TWI443197B - Steel-making process of a weathering steel - Google Patents

Description

Weathering steel steelmaking process

The present invention relates to a steelmaking process for weathering steel, and more particularly to a steelmaking process for weathering steel in which a rare earth alloy (generally represented by RE) is added by a cored wire.

Traditional weathering steels are mainly made of nickel added to the steel to improve the weatherability of the steel, which in turn makes the steel resistant to use in harsher climates. Due to the high cost of nickel, in recent years, it has tended to replace some nickel with rare earth alloys to reduce the manufacturing cost of weathering steel.

In the prior art, the steelmaking process of the weathering steel containing the rare earth alloy mainly has the following several ways.

The first type is called the "direct input method", which is directly used to feed the bulk rare earth lanthanum iron into the molten steel in the steel drum. The second type is called "spraying method", which directly injects the powder of rare earth lanthanum iron into the molten steel in the steel drum. The disadvantages of the above two methods are: most of the rare earth elements are oxidized or volatilized and discharged from the molten steel, wherein only a small part of the rare earth elements remain in the molten steel, so the recovery rate of rare earth elements is less than 10%, and finally weathering The quality of steel products is very unstable. The recovery rate of the above rare earth element is defined as the ratio of the rare earth element remaining in the molten steel to the rare earth element added. Since most of the added rare earth elements are discharged from the molten steel, the above two methods tend to increase the cost of the steel making process.

The third type is called "in-mold hanging rare earth rod method", which is to set a light shelf on the mouth of a steel ingot mold for casting weathering steel, and the shelf is provided with a small hole for inserting a rare earth rod, using a rare earth rod A small hole is drilled at the upper end to attach the hook so that the above rare earth rod can be hung on the shelf. When the rare earth rod is to be added to the molten steel, the bet method is used, that is, the molten steel is placed in the molten steel in the ingot mold, and the rare earth rod disposed above is smoothly incorporated into the molten steel. The disadvantage of this method is that the rare earth media is not easy to float and be removed. In addition, the bet method cannot add an additional rare earth rod, and the rare earth raw material must be made into a rare earth rod at a time and added to the molten steel, so that the rare earth content in the molten steel cannot be immediately adjusted. Furthermore, due to the limitation of the space inside the ingot mold, it is necessary to use a rare earth rod with a purity of 98% or more in order to obtain a sufficient rare earth content for the final weathering steel product, and the rare earth metal is easily self-igniting, so before the steel making, during the handling and storage process There is a considerable risk in it.

The fourth type is called "in-mold addition method", which is to add rare earth wire into the molten steel in the continuous casting mold, wherein the rare earth and the reaction product of oxygen and sulfur in the molten steel are difficult to float, so most of the residue remains in the steel. In the liquid. Since the rare earth wire is no longer stirred after being added to the molten steel in the continuous casting mold, the rare earth does not have sufficient time to diffuse in the molten steel in the continuous casting mold, thereby causing uneven distribution of the rare earth in the final weathering steel product. In addition, since the melting point of the rare earth is low, when the slag layer is passed through, part of the rare earth reacts with the oxide in the slag to form a rare earth oxide, which causes a change in the characteristics of the protective slag and affects the quality of the final weathering steel.

Therefore, there is a need for a new type of steelmaking process for weathering steel.

Therefore, the object of the present invention is to provide a steelmaking process for weathering steel, which uses a cored wire to add a rare earth alloy to a molten steel in a steel ladle, and at the same time reduces desulfurization of the molten steel in a steel ladle. The sulfur content is less than 0.0015 wt% in terms of weight percent (wt%), which avoids the problems of low recovery, the problem of not being able to adjust the composition of the molten steel, the risk of handling and storage, and the ultimate weather resistance. The problem of uneven distribution of rare earth in steel products.

