into billets; S2: Hot rolling: The ingot is heated to complete hot rolling, the furnace dwelling time is 9mm / 10min, the furnace dwelling temperature is 1200-1300℃, the total rolling deformation is 92%, and the coiling is cooled after hot rolling, and the coiling is not subjected to laminar cooling; S3: bell furnace annealing: The hot rolled coil is bell furnace annealed at 860°C for 19 hours, then furnace cooled to 650°C, rapidly cooled to 300°C, and then air cooled; S4: Pickling-free pre-descaling rolling: After shot blasting and rolling, the shot blasting speed is 2000rpm, the shot blasting current is 110A; the shot blasting size adopts a mixed ratio of 0.2mm, and the sanding rate is 2.5%; the rolling passes are 3 times, and the rolling reduction rate is 20%.

[0011] The iron oxide scale removal rate using this method reaches 91%. Example 2

[0012] A direct rolling process for martensitic stainless steel without pickling, the specific steps are as follows: S1: Smelting: The chemical composition of the molten steel alloy is as follows: C: 0.35%, Si: 0.35%, Mn: 0.76%, P: 0.032%, S: 0.0012%, Ni: 0.11%, Cr: 13.20%, and the rest is Fe and unavoidable impurities. The smelting process is molten iron pretreatment → oxygen bottom blowing converter → decarburization by argon blowing → LF refining → continuous casting into billets; S2: Hot rolling: The ingot is heated and hot rolled, the furnace dwelling time is 10mm / 10min, the furnace dwelling temperature is 1200-1300℃, the total rolling deformation is 94%, and the coiling is cooled after hot rolling, and the coiling is not subjected to laminar cooling; S3: bell furnace annealing: the hot rolled coil is bell furnace annealed at 850°C for 20 hours, then furnace cooled to 650°C, rapidly cooled to 300°C, and then air cooled; S4: Pickling-free pre-descaling rolling: After shot blasting and rolling, the shot blasting speed is 2100rpm, the shot blasting current is 115A; the shot blasting size adopts a mixed ratio of 0.3mm, and the sanding rate is 2%; the rolling passes are 3 times, and the rolling reduction rate is 30%.

[0013] The iron oxide scale removal rate using this method reaches 90.5%. Example 3

[0014] A direct rolling process for martensitic stainless steel without pickling, the specific steps are as follows: S1: Smelting: The chemical composition of the molten steel alloy is as follows: C: 0.19%, Si: 0.34%, Mn: 0.55%, P: 0.017%, S: 0.002%, Ni: 0.06%, Cr: 13.22%, and the rest is Fe and unavoidable impurities. The smelting process is molten iron pretreatment → oxygen bottom blowing converter → decarburization by argon blowing → LF refining → continuous casting into billets; S2: Hot rolling: The continuous casting billet is heated and hot rolled, the furnace dwelling time is 11mm / 10min, the furnace dwelling temperature is 1200-1300℃, the total rolling deformation is 95%, and the billet is coiled and cooled after hot rolling, and the coiling is not subjected to laminar cooling; S3: bell furnace annealing: the hot rolled coil is bell furnace annealed at 870℃ for 20 hours, then furnace cooled to 650℃, rapidly cooled to 300℃, and then air cooled; S4: Pickling-free pre-descaling rolling: After shot blasting and rolling, the shot blasting speed is 1900rpm, the shot blasting current is 110A; the shot blasting size adopts a mixing ratio of 0.5mm, and the sanding rate is 4%; the rolling passes are 2 passes, and the rolling reduction rate is 40%.

[0015] The iron oxide scale removal rate using this method reaches 92%. Example 4

