KR20210091181A - Low Steel Grade Pipeline Clean Steel and Smelting Method - Google Patents

Abstract

The present invention discloses low steel grade pipeline clean steel, and relates to the field of metallurgical technology, the chemical composition and mass percentage of which are C: 0.04% to 0.07%, Si: 0.10% to 0.35%, Mn: 1.00% to 1.50%, P≤0.015%, S:0.0020%~0.0050%, Nb:0.030%~0.070%, Ti:0.006%~0.020%, Ni≤0.30%, Cr≤0.30%, Cu≤0.30%, Al:0.015 %~0.050%, the remainder is Fe and impurities. The present invention systematically and accurately analyzes the formation control mechanism of inclusions, carries out the calcium treatment method after RH vacuum treatment through rational component design, and achieves the purpose of improving the purity of molten iron by rationally controlling the degree of superheat, thereby achieving the internal quality of steel and improve the economic effect.

Description

Low Steel Grade Pipeline Clean Steel and Smelting Method

The present invention relates to the field of metallurgical technology, and more particularly, to low-steel-grade pipeline clean steel and smelting methods.

As the energy demand of the global economy continues to increase, more and more reliance on pipeline transportation of oil and natural gas, the demands on the service provision environment of transportation pipelines are getting stricter, and the safety and reliability of transport pipelines ensure the quality of steel materials Since it cannot be separated from the steel, only steel with relatively high cleanliness and relatively good low-temperature toughness can occupy the market. Pipeline steel is mainly used for transportation pipelines such as oil and natural gas, and the product performance must satisfy extreme areas, high-pressure transportation, high-strength cryogenic impact toughness, and have good welding performance required for long-distance transportation. If there is only a large amount of big-size inclusions in the pipeline steel plate base material, welding cracks occur and ultrasonic bonding detection is rejected, thereby reducing the mechanical performance of the steel plate.

The present invention was created to solve the above problems, and the purpose is that the chemical composition and mass percentage are C: 0.04% to 0.07%, Si: 0.10% to 0.35%, Mn: 1.00% to 1.50%, P≤0.015% , S: 0.0020%~0.0050%, Nb: 0.030%~0.070%, Ti: 0.006%~0.020%, Ni≤0.30%, Cr≤0.30%, Cu≤0.30%, Al: 0.015%~0.050%, the rest To provide low-steel-grade pipeline clean steel with Fe and impurities.

Technical Effect: The present invention improves the cleanliness of molten metal and satisfies customers' demands by systematically analyzing the mechanism for generating inclusions and suggesting a pipeline clean steel and smelting method in combination with the actual production situation. Low steel grade pipeline steel requires low carbon, low phosphorus, low sulfur, and mainly uses aluminum and lime as main raw materials, so a large amount of CaO, Al ₂ O ₃ To create a series inclusion, the results of analysis through thermodynamics are as follows.

Calcium treatment is performed after the RH vacuum is completed. As can be seen from thermodynamic analysis, Ca in the steel liquid first _{reacts with Al 2} O _{3 in the} inclusion material and O and S in the steel to form CaO and CaS, and the rest of Al ₂ O ₃ to form CaO-Al ₂ O ₃ -CaS, then CaO in the inclusions reacts with S in the steel to lower the CaO content in the inclusions, and CaO in the low TO content forms S Since the degree of reaction with molten iron is high, by lowering the molten iron TO content so that CaO in the inclusion material reacts with S, the CaO content in the inclusion material is lowered and finally CaS-Al ₂ O ₃ is formed.

The technical solution to further limit the present invention is as follows.

The above-described low steel grade pipeline clean steel has a chemical composition and mass percentage of C: 0.060%, Si: 0.281%, Mn: 1.011%, P: 0.013%, S: 0.0041%, Nb: 0.038%, Ti: 0.013 %, Ni:0.019%, Cr:0.02%, Cu:0.019%, Alt:0.037%, Mo:0.007%, V:0.001%, Ca:0.0019%, Ceq:0.27%, Pcm:0.13%.

The above-described low steel grade pipeline clean steel has a chemical composition and mass percentage of C:0.041%, Si:0.121%, Mn:1.191%, P:0.012%, S:0.0030%, Nb:0.066%, Ti:0.012 %, Ni: 0.011%, Cr: 0.03%, Cu: 0.011%, Alt: 0.033%, Mo: 0.008%, V: 0.001%, Ca: 0.0016%, Ceq: 0.28%, Pcm: 0.13%.

The above-described low steel grade pipeline clean steel has a chemical composition and mass percentage of C:0.050%, Si:0.181%, Mn:1.311%, P:0.012%, S:0.0031%, Nb:0.066%, Ti:0.011 %, Ni:0.019%, Cr:0.02%, Cu:0.011%, Alt:0.036%, Mo:0.009%, V:0.001%, Ca:0.0018%, Ceq:0.27%, Pcm:0.13%.