According to an embodiment of the present invention, a steelmaking process for weathering steel is provided. The weathering steel comprises a plurality of components in wt%, wherein the components are: carbon, cerium, manganese, phosphorus, copper, chromium, nickel, a rare earth alloy, oxygen, and a residue composed of iron. The steelmaking process comprises: performing a steelmaking step before preparing the molten steel liquid; performing a first desulfurization step to place the molten steel liquid into a steel ladle, and performing a desulfurization process to make the molten steel liquid The sulfur content is less than 0.0015 wt% when calculated in wt%; the rare earth iron-clad cored wire is added to the molten steel containing less than 0.0015 wt% of sulfur, wherein the rare earth neodymium iron cored wire comprises a hollow package. a core shell and a rare earth lanthanum iron powder located inside the hollow cored shell, the rare earth lanthanum iron powder comprising a plurality of components: titanium, lanthanum, manganese, calcium, a rare earth alloy, and a residue composed of iron; A post-steel step is performed to obtain the weathering steel described above.

According to another embodiment of the present invention, in the steelmaking process described above, the composition of the weathering steel is calculated in wt%, and the contents of the components are: 0.12 wt% or less of carbon, and 0.25 to 0.55 wt% of bismuth. 0.20~0.50 wt% manganese, 0.07~0.15 wt% phosphorus, 0.25~0.55 wt% copper, 0.30~1.25 wt% chromium, 0.65 wt% nickel, 0.07 wt% rare earth alloy, 0.0050 wt Oxygen below %, and a residue consisting of iron.

According to still another embodiment of the present invention, in the steelmaking process described above, the composition of the rare earth lanthanum iron powder is calculated by wt%, and the content of the components is respectively: 3% by weight or less of titanium and 44% by weight or less, 3 wt% or less of manganese, 5 wt% or less of calcium, 21 to 42 wt% of rare earth alloy, and a residue composed of iron. Further, the rare earth alloy of the above rare earth lanthanum iron powder contains cerium (Ce), lanthanum (La) and cerium (Nd), wherein when yttrium is calculated by wt%, the total content of the rare earth alloy is more than 46%.

According to still another embodiment of the present invention, in the steelmaking process described above, the material of the hollow cored shell of the rare earth neodymium iron cored wire is carbon steel.

The advantage of the present invention is that the material cost of the steelmaking process can be reduced because the recovery rate has been increased. In addition, since it is not necessary to use a high-purity rare earth rod to manufacture the final weathering steel product, the material cost of the steelmaking process can also be reduced. Furthermore, since the sulfur content in the molten steel in the ladle has fallen below 0.0015 wt%, the rare earth element and the sulfur do not easily react to form a mesoporous material, thereby avoiding blocking the long nozzle used in casting ( Long Nozzle) and immersion nozzle (SEN).

Please refer to FIG. 1 , which is a flow chart showing a steelmaking process of a weathering steel according to an embodiment of the present invention, wherein the weathering steel comprises a plurality of components, such as carbon, germanium, manganese, phosphorus, Copper, chromium, nickel, rare earth alloys, oxygen, and other parts composed of iron (may be referred to as residues). The steelmaking process 100 for weathering steel (hereinafter referred to as "steelmaking process 100" for the sake of explanation) begins in the pre-steel step 102 to prepare a molten steel. In the above-mentioned steelmaking step 102, since the iron making and steel making systems are the same as the steel making and steel making processes of the conventional steel, they will not be described again. In a particular embodiment, the pre-steel step 102 further includes performing a desulfurization step whereby the sulfur content of the molten steel is reduced. Moreover, in certain embodiments, the pre-steel step 102 can also include performing a deoxygenation step to reduce the oxygen content of the molten steel.

After the pre-steel step 102 is completed, the steelmaking process 100 proceeds to the desulfurization step 104 to place the molten steel in the pre-steel step 102 into a ladle, followed by a desulfurization process whereby the melt is melted The sulfur content in the molten steel is less than 0.0015 wt% when calculated in wt%.

