Surface treatment process for ultra-pure iron
Through the surface pretreatment, heating, rolling and cooling processes of ultra-pure iron ingots, the problems of impurity introduction and parameter control during the ultra-pure iron rolling process are solved, and the production of high-quality ultra-pure iron products is achieved to meet the requirements of high-end applications.
Patent Information
- Application Number
- CN202510833025.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-20
- Publication Date
- 2025-09-23
AI Technical Summary
The existing ultrapure iron rolling process is prone to introducing impurities and is difficult to accurately control rolling parameters, resulting in defects in the thickness uniformity, surface quality and internal structure of ultrapure iron products, affecting their physical properties and performance.
It adopts ultra-pure iron ingot surface pretreatment, three-stage heating-up and insulation heating, rough rolling and finishing rolling combined with progressive cooling process, including hydrochloric acid pickling, grinding wheel grinding, ultrasonic cleaning, vacuum drying, special material rollers, precise control of rolling parameters and real-time temperature monitoring.
Effectively avoid the introduction of impurities, ensure the stability of the rolling process, and obtain high-quality ultra-pure iron products with a smooth and defect-free surface and uniform internal structure to meet the needs of high-end applications.
Smart Images
Figure CN120679850A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of metal surface treatment, and in particular to a surface treatment process for ultrapure iron. Background Art
[0002] Ultrapure iron refers to elemental iron materials with a purity of 99.99 wt.% or greater. Due to its extremely low impurity content, ultrapure iron possesses excellent physical properties, particularly magnetic conductivity. This makes it widely used in numerous fields, including electronic circuits, aerospace, and high-end equipment manufacturing. However, existing ultrapure iron rolling processes present numerous challenges. Firstly, the rolling process can easily introduce a large amount of impurities onto the surface of the ultrapure iron, severely impacting its purity and limiting its application in high-end applications. Secondly, existing processes struggle to precisely control various rolling parameters, leading to defects in thickness uniformity, surface quality, and internal structure of the rolled ultrapure iron sheets or coils. These defects, such as large thickness deviations, surface scratches or pitting, and uneven grain size, further impact their physical properties and performance. Therefore, developing a rolling process that can effectively prevent the introduction of impurities and precisely control rolling parameters to produce high-quality ultrapure iron products is of great practical significance and application demand. Summary of the Invention
[0003] In view of this, the present application provides a surface treatment process for ultrapure iron, which can effectively overcome the defects of the above-mentioned prior art.
[0004] The present application provides a surface treatment process for ultrapure iron, comprising the following steps:
[0005] (1) Ultrapure iron ingots are selected as rolling materials and their surfaces are pretreated;
[0006] (2) using a three-stage heating-maintaining method to heat the ultrapure iron ingot;
[0007] (3) rolling the ultrapure iron ingot by combining rough rolling and finish rolling;
[0008] (4) Cooling process: The ultrapure iron rolled plate product is cooled by a progressive cooling method.
[0009] Preferably, the purity of the ultrapure iron ingot is not less than 99.99%.
[0010] Preferably, the pretreatment specifically includes the following steps:
[0011] S1. Pickling: Soak the ultrapure iron ingot in hydrochloric acid solution for 15-60 minutes;
[0012] Specifically, during soaking, the loose oxide scale and dirt attached to the surface of the iron ingot will quickly fall off and dissolve in the hydrochloric acid solution. However, the deeper oxidized structure and dirt embedded in the pure iron grain boundaries are difficult to soak out and require long soaking in acid.
[0013] S2. Cleaning: After the hydrochloric acid soaking is completed, the ultrapure iron ingot is transferred to a distilled water pool and the surface of the ultrapure iron ingot is repeatedly washed with a rotating water flow for more than 15-30 minutes;
[0014] S3. Grinding: Use a grinding wheel grinder to carefully grind the surface of the ultrapure iron ingot, especially to remove the difficult-to-dissolve oxide layer, dirt and impurities on the surface of the ultrapure iron ingot. After grinding and removing, use #800, #1000, #1500, and #2000 sandpaper to finely grind the surface of the ultrapure iron ingot one by one;
[0015] Specifically, after grinding is completed, the surface of the iron ingot is repeatedly polished with a polishing cloth. When the surface of the iron ingot presents a crystal reflective state, it can be ensured that the surface of the iron ingot is clean.
