CN115652212A - Low-carbon copper-containing steel and production process for improving surface quality of low-carbon copper-containing steel - Google Patents
Low-carbon copper-containing steel and production process for improving surface quality of low-carbon copper-containing steel Download PDFInfo
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Abstract
The invention belongs to the technical field of steel manufacturing in metallurgical industry, and discloses low-carbon copper-containing steel and a production process for improving the surface quality of the low-carbon copper-containing steel. The invention controls the content of Si element in steel by steelmaking process to ensure that the steel is oxidized at high temperatureAfter the reaction, an internal oxidation product 2FeO & SiO is formed 2 And the oxidation resistance of the steel is improved. The micro-alloy elements such as Ti, al and the like are added to refine the crystal grains, and the problem of copper-caused cracks on the surface of the copper-containing steel is effectively solved by matching with a proper heating system of steel rolling, ni precious alloy is not required to be added or production equipment is not required to be modified, and the round steel can have good surface quality only by adding the micro-refined crystal grain elements and adjusting the production process.
Description
Technical Field
The invention belongs to the technical field of steel manufacturing in the metallurgical industry, and relates to low-carbon copper-containing steel and a production process for improving the surface quality of the low-carbon copper-containing steel.
Background
The alloy element copper is added into the steel, so that the corrosion resistance of the steel can be obviously improved, and the reliability and the durability of the steel structure are improved, therefore, the copper-containing steel is widely applied to the series of products with corrosive severe working conditions, such as acid corrosion resistant steel, ship steel, weather resistant steel and the like. However, because the melting point of Cu is low (only 1085 ℃), the heating temperature of the copper-containing steel is generally higher than the melting point of Cu in the production and processing engineering, so that Cu in the steel is in a molten state and is converted into liquid copper, the liquid copper can penetrate inwards along austenite grain boundaries, the inter-grain connection is weakened, and a large number of cracks, namely copper brittleness, appear during the rolling and processing deformation of the copper-containing steel. The problem of "copper embrittlement" is a common problem in the production of copper-containing steel, and the root cause is: copper element has a low melting point (1083 ℃) and a stronger oxidizing property than iron, and when rolling is performed under high temperature and oxidizing atmosphere conditions, copper is segregated to form a copper-rich liquid phase. In addition, since iron is more easily oxidized than copper, iron scale formed during high temperature rolling of steel extrudes the copper-rich phase, thereby further promoting segregation of copper.
In order to solve the surface quality problem of copper-containing steel, steel mills generally use means of adding noble alloy Ni, turning the surface of steel, peeling and the like. However, these methods will greatly increase the production cost or prolong the production period, so how to efficiently improve the surface of copper-containing steel while controlling the production cost is a big problem in the steel industry.
Disclosure of Invention
Aiming at the defects in the prior art, the technical idea of the invention is as follows: 1) Adding Si element 0.30-0.40% in steel making process to make steel form internal oxidation product 2FeO SiO after high temperature oxidation 2 The composition of an oxide layer of the steel is changed, the oxidation resistance of the steel is improved, and the copper is prevented from forming a liquid copper phase on an Fe-iron scale interface, so that the segregation of the copper is inhibited; 2) Adding trace Al (0.05-0.015%), ti (0.020-0.030%) and other elements to refine austenite grains and inhibit the liquid copper from permeating to austenite grain boundaries; 3) The rolling heating adopts a low-temperature heating process, the temperature is lower than the melting point of copper, namely the temperature of a soaking section is controlled to be 1050 +/-30 ℃, and the segregation of Cu is avoided.
The invention aims to provide a production process for improving the surface quality of low-carbon copper-containing steel, and the flux leakage flaw detection qualification rate of the surface of the copper-containing steel can reach more than 92% in an easy-to-operate and efficient mode through an innovative copper-containing steel hot-rolled round steel surface quality control method, and the surface crack defect depth is reduced from 0.5mm to 0.055mm, so that the round steel can be delivered in a black skin state. Meanwhile, when hot perforation is carried out, the surface of the steel pipe has no external folding defect.
The invention provides low-carbon copper-containing steel which comprises the following components in percentage by weight: c: less than or equal to 0.12 percent, mn:0.35 to 0.65%, si:0.20 to 0.40%, cr: 0.70-1.10%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, cu:0.25 to 0.45%, sb:0.04 to 0.10%, al: less than or equal to 0.050 percent and less than or equal to 0.030 percent of Ti; the balance being Fe and unavoidable impurities.