After the desulfurization step 104 is completed, the steelmaking process 100 performs a rare earth alloy addition step 106 to add the rare earth neodymium iron cored wire to the molten steel having a sulfur content of less than 0.0015 wt%. The rare earth neodymium iron cored wire comprises a hollow cored shell and a rare earth lanthanum iron powder located inside the hollow core shell, and the rare earth lanthanum iron powder comprises a plurality of components, such as titanium, tantalum and manganese. , calcium, rare earth alloys, and residues consisting of iron. Since the content ratio of each component in the rare earth lanthanum iron powder contained in the core wire of the rare earth lanthanum iron is known, the weight of the rare earth lanthanum iron powder contained in the unit length of the core wire of the rare earth lanthanum iron and the added rare earth may be used. The length of the core of the neodymium iron core is used to calculate the proportion of rare earth elements added to the molten steel. In addition, the exact content of the rare earth element in the molten steel can be analyzed by taking molten steel in the field, thereby calculating the recovery rate of the rare earth element.

In a specific embodiment, the hollow cored shell of the rare earth lanthanum iron cored wire is substantially a hollow cylinder, and the material thereof may be carbon steel. In practice, the rare earth lanthanum iron core wire is generally wound around a columnar body (generally referred to as a reel), and the crimped rare earth lanthanum cored wire is placed beside the above-mentioned steel drum, and is automatically advanced. The material mechanism puts the rare earth lanthanum iron core wire into the molten steel liquid of the steel drum. In a specific embodiment, the above-mentioned columnar body covered by the rare earth lanthanum iron core wire is horizontally placed beside the steel ladle, so that the rare earth lanthanum iron core wire can be added to the molten steel drum in a substantially horizontal manner. In molten steel. However, in other embodiments, the columnar body of the rare earth neodymium iron cored wire crimped cladding may be disposed above the ladle, so that the rare earth neodymium iron core wire can be added to the vertical in a substantially vertical manner. The molten steel in the steel drum.

Finally, the steelmaking process 100 performs a post-smelting step 108 whereby the weathering steel described above is obtained. In a particular embodiment, the post-steel step 108 further includes performing a continuous casting step of casting molten steel in the ladle into the mold by continuous casting to obtain the weathering steel described above.

Moreover, in a particular embodiment, the steelmaking process 100 further includes performing a rolling step to roll the weathering steel described above to a predetermined thickness, wherein the rolling step can be a hot rolling step or a cold rolling step.

In a preferred embodiment, the plurality of components of the weathering steel produced by the steelmaking process 100 are calculated in wt%, and the contents of the components are: 0.12 wt% or less, 0.25 to 0.55 wt%, 0.20. ~0.50 wt% of manganese, 0.07 to 0.15 wt% of phosphorus, 0.25 to 0.55 wt% of copper, 0.30 to 1.25 wt% of chromium, 0.65 wt% of nickel, 0.07 wt% or less of rare earth alloy, 0.0050 wt% or less Oxygen, and the residue consisting of iron. The contents of the above respective components are shown in Table 1 below.

In other embodiments, the composition of the rare earth lanthanum iron powder used in the rare earth lanthanum iron core wire in the steel making process 100 is calculated in wt%, wherein the content of the components is: 3 wt% or less of titanium, 44 wt% % below 5%, manganese below 3 wt%, calcium below 5 wt%, rare earth alloy of 21 to 42 wt%, and a residue composed of iron. Furthermore, in a specific embodiment, the rare earth alloy comprises a plurality of components such as cerium (Ce), lanthanum (La) and cerium (Nd). When calculated in wt%, the proportion of lanthanum to the total rare earth alloy is greater than 46. %, wherein the total rare earth alloy is the sum of 铈, 镧 and 铷.

In addition, according to the experiment, it is known whether the long nozzle used in casting and the immersion nozzle are blocked, which is related to the sulfur content of the molten steel in the steel drum and the presence or absence of rare earth elements, and in the steel drum. There is no absolute relationship between the oxygen content of the molten steel. Therefore, in the above desulfurization step 104, a desulfurization process is performed to reduce the sulfur content in the molten steel to less than 0.0015 wt%, mainly to prevent the rare earth element from reacting with sulfur to cause a mesophase, thereby causing the above-mentioned blockage. The following is based on the relevant experimental data and results, the clogging of the long nozzle and the immersion nozzle and the sulphur content of the molten steel in the steel drum, the oxygen content of the molten steel and the presence or absence of rare earth elements. Relationship.