[0016] S4. Secondary cleaning: Place the polished ultrapure iron ingot in an ultrasonic cleaning device for 30 minutes. After cleaning, rinse with deionized water.
[0017] S5. Drying: Place the cleaned ultrapure iron ingot in a vacuum drying oven at a temperature of 60-90° C. and dry for 1-2 hours.
[0018] Preferably, the specific process of the three-stage heating-keeping method is as follows:
[0019] The first stage of heating-holding process: the ultrapure iron ingot is heated from room temperature to 600℃ at a heating rate of 10-15℃ / min and held at this temperature for 30-60 minutes to make the temperature inside the iron ingot uniform;
[0020] The second stage of heating-holding process: the ultrapure iron ingot is heated from 600°C to 900-910°C (below the austenite temperature of pure iron, i.e. below 912°C) at a heating rate of 6-10°C / min, and held at this temperature for 60-90 minutes;
[0021] The third heating-holding process: the ultrapure iron ingot is heated to 1050-1150°C at a heating rate of 2-6°C / min, and then held at this temperature for 90-120 minutes.
[0022] Preferably, the heating treatment is performed in a vacuum heating furnace.
[0023] Specifically, after the above-mentioned heating treatment, the pure iron structure is completely transformed into a face-centered cubic austenite structure, and the grain size of the austenite structure has been stabilized through long-term heat preservation.
[0024] Preferably, the specific process of combining rough rolling and finish rolling is as follows:
[0025] Rough rolling process: Rough rolling uses a large hot rolling mill, the total reduction rate of rough rolling is controlled at 40-50%, the first pass reduction rate is controlled at 20-25%, and the subsequent passes gradually reduce the reduction rate to 10-15%. The rolling speed of rough rolling is controlled at 1-2 m / s. The rollers are continuously cooled and lubricated during the rolling process. The cooling medium is water-based coolant, and the lubrication is pure vegetable oil-based lubricant.
[0026] Specifically, a large hot rolling mill is used, and the rollers are made of special materials and undergo high-precision grinding to reduce damage to the ultrapure iron surface and impurity contamination during the rolling process. The total reduction rate for rough rolling is controlled at 40-50%, and the reduction rate for each pass is reasonably allocated according to actual conditions. The reduction rate for the first pass is controlled at 20-25%, and the reduction rate for subsequent passes gradually decreases to ensure the stability of the rolling process and the uniformity of material deformation. The rolling speed for rough rolling is controlled at 1-2 meters per second. The rollers are continuously cooled and lubricated during the rolling process. The cooling medium is a special coolant, and the lubrication is a pure vegetable oil-based lubricant. This ensures that the rollers operate in good working condition, while preventing impurities in the coolant and lubricant from contaminating the ultrapure iron.
[0027] Finishing rolling process: High-precision rolling mill is used for finishing rolling. The total reduction rate of finishing rolling is controlled at 20-30%, the reduction rate of each pass is controlled at 4-10%, and the rolling speed of finishing rolling is controlled at 0.5-1 m / s.
[0028] Specifically, finishing rolling utilizes a high-precision rolling mill, with a total reduction rate controlled at 20-30%. Multiple rolling passes are also employed, with each pass reducing the reduction rate at 5-10%. During finishing rolling, the rolling environment undergoes rigorous purification to maintain the air cleanliness level in the rolling mill at Class 10,000, preventing impurities such as dust from settling on the surface of the ultrapure iron. The finishing speed is controlled at 0.5-1 m / s, and the thickness accuracy and flatness of the ultrapure iron sheet or coil are guaranteed by precisely controlling the gap and pressure between the rollers. During finishing rolling, parameters such as rolling force, rolling speed, and sheet thickness are monitored in real time. These parameters are adjusted and optimized via an automated control system to ensure the stability of the rolling process and consistent product quality.