A production process for improving the surface quality of low-carbon copper-containing steel comprises the following steps:
1) The steel making process comprises the following steps:
according to the control requirements of each component, the 220 multiplied by 220mm continuous casting billet is obtained through converter smelting, LF refining, VD vacuum degassing and square billet continuous casting, then enters a slow cooling pit, slowly cools for 36-72 hours, and is transported to a steel rolling workshop billet storage yard by a heat preservation vehicle when the surface temperature of the continuous casting billet is less than or equal to 150 ℃, and is rolled in a furnace;
2) The heating and rolling process is as follows:
a walking beam type heating furnace is adopted to heat the continuous casting billet in a four-section way. Controlling the temperature of a preheating section of the heating furnace to be less than or equal to 650 ℃, the temperature of a first heating section to be 900-960 ℃, the temperature of a second heating section to be 1015-1075 ℃ and the temperature of a soaking section to be 1020-1080 ℃; after the continuous casting billet is taken out of the heating furnace, high-pressure water is started for descaling and removing the scale on the surface of the billet, and the starting rolling temperature is controlled to be 950-1000 ℃.
Wherein, the heating time of the second heating section and the soaking section is controlled to be 60-90 min; the total heating time of the preheating section, the first heating section, the second heating section and the soaking section is 180-240 min; the pressure of the descaling water is 23-27 Mpa;
3) The round steel is collected and packed after being put into a cooling bed, and is cooled by wind shielding and piling for more than 24 hours;
4) The magnetic leakage process is as follows:
after the round steel is cooled, carrying out magnetic flux leakage flaw detection on the surface, and executing depth multiplied by width multiplied by length according to flaw detection standards: 0.3mm × 0.2mm × 25mm;
5) The round steel hot punching process comprises the following steps:
and (3) heating the round steel in an inclined bottom furnace at 1200-1260 ℃, preserving heat for 1h, then discharging from the furnace, and performing hot perforation and cold drawing machining to obtain the required steel pipe product.
Compared with the prior art, the invention has the advantages that:
(1) After the production process disclosed by the invention is adopted for the copper-containing steel, the surface quality is good, the pass percent of black skin state magnetic flux leakage flaw detection on the surface of the round steel is improved to 92% from 13.8%, and the crack depth is reduced to 0.055mm from 0.7 mm. Meanwhile, when the round steel is subjected to hot perforation and cold drawing, the surface of the steel pipe has no external folding defect.
(2) Compared with the conventional process, the invention does not need to add noble alloy Ni into the steel, omits the peeling/turning process of the surface of the round steel, reduces the alloy and process cost, shortens the production period, and simultaneously has no surface defect in the pipe penetrating processing process.
Drawings
FIG. 1 shows the magnetic flux leakage flaw detection patterns of comparative example and example 1, a-comparative example, b-example 1.
Fig. 2 is a surface crack morphology diagram of the round steel of the comparative example and the round steel of the example 1, a represents the defect morphology of the comparative example, b represents the metallographic phase after corrosion of the comparative example, c represents the defect morphology of the example 1, and d represents the metallographic phase after corrosion of the example 1.
Fig. 3 is a photograph showing the surface quality of steel pipes after hot piercing of round steels according to comparative examples and example 1.
Detailed Description
The invention will be further described with reference to the following figures and specific examples, without limiting the scope of the invention thereto.
Comparative example
The components are shown in Table 1
| C | Mn | Si | Cr | P | S | Cu | Sb | Al | Ti | Others |
| 0.09 | 0.42 | 0.15 | 0.98 | 0.009 | 0.002 | 0.27 | 0.05 | - | - | Fe |
The method comprises the following steps: converter steelmaking, LF refining, VD vacuum treatment and square billet continuous casting to obtain a 220 x 220mm casting blank; then the continuous casting billet enters a slow cooling pit to be slowly cooled, enters a heating furnace to be heated, is descaled by high-pressure water, is rolled to a phi 80mm specification, is collected and packed, is manually finished, is subjected to magnetic flux leakage flaw detection, is heated by natural gas, is perforated and is cold drawn.