The aforementioned low steel grade pipeline clean steel has a chemical composition and mass percentage of C:0.046%, Si:0.304%, Mn:1.236%, P:0.011%, S:0.0048%, Nb:0.053%, Ti:0.013 %, Ni:0.019%, Cr:0.03%, Cu:0.011%, Alt:0.039%, Mo:0.006%, V:0.001%, Ca:0.0019%, Ceq:0.28%, Pcm:0.13%.

The above-mentioned low steel grade pipeline clean steel has a chemical composition and mass percentage of C:0.054%, Si:0.228%, Mn:1.120%, P:0.009%, S:0.0021%, Nb:0.033%, Ti:0.011 %, Ni: 0.011%, Cr: 0.02%, Cu: 0.011%, Alt: 0.035%, Mo: 0.009%, V: 0.001%, Ca: 0.0016%, Ceq: 0.27%, Pcm: 0.13%.

Another object of the present invention is to provide a low steel grade pipeline clean steel smelting method, specifically,

The desulfurization station performs desulfurization by mixing liquid calcium oxide and magnesium powder and blowing it out, and after the desulfurization is finished, deep removal of scum is carried out. The desulfurization station desulfurization standard is lower than or equal to 0.005%, and the rotation The furnace ensures that the sulfur of the molten iron discharged by using the waste iron is less than or equal to 0.010%, and strong deoxidation is performed by adding an aluminum block to the molten iron discharged from the rotation, but the addition amount is 35kg/100ppm, prepared for LF desulfurization step S1;

LF is mainly responsible for desulfurization and alloying, and the finished product sulfur is set to 0.002% to 0.005%, step S2;

In the RH vacuum treatment, the vacuum degree is lower than 3 MPa, the pure vacuum time is 18 min or more, and after the RH vacuum is finished, a 150 m to 200 m seamless pure calcium core wire is fed to perform calcium treatment, and after calcium treatment, static for 12 minutes step S3 of performing mixing;

In the CCM injection process, controlling the superheating degree from 30℃ to 35℃ and using matching electromagnetic mixer technology to ensure that the low-power evaluation reaches within the YB/T 4003 standard C1.0 or B0.5; includes step S4; do.

The beneficial effects of the present invention are as follows.

(1) In the present invention, the low steel grade pipeline steel finished product has relatively few alloying elements, the alloying pressure is relatively small, and the finished product sulfur is set to 0.002% to 0.005%, the purpose of which is mainly to obtain high sulfur molten iron to provide prerequisites for the production of high melting point CaS-Al ₂ O _{3 type solid inclusions;}

(2) In the present invention, by extending the vacuum time of the low vacuum degree, the gas content in the molten iron is reduced as much as possible to improve the cleanliness of the molten iron;

(3) In the present invention, calcium treatment is carried out after the RH vacuum is completed. At this time, CaS-Al ₂ O ₃ type solid encapsulation so that the molten metal environment is placed in an environment of high sulfur and low oxygen It is beneficial to form water, and static mixing is performed after calcium treatment to ensure that the inclusions in the molten iron are sufficiently floated;

(4) In the present invention, the superheat degree of the CCM injection process is controlled to be 30° C. to 35° C., and the high-superheat degree control is beneficial for improving the dynamics and thermodynamic conditions during the static mixing, transportation, and pouring of molten metal. Rather, it ensures that the obtained solid inclusion is sufficiently floated and removed, and effectively improves the cleanliness of the molten metal;

(5) In the present invention, the electromagnetic mixer technology is matched and used in the CCM injection process to reduce central segregation and prevent the formation of MnS mixtures.

The low steel grade pipeline clean steel provided by the present invention has a chemical composition and mass percentage of C: 0.04% to 0.07%, Si: 0.10% to 0.35%, Mn: 1.00% to 1.50%, P≤0.015%, S: 0.0020%~0.0050%, Nb: 0.030%~0.070%, Ti: 0.006%~0.020%, Ni≤0.30%, Cr≤0.30%, Cu≤0.30%, Al: 0.015%~0.050%, remaining Fe and impurities .

The smelting method is

The desulfurization station performs desulfurization by mixing liquid calcium oxide and magnesium powder and blowing it out, and after the desulfurization is finished, deep-dash removal treatment is performed. The desulfurization station desulfurization standard is lower than or equal to 0.005%, and the rotary furnace guarantees that the sulfur of the molten iron discharged using waste iron is less than or equal to 0.010%, and strong deoxidation is performed by adding an aluminum block to the molten iron discharged from the rotation, but the addition amount is 35kg/100ppm, step S1;

LF is mainly responsible for desulfurization and alloying, and the finished product sulfur is set to 0.002% to 0.005%, step S2;

In the RH vacuum treatment, the vacuum degree is lower than 3 MPa, the pure vacuum time is 18 min or more, and after the RH vacuum is finished, a 150 m to 200 m seamless pure calcium core wire is fed to perform calcium treatment, and after calcium treatment, static for 12 minutes step S3 of performing mixing;

In the CCM injection process, controlling the superheating degree from 30℃ to 35℃ and using matching electromagnetic mixer technology to ensure that the low-power evaluation reaches within the YB/T 4003 standard C1.0 or B0.5; includes step S4; do.

