Production method of soft magnetic steel stainless steel 430FRT straight bar

Abstract

The invention relates to a production method of a soft magnetic steel bar stainless steel 430FRT straight bar, and the production method of a wire rod comprises the following steps of: heating a steel billet at 1200-1260 DEG C according to the size requirement of (205-220) mm * (205-220) mm; a two-roller reversible cogging mill is used for rolling for 11 passes, and the initial rolling temperature is 1100-1150 DEG C; rolling the round steel with the diameter of 85mm into round steel with the diameter of 85mm, rolling the round steel with the diameter of 85mm in a high-speed wire continuous rolling machine, rolling a bar after high-speed wire continuous rolling, discharging a finished product from a frame at the end of bar rolling, controlling the finish rolling temperature to be 850-900 DEG C, and performing a hot charging and hot annealing heat treatment process after rolling. The heat treatment process after rolling is the key point, a hot charging furnace and an annealing furnace are executed after rolling, the charging temperature is larger than or equal to 350 DEG C, the heating speed of a trolley furnace is smaller than or equal to 90 DEG C / h, the heat preservation temperature of the annealing furnace is 860 DEG C, the heat preservation time is 12 hours, and after furnace cooling is conducted to 400 DEG C, discharging and air cooling are conducted to the normal temperature. And the mechanical property, the grain size and the hardness value of the straight bar are controlled within the qualified range.

Description

Technical Field

[0001] The present invention relates to a production method of a 430FRT straight bar of soft magnetic steel stainless steel, specifically to a method of obtaining a 430FRT straight bar of soft magnetic steel having good mechanical properties, grain size and hardness value that meet requirements through reasonable heating, temperature-controlled rolling and heat treatment processes for a 430FRT steel billet with a certain chemical composition. Background Art

[0002] 430FRT contains C, Si, Cr, Mn, Ni, Cu, N and other elements. It is a ferrite structure at room temperature and a ferrite structure when heated at high temperature. The rods are mainly used to make magnetic materials. 430FRT hot-rolled bars have strong magnetism, high brittleness and low strength. If they are not promptly heat-treated after hot rolling, they may break and crack. The grains inside the material are coarse after hot rolling. Heat treatment can reduce the grain size and improve the grain size level. Therefore, it is key to load 430FRT into an annealing furnace in time after hot rolling. Hot loading and hot annealing processes are required. After heat treatment, the fractures and cracks are solved (completely eliminating the internal stress generated during cooling), the grain size level is improved, the hardness is reduced, and the mechanical properties are improved, which is conducive to subsequent straightening, turning and other processing.

[0003] In view of the above problems, the present invention provides a method for producing soft magnetic steel stainless steel 430FRT straight bars to solve the above problems and obtain 430FRT straight bar products with good mechanical properties, grain size, hardness and mechanical properties.

[0004] The invention discloses a production method of a soft magnetic steel bar stainless steel 430FRT straight bar, which is suitable for a production method of a rolling and post-rolling hot-loading heat treatment process of a 430FRT straight bar.

[0005] The invention can achieve the purpose of obtaining good heat treatment mechanical properties, grain size level, hardness and mechanical properties for the soft magnetic steel stainless steel 430FRT straight bar. Summary of the invention

[0006] The purpose of the present invention is to provide a method for producing soft magnetic steel stainless steel 430FRT straight bars in view of the above problems.

[0007] The object of the present invention is achieved in this way: a production method of 430FRT straight bars of soft magnetic steel stainless steel, comprising the following steps: step 1: the steel billet is a die casting billet or a continuous casting billet, the cross-sectional size of the steel billet is (205-220) × (205-220) mm, and the weight of the steel billet is 1100-1250 kg; step 2: the steel billet is heated by a walking beam heating furnace, the heating stage temperature is 900-1050°C, the heating stage temperature is 1220-1260°C, and the soaking stage temperature is 1200-1240°C; the heating time for the heating stage is 1.0 hour-3.5 hours, the heating time for the heating stage is 1.5 hours-2.5 hours, and the heating time for the soaking stage is 1.0 hour-2.5 hours; step 3: using a two-roller reversible billet opening machine, Rolling 11 times, the starting rolling temperature is 1100-1150℃, and the round steel of Φ85mm-Φ86.5mm is rolled. The round steel enters the high-speed continuous rolling mill for rolling, and enters the bar rolling after the high-speed continuous rolling. The finished product is produced at the final stand of the bar rolling, and the final rolling temperature is controlled at 850-900℃. After rolling, the hot charging and hot annealing treatment process is performed; Step 4: After rolling, the hot charging furnace annealing furnace is performed and the heat treatment process is performed, the furnace temperature is ≥350℃, the trolley furnace is heated at a rate of ≤90℃ / h, the annealing furnace is kept at a temperature of 860℃-900℃, the holding time is 8 hours-12 hours, and after cooling to 350℃-400℃ with the furnace, it is air-cooled to room temperature after being taken out of the furnace; the mechanical properties of the straight bar are tensile strength Rm≥450MPa, the grain size level is 4-9, and the Brinell hardness value is controlled to be 160-210.

[0008] The chemical composition range of the soft magnetic stainless steel 430FRT straight bar applicable to this method is: C≤0.03%, Si: 1.20-1.60%, Mn≤0.50%, P≤0.020%, S≤0.020%, Cr: 17.20-18.00%, Ni: 0.20-0.40%, Mo: 1.00-1.50%, Cu: 0.15-0.30%, N≤0.03%.

[0009] The beneficial effect of the present invention is that the method can enable the 430FRT straight bar to obtain good heat treatment mechanical properties, grain size level, hardness, and mechanical properties, and meet the requirements of subsequent processing and use. DETAILED DESCRIPTION

[0010] The technical solution of the present invention is as follows: 1. The chemical composition range of the soft magnetic steel stainless steel 430FRT straight bar applicable to the present invention is as shown in the following table.