Please refer to FIGS. 2A and 2B , which respectively show the sulfur content in the molten steel before the addition of the rare earth lanthanum iron core wire in the ladle according to an embodiment of the present invention and the comparative example, and the rare earth in the final weathering steel. The relationship between the alloy content and the oxygen content in the molten steel before the addition of the rare earth lanthanum iron core in the ladle is related to the content of the rare earth alloy in the final weathering steel. In Figures 2A and 2B, except for the weathering steel No. 5, the rare earth alloy was not added, and the weathering steels Nos. 1 to 4 were all added with a rare earth alloy. Therefore, the weathering steel No. 5 was a comparative example. The steelmaking and steelmaking processes of weathering steel Nos. 1 to 5 are the same as those of conventional steel. Only the weathering steels numbered 1 to 4 are added with rare earth lanthanum iron cored wire in the molten steel of the steel drum during the steel making process. Before the addition of the rare earth alloy step 106), the molten steel liquid corresponding to the specific number of weathering steel is subjected to desulfurization (desulfurization step 104) and temperature rise, and some are not, thereby making the molten steel liquid corresponding to the different number of weathering steels Get different sulphur content. In addition, the hot rolling process of weathering steel Nos. 1 to 5 is also the same as that of conventional weathering steel. The analysis of the sulfur content in the weathering steels Nos. 1 to 5 is carried out by taking the molten steel from the steelmaking process for analysis, and the analysis of the oxygen content is taken from the weathering steel product after the rolling, as for other alloys (for example, the rare earth alloy, Rare earth elements such as lanthanum and cerium, and conventional alloys (such as elements such as copper, chromium, nickel and phosphorus) are analyzed after continuous casting in the field.

As can be seen from Fig. 2A, the weathering steel of No. 5 did not cause clogging even if the sulfur content was as high as 0.0040% by weight. On the other hand, the weathering steels Nos. 4 and 3 contain 0.017 wt% and 0.036 wt% of rare earth alloys, respectively, and their sulfur contents are 0.0040 wt% and 0.0029 wt%, respectively, and clogging occurs during the manufacturing process. The weathering steels Nos. 2 and 1 respectively contained 0.038 wt% or 0.064 wt% of the rare earth alloy, and the sulfur content thereof was 0.0015 wt%, and no clogging occurred during the manufacturing process.

According to the above results, it is known that the occurrence of clogging is related to the sulfur content of the ladle and the presence or absence of the addition of the rare earth alloy. In addition, the experimental results show that before the rare earth lanthanum iron cored wire is added to the molten steel of the steel drum, the slag phenomenon can be avoided by desulfurizing the molten steel liquid to 0.0015 wt% or less by the prior art.

Further, as shown in Fig. 2B, the weathering steels of Nos. 4 and 3 in which the clogging phenomenon occurred during the manufacturing process have an oxygen content of 0.0023 wt% (the lowest value of the oxygen content in all the weathering steels) and 0.0039 wt%. According to the above results, it can be concluded that whether or not clogging occurs is not absolutely related to oxygen content. Therefore, the oxygen content only needs to be deoxidized to about 0.0050 wt% according to the traditional weathering steel before the steel furnace (Blast Furnace) is tapped, without the need to additionally establish measurement or control technology in the steel drum. .

Further, the following experimental data will be used to illustrate that the recovery of the rare earth alloy and the occurrence of clogging can be improved by the present invention. Please refer to Tables 2 to 4 below. Table 2 shows the content of each component of the rare earth lanthanum iron powder in the rare earth lanthanum iron cored wire of the first embodiment of the present invention. Table 3 is used to indicate the block added in the first comparative example. The content of each component of the rare earth lanthanum iron raw material, and Table 4 shows the type, the added amount of the rare earth lanthanum iron raw material, the recovery rate of the rare earth alloy, and the rare earth lanthanum iron raw material in the first comparative example 1 and the third comparative example of Table 2. The sulphur content of the former molten steel, the rare earth alloy content of the weathering steel product, and whether the molten steel is clogged. The rare earth lanthanum iron powder corresponding to Table 2 is filled in the core wire of the carbon steel material, and the direction of the reel of the core wire is horizontal as described above. Further, in the first embodiment and the first comparative example described above, the content of each component of the final weathering steel falls within the range shown in the above Table 1.