The chemical composition and mass percentage of the low steel grade pipeline clean steel provided in Examples 1 to 5 are as shown in Table 1, and the detailed process parameters of the smelting process are as shown in Table 2.

Table 1: Example smelting chemical composition (%)

Table 2 Smelting and inclusion material detection status

The present invention closely analyzes the inclusion material creation mechanism and combines it with calcium treatment technology with a special component design to obtain a stable CaS-Al ₂ O ₃ type solid inclusion material, and to control a reasonable high-superheat degree of 30°C to 35°C ensures that the inclusions float and are removed, so that clean molten iron with higher molten iron purity can be obtained, and the quality of the molten iron is improved to satisfy customer demands. After the improvement of the method, the cleanliness of the molten metal is effectively improved, and the harmful effect of the big-size inclusions on the performance of the steel sheet is reduced, thereby improving the welding performance after the pipe is manufactured, and the economic effect is clear.

In addition to the above embodiment, the present invention may be implemented in other embodiments. All technical solutions formed using substitution of equivalents or equivalent transformations are included in the protection claims of the present invention.

Claims (7)

In the low steel grade pipeline clean steel,
The chemical composition and mass percentage are C: 0.04% to 0.07%, Si: 0.10% to 0.35%, Mn: 1.00% to 1.50%, P≤0.015%, S: 0.0020% to 0.0050%, Nb: 0.030% to 0.070 %, Ti: 0.006%~0.020%, Ni≤0.30%, Cr≤0.30%, Cu≤0.30%, Al: 0.015%~0.050%, the remainder is Fe and impurities. . According to claim 1,
Its chemical composition and mass percentage are C: 0.060%, Si: 0.281%, Mn: 1.011%, P: 0.013%, S: 0.0041%, Nb: 0.038%, Ti: 0.013%, Ni: 0.019%, Cr: 0.02 %, Cu:0.019%, Alt:0.037%, Mo:0.007%, V:0.001%, Ca:0.0019%, Ceq:0.27%, Pcm:0.13%. According to claim 1,
Its chemical composition and mass percentage are C:0.041%, Si:0.121%, Mn:1.191%, P:0.012%, S:0.0030%, Nb:0.066%, Ti:0.012%, Ni:0.011%, Cr:0.03 %, Cu:0.011%, Alt:0.033%, Mo:0.008%, V:0.001%, Ca:0.0016%, Ceq:0.28%, Pcm:0.13%. According to claim 1,
The chemical composition and mass percentage are C:0.050%, Si:0.181%, Mn:1.311%, P:0.012%, S:0.0031%, Nb:0.066%, Ti:0.011%, Ni:0.019%, Cr:0.02 %, Cu:0.011%, Alt:0.036%, Mo:0.009%, V:0.001%, Ca:0.0018%, Ceq:0.27%, Pcm:0.13%. According to claim 1,
The chemical composition and mass percentage are C:0.046%, Si:0.304%, Mn:1.236%, P:0.011%, S:0.0048%, Nb:0.053%, Ti:0.013%, Ni:0.019%, Cr:0.03 %, Cu:0.011%, Alt:0.039%, Mo:0.006%, V:0.001%, Ca:0.0019%, Ceq:0.28%, Pcm:0.13%. According to claim 1,
Its chemical composition and mass percentage are C:0.054%, Si:0.228%, Mn:1.120%, P:0.009%, S:0.0021%, Nb:0.033%, Ti:0.011%, Ni:0.011%, Cr:0.02 %, Cu:0.011%, Alt:0.035%, Mo:0.009%, V:0.001%, Ca:0.0016%, Ceq:0.27%, Pcm:0.13%. In the low steel grade pipeline clean steel smelting method,
Specifically, the following steps,
The desulfurization station performs desulfurization by mixing liquid calcium oxide and magnesium powder and blowing it out, and after the desulfurization is finished, deep removal of scum is carried out. The desulfurization station desulfurization standard is lower than or equal to 0.005%, and the rotation The furnace ensures that the sulfur of the molten iron discharged using the waste iron is less than or equal to 0.010%, and strong deoxidation is performed by adding an aluminum block to the molten iron discharged from the rotary furnace, but the addition amount is 35kg/100ppm, for LF desulfurization preparing step S1;
LF is mainly responsible for desulfurization and alloying, step S2 of setting the finished product sulfur to 0.002% to 0.005%;
In the RH vacuum treatment, the vacuum degree is lower than 3 MPa, the pure vacuum time is 18 min or more, and after the RH vacuum is finished, the calcium treatment is performed by feeding a 150 m to 200 m seamless pure calcium core wire, and after calcium treatment 12 Step S3 of performing static mixing for minutes;
In the CCM injection process, controlling the superheating degree from 30℃ to 35℃ and using the matching electromagnetic mixer technology to ensure that the low-power evaluation reaches within the YB/T 4003 standard C1.0 or B0.5; step S4; Low steel grade pipeline clean steel smelting method comprising the.