1) Steel making: according to the control requirements of each component, the 220 multiplied by 220mm continuous casting billet is obtained through converter smelting, LF refining, VD vacuum degassing and square billet continuous casting.
2) The slab then entered a buffer cooling pit for a period of 42 hours. The surface temperature of the continuous casting billet is 121 ℃, and the continuous casting billet is conveyed to a steel rolling workshop billet storage yard by a heat preservation vehicle to be rolled in a furnace.
3) Charging a continuous casting billet into a furnace, heating and rolling: a walking beam type heating furnace is adopted for four-stage heating. The temperature of the preheating section is 625 ℃, and the retention time is 42min; the temperature of a heating section is 930 ℃, and the retention time is 63min; the temperature of the second heating section is 1045 ℃ and 36mim; the temperature of the soaking section is 1050 ℃, and the retention time is 43min; total heating time 184min.
4) After the continuous casting slab exits from the heating furnace, high-pressure water descaling is carried out to remove surface iron scales, the descaling water pressure is 24.5MPa, and the rolling temperature is 978 ℃.
5) The round steel is collected after being put into a cooling bed and cooled by adopting a wind-shielding pile for 32 hours.
6) The round steel is subjected to surface magnetic flux leakage flaw detection (flaw detection standard 0.3 × 0.2 × 25mm), and the yield is 13.8%.
7) And (3) heating the round steel in an inclined bottom furnace at 1230 ℃, preserving heat for 1h, taking the round steel out of the furnace, and performing hot perforation and cold drawing machining to obtain the required steel pipe product.
Example 1
The components are shown in Table 2
| C | Mn | Si | Cr | P | S | Cu | Sb | Al | Ti | Others |
| 0.08 | 0.40 | 0.38 | 0.95 | 0.008 | 0.003 | 0.28 | 0.06 | 0.033 | 0.027 | Fe |
The method comprises the following steps: converter steelmaking, LF refining, VD vacuum treatment and square billet continuous casting to obtain a 220 x 220mm casting blank; then the continuous casting billet enters a slow cooling pit to be slowly cooled, enters a heating furnace to be heated, is descaled by high-pressure water, is rolled to a phi 80mm specification, is collected and packed, is manually finished, is subjected to magnetic flux leakage flaw detection, is heated by natural gas, is perforated and is cold drawn.
1) Steel making: according to the control requirements of each component, the 220 multiplied by 220mm continuous casting billet is obtained through converter smelting, LF refining, VD vacuum degassing and square billet continuous casting.
2) The slab then entered a buffer cooling pit for a period of 42 hours. The surface temperature of the continuous casting billet is 118 ℃, and the continuous casting billet is transported to a steel rolling workshop billet storage yard by a heat preservation vehicle to be rolled in a furnace.
3) Charging a continuous casting billet into a furnace, heating and rolling: a walking beam type heating furnace is adopted for four-stage heating. The temperature of the preheating section is 625 ℃, and the retention time is 42min; the temperature of a heating section is 930 ℃, and the retention time is 63min; the temperature of the heating section is 1045 ℃,36mim; the temperature of the soaking section is 1050 ℃, and the retention time is 43min; total heating time 184min.
4) After the continuous casting slab exits from the heating furnace, high-pressure water descaling is carried out to remove surface iron scales, the descaling water pressure is 24.5MPa, and the rolling temperature is 978 ℃.
5) The round steel is collected after being put into a cooling bed and cooled by adopting a wind-shielding pile for 32 hours.
6) The round steel is subjected to surface magnetic flux leakage flaw detection (flaw detection standard 0.3 × 0.2 × 25mm), and the yield is 92.9%.
7) And (3) heating the round steel in an inclined bottom furnace at 1230 ℃, preserving heat for 1h, taking the round steel out of the furnace, and performing hot perforation and cold drawing machining to obtain the required steel pipe product.
The results were compared with the round steel leakage flux tests of example 1 and comparative example:
TABLE 3 comparison of results of magnetic flux leakage inspection of round steel (Standard 0.3X 0.2X 25mm)
| Examples of the invention | Round steel detection count | Number of qualified counts | Small defect count | Large defect count | Magnetic leakage qualification rate |
| Comparative example | 152 | 21 | 100 | 31 | 13.8％ |
| Example 1 | 154 | 143 | 11 | 0 | 92.9％ |
As shown in FIG. 1, the flaw detection pattern of the comparative example in the step a is very noisy, which indicates that the round steel has a large number of cracks and has a large depth; in the embodiment 1, the curve of the flaw detection map is smooth, and the surface defects and the depth of the round steel are less.