According to the above Table 4, although the rare earth lanthanum iron is added in the first embodiment, since the raw material type is the cored wire, the rare earth lanthanum iron is directly injected into the molten steel under the protection of the cored wire shell, and the rare earth lanthanum iron is added. Previously, the sulfur content of the molten steel was controlled to 0.0015 wt% by means of desulfurization (the above-mentioned desulfurization step 104), so that a recovery rate of the rare earth alloy of about 38.5% was obtained, and no clogging of the molten steel occurred during continuous casting. On the contrary, since the raw material type of the comparative example is a block-shaped rare earth lanthanum iron, although the sulfur content of the molten steel is not controlled by the desulfurization method to 0.0015 wt% before the addition of the rare earth lanthanum iron, it can also prevent the continuous casting. The steel blockage occurred. However, in Comparative Example 1, since the rare earth alloy added was almost completely volatilized, the rare earth alloy recovery rate was only about 0.6%. Therefore, compared with the conventional rare earth lanthanum iron raw material type, the bulk type is adopted. If the rare earth lanthanum iron raw material type adopts the core-core type of the invention, the recovery rate of the rare earth alloy can be improved and the manufacturing cost can be reduced.

In addition, the RE content in Table 4 is the result of analyzing the steel liquid samples from 1/3 and 1/2 of the continuous casting, respectively. According to the results of Table 4, the rare earth of the process weathering steel of the present invention is used. The alloy has good distribution uniformity in molten steel. The definitions of the above 1/3 and 1/2 are explained by the following example. It is assumed that there are 150 tons of molten steel to be continuously cast, and 50 tons of them are continuously cast into the continuous casting mold, and the immersion nozzle is used. The molten steel sample is taken out, which is the definition of sampling at 1/3. Similarly, when 75 tons of continuous casting into the continuous casting mold, the steel liquid sample is taken at the immersion nozzle, which is the definition of sampling at 1/2.

The following is a description of the relationship between the sulfur content of the molten steel before the addition of the rare earth lanthanum iron raw material and the occurrence of clogging. Please refer to Table 5 below. Table 5 shows the type and amount of rare earth lanthanum iron raw material, the recovery rate of rare earth alloy, the sulphur content of molten steel before adding rare earth lanthanum iron raw material, and the weathering steel in the second and comparative examples. The content of the rare earth alloy and the clogging of the molten steel. In the second embodiment and the second comparative example, the content of each component of the rare earth lanthanum iron powder added is the same as that listed in the above Table 2. In addition, the rare earth lanthanum iron powder is also filled in the core wire of the carbon steel material, and the direction of the reel of the core wire is also horizontal.

According to Table 5, although the rare earth lanthanum iron is added in the second embodiment, since the sulfur content of the molten steel is controlled to 0.0015 wt% by the desulfurization method (the above-mentioned desulfurization step 104) before the addition of the rare earth lanthanum iron, There was no blockage of molten steel during casting. On the contrary, in Comparative Example 2, although rare earth lanthanum iron was added, the sulphur content of the molten steel was not controlled by desulfurization to 0.0015 wt% before the addition of rare earth lanthanum iron, so the sulphur content was as high as 0.0040 wt%. The steel blockage occurred during continuous casting. In addition, the RE content in Table 5 is the result of analyzing the steel liquid samples from 1/3 and 1/2 of the continuous casting, and the distribution of the rare earth alloys of the molten steel at different positions according to the results of Table 5. The uniformity is good.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and the present invention can be modified and modified without departing from the spirit and scope of the present invention. The scope is subject to the definition of the scope of the patent application attached.