[0016] A direct rolling process for martensitic stainless steel without pickling, the specific steps are as follows: S1: Smelting: The chemical composition of the molten steel alloy is as follows: C: 0.18%, Si: 0.33%, Mn: 0.55%, P: 0.023%, S: 0.0025%, Ni: 0.06%, Cr: 13.21%, and the rest is Fe and unavoidable impurities. The smelting process is molten iron pretreatment → oxygen bottom blowing converter → decarburization by argon blowing → LF refining → continuous casting into billets; S2: Hot rolling: The continuous casting billet is heated and hot rolled, the furnace dwelling time is 12mm / 10min, the furnace dwelling temperature is 1200-1300℃, the total rolling deformation is 96%, and the billet is coiled and cooled after hot rolling, and the coiling is not subjected to laminar cooling; S3: bell furnace annealing: The hot rolled coil is bell furnace annealed at 860°C for 19 hours, then furnace cooled to 650°C, rapidly cooled to 300°C, and then air cooled; S4: Pickling-free pre-descaling rolling: After shot blasting and rolling, the shot blasting speed is 1950rpm, the shot blasting current is 150A; the shot blasting size adopts a mixing ratio of 0.5mm, and the sanding rate is 3.5%; the rolling passes are 2 passes, and the rolling reduction rate is 30%.

[0017] The iron oxide scale removal rate using this method reaches 93%.

[0018] Comparative Example 1 A direct rolling process for martensitic stainless steel without pickling, the specific steps are as follows: S1: Smelting: The chemical composition of the molten steel alloy is as follows: C: 0.18%, Si: 0.33%, Mn: 0.55%, P: 0.023%, S: 0.0025%, Ni: 0.06%, Cr: 13.21%, and the rest is Fe and unavoidable impurities. The smelting process is molten iron pretreatment → oxygen bottom blowing converter → decarburization by argon blowing → LF refining → continuous casting into billets; S2: Hot rolling: The continuous casting billet is heated and hot rolled, the furnace dwelling time is 12mm / 10min, the furnace dwelling temperature is 1200-1300℃, the total rolling deformation is 96%, and the billet is coiled and cooled after hot rolling, and the coiling is not subjected to laminar cooling; S3: bell furnace annealing: The hot rolled coil is bell furnace annealed at 860°C for 19 hours, then furnace cooled to 650°C, rapidly cooled to 300°C, and then air cooled; S4: Black skin direct rolling: The bell-type furnace annealed coil is directly rolled without pickling after cooling, with 2 rolling passes.

[0019] The removal rate of iron oxide scale using this method reaches 0%.

[0020] By adopting the "bell furnace annealing + pickling-free pre-descaling rolling process", the iron oxide scale elimination rate on the steel plate surface reaches 90%-95%, reducing the pickling process, reducing production costs, reducing users' subsequent processing procedures, and reducing use costs.

Claims

1. A direct rolling process for martensitic stainless steel without pickling, characterized in that: The specific steps are as follows: S1: Smelting: The chemical composition of molten steel alloy is as follows: C: 0.16%-0.35%, Si: ≤1.00%, Mn: ≤1.00%, P: ≤0.040%, S: ≤0.030%, Ni: ≤0.60%, Cr: 12.00%-14.00%, and the rest is Fe and unavoidable impurities. The smelting process is molten iron pretreatment → oxygen bottom blowing converter → decarburization by argon blowing → LF refining → continuous casting into billets; S2: Hot rolling: The continuous casting billet or the cast billet is heated to complete hot rolling, the furnace dwelling time is 9-12mm / 10min, the furnace dwelling temperature is 1200-1300℃, the total rolling deformation is 92%-98%, and the coiling is cooled after hot rolling, and the coiling is not subjected to laminar cooling; S3: bell furnace annealing: the hot rolled coil is bell furnace annealed at 800℃~950℃, the holding time is 18-22 hours, the furnace is cooled, the rapid cooling is carried out, and then the air cooling is carried out; S4: Pickling-free pre-descaling rolling: After shot blasting and rolling, the shot blasting speed is 1800-2200rpm, the shot blasting current is 100-130A, and the rolling passes are 2-3 times.

2. A direct rolling process for martensitic stainless steel without pickling according to claim 1, characterized in that: In step S3, after heat preservation, the mixture is cooled to 650° C. in the furnace and then rapidly cooled to 300° C.

3. A direct rolling process for martensitic stainless steel without pickling according to claim 1, characterized in that: In step S4, the shot blasting size is mixed in a ratio of 0.2-0.5 mm, and the sanding rate is 2%-4%.

4. A direct rolling process for martensitic stainless steel without pickling according to claim 1, characterized in that: The rolling reduction rate in step S4 is 20-40%.