CN108994268A - A kind of 550MPa grades of hot rolling container weathering steel and its manufacturing method - Google Patents

Abstract

The present invention provides a kind of 550MPa grades of hot rolling container weathering steel and its manufacturing method, the container weathering steel, by mass percentage, including following component, C:0.05~0.09%, Mn:0.55~0.80%, Si:0.35~0.50%, Al:0.020~0.050%, Cr:0.50~0.70%, Cu:0.20~0.35%, Ti:0.065~0.085%, P: it is not more than 0.015%, S: is not more than 0.005%, N: it is not more than 0.060%, O: is not more than 0.005%；Surplus is iron and inevitable impurity, and the High Strength Container weathering steel is at low cost, while having excellent performance and good corrosion resistance, fully meets the use demand of user, promotes lightweight, the enlargement of container field product.

Description

A kind of weathering steel for 550MPa grade hot-rolled container and its manufacturing method

technical field

The invention relates to the production of steel for containers, in particular to a weather-resistant steel for 550MPa hot-rolled containers and a manufacturing method thereof.

Background technique

Affected by factors such as increasing world trade volume, soaring oil prices, and soaring shipping costs, the transportation industry urgently needs to use high-strength steel to manufacture containers and other transportation tools to reduce the weight of the box and improve transportation efficiency. Steel for containers is a high-tech, high-value-added steel for the production of land and ocean transport containers. It is extremely demanding on its strength, toughness, and corrosion resistance. Good welding performance and corrosion resistance. Containers widely use hot-rolled steel plates with a yield strength of 550MPa to manufacture box components. With the continuous development of the container industry, the requirements for steel used in containers are tending to be high-strength, lightweight, and thin. At the same time, in the current economic growth Under the background of fatigue and high cost, how to produce at low cost and meet the product requirements has become a focus of great concern to both steel mills and container users.

Contents of the invention

The invention provides a weathering steel for 550MPa grade hot-rolled containers and a manufacturing method thereof, so as to solve the problems existing in the prior art.

One aspect of the present invention provides a 550MPa grade hot-rolled weathering steel for containers, which comprises the following components by mass percentage, C: 0.05-0.09%, Mn: 0.55-0.80%, Si: 0.35-0.50%, Al: 0.020 ～0.050%, Cr: 0.50～0.70%, Cu: 0.20～0.35%, Ti: 0.065～0.085%, P: not more than 0.015%, S: not more than 0.005%, N: not more than 0.060%, O: not more than 0.005%; the balance is iron and unavoidable impurities.

Preferably, the weather-resistant steel for containers includes the following components by mass percentage, C: 0.05-0.07%, Mn: 0.55-0.80%, Si: 0.35-0.50%, Al: 0.020-0.050%, Cr: 0.58- 0.70%, Cu: 0.28～0.35%, Ti: 0.073～0.085%, P: not more than 0.015%, S: not more than 0.005%, N: not more than 0.060%, O: not more than 0.005%; the balance is iron and unavoidable impurities.

Further preferably, the weather-resistant steel for containers includes the following components by mass percentage, C: 0.05-0.07%, Mn: 0.65-0.80%, Si: 0.35-0.40%, Al: 0.030-0.050%, Cr: 0.63 ～0.70%, Cu: 0.28～0.35%, Ti: 0.079～0.085%, P: not more than 0.015%, S: not more than 0.005%, N: not more than 0.060%, O: not more than 0.005%; the balance is iron and unavoidable impurities.

Further preferably, the weathering steel for containers includes the following components by mass percentage, C: 0.05%, Mn: 0.80%, Si: 0.35%, Al: 0.050%, Cr: 0.70%, Cu: 0.35%, Ti : 0.085%, P: not more than 0.015%, S: not more than 0.005%, N: not more than 0.060%, O: not more than 0.005%; the balance is iron and unavoidable impurities.

On the other hand, the present invention also provides a production process of weathering steel for 550MPa grade hot-rolled containers, the process of which is: molten iron pretreatment→converter smelting→LF refining→continuous casting→heating→hot continuous rolling→controlled cooling→coiling , and includes the following steps:

Heating process: increase the heating temperature of the heating furnace, shorten the holding time, the heating temperature is 1210 ~ 1260 ℃, and the holding time is 30 minutes; high temperature and fast burning ensure the full integration of alloy elements and good plasticity and good performance of high-strength steel during rolling. The plate shape meets the rolling process requirements;

Hot continuous rolling and coiling process: the compression ratio of finishing rolling is more than 3; the metallographic structure and physical properties of the finished product are improved, and the product quality is improved;

Control the final rolling temperature, final rolling temperature: ≥850; medium temperature coiling, coiling temperature: ≥550; there is sufficient time to form intermetallic precipitates, refine grains, and increase strength.