100. . . Steel making process

102. . . Pre-steel step

104. . . Desulfurization step

106. . . Add rare earth alloy step

108. . . Post steelmaking step

For a better understanding of the present invention, reference is made to the above detailed description and the accompanying drawings. It is emphasized that, in accordance with the standard of the industry, the various features in the drawings are not to scale. In fact, the dimensions of the various features may be arbitrarily enlarged or reduced in order to clearly illustrate the above embodiments. The relevant schema description is as follows.

1 is a flow chart showing a steelmaking process of weathering steel according to an embodiment of the present invention.

2A and 2B are respectively a graph showing the relationship between the sulfur content in the molten steel before the addition of the rare earth lanthanum iron core wire in the ladle and the content of the rare earth alloy in the final weathering steel according to an embodiment of the present invention and a comparative example. And the oxygen content in the steel, and the relationship between the content of rare earth alloys in the final weathering steel.

100. . . Steel making process

102. . . Pre-steel step

104. . . Desulfurization step

106. . . Add rare earth alloy step

108. . . Post steelmaking step

Claims (10)

A steelmaking process for weathering steel, the weathering steel comprising a plurality of components, wherein the components are: carbon, bismuth, manganese, phosphorus, copper, chromium, nickel, rare earth alloy, oxygen, and a residue composed of iron The steelmaking process comprises: performing a pre-steeling step to prepare a molten steel liquid; performing a first desulfurization step to place the molten steel liquid in a steel ladle and performing a desulfurization process The sulphur content in the molten steel solution is less than 0.0015 wt% when calculated by weight percent (wt%); and a rare earth lanthanum core wire is added to the sulphur content less than 0.0015 wt%. In the molten steel liquid, the rare earth neodymium iron cored wire comprises a hollow cored casing and a rare earth lanthanum iron powder located inside the hollow cored shell, the rare earth lanthanum iron powder comprising a plurality of components: titanium, a ruthenium, manganese, calcium, a rare earth alloy, and a residue composed of iron; and a subsequent steelmaking step to obtain the weathering steel. The steelmaking process of claim 1, wherein the components of the weathering steel are calculated in wt%, and the content of the components is: 0.12 wt% or less of carbon, 0.25 to 0.55 wt% of bismuth, 0.20 to 0.50. Wt% manganese, 0.07~0.15 wt% phosphorus, 0.25~0.55 wt% copper, 0.30~1.25 wt% chromium, 0.65 wt% nickel, 0.07 wt% rare earth alloy, 0.0050 wt% or less oxygen And the remnant of iron. The steelmaking process according to claim 1, wherein the components of the rare earth lanthanum iron powder are calculated in wt%, and the content of the components are respectively: 3 wt% or less of titanium, 44 wt% or less, and 3 wt%. Manganese below 5%, calcium below 5 wt%, rare earth alloy of 21 to 42 wt%, and a residue composed of iron. The steelmaking process of claim 3, wherein the rare earth alloy of the rare earth lanthanum iron powder comprises a plurality of components, respectively, lanthanum, cerium and lanthanum, and when calculated in wt%, the cerium accounts for the rare earth alloy The overall ratio is greater than 46%. The steelmaking process of claim 1, wherein the hollow cored shell of the rare earth lanthanum cored wire is made of carbon steel. The steelmaking process of claim 1, wherein the pre-steeling step further comprises: performing a second desulfurization step to reduce the sulfur content in the molten steel. The steelmaking process of claim 1, wherein the pre-steel step further comprises: performing a deoxidation step to reduce the oxygen content in the molten steel. The steelmaking process of claim 1, wherein the post-smelting step further comprises: performing a continuous casting step of casting the molten steel in the ladle into a mold by continuous casting to obtain the Weathering steel. The steelmaking process of claim 1, further comprising: performing a rolling step to roll the weathering steel to a predetermined thickness. The steelmaking process of claim 9, wherein the rolling step is selected from the group consisting of a hot rolling step and a cold rolling step.