[0011]

[0012] 2. Use die-cast billets or continuous casting billets with a billet cross-sectional size of (205-220) × (205-220) mm and a billet weight of 1100-1250 kg. There should be no defects on the billet surface that would affect the processing and use of wire rods.

[0013] 3. Billet heating: Walking beam heating furnace, heating stage temperature 900 ~ 1050 ° C, heating stage 2 temperature 1220 ~ 1260 ° C, soaking stage temperature 1200 ~ 1240 ° C.

[0014] 4. Wire rod rolling: Use a two-roller reversible billet mill, roll 11 times, start rolling temperature 1100 ~ 1150 ℃, and roll into Φ85mm round steel. Φ85mm round steel enters the high-speed continuous rolling mill for rolling, and then enters the bar rolling. The finished product is Φ25 ~ 60mm straight bar, the final rolling temperature is controlled at 850 ~ 900 ℃, and the hot charging and heat annealing treatment process is performed after rolling.

[0015] 5. Heat treatment after rolling: hot charging annealing furnace after rolling, heat treatment process after coil rolling is the key point, hot charging annealing furnace and process are carried out after rolling, the temperature of entering the furnace is ≥350℃, to ensure that the bar will not break and crack, and heat treatment process is carried out, the trolley furnace is heated at a rate of ≤90℃ / h, the annealing furnace is kept at 860℃, the holding time is 12 hours, and after cooling to 400℃ with the furnace, it is air-cooled to room temperature after being taken out of the furnace. The mechanical properties, grain size and hardness of the straight bar are controlled within the standard values. Example

[0016] This embodiment is a method for producing 430FRT straight strips with a specification of Φ30mm.

[0017] 1.The chemical composition is as shown in the following table.

[0018]

[0019] 2. Continuous casting cutting billet, the billet cross-sectional size is 211×206mm, the billet weight is 1.224kg, and there is no defect on the billet surface that affects the straight bar processing and use.

[0020] 3. Walking beam heating furnace, heating stage temperature 955℃, heating stage 2 temperature 1246℃, soaking stage temperature 1227℃.

[0021] 4. Use a two-roller reversible billet mill, roll 11 times, start rolling temperature 1123℃, and roll into Φ85mm round steel. The Φ85mm round steel enters the high-speed continuous rolling mill for rolling, and then enters the bar rolling. The finished product is Φ30mm straight bar, the final rolling temperature is 886℃, and the hot charging and heat annealing treatment process is performed after rolling.

[0022] 5. After rolling, the hot-charged annealing furnace is set at 425°C, and the heat treatment process is carried out. The heating rate of the annealing furnace is 70°C / h, and the heating time is 6.21 hours. The insulation temperature of the annealing furnace is set at 860°C, and the insulation time is 12 hours. After cooling to 400°C with the furnace, it is air-cooled to room temperature after being taken out of the furnace.

[0023] 6. Performance quality of straight bars: The internal grain size of the 430FRT straight bars after hot-loading and annealing treatment is uniform, with a grain size of grade 5, meeting the standard grades 4 to 9; the Brinell hardness is 175, meeting the standard Brinell hardness of 160 to 210; the tensile strength Rm is 472MPa and 476MPa. The tensile strength meets the requirement of ≥450MPa.

[0024]

[0025] The above description is only a specific embodiment of the present invention, but the structural features of the protection scope of the present invention are not limited thereto. Any changes or modifications made by any technician in the field of the present invention are all covered by the patent scope of the present invention.

Claims

1. A method for producing soft magnetic steel stainless steel 430FRT straight bars, characterized in that: The following steps are involved: Step 1: The steel billet is a die casting billet or a continuous casting billet, the cross-sectional size of the steel billet is (205-220) × (205-220) mm, and the weight of the steel billet is 1100-1250 kg; Step 2: The steel billet is heated in a walking beam heating furnace, with the first heating stage at 900-1050°C, the second heating stage at 1220-1260°C, and the soaking stage at 1200-1240°C; the first heating stage heating time is 1.0-3.5 hours, the second heating stage heating time is 1.5-2.5 hours, and the soaking stage heating time is 1.0-2.5 hours; Step 3: Use a two-roll reversible blooming mill, roll 11 times, the rolling temperature is 1100-1150℃, and roll into Φ85mm-Φ86.5mm round steel. The round steel enters the high-speed continuous rolling mill for rolling, and then enters the bar rolling after the high-speed continuous rolling. The bar rolling end stand produces the finished product, the final rolling temperature is controlled at 850-900℃, and the hot charging and heat annealing treatment process is performed after rolling; Step 4: After rolling, perform hot charging annealing furnace and perform heat treatment process, the furnace temperature is ≥350℃, the trolley furnace is heated at a rate of ≤90℃ / h, the annealing furnace is kept at 860℃-900℃, the holding time is 8 hours-12 hours, and after cooling to 350℃-400℃ with the furnace, it is air-cooled to room temperature after being taken out of the furnace; the mechanical properties of the straight bar are controlled to have tensile strength Rm ≥450MPa, grain size level 4-9, and Brinell hardness value of 160-210.

2. The method for producing a 430FRT straight strip of soft magnetic steel stainless steel according to claim 1, characterized in that: The chemical composition range of the soft magnetic stainless steel 430FRT straight bar applicable to this method is: C≤0.03%, Si: 1.20-1.60%, Mn≤0.50%, P≤0.020%, S≤0.020%, Cr: 17.20-18.00%, Ni: 0.20-0.40%, Mo: 1.00-1.50%, Cu: 0.15-0.30%, N≤0.03%.

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