Further, in the molten iron pretreatment process, pretreatment into the furnace S≤0.006%.

Further, in the converter process, the ladle Als is controlled at 0.025-0.035%.

Further, in the refining process, calcium-silicon wire is used for calcium treatment, and 500 meters of CaSi wire is fed to fully spheroidize inclusions and improve product performance.

Further, in the continuous casting process, the control target of the superheat of continuous casting is not greater than 25°C.

The operating methods not involved in the production process of the present invention are conventional methods.

Compared with prior art, the advantage of the present invention is:

(1) In terms of composition design, the alloy content is low, and the molten steel is pure. On the basis of ensuring excellent performance, cost is saved. The composition design without Ni is adopted, which reduces the cost per ton of steel by more than 100 yuan compared with the composition design of Ni addition.

(2) A higher compression ratio improves the structure and performance of the finished product.

(3) In terms of mechanical properties, all indicators meet the requirements, and the margin is relatively sufficient.

(4) The high-strength weather-resistant steel for containers produced by this process has low cost, excellent performance and good corrosion resistance, fully meets the needs of users, and promotes the lightweight and large-scale of products in the container field.

(5) The high-strength weather-resistant steel for containers produced by this technology reduces the cost of the enterprise, reflects high product quality and yield, and has good economic benefits.

Detailed ways

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The invention provides a 550MPa grade hot-rolled weathering steel for containers, which comprises the following components by mass percentage: C: 0.05-0.09%, Mn: 0.55-0.80%, Si: 0.35-0.50%, Al: 0.020-0.050 %, Cr: 0.50~0.70%, Cu: 0.20~0.35%, Ti: 0.065~0.085%, P: not more than 0.015%, S: not more than 0.005%, N: not more than 0.060%, O: not more than 0.005% ; The balance is iron and unavoidable impurities.

High-strength weather-resistant steel for containers needs to obtain good comprehensive properties. Therefore, the component design of the weather-resistant steel for containers must ensure certain toughness and strength, and have corrosion resistance and cold-bending performance, while saving costs.

The composition of Examples 1 to 5 is shown in Table 1, and the balance is iron and unavoidable impurities. The preparation process is: molten iron pretreatment→converter smelting→LF refining→continuous casting→heating→2300mm hot continuous rolling→control Cooling → coiling, the specific operation is as follows:

1. Steelmaking

1. Hot metal pretreatment process

S ≤ 0.006% into the furnace for pretreatment, remove the slag; use fine scrap steel.

2. Converter process

The converter pulls carbon once and avoids spot blowing; high manganese, ferrosilicon, and ferromolybdenum are used for tapping; argon purges the ladle before tapping to control the tapping port and avoid scattered flow, and the Als of the ladle is controlled at 0.025-0.035%.

3. Refining process

The LF refining process is adopted, and the gas content is strictly controlled. It is required to maintain a slight positive pressure in the LF treatment process, strictly control the increase of N in LF, and the amount of N increase is required to be ≤10ppm; LF uses active lime and fluorite to make reducing slag with good fluidity, strictly controls the intensity of argon blowing, and avoids the exposure of molten steel as much as possible; uses silicon Calcium wire Calcium treatment, feed CaSi wire 500 meters, make the inclusions fully spheroidized, and improve product performance.

4. Continuous casting process

Protective pouring is carried out throughout the process. Use argon gas to purge the tundish before pouring, so that no molten steel is exposed during the pouring process, strictly control the intake of N at the nozzle, and control the increase of N≤5ppm; use high-basic slag in the tundish to facilitate the removal of inclusions in the steel; cast steel The process is put into soft reduction function; the steel casting process maintains a constant casting speed; the control target of the superheat of continuous casting is not more than 25°C. The slabs are overheated and charged, and the remaining slabs are placed in the slow cooling zone in the warehouse.

2. Hot rolling

1. Heating furnace part

The heating temperature is 1210-1260°C, and the target firing temperature is 1180-1250°C. Control the furnace atmosphere of the heating furnace, reduce the generation of iron oxide scales in the slab, ensure uniform heating temperature, and provide a basis for ensuring the shape of the plate.

