CN102010937B - Ladle furnace refining stirring process for preventing large quantity of slags from lumping by weak bottom blowing - Google Patents

Abstract

A stirring method for ladle furnace refining with weak bottom blowing to prevent a large amount of slag from agglomerating, which belongs to the technical field of ladle refining, and realizes through online wire feeding machine and bottom blowing stirring together: the aluminum content in steel is controlled to 0.02 before ladle furnace refining %～0.04%, start the ladle bottom blowing and stirring, add 1/2～2/3 of the required amount of slag, and use the online wire feeder to feed the aluminum wire into the ladle, the wire feeding speed is 2-3m/s, and start feeding the wire At the same time as the slag is added or within the first third of the slag addition, the aluminum content in the steel is 0.04% to 0.10% after feeding, and the slag is mechanically stirred by the aluminum wire and bottom-blown to make the slag easily Spreading out and melting, followed by normal refining can meet the requirements of low carbon and low sulfur steel. The present invention utilizes the existing wire feeding machine without adding new equipment, solves the problem that the weak bottom blowing strength of the ladle caused by abnormal conditions cannot realize normal refining, and is easy to operate, simple in method, and does not increase additional costs.

Description

A mixing process for ladle furnace refining with weak bottom blowing and large amount of slag to prevent clumping

technical field

The invention belongs to the technical field of ladle furnace refining, and in particular relates to a mixing process for ladle furnace refining with weak bottom blowing and large amount of slag to prevent clumping, and is especially suitable for smelting steel with high requirements for impurities such as sulfur content and low carbon content. High-grade medium and thick steel plate varieties.

Background technique

In order to achieve high mechanical properties, most of today's steel types generally require very low sulfur content in steel, less than 0.001% to 0.004%, except for individual steel types such as free-cutting steel. At the same time, in order to have good welding and processing properties , all require low carbon content and high cleanliness, especially for medium and heavy plate steel mills.

In the smelting process of low-carbon high-grade steel grades, deep desulfurization is generally completed by the refining process. The refining cycle must match the cycle of the continuous casting machine. In order to obtain good internal quality of the slab, high-speed casting is technically advocated. Therefore, it is required that refining must quickly complete the tasks of desulfurization, deoxidation, and removal of inclusions, and the prerequisite for achieving this goal is to quickly form slag. In order to achieve rapid slag formation in the ladle furnace and other refining processes, a large amount of slag is generally added immediately after the refining process begins. However, when adding slag, due to the large amount of one-time addition and the concentrated position of adding through the silo, and in actual production due to equipment conditions or other reasons, the bottom blowing strength may be weak, so that It will cause the slag to pile up into lumps, and it is not easy to melt. The slag melting time may reach 10min to 25min. If the drop is too large, electrode heating must be used to compensate, so that the graphite electrode is easy to cause carbon increase, which not only affects the smooth production, but also easily causes the carbon content to exceed the standard and cause the furnace to be returned or the judgment to be changed.

The invention with the application number of 200610118625.3 provides a method for smelting stainless steel oxidized slag in an argon-oxygen furnace. It mainly provides a method for smelting stainless steel by adding lime and poor manganese ore during the oxidation period, adding ferrosilicon and using argon gas during the reduction period. Blowing, the method of adjusting the target composition during the refining period, can increase the decarburization speed, shorten the smelting time, improve production efficiency, prolong the life of the furnace lining, and reduce consumption and cost. The invention with application number 200510038233.1 provides an efficient integrated slag for steelmaking deoxidation-slag washing-external refining and its use method. The energy consumption is reduced, the slag removal time is shortened, and the product quality is improved. Conducive to process connection and production organization. Above patents all do not have a kind of quick slag and prevent the way of lumping and crusting.

Contents of the invention

In order to solve the above problems, the present invention aims to provide a mixing method for ladle furnace refining with weak bottom blowing to prevent a large amount of slag from agglomerating, which is realized by the online wire feeder and bottom blowing mixing, especially for the production of low-carbon, low-sulfur, high-quality steel .

The present invention is realized through the following technical solutions:

Before the molten steel enters the ladle furnace for refining, the aluminum content in the steel is controlled to a mass percentage of 0.02% to 0.04%, so as to ensure that the oxygen content in the steel is in a mass percentage of 0.0003% to 0.0015%. The flow rate is 2-6NL/(min·t), and then add 1/2~2/3 of the required amount of slag, and feed the aluminum wire with a diameter of 9~15mm into the ladle with an online wire feeder, and the wire feeding speed is 2 -3m/s, the time to start feeding the line is at the same time as the time to add slag material or within the first third of the process of adding slag material, stop or continue feeding the line after adding slag material according to the stirring situation and the amount of aluminum added, the total feeding amount 0.30～1.00kg/t, after feeding, the mass percentage of aluminum content in the steel is 0.04%～0.10%, the slag material is melted within 4min～9min after adding, and then normal refining can meet the requirements of low carbon and low sulfur steel. Due to the double action of the aluminum wire on the slag stirring and the bottom blowing, the slag cannot be lumped and crusted on the slag surface, which solves the problem of smelting high-grade low-carbon and low-sulfur steel slag in the case of weak bottom blowing. Crust problem.

