Rolling method of electromagnetic pure iron wire rod

Abstract

The invention discloses a rolling method of an electromagnetic pure iron wire rod, and belongs to the technical field of metallurgical industry wire production. According to the technical scheme, the steel billet heating temperature is 1050-1190 DEG C, the soaking temperature is 1050-1190 DEG C, the finish rolling temperature is 830-900 DEG C, and the spinning temperature is 820-900 DEG C; the spinning temperature ranges from 820-900 DEG C to 750 DEG C, and the cooling speed ranges from 2 DEG C / s to 3 DEG C / s; from 750 DEG C to 500 DEG C, the cooling speed is less than 2 DEG C / s; the cooling speed below 500 DEG C is greater than 3 DEG C / s, and the steel comprises the following chemical elements in percentage by mass: less than or equal to 0.01% of C, less than or equal to 0.10% of Si, less than or equal to 0.25% of Mn, less than or equal to 0.015% of P, less than or equal to 0.010% of S, 0.2-0.6% of Al, less than or equal to 0.005% of N, less than or equal to 0.005% of O and the balance of Fe and unavoidable impurities. By means of the method, the electromagnetic pure iron wire rod which is free of mixed crystals on the edge, free of abnormally thick ferrite and good in electromagnetic performance can be obtained.

Description

Technical Field

[0001] The invention relates to a rolling method for an electromagnetic pure iron wire rod, and belongs to the technical field of production of steel wires for electromagnetic pure iron in the metallurgical industry. Background Art

[0002] Electromagnetic pure iron is one of the soft magnetic materials. It has excellent soft magnetic properties such as low coercive resistance, high magnetic permeability and stable magnetic properties. It is mainly used in electrical appliances, telecommunications, electronic defense and other industries. Electromagnetic pure iron is a high-quality special steel with an iron content of more than 99.5%, ultra-low carbon content, sulfur content and phosphorus content, high technical content and high product added value. In recent years, with the rapid development of my country's electronics, telecommunications, new energy and other industries, electromagnetic pure iron has been widely used in daily life, such as electricity, machinery, transportation and other fields. At the same time, it also plays an increasingly important role in meteorology, medical care, military and other fields.

[0003] As a soft magnetic material, electromagnetic pure iron requires the coercivity to be as low as possible, and the coercivity is closely related to the composition and structure. At present, most steel mills use composition adjustment to reduce the coercivity, such as reducing the content of harmful elements such as C, N and S, and increasing the Al content. The present invention further reduces the coercivity by controlling the final rolling temperature, the spinning temperature, the heating temperature and the cooling rate to obtain a uniform and larger equiaxed ferrite structure with grains.

[0004] The patent application number 202410358717.7 discloses an industrial pure iron bar and a preparation method thereof, which belongs to the field of materials and metallurgy technology. The industrial pure iron bar includes the following components in weight percentage: C: ≤0.004%, Si: ≤0.010%, Mn: ≤0.050%, P: ≤0.004%, S: ≤0.005%, Co: ≤0.005%, Mo: ≤0.009%, Cu: ≤0.012%, Alt: ≤0.020%, Ti: ≤0.009%, Nb: ≤0.009%, Ni: ≤0.009%. This patent adopts "converter + LF + RH + continuous casting + rolling process" to produce industrial pure iron bars, which not only ensures that the chemical composition of the steel and the purity of the steel meet the standard requirements, but also ensures the surface quality level of the industrial pure iron bars, meets the use requirements of high-end steel products, and achieves a breakthrough in the mass production of industrial pure iron bars by the converter continuous casting process.

[0005] The patent with application number 202311707117.9 discloses a method for preparing high-aluminum industrial pure iron, which belongs to the field of metallurgical technology. The chemical composition of the high-aluminum industrial pure iron is calculated by weight percentage as follows: [C]≤0.01%, [Si]≤0.05%, [Mn]≤0.10%, [P]≤0.015%, [S]≤0.010%, [Al]: 0.2 ~ 0.8%, and the rest is Fe; the process flow is KR molten iron desulfurization → BOF smelting → LF refining → RH decarburization and deoxidation → continuous casting. This patent uses a transition casting method, adopts a low-aluminum steel grade with a cross-composition to start pouring, gradually increases the aluminum content of the molten steel, and controls the oxygen content of the molten steel, thereby achieving stable production of high-aluminum industrial pure iron.