[0029] Preferably, the specific process of the progressive cooling method is:
[0030] First, the finished ultrapure iron rolled plate is initially cooled by an air cooling device. The wind speed of the air cooling is controlled at 5-8 m / s and the cooling time is 10-15 minutes, so that the temperature of the finished ultrapure iron rolled plate is quickly reduced to 500-600°C; then, the finished ultrapure iron rolled plate is placed in a water cooling tank for secondary cooling. The water temperature in the water cooling tank is controlled at 20-30°C and the cooling time is 5-10 minutes, so that the temperature of the finished ultrapure iron rolled plate is further reduced to 100-150°C; finally, the finished ultrapure iron rolled plate is placed in the air to cool naturally to room temperature.
[0031] Specifically, during the cooling process, the temperature of the ultrapure iron product is monitored in real time to ensure that the cooling process is uniform and stable, and to avoid defects such as internal stress concentration, deformation or cracks in the product caused by excessively fast or uneven cooling speed.
[0032] Preferably, the method further comprises the following steps:
[0033] (5) The surface quality of the ultrapure iron rolled plate finished product after cooling is inspected. A high-precision optical detector is used to comprehensively scan the surface of the ultrapure iron rolled plate finished product to detect whether there are scratches, pits, and oxidation defects on the surface. For ultrapure iron rolled plate finished products with slight surface defects, they are repaired by polishing and grinding; for ultrapure iron rolled plate finished products with serious surface defects, they are scrapped; for defects below the surface of the ultrapure iron rolled plate finished product, ultrasonic CT is used to explore and detect whether there are holes and cracks.
[0034] In a second aspect, the present application also provides the application of the above-mentioned surface treatment process of ultrapure iron in the field of metal surface treatment.
[0035] Compared with the prior art, this application has the following beneficial effects:
[0036] The surface pretreatment-heating-rolling-cooling process of ultrapure iron in this application. The hydrochloric acid pickling and soaking method is used to remove the loose oxide scale and dirt attached to the surface of the ultrapure iron ingot; the insoluble substances on the surface of the iron ingot are cleaned by a grinding wheel grinder; the iron ingot is then ultrasonically cleaned and placed in a vacuum drying oven to dry at a temperature of 60-90°C for 1-2 hours. A three-stage heating method is selected to gradually heat the ultrapure iron ingot to 1050-1150°C, and then the heat is evenly maintained for 90-120 minutes. The rolling process adopts a combination of rough rolling and finishing rolling; a large hot rolling mill is used, and the rollers are made of special materials, and the surface is high-precision ground to reduce damage to the ultrapure iron surface and impurity contamination during the rolling process; the total reduction rate of rough rolling is controlled at 40-50%, and the rolling speed of rough rolling is controlled at 1-2 meters per second; a high-precision cold rolling mill is used for finishing rolling, and the total reduction rate of finishing rolling is controlled at 20-30%, and the rolling speed is controlled at 0.5-1 meters per second. After finishing, ultrapure iron products are primarily cooled by air. During the cooling process, real-time temperature monitoring is performed to ensure uniform and stable cooling, avoiding defects such as internal stress concentration, deformation, or cracks in the product caused by excessively fast or uneven cooling. The surface treatment process for ultrapure iron in this application effectively prevents the introduction of impurities and precisely controls rolling parameters to produce high-quality ultrapure iron products. BRIEF DESCRIPTION OF THE DRAWINGS
[0037] In order to more clearly illustrate the technical solutions in the present application or the prior art, the following briefly introduces the drawings required for use in the description of the present application or the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.
[0038] Figure 1 This is a sample and scanning diagram of Example 1 of this application;
[0039] Figure 2 This is a C-scan image of the front of the sample in Example 1 of the present application;
[0040] Figure 3 This is a C-scan image of the reverse side of the sample in Example 1 of the present application;
[0041] Figure 4 This is the waveform of the front and back a scan of the sample in Example 1 of the present application, wherein Figure 4 (a) is the front a-scan waveform, Figure 4 (b) is the reverse side a-scan waveform. DETAILED DESCRIPTION
[0042] To make the objectives, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.