2. Rolling and coiling part

Choose 3+3 mode control for rough rolling passes; do a good job in load distribution of the finishing rolling model to ensure rolling stability; finishing rolling temperature: ≥850°C; coiling temperature: ≥550°C, and the cooling mode adopts the fifth group of on-cooling , Continuous cooling method. Guarantee the precise control of the final rolling and coiling temperature; according to the actual condition of the strip surface, selectively put into the F1 and F2 machines for small descaling; optimize and adjust the control of the cooling water between the stands.

The performance test results of the finished steel products of Examples 1-5 are shown in Table 2 and Table 3.

Table 1 Embodiment 1～5 composition table

Table 2 mechanical properties test results

Table 3 Corrosion Resistance Test Results (TB/T 2375-93)

Example Test time Corrosion rate (g/m2*h) Relative corrosion rate (%) standard 72 ≤60 Q345B (comparative example) 72 2.712 100 1 72 1.411 52 2 72 1.465 54 3 72 1.492 55 4 72 1.546 57 5 72 1.550 57

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than limit them. Although the present invention has been described in detail with reference to the embodiments, those of ordinary skill in the art should understand that modifications or equivalent replacements to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all of them should be included in the scope of the present invention. within the scope of the claims.

Claims (9)

1. A weather-resistant steel for 550MPa-grade hot-rolled containers, characterized in that: by mass percentage, it includes the following components: C: 0.05-0.09%, Mn: 0.55-0.80%, Si: 0.35-0.50%, Al: 0.020 ～0.050%, Cr: 0.50～0.70%, Cu: 0.20～0.35%, Ti: 0.065～0.085%, P: not more than 0.015%, S: not more than 0.005%, N: not more than 0.060%, O: not more than 0.005%; the balance is iron and unavoidable impurities. 2. A weathering steel for 550MPa grade hot-rolled containers according to claim 1, characterized in that: by mass percentage, it comprises the following components: C: 0.05-0.07%, Mn: 0.55-0.80%, Si: 0.35 ～0.50%, Al: 0.020～0.050%, Cr: 0.58～0.70%, Cu: 0.28～0.35%, Ti: 0.073～0.085%, P: not more than 0.015%, S: not more than 0.005%, N: not more than 0.060%, O: not more than 0.005%; the balance is iron and unavoidable impurities. 3. A weathering steel for 550MPa grade hot-rolled containers according to claim 1, characterized in that: by mass percentage, it comprises the following components: C: 0.05-0.07%, Mn: 0.65-0.80%, Si: 0.35 ～0.40%, Al: 0.030～0.050%, Cr: 0.63～0.70%, Cu: 0.28～0.35%, Ti: 0.079～0.085%, P: not more than 0.015%, S: not more than 0.005%, N: not more than 0.060%, O: not more than 0.005%; the balance is iron and unavoidable impurities. 4. A 550MPa grade hot-rolled weathering steel for containers according to claim 1, characterized in that: by mass percentage, it comprises the following components: C: 0.05%, Mn: 0.80%, Si: 0.35%, Al: 0.050%, Cr: 0.70%, Cu: 0.35%, Ti: 0.085%, P: not more than 0.015%, S: not more than 0.005%, N: not more than 0.060%, O: not more than 0.005%; the balance is iron and unavoidable impurities. 5. A method for manufacturing a 550MPa-grade hot-rolled weathering steel for containers according to any one of claims 1 to 4, the production process is: molten iron pretreatment→converter smelting→LF refining→continuous casting→heating→heating Continuous rolling → controlled cooling → coiling is characterized in that it specifically includes the following operations: Heating process: heating temperature 1210-1260 ℃, holding time 30 minutes; Hot continuous rolling and coiling process: the compression ratio of finishing rolling is more than 3; Control the finish rolling temperature, finish rolling temperature: ≥850; medium temperature coiling, coiling temperature: ≥550. 6. A method for manufacturing weather-resistant steel for 550MPa grade hot-rolled containers according to claim 5, characterized in that: in the molten iron pretreatment process, pretreatment into the furnace S≤0.006%. 7. The manufacturing method of a 550MPa class hot-rolled weathering steel for containers according to claim 5, characterized in that: in the converter process, the ladle Als is controlled at 0.025-0.035%. 8. The manufacturing method of a 550MPa-grade hot-rolled weathering steel for containers according to claim 5, characterized in that: in the refining process, calcium silicon-calcium wire is used for calcium treatment, and 500 meters of CaSi wire is fed to make the inclusions fully Spheroidization to improve product performance. 9. The manufacturing method of a 550MPa class hot-rolled weathering steel for containers according to claim 5, characterized in that: in the continuous casting process, the control target of the superheat of the continuous casting is not greater than 25°C.