FIG. 2 is a surface crack morphology diagram of round steel of comparative example and example 1, a-defect morphology of comparative example, b-metallographic phase after corrosion of comparative example, c-defect morphology of example 1, d-metallographic phase after corrosion of example 1. As shown in FIG. 2, the surface crack depth of the comparative example round steel reached 0.52mm, and the crystal grains were coarse. In the embodiment 1, the crack depth on the surface of the round steel is only 0.055mm, and the crystal grains are fine.
FIG. 3 is a photograph showing the surface quality of steel pipes after hot piercing of round steels of comparative example and example 1. The surface of the steel pipe of the comparative example has an outer folding defect, and the surface of the steel pipe of the example 1 has no defect.
The present invention is not limited to the above-described embodiments, and any obvious improvements, substitutions or modifications can be made by those skilled in the art without departing from the spirit of the present invention.
Claims (8)
1. The low-carbon copper-containing steel is characterized by comprising the following components in percentage by weight: c: less than or equal to 0.12 percent, mn:0.35 to 0.65%, si:0.20 to 0.40%, cr: 0.70-1.10%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, cu:0.25 to 0.45%, sb:0.04 to 0.10%, al: less than or equal to 0.050 percent and less than or equal to 0.030 percent of Ti; the balance being Fe and unavoidable impurities.
2. A production process for improving the surface quality of low-carbon copper-containing steel is characterized by comprising the following steps:
1) Steel making:
according to the control requirements of each component, carrying out converter smelting, LF refining, VD vacuum degassing and square billet continuous casting to obtain a continuous casting billet, then slowly cooling the continuous casting billet in a slow cooling pit, conveying the continuous casting billet to a steel rolling workshop billet storage yard by a heat preservation vehicle when the surface temperature of the continuous casting billet is less than or equal to 150 ℃, and carrying out furnace rolling;
2) Heating and rolling:
a walking beam type heating furnace is adopted to heat the continuous casting billet in a four-section mode: controlling the temperature of a preheating section of the heating furnace to be less than or equal to 650 ℃, the temperature of a first heating section to be 900-960 ℃, the temperature of a second heating section to be 1015-1075 ℃ and the temperature of a soaking section to be 1020-1080 ℃; after the continuous casting billet is discharged from a heating furnace, high-pressure water is started to remove scales and remove oxide scales on the surface of the billet, and the starting rolling temperature is controlled to be 950-1000 ℃;
3) The round steel is collected and packed after being put into a cooling bed, and is cooled by wind;
4) The magnetic leakage process is as follows:
after the round steel is cooled, magnetic flux leakage flaw detection is carried out on the surface,
5) The round steel hot punching process comprises the following steps:
and (3) heating the round steel in an inclined bottom furnace for a period of time, and then discharging the round steel out of the furnace for hot perforation and cold drawing machining to obtain the required steel pipe product.
3. The production process according to claim 2, wherein in step 1), the size of the slab is 220 x 220mm; the slow cooling time is 36 to 72 hours.
4. The production process according to claim 2, wherein in the step 2), the sum of the heating time of the second heating section and the soaking section is controlled to be 60-90 min; the total heating time of the preheating section, the first heating section, the second heating section and the soaking section is 180-240 min.
5. The production process according to claim 2, wherein in the step 2), the descaling water pressure is 23 to 27MPa.
6. The production process according to claim 2, wherein in the step 3), the cooling time of the wind shielding pile is more than 24 h.
7. The production process according to claim 2, wherein in step 4), the magnetic flux leakage inspection standard is performed by a depth x width x length: 0.3 mm. Times.0.2 mm. Times.25 mm.
8. The production process according to claim 2, wherein in the step 5), the mixture is heated in a slant-hearth furnace at 1200-1260 ℃ and kept for 1h.
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| CN103589972A (en) * | 2013-10-10 | 2014-02-19 | 中天钢铁集团有限公司 | Low-cost low alloy steel for resistance to dew point corrosion of sulfuric acid as well as production process and application of low alloy steel |
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