[0043] Unless otherwise specified, the experimental methods used in the examples of this application are all conventional methods.
[0044] In the following examples, unless otherwise specified, all raw materials can be purchased commercially or prepared by conventional methods.
[0045] Example 1
[0046] 1. Raw material preparation: Select an ultrapure iron ingot with a mass of 500 kg and a purity of 99.995% as the rolling material.
[0047] 2. Surface pretreatment: First, place the ultrapure iron ingot in a hydrochloric acid solution and soak it for 30 minutes to remove surface contaminants and oxide layers. After soaking, remove the iron ingot and rinse it repeatedly with deionized water for 15 minutes. Use sandpaper and / or a grinding wheel to remove the black oxide on the surface of the iron ingot that is difficult to remove. After grinding it away, use #800, #1000, #1500, and #2000 sandpaper to finely polish the surface of the ultrapure iron ingot one by one. Then, use an ultrasonic container to ultrasonicate the ultrapure iron ingot for 30 minutes, then rinse it with deionized water, and finally dry it in a vacuum drying oven at 70°C for 1.5 hours.
[0048] 3. Heating process: Place the pretreated iron ingot into the heating furnace. In the first stage, the temperature is raised from room temperature to 600°C at a heating rate of 12°C / min and kept at this temperature for 45 minutes. In the second stage, the temperature is raised to 900°C at a heating rate of 8°C / min and kept at this temperature for 80 minutes. In the third stage, the temperature is raised to 1150°C at a heating rate of 3°C / min and kept at this temperature for 120 minutes.
[0049] 4. Rolling Process: Rough rolling is performed on a large four-roll hot rolling mill, with rolls made of special alloy steel and a surface roughness of Ra ≤ 0.05 μm. The total reduction is controlled at 45%, with an 18% reduction for the first pass and decreasing for subsequent passes. The rolling speed is 1.5 m / s. The coolant is a water-based coolant (Baoma water-based), and the lubricant is a purified vegetable oil-based lubricant (Total ENERGY lubricant). Finishing rolling is performed on a high-precision cold rolling mill, with a total reduction of 25% and a 4% reduction per pass. The rolling speed is 0.8 m / s.
[0050] 5. Cooling process: The ultrapure iron after fine rolling first passes through an air cooling device with a wind speed of 6 m / s for 12 minutes to reduce the temperature to 550°C; then it is placed in a water cooling tank with a water temperature of 25°C and cooled for 7 minutes to reduce the temperature to 120°C; finally, it is naturally cooled to room temperature in the air.
[0051] 6. Quality inspection: Use optical detector to inspect the surface quality of the cooled ultrapure iron product and no cracks are found. Use ultrasonic exploration equipment to inspect the ultrapure iron ingots, such as Figure 1 shown. Figure 2 and Figure 3 This is an ultrasonic C-scan image of the sample with a thickness of 0mm to 25mm. There is no obvious white defect area, and the test results show that there are no obvious defects. Figure 4 The A-scan waveforms of the front and back sides of the sample show no obvious defect waves. Therefore, the surface of the ultrapure iron rolled using the method of the present application is smooth, with no defects or cracks on the surface or inside.
[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.
Claims
1. A surface treatment process for ultrapure iron, characterized in that: The following steps are involved: (1) Ultrapure iron ingots are selected as rolling materials and their surfaces are pretreated; (2) using a three-stage heating-maintaining method to heat the ultrapure iron ingot; (3) rolling the ultrapure iron ingot by combining rough rolling and finish rolling; (4) The ultrapure iron rolled plate product is cooled by a progressive cooling method.
2. The surface treatment process of ultrapure iron according to claim 1, characterized in that: The purity of the ultrapure iron ingot is not less than 99.99%.