The fed wire can also be silicon-calcium wire besides aluminum wire.

In addition to being suitable for smelting low-carbon and low-sulfur steel and other high-grade steels, the invention is also suitable for rapid slag melting during smelting of non-low-carbon and low-sulfur steels.

The present invention has the following advantages and effects: 1) solves the problem of a large amount of slag added at one time in the case of weak bottom blowing and is easy to form lumps and crusts; 2) solves the problem that the weak bottom blowing strength of the ladle caused by abnormal conditions cannot realize normal refining , which is beneficial to the normal production organization and avoids the loss caused by it; 3) The use of the existing wire feeder does not require new equipment; 4) The operation is simple, the method is simple, and there is no additional cost, and it is easy to realize the control of carbon increase. The LF furnace quickly melts slag and desulfurizes deeply, shortening the smelting cycle.

Detailed ways

Example 1: The steel type is pipeline steel X60, the steel output of the converter is 100 tons, the production process is "hot metal pretreatment desulfurization-converter smelting-ladle furnace refining-RH vacuum treatment-slab continuous casting", the ladle furnace refining starts and ends And the composition of the finished product is shown in Table 1. At the beginning of refining, blow argon at the bottom of the ladle and stir, the argon flow rate is 4.2NL/(min·t), and a total of 15 kg/ton of refining slag needs to be added. The first batch of 1/2 of the amount of slag is added, a total of 750kg. The online wire feeder feeds aluminum wire with a diameter of 10mm into the ladle, the wire feeding speed is 2.5m/s, and the feeding time is 90s. After the slag is added, the wire feeding is stopped. The feeding time is 80s and the feeding amount is 0.42kg/t. The yield is 80%. After feeding, the aluminum content in the steel is 0.056% by mass. The slag is melted 6 minutes after the addition, and then refined normally. The remaining slag is added in one to three times during the refining process. The composition of the finished product meets the requirements.

Table 1 Relevant components of molten steel, mass percentage %

Ladle Furnace Arrival Finished feeding the aluminum wire Ladle furnace refining completed finished product C% 0.058 0.079% 0.085% Al% 0.022 0.056 0.052% 0.032% S% 0.0082% 0.0027% 0.0028% [O] 0.0010%

Example 2: The steel type is pipeline steel X70, the steel output of the converter is 208 tons, the production process is "hot metal pretreatment desulfurization-converter smelting-ladle furnace refining-RH vacuum treatment-slab continuous casting", the ladle furnace refining starts and ends And finished product composition as shown in Table 2. At the beginning of refining, blow argon at the bottom of the ladle and stir, the flow rate of argon gas is 3.3NL/(min·t), and a total of 17kg/ton of steel needs to be added to the refining slag. The first batch of 2/3 of the amount of slag to be added, a total of 2357kg, will be used 20s after the feeding starts. The online wire feeder feeds aluminum wire with a diameter of 15mm into the ladle, the feeding speed is 2.0m/s, and the feeding time is 160s. After the slag is added, the wire feeding is stopped. The feeding time is 140s, and the feeding amount is 0.64kg/t. The yield rate is 85%. After feeding, the aluminum content in the steel is 0.087% by mass. The slag material is melted 7 minutes after the addition, and then refined normally. The remaining slag material is added in one to three times during the refining process, and the composition of the finished product meets the requirements.

Table 2 Related components of molten steel, mass percent

Ladle Furnace Arrival Finished feeding the aluminum wire Ladle furnace refining completed finished product C% 0.045 0.068 0.072 Al% 0.032 0.087 0.052 0.035 S% 0.0076 0.0018 0.0017 [O] 0.0008

Claims (1)

1. A mixing process for ladle furnace refining with weak bottom blowing and large amount of slag to prevent clumping: before the molten steel enters the ladle furnace for refining, the aluminum content in the steel is controlled to a mass percentage of 0.02% to 0.04%, so as to ensure the quality of the oxygen content in the steel The percentage is 0.0003% to 0.0015%. At the beginning of refining, firstly turn on the bottom of the ladle to blow argon for stirring. It is: use the online wire feeder to feed aluminum wires with a diameter of 9mm to 15mm into the ladle at a feeding speed of 2-3m/s. At the same time or within the first third of the process of adding slag, stop or continue feeding the line after adding slag according to the stirring situation and the amount of aluminum added. The total feeding amount is 0.30kg/t~1.00kg/t. Finally, the mass percentage of the aluminum content in the steel is 0.04%-0.10%, and the slag can be dispersed by the double action of the aluminum wire inserted above and the bottom blowing stirring, and melted within 4min-9min.