JPH0314896B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a continuous casting mold that has excellent heat resistance and is suitable for continuous casting of steel, and a method for manufacturing the same. [Conventional technology] In recent years, continuous steel casting has undergone operational technological improvements such as faster casting speeds and shorter casting cycles, which has resulted in molds being used in harsher environments. It has become a thing. BACKGROUND ART Conventionally, phosphorus-deoxidized steel, which has good thermal conductivity, easy production, and low cost, has been generally used as a mold material for continuous steel casting. However, when the temperature of the inner wall of the mold rises to a high temperature of approximately 250°C during continuous casting, the inner wall of the mold softens and becomes difficult to withstand the thermal stress generated between the inner and outer walls of the mold, causing deformation and wear. Become.
For this reason, conventional phosphorus-deoxidized copper molds have a short lifespan. Therefore, there is a need to develop a mold for continuous steel casting that has excellent wear resistance and heat deformation resistance in place of the conventional phosphorus-deoxidized copper. Therefore, as a material that meets this demand, Cu-Cr
-Zr-based alloys and Cu-Fe-P-based alloys are attracting attention. [Problems to be solved by the invention] However, Cu-Cr-Zr alloys are difficult to form into agglomerates in the air, and in order to manufacture them, casting methods that can be melted in a vacuum or under an inert gas atmosphere are required. Requires equipment. For this reason, manufacturing costs for castings made from this alloy are high. Moreover,
Because it contains Cr, it is subject to restrictions in terms of pollution. Cu-Fe-P alloy is a precipitation-strengthened copper alloy, which requires a cold drawing process at a low processing rate after hot working.
It is manufactured by aging treatment and an annealing process to remove local stress. By the way, it is necessary that the mold can be manufactured at the same cost as conventional phosphorus-deoxidized copper, and for this purpose, it is a prerequisite that it can be manufactured in the same manufacturing process as phosphorus-deoxidized copper. That is, if it can be manufactured by hot piercing similar to phosphorus-deoxidized copper, conventional equipment can be used as is. However, when the inventors of the present application repeated manufacturing experiments, they found that the cold working rate after piercing hot working was low. Therefore, Cu−Fe
It was found that the -P-based alloy did not recrystallize, causing an abnormal structure and weakening the grain boundaries. If the grain boundaries are weak in this way, cracks will occur during the subsequent cold drawing process, making it difficult to commercialize the product. The present invention has been made in view of such problems, and provides a continuous casting mold that has properties superior to Cu-Fe-P alloys, has particularly excellent heat resistance, and has a long life. For continuous casting, this mold can be manufactured by applying the hot piercing method in the same way as the manufacturing process of conventional phosphorus-deoxidized copper molds, while avoiding the occurrence of cracks in the cold drawing process after hot piercing. The purpose is to provide a method for manufacturing a mold. [Means for solving the problems] The heat-resistant continuous casting mold according to the present invention contains 0.05 to 0.20% by weight of Fe, 0.02 to 0.05% by weight of P,
The present invention is characterized in that a copper alloy containing 0.05 to 0.20% by weight of Ag, 0.05 to 0.15% by weight of Ni, and the balance being substantially Cu is produced. The method for manufacturing a heat-resistant continuous casting mold according to the present invention contains 0.05 to 0.20% by weight of Fe, 0.02 to 0.05% by weight of P, 0.05 to 0.20% by weight of Ag, and 0.05 to 0.15% by weight of Ni. The remainder is essentially Cu.
The process involves heating a copper alloy ingot to a temperature of 750 to 900°C and piercing it, and then using the resulting raw pipe.
A process of cold drawing with an area reduction rate of 30 to 45%,
A first stage annealing step of heating at a temperature of 650 to 750°C for 30 minutes to 4 hours; a second stage annealing step of heating at a temperature of 500 to 625°C for 30 minutes to 4 hours;
A process of cold drawing and drawing into mold shape with a total area reduction of 45%, and a process of cold drawing and drawing into a mold shape at a temperature of 250 to 400°C.
It is characterized by having a third stage annealing step in which local stress is removed by heating for a minute to four hours. [Example] The present invention will be specifically described below. First, the reasons for adding the components of the heat-resistant copper alloy constituting the heat-resistant continuous casting mold according to the present invention and the reasons for limiting the composition thereof will be explained. Fe (iron), which is an Fe-containing component, has a small effect of improving wear resistance and strength when used alone, and also has a small effect of improving high temperature properties such as heat resistance and high temperature tensile strength. However, by containing Fe together with P (phosphorus), iron phosphide of Fe ₂ P is formed, which improves wear resistance, strength,
Both heat resistance and high temperature tensile strength are increased, and excellent properties can be exhibited. In this case, if the Fe content is less than 0.05% by weight, the above effects will be small. Furthermore, if Fe is contained in an amount exceeding 0.20% by weight, even if P is contained in a range of 0.02 to 0.05% by weight, Fe is dissolved in the copper alloy base material, resulting in a decrease in electrical conductivity. Therefore, the Fe content is between 0.05 and
The content shall be 0.20% by weight. As mentioned above, P P becomes iron phosphide Fe ₂ P due to coexistence with Fe.
to increase wear resistance, heat resistance, and high and room temperature strength. 0.05 if the P content is less than 0.20% by weight
Fe ₂ P formed by combining with 0.20% by weight of Fe
Since the amount is small, the above-mentioned effect of improving mechanical strength is small. Additionally, if the P content exceeds 0.05% by weight, a eutectic of Cu + Cu ₃ P (melting point 174°C) will occur at the grain boundaries of the ingot itself, resulting in intergranular cracking during hot piercing at temperatures of 700 to 900°C. Occur. Furthermore,
At temperatures lower than 700℃, the deformation resistance increases,
Processing becomes difficult. Therefore, the P content is between 0.02 and
The content shall be 0.05% by weight. Ag The present invention is characterized by containing Ag (silver). This Ag is an essential element for improving heat resistance, and even if this element is solidly dissolved in the copper alloy base material, it does not significantly reduce the electrical conductivity and improves the strength and heat resistance. When the Ag content is less than 0.05% by weight, the above-mentioned heat resistance improvement effect is small;
On the other hand, containing more than 0.20% by weight of Ag
This is a waste considering that it is expensive. Therefore, the Ag content is set to 0.05 to 0.20% by weight. Ni Ni (nickel) is an element that contributes to improving the strength of copper alloys. This effect is small when the Ni content is less than 0.05% by weight, and when it exceeds 0.15% by weight.
When Ni is contained, the conductivity of the copper alloy decreases.
Therefore, the Ni content is set to 0.05 to 0.15% by weight. A copper alloy with such a composition is Cu-Fe-
Compared to P-based alloys, the conductivity does not decrease,
Its heat resistance has been significantly improved. This copper alloy also has excellent strength at room temperature and high temperature. Therefore, the continuous casting mold made of this copper alloy is
It is difficult to deform even if thermal stress is applied during continuous casting operation, resulting in a longer service life, smoother operation, and improved productivity. Next, a method for manufacturing a heat-resistