WO2022011936A1 - High-strength vessel plate having excellent low-temperature toughness and manufacturing method - Google Patents

Abstract

A high-strength vessel plate having excellent low-temperature toughness and a manufacturing method, relating to the technical field of iron and steel production. The high-strength vessel plate comprises the following chemical components in mass percentage: 0.07% to 0.11% of C, 0.10% to 0.30% of Si, 1.30% to 1.60% of Mn, 0.40% to 0.80% of Ni, 0.05% to 0.12% of Mo, 0.02% to 0.05% of V, 0.02% to 0.05% of Alt, 0.008% or less of P, and 0.002% or less of S, with the balance being Fe and inevitable impurities. By adding a small amount of alloy to implement material strength upgrade, the alloy cost is low, accurate control is easily achieved, the use temperature is lower, and the strength is significantly improved, thus the material consumption for storage tank construction can be reduced.

Description

High-strength container plate with excellent low-temperature toughness and manufacturing method technical field

The invention relates to the technical field of steel production, in particular to a high-strength container plate with excellent low-temperature toughness and a manufacturing method.

Background technique

With the high-parameterization development of low-temperature container steel in the chemical industry, some low-strength mature grades such as 09MnNiDR have been difficult to meet the needs of large-scale development of low-temperature spherical tanks such as ethylene. It is urgent to ensure the low-temperature toughness of the material. Reduce the thickness of steel used, reduce the risk of toughness of large-thickness steel plates welded joints, reduce construction volume and welds, improve equipment construction efficiency, and reduce material costs.

In terms of research and development of domestic high-strength and low-temperature steel, the Chinese invention patent with publication number CN110724878A proposes a 0.5Ni low-temperature steel and its manufacturing method, adding B element, adopting two-stage controlled rolling, normalizing + tempering process heat treatment, the minimum use The temperature can be lowered to -80℃, but the actual yield strength is about 400MPa, and the tensile strength is only about 520MPa. The Chinese patent with publication number CN106467951B proposes a high-strength, high-toughness, low-yield-strength-ratio low-temperature steel for -70°C and its manufacturing method, adding Mo≤0.10, Nb≤0.05, Ti≤0.025, Ca≤0.005 Any one or several of them can meet the requirements of -70 ℃, but the physical yield strength is less than 400MPa. The Chinese patent with publication number CN108893681A proposes a high-strength and high-toughness pressure vessel steel plate and a preparation method thereof. The V-Ni-N alloy system is used to improve the low-temperature fracture toughness and reduce the ductile-brittle transition temperature. The fine dispersion effect of the core and the control methods of Al, N and V components enable the obtained steel to exhibit good low temperature, high strength and high toughness, yield strength ≥ 480MPa, tensile strength 640-740MPa, yield ratio ≤ 0.85, elongation ≥ 21% , the transverse direction of the steel plate is -60℃ KV ₂ ≥80J, the ferrite grain size reaches 10.5 to 13.5, and the minimum operating temperature is only -60℃.

To sum up, in the prior art, there is no relevant report on the low-temperature C-Mn steel which can be used at a temperature of -80°C and can satisfy the yield strength ≥ 460 MPa and tensile strength ≥ 570 MPa at the same time.

SUMMARY OF THE INVENTION

In order to solve the above technical problems, the present invention provides a high-strength container plate with excellent low-temperature toughness, whose chemical composition and mass percentage are as follows: C: 0.07%-0.11%, Si: 0.10%-0.30%, Mn: 1.30%- 1.60%, Ni: 0.40%~0.80%, Mo: 0.05%~0.12%, V: 0.02%~0.05%, Alt: 0.02%~0.05%, P≤0.008%, S≤0.002%, the balance is Fe and inevitable impurities.

Technical effect: the present invention realizes the material strength upgrade by adding a small amount of alloy Mo and V, the alloy cost is not high and it is easy to achieve precise control, not only the use temperature is lower, but the strength is also significantly improved, which can reduce the material consumption for the construction of the storage tank.

The technical scheme that the present invention is further limited is:

The aforementioned high-strength container plate with excellent low-temperature toughness has the following chemical composition and mass percentage: C: 0.07%-0.08%, Si: 0.10%-0.21%, Mn: 1.30%-1.55%, Ni: 0.40%～0.47%, Mo: 0.05%～0.07%, V: 0.02%～0.045%, Alt: 0.02%～0.038%, P≤0.005%, S≤0.001%, the balance is Fe and inevitable impurities.

The aforementioned high-strength container plate with excellent low-temperature toughness has the following chemical composition and mass percentage: C: 0.09%-0.10%, Si: 0.15%-0.24%, Mn: 1.32%-1.47%, Ni: 0.50%～0.65%, Mo: 0.08%～0.11%, V: 0.029%～0.035%, Alt: 0.030%～0.044%, P: 0.004%～0.005%, S: 0.0007%～0.002%, the balance is Fe and inevitable impurities.

In the aforementioned high-strength container plate with excellent low-temperature toughness, the thickness of the steel plate is 10-50 mm.

Another object of the present invention is to provide a method for manufacturing a high-strength container plate with excellent low-temperature toughness, comprising:

Steelmaking and continuous casting: hot metal pretreatment, top and bottom blowing smelting in converter, LF+RH refining, composition control according to composition design requirements, to produce 260mm thick billets;

Slab heating: The slab is heated to 1130～1160℃, the total time in the furnace is ≥220min, the holding time of the soaking section is 30～60min, and the temperature uniformity of the whole slab is ≤10℃;

Controlled rolling and controlled cooling: After the slab is released from the furnace, high-pressure water is used for descaling, and the descaling water pressure is ≥18MPa. Two-stage controlled rolling is adopted. The first stage is rolled in the austenite recrystallization zone, and the second stage is rolled in the austenite unprocessed Finish rolling in the recrystallization zone, and control cooling after rolling;

Heat treatment: adopt off-line quenching + tempering process for heat treatment.

The aforementioned manufacturing method of a high-strength container plate with excellent low-temperature toughness, steelmaking and continuous casting: pretreatment of molten iron, S content in molten iron <0.002wt%, converter steelmaking, deep desulfurization and deoxidation in LF furnace, Adjust the alloy composition to achieve the target range and superheat control, degas the RH furnace, vacuum degree ≤ 0.3torr, feed pure calcium wire for calcium treatment after RH refining, static stirring time after feeding wire ≥ 15min, and continuously cast into 260mm thick billets , The billet is subjected to stack cooling treatment, and the stack cooling time is ≥ 48 hours.

The above-mentioned manufacturing method of a high-strength container plate with excellent low-temperature toughness adopts controlled rolling and controlled cooling in the hot rolling process: rolling in the austenite recrystallization zone in the first stage, and the cumulative reduction in rough rolling is 55% to 85%. In the second stage, finish rolling is carried out in the austenite unrecrystallized area. The accumulated reduction of finishing rolling is 50% to 80%, and the final rolling temperature is 820 to 860°C. , control the temperature of returning red to 600~640℃.

The above-mentioned manufacturing method of a high-strength container plate with excellent low temperature toughness, the heat treatment adopts off-line quenching and tempering, the quenching temperature is 880-910 ° C, the quenching cooling rate is ≥ 15 ° C/s, directly quenched to room temperature, and offline quenching The steel plate is heated to 600～640℃ and tempered for 40-75min to obtain a tempered sorbite structure.

The beneficial effects of the present invention are:

(1) composition design thinking of the present invention:

C: Strengthening element and austenite stabilizing element of steel, carbon content in steel increases, yield point and tensile strength increase, for every 0.1% increase in carbon content, tensile strength increases by about 90MPa, and yield strength increases by about 40-50MPa , but the plasticity and impact are reduced, and the ductile-brittle transition temperature is increased, which is harmful to the low temperature toughness of HAZ, and the strength is ensured during design;

Ni: It can form α and γ phase solid solutions with Fe, and can be infinitely dissolved in the γ phase. It can expand the γ phase region. It is austenite forming and stabilizing element, making the screw dislocation difficult to decompose and ensuring cross slip. The occurrence of Ni can improve the plastic deformation performance of the material; Ni is also a precious metal element, and the addition amount should be minimized under the premise of ensuring performance;

Mn: Austenite stabilizing element, also a matrix strengthening element, can improve the strength through solid solution strengthening and precipitation strengthening. When the content is below 1.8%, the steel can still maintain high plasticity and toughness while improving the strength of the steel;

Si: a deoxidizing element, which can dissolve into ferrite and produce solid solution strengthening, which increases the strength and hardness of ferrite, but decreases its plasticity and toughness, which is not conducive to the low temperature toughness of the heat-affected zone (HAZ) of welding;

Mo: It can improve the hardenability, thereby improving the strength and the tempering stability of the steel. When coexisting with chromium or manganese, it can reduce or suppress the tempering brittleness caused by other elements, but Mo is also a precious metal. Too much will significantly increase the alloy cost;

V: A strong carbonitride forming element, it can improve the strength of steel by refining grains and carbide precipitation. When V, Cr and Mo exist at the same time, it will form complex carbides during tempering and reduce For the plastic toughness of welded joints, the V amount is strictly controlled to ensure plastic toughness or stress relief to avoid cracks;

S and P: S is easy to form the precipitate MnS with Mn, which reduces the low temperature toughness, and P is easy to segregate at the grain boundary, which reduces the crack growth resistance of the grain boundary and deteriorates the low temperature toughness;

Al: The main deoxidizing element in the steel, which is beneficial to refine the grains. When the Al content is too high, it is easy to lead to the increase of inclusions in the steel, which is not good for the toughness of the steel;

(2) Off-line quenching + tempering heat treatment is adopted in the present invention to obtain uniform structure and properties of the steel plate and good shape control;

(3) On the basis of the existing low-temperature C-Mn steel, the present invention significantly improves the low-temperature toughness and strength, and develops a brand-new low-temperature C-Mn steel, which can replace the domestic and foreign 0.5Ni steel grades such as 09MnNiDR for ethylene Wait for the construction of low-temperature spherical tanks or storage tanks, and realize the upgrade and upgrade of low-temperature C-Mn steel materials.

Description of drawings

Figure 1 is a photo of the tempered microstructure at a 1/4 thickness of a 50mm steel plate corroded by a 4% nitric acid alcohol solution.

detailed description

The following examples provide a high-strength container plate with excellent low-temperature toughness and its manufacturing method. The chemical composition is shown in Table 1, the smelting and rolling process parameters are shown in Table 2, and the heat treatment process parameters are shown in Table 3. The steps are:

Steelmaking and continuous casting: Steelmaking and continuous casting: Pretreatment of molten iron, S content in molten iron <0.002wt%, converter steelmaking, deep desulfurization and deoxidation in LF furnace, adjusting alloy composition to achieve the target range and superheat control, RH furnace desulfurization Gas, vacuum degree ≤0.3torr, RH refining and feeding pure calcium wire for calcium treatment, static stirring time ≥15min after feeding, continuous casting into 260mm thick billet, casting billet for stack cooling treatment, stack cooling time ≥48 hours;

Slab heating: The slab is heated to 1130～1160℃, the total time in the furnace is ≥220min, the holding time of the soaking section is 30～60min, and the temperature uniformity of the whole slab is ≤10℃;

Controlled rolling and controlled cooling: After the slab is released from the furnace, high-pressure water is used for descaling, and the descaling water pressure is ≥18MPa. Two-stage controlled rolling is adopted. The first stage is rolled in the austenite recrystallization zone, and the cumulative reduction in rough rolling is 55 %～85%, in the second stage, finish rolling is carried out in the austenite unrecrystallized area, the accumulated reduction of finishing rolling is 50%～80%, and the final rolling temperature is 820～860℃; after rolling, the steel plate is cooled by laminar flow, Control the reddening temperature to 600～640℃;

Heat treatment: adopt off-line quenching + tempering process for heat treatment, quenching temperature is 880～910℃, quenching cooling rate is ≥15℃/s, directly quenched to room temperature, off-line quenched steel plate is heated to 600～640℃ and tempered for 40-75min. Pyrostenite structure.

Table 1

example	C(%)	Mn(%)	Si(%)	S(%)	P(%)	Ni(%)	Mo(%)	V(%)	Al(%)
Example 1	0.08	1.55	0.21	0.001	0.005	0.47	0.07	0.045	0.038
Example 2	0.10	1.47	0.15	0.0007	0.004	0.50	0.08	0.029	0.044
Example 3	0.09	1.32	0.24	0.002	0.005	0.65	0.11	0.035	0.030

Table 2

table 3

steel sample	Quenching temperature	Quenching holding time, min	Cooling rate, °C/s	Tempering temperature, °C	Tempering holding time, min
A	908	30	50	632	47
B	898	40	30	622	55
C	895	45	18	613	62
D	885	50	16	605	70

The mechanical properties of the embodiment products are shown in Table 4,

Table 4

At the same time, it can be seen from Figure 1 that the structure obtained by the product of the present invention is a tempered sorbite structure that retains the lath orientation, has excellent strength and toughness, and can obtain good comprehensive mechanical properties. Charpy impact under the low temperature condition of -80 ° C Work ≥150J, yield strength ≥460MPa, tensile strength ≥570MPa. On the basis of the existing 0.5Ni steel, the strength is significantly improved, the wall thickness of the material used in the construction of the low temperature spherical tank or storage tank is reduced, the construction period is shortened and the cost is saved.