[0006] The patent with application number 202310236937.8 discloses a production and preparation method of electromagnetic pure iron DT4 hot-rolled round steel produced by VD process, which belongs to the preparation method of bar. Including: steelmaking process: blast furnace molten iron - molten iron pretreatment - converter top and bottom blowing smelting - LF refining outside the furnace - VD vacuum treatment - continuous casting; steel rolling process: billet heating - high-pressure water dephosphorization - Ф850mm billet opening machine - Ф700mm×3+Ф550mm×4 continuous rolling mill group rolling - sawing (sampling) - straightening - stacking (cooling, heat collection) - inspection - grinding - bundling - warehousing - delivery. The purpose of this patent is to provide a production and preparation method of electromagnetic pure iron DT4 hot-rolled round steel produced by VD process, and its performance indicators meet the following requirements: tensile strength Rel≥265MPa, elongation A≥25%, Vickers hardness≤195HV.

[0007] The patent with application number 202310879894.5 discloses an extremely low sulfur industrial pure iron and its preparation method, which belongs to the field of metallurgical technology. The method comprises the following steps: converter steelmaking, primary slag removal, wire feeding treatment, LF furnace refining, secondary slag removal, RH refining, and continuous casting. The composition of molten steel after the converter is controlled as follows: C≤0.05%, Si≤0.02%, Mn≤0.03%, P≤0.008%, S≤0.005%, Al≥0.02%. The amount of residual slag in the ladle after primary and secondary slag removal is controlled to be no more than 6kg / ton of steel. Pure calcium wire is fed after primary slag removal. During LF furnace refining, electricity is supplied for heating and slag desulfurization according to the temperature of the molten steel. When the sulfur content of the molten steel in the LF furnace is controlled to no more than 0.0006%, the LF furnace refining is terminated. Oxygen is blown into the molten steel 3 minutes after the start of RH refining, and finally the molten steel is continuously cast into continuous casting billets. The patented ultra-low sulfur industrial pure iron has high purity, and the sulfur content is stably controlled at an extremely low level of no more than 0.0006%, which fully meets the requirements of powder metallurgy, high-temperature alloys, amorphous, ultra-low sulfur stainless steel and other industries for sulfur content within 0.0008%. Summary of the invention

[0008] The purpose of the present invention is to provide a rolling method for electromagnetic pure iron wire rod, which can obtain ferrite without mixed crystals and abnormally coarse edges, improve electromagnetic properties, and solve the problems existing in the background technology.

[0009] The technical solution of the present invention is: The invention discloses a method for rolling an electromagnetic pure iron wire rod, wherein the billet heating temperature is 1050-1190°C, the soaking temperature is 1050-1190°C, the final rolling temperature is 830-900°C, and the wire laying temperature is 820-900°C.

[0010] The above electromagnetic pure iron wire rod rolling method has a wire drawing temperature from 820-900°C to 750°C, and a cooling rate of 2-3°C / S; from 750°C to 500°C, the cooling rate is <2°C / s; and the cooling rate below 500°C is >3°C / s.

[0011] The above-mentioned electromagnetic pure iron wire rod rolling method, the mass percentage of chemical elements of the electromagnetic pure iron wire rod is: C≤0.01%, Si≤0.10%, Mn: ≤0.25%, P≤0.015%, S≤0.010%, Al: 0.2~0.6%, N≤0.005%, O≤0.005%, and the remainder is Fe and other inevitable impurities.

[0012] In the above-mentioned rolling method of electromagnetic pure iron wire rod, the specification of electromagnetic pure iron wire rod is Ф5.5-40mm.