3. The surface treatment process of ultrapure iron according to claim 1, characterized in that: The pretreatment specifically comprises the following steps: S1. Pickling: Soak the ultrapure iron ingot in hydrochloric acid solution for 15-60 minutes; S2. Cleaning: After the hydrochloric acid soaking is completed, the ultrapure iron ingot is transferred to a distilled water pool and the surface of the ultrapure iron ingot is repeatedly washed with a rotating water flow for more than 15-30 minutes; S3. Grinding: Use a grinding wheel grinder to carefully grind the surface of the ultrapure iron ingot, especially to remove the difficult-to-dissolve oxide layer, dirt and impurities on the surface of the ultrapure iron ingot. After grinding and removing, use #800, #1000, #1500, and #2000 sandpaper to finely grind the surface of the ultrapure iron ingot one by one; S4. Secondary cleaning: Place the polished ultrapure iron ingot in an ultrasonic cleaning device for 30 minutes. After cleaning, rinse with deionized water. S5. Drying: Place the cleaned ultrapure iron ingot in a vacuum drying oven at a temperature of 60-90° C. and dry for 1-2 hours.
4. The surface treatment process of ultrapure iron according to claim 1, characterized in that: The specific process of the three-stage heating-insulation method is as follows: The first stage of heating-holding process: the ultrapure iron ingot is heated from room temperature to 600℃ at a heating rate of 10-15℃ / min and kept at this temperature for 30-60 minutes; The second stage of heating-holding process: the ultrapure iron ingot is heated from 600°C to 900-910°C at a heating rate of 6-10°C / min, and held at this temperature for 60-90 minutes; The third heating-holding process: the ultrapure iron ingot is heated to 1050-1150°C at a heating rate of 2-6°C / min, and then held at this temperature for 90-120 minutes.
5. The surface treatment process of ultrapure iron according to claim 1, characterized in that: The heating treatment is carried out in a vacuum heating furnace.
6. The surface treatment process of ultrapure iron according to claim 1, characterized in that: The specific process of combining rough rolling and finish rolling is as follows: Rough rolling process: Rough rolling uses a large hot rolling mill, the total reduction rate of rough rolling is controlled at 40-50%, the first pass reduction rate is controlled at 20-25%, and the subsequent passes gradually reduce the reduction rate to 10-15%. The rolling speed of rough rolling is controlled at 1-2 m / s. The rollers are continuously cooled and lubricated during the rolling process. The cooling medium is water-based coolant, and the lubrication is pure vegetable oil-based lubricant. Finishing rolling process: High-precision rolling mill is used for finishing rolling. The total reduction rate of finishing rolling is controlled at 20-30%, the reduction rate of each pass is controlled at 4-10%, and the rolling speed of finishing rolling is controlled at 0.5-1 m / s.
7. The surface treatment process of ultrapure iron according to claim 1, characterized in that: The specific process of the progressive cooling method is as follows: First, the finished ultrapure iron rolled plate is initially cooled by an air cooling device. The wind speed of the air cooling is controlled at 5-8 m / s and the cooling time is 10-15 minutes, so that the temperature of the finished ultrapure iron rolled plate is quickly reduced to 500-600°C; then, the finished ultrapure iron rolled plate is placed in a water cooling tank for secondary cooling. The water temperature in the water cooling tank is controlled at 20-30°C and the cooling time is 5-10 minutes, so that the temperature of the finished ultrapure iron rolled plate is further reduced to 100-150°C; finally, the finished ultrapure iron rolled plate is placed in the air to cool naturally to room temperature.
8. The surface treatment process of ultrapure iron according to claim 1, characterized in that: The following steps are also included: (5) The surface quality of the ultrapure iron rolled plate finished product after cooling is inspected. A high-precision optical detector is used to comprehensively scan the surface of the ultrapure iron rolled plate finished product to detect whether there are scratches, pits, and oxidation defects on the surface. For ultrapure iron rolled plate finished products with slight surface defects, they are repaired by polishing and grinding; for ultrapure iron rolled plate finished products with serious surface defects, they are scrapped; for defects below the surface of the ultrapure iron rolled plate finished product, ultrasonic CT is used to explore and detect whether there are holes and cracks.
9. Application of the surface treatment process of ultrapure iron according to any one of claims 1 to 8 in the field of metal surface treatment.