In addition to the above-described embodiments, the present invention may also have other embodiments. All technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims (8)

1. A high-strength container plate with excellent low temperature toughness is characterized in that its chemical composition and mass percentage are as follows: C: 0.07%-0.11%, Si: 0.10%-0.30%, Mn: 1.30%-1.60%, Ni: 0.40%～0.80%, Mo: 0.05%～0.12%, V: 0.02%～0.05%, Alt: 0.02%～0.05%, P≤0.008%, S≤0.002%, the balance is Fe and inevitable impurities.
2. A high-strength container plate with excellent low-temperature toughness according to claim 1, characterized in that: its chemical composition and mass percentage are as follows: C: 0.07%-0.08%, Si: 0.10%-0.21%, Mn: 1.30 %～1.55%, Ni: 0.40%～0.47%, Mo: 0.05%～0.07%, V: 0.02%～0.045%, Alt: 0.02%～0.038%, P≤0.005%, S≤0.001%, the balance is Fe and inevitable impurities.
3. A high-strength container plate with excellent low-temperature toughness according to claim 1, characterized in that: C: 0.09%-0.10%, Si: 0.15%-0.24%, Mn: 1.32%-1.47%, Ni: 0.50 %～0.65%, Mo: 0.08%～0.11%, V: 0.029%～0.035%, Alt: 0.030%～0.044%, P: 0.004%～0.005%, S: 0.0007%～0.002%, the balance is Fe and inevitable impurities.
4. The high-strength container plate with excellent low-temperature toughness according to claim 1, characterized in that the thickness of the steel plate is 10-50 mm.
5. The method for manufacturing a high-strength container plate with excellent low-temperature toughness according to any one of claims 1-4, characterized in that: comprising:

   Steelmaking and continuous casting: using molten iron pretreatment, top and bottom blowing smelting in converter, LF+RH refining, component control according to component design requirements, to produce 260mm thick billets;

   Slab heating: The slab is heated to 1130～1160℃, the total time in the furnace is ≥220min, the holding time of the soaking section is 30～60min, and the temperature uniformity of the whole slab is ≤10℃;

   Controlled rolling and controlled cooling: After the slab is released from the furnace, high-pressure water is used for descaling, and the descaling water pressure is ≥18MPa. Two-stage controlled rolling is adopted. The first stage is rolled in the austenite recrystallization zone, and the second stage is rolled in the austenite unprocessed Finish rolling in the recrystallization zone, and control cooling after rolling;

   Heat treatment: adopt off-line quenching + tempering process for heat treatment.
6. The method for manufacturing a high-strength container plate with excellent low-temperature toughness according to claim 5, characterized in that: steelmaking and continuous casting: pretreatment of molten iron, S content in molten iron <0.002wt%, converter steelmaking, The LF furnace is deeply desulfurized and deoxidized, and the alloy composition is adjusted to achieve the target range and superheat control. The RH furnace is degassed, and the vacuum degree is less than or equal to 0.3torr. After RH refining, it is fed into pure calcium wire for calcium treatment. Continuous casting is made into 260mm thick billets, and the casting billets are subjected to pile cooling treatment, and the pile cooling time is ≥ 48 hours.
7. The method for manufacturing a high-strength container plate with excellent low-temperature toughness according to claim 5, characterized in that: the hot rolling process adopts controlled rolling and controlled cooling: the first stage is rolled in the austenite recrystallization zone, The cumulative reduction in rough rolling is 55% to 85%. In the second stage, finishing rolling is performed in the austenite non-recrystallized area. The cumulative reduction in finishing rolling is 50% to 80%, and the final rolling temperature is 820 to 860°C; After rolling, the steel plate is cooled by laminar flow, and the reddening temperature is controlled to be 600-640 °C.
8. The method for manufacturing a high-strength container plate with excellent low-temperature toughness according to claim 5, wherein the heat treatment adopts off-line quenching + tempering, the quenching temperature is 880-910°C, the quenching cooling rate is ≥15°C/s, Directly quenched to room temperature, the off-line quenched steel plate is heated to 600-640 ℃ and tempered for 40-75min to obtain a tempered sorbite structure.

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