[0013] The present invention controls the final rolling temperature to 830-900℃, realizes rolling in the pure ferrite region without phase change, avoids the two-phase region rolling which can induce ferrite precipitation and lead to uneven grains and complete recrystallization leading to grain refinement, or the pure austenite phase region rolling which leads to complete recrystallization leading to grain refinement; the wire laying temperature is 820-900℃, and the wire laying and final rolling temperatures are controlled similarly, which can avoid the uneven structure of the core and surface of the wire rod caused by excessive water cooling intensity before wire laying, and can avoid the generation of abnormally coarse ferrite at the edge. The heating process controls the heating temperature of the steel billet in the heating furnace to 1050-1190℃, and the soaking temperature to 1050-1190℃. When the heating temperature exceeds 1190℃, the steel grade MnS, AlN and other inclusions will be dissolved in the austenite, and fine inclusions will be precipitated during rolling, hindering recrystallization and grain growth. From spinning to 750℃, the cooling rate is 2-3℃ / s to avoid the formation of thick FeO scale structure that is not conducive to removal. From 750℃ to 500℃, the cooling rate is controlled to be less than 2℃ / s, and cooling is carried out at a slower cooling rate to obtain a uniformly grown equiaxed ferrite structure, avoid the formation of abnormally grown mixed crystals at the edge, and generate a scale structure that is easy to remove. From the cooling process below 500℃, the cooling rate is controlled to be greater than 3℃ / s to avoid scratches on the surface of the wire rod due to high temperature.

[0014] The beneficial effects of the present invention are: being able to obtain electromagnetic pure iron wire rods which have no mixed crystals at the edges, no abnormally coarse ferrite and good electromagnetic properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The metallographic structure of the core cross section of the electromagnetic pure iron wire rod of Example 1; Figure 2 The metallographic structure of the cross section at 1 / 2 radius of the electromagnetic pure iron wire rod of Example 1; Figure 3 The metallographic structure of the surface cross section of the electromagnetic pure iron wire rod in Example 1; Figure 4 This is the metallographic structure of the core cross section of the electromagnetic pure iron wire rod of comparative example 1; Figure 5 This is the metallographic structure of the cross section at 1 / 2 radius of the electromagnetic pure iron wire rod of comparative example 2; Figure 6 The metallographic structure of the surface cross section of the electromagnetic pure iron wire rod of comparative example 2; DETAILED DESCRIPTION

[0016] The present invention will be further described below by way of examples with reference to the accompanying drawings.

[0017] See attached Figure 1-6 , a rolling method for electromagnetic pure iron wire rod, the billet heating temperature is 1050-1190℃, the soaking temperature is 1050-1190℃, the final rolling temperature is 830-900℃, and the spinning temperature is 820-900℃.

[0018] The spinning temperature ranges from 820-900℃ to 750℃, and the cooling rate is 2-3℃ / S; from 750℃ to 500℃, the cooling rate is <2℃ / s; and the cooling rate below 500℃ is >3℃ / s.

[0019] The mass percentage of chemical elements of electromagnetic pure iron wire rod is: C≤0.01%, Si≤0.10%, Mn: ≤0.25%, P≤0.015%, S≤0.010%, Al: 0.2~0.6%, N≤0.005%, O≤0.005%, and the balance is Fe and other inevitable impurities.

[0020] The specification of electromagnetic pure iron wire rod is Ф5.5-40mm. Example 1

[0021] The steel grade is DT4C, the chemical composition is shown in Table 1, the rolling specification is Ф5.5mm, and the hot rolled wire rod rolling process is: billet heating → controlled rolling → controlled cooling. Billet controlled rolling process, final rolling temperature 900℃, wire laying temperature 890℃. Heating process, heating temperature 1180, soaking temperature 1190℃. Controlled cooling process, after wire laying, segmented cooling: 1) From spinning to 750℃, cooling rate 3℃ / S; 2) From 750℃ to 500℃, control the cooling rate to 0.5℃ / s; 3) During the cooling process below 500°C, the cooling rate is controlled at 4°C / s.

[0022] The finished wire rod has uniform and large equiaxed ferrite structure from the core to the edge, and no mixed crystals or abnormally coarse ferrite at the edge. The grain size of the wire rod core, 1 / 2 radius and surface is shown in Table 2. The coercivity Hc is shown in Table 2, and the metallographic structure is shown in Table 2. Figure 1 , Figure 2 , Figure 3 . Example 2

[0023] The steel grade is DT4C, the chemical composition is shown in Table 1, the rolling specification is Ф8mm, and the hot-rolled wire rod rolling process is: billet heating → controlled rolling → controlled cooling. Billet controlled rolling process, final rolling temperature 830℃, wire laying temperature 820℃. Heating process, heating temperature 1050, soaking temperature 1080℃. Controlled cooling process, after wire laying, segmented cooling: 1) From spinning to 750℃, cooling rate 2℃ / S; 2) From 750℃ to 500℃, control the cooling rate to 1.5℃ / s; 3) During the cooling process below 500°C, the cooling rate is controlled at 5°C / s.

[0024] The finished wire rod has uniform and large equiaxed ferrite structure from the center to the edge, and no mixed crystals or abnormally coarse ferrite at the edge. The grain size of the wire rod center, 1 / 2 radius and surface is shown in Table 2. The coercive force Hc is shown in Table 2. Example 3

[0025] The steel grade is DT4C, the chemical composition is shown in Table 1, the rolling specification is Ф20mm, and the hot rolling process is as follows: billet heating → controlled rolling → controlled cooling. Billet controlled rolling process, final rolling temperature 860℃, wire laying temperature 870℃. Heating process, heating temperature 1090, soaking temperature 1090℃. Controlled cooling process, after wire laying, segmented cooling: 1) From spinning to 750℃, cooling rate 2.5℃ / S; 2) From 750℃ to 500℃, control the cooling rate to 1℃ / s; 3) During the cooling process below 500°C, the cooling rate is controlled at 8°C / s.

[0026] The finished wire rod has uniform and large equiaxed ferrite structure from the center to the edge, and no mixed crystals or abnormally coarse ferrite at the edge. The grain size of the wire rod center, 1 / 2 radius and surface is shown in Table 2. The coercive force Hc is shown in Table 2. Example 4

[0027] The steel grade is DT4C, the chemical composition is shown in Table 1, the rolling specification is Ф30mm, and the hot-rolled wire rod rolling process is: billet heating → controlled rolling → controlled cooling. Billet controlled rolling process, final rolling temperature 890℃, wire laying temperature 860℃. Heating process, heating temperature 1150, soaking temperature 1130℃. Controlled cooling process, after wire laying, segmented cooling: 1) From spinning to 750℃, cooling rate 3℃ / S; 2) From 750℃ to 500℃, control the cooling rate to 0.6℃ / s; 3) During the cooling process below 500°C, the cooling rate is controlled at 10°C / s.

[0028] The finished wire rod has uniform and large equiaxed ferrite structure from the center to the edge, and no mixed crystals or abnormally coarse ferrite at the edge. The grain size of the wire rod center, 1 / 2 radius and surface is shown in Table 2. The coercive force Hc is shown in Table 2. Example 5

[0029] The steel grade is DT4C, the chemical composition is shown in Table 1, the rolling specification is Ф40mm, and the hot-rolled wire rod rolling process is: billet heating → controlled rolling → controlled cooling. Billet controlled rolling process, final rolling temperature 880℃, wire laying temperature 900℃. Heating process, heating temperature 1120, soaking temperature 1110℃. Controlled cooling process, after wire laying, segmented cooling: 1) From spinning to 750℃, cooling rate is 2.8℃ / S; 2) From 750℃ to 500℃, control the cooling rate to 0.8℃ / s; 3) During the cooling process below 500°C, the cooling rate is controlled at 3°C / s.

[0030] The finished wire rod has uniform and large equiaxed ferrite structure from the center to the edge, and no mixed crystals or abnormally coarse ferrite at the edge. The grain size of the wire rod center, 1 / 2 radius and surface is shown in Table 2. The coercive force Hc is shown in Table 2. Example 6

[0031] The steel grade is DT4C, the chemical composition is shown in Table 1, the rolling specification is Ф16mm, and the hot-rolled wire rod rolling process is: billet heating → controlled rolling → controlled cooling. Billet controlled rolling process, final rolling temperature 840℃, wire laying temperature 850℃. Heating process, heating temperature 1100℃, soaking temperature 1100℃. Controlled cooling process, after wire laying, segmented cooling: 1) From spinning to 750℃, cooling rate 2℃ / S; 2) From 750℃ to 500℃, control the cooling rate to 0.4℃ / s; 3) During the cooling process below 500°C, the cooling rate is controlled at 15°C / s.

[0032] The finished wire rod has uniform and large equiaxed ferrite structure from the center to the edge, and no mixed crystals or abnormally coarse ferrite at the edge. The grain size of the wire rod center, 1 / 2 radius and surface is shown in Table 2. The coercive force Hc is shown in Table 2. Comparative Example 1

[0033] The steel grade is DT4C, the chemical composition is shown in Table 1, the rolling specification is Ф6.5mm, and the hot rolled wire rod rolling process is: billet heating → controlled rolling → controlled cooling. Billet controlled rolling process, final rolling temperature 950℃, wire laying temperature 960℃. Heating process, heating temperature 1170, soaking temperature 1220℃. Controlled cooling process, after wire laying, segmented cooling: 1) From spinning to 750℃, cooling rate is 1.5℃ / S; 2) From 750℃ to 500℃, control the cooling rate to 0.3℃ / s; 3) During the cooling process below 500°C, the cooling rate is controlled at 5°C / s.

[0034] The grain size of the finished wire rod core, 1 / 2 radius and surface is shown in Table 2. The coercive force Hc is shown in Table 2. (See Figure 4 , 5 , 6). Comparative Example 2

[0035] The steel grade is DT4C, the chemical composition is shown in Table 1, the rolling specification is Ф20mm, and the hot-rolled wire rod rolling process is: billet heating → controlled rolling → controlled cooling. Billet controlled rolling process, final rolling temperature 940℃, wire laying temperature 930℃. Heating process, heating temperature 1220, soaking temperature 1220℃. Controlled cooling process, after wire laying, segmented cooling: 1) From spinning to 750℃, cooling rate 2℃ / S; 2) From 750℃ to 500℃, control the cooling rate to 0.8℃ / s; 3) During the cooling process below 500°C, the cooling rate is controlled at 3°C / s.

[0036] The grain sizes of the core, 1 / 2 radius and surface of the finished wire rod are shown in Table 2. The coercive force Hc is shown in Table 2.

[0037] Table 1 Chemical composition and mass percentage of electromagnetic pure iron wire rods of Examples 1-6 and Comparative Examples 1-2 (%)

[0038] Table 2 Grain size (grade) and coercive force Hc (A / m) of electromagnetic pure iron wire rods of Examples 1-6 and Comparative Examples 1-2 。

Claims

1. A method for rolling an electromagnetic pure iron wire rod, characterized in that: The billet heating temperature is 1050-1190℃, the soaking temperature is 1050-1190℃, the final rolling temperature is 830-900℃, and the spinning temperature is 820-900℃.

2. The method for rolling an electromagnetic pure iron wire rod according to claim 1, characterized in that: The spinning temperature ranges from 820-900℃ to 750℃, and the cooling rate is 2-3℃ / S; from 750℃ to 500℃, the cooling rate is <2℃ / s; and the cooling rate below 500℃ is >3℃ / s.

3. The method for rolling an electromagnetic pure iron wire rod according to claim 1, characterized in that: The mass percentage of chemical elements of electromagnetic pure iron wire rod is: C≤0.01%, Si≤0.10%, Mn: ≤0.25%, P≤0.015%, S≤0.010%, Al: 0.2~0.6%, N≤0.005%, O≤0.005%, and the balance is Fe and other inevitable impurities.

4. The method for rolling an electromagnetic pure iron wire rod according to claim 1, characterized in that: The specification of electromagnetic pure iron wire rod is Ф5.5-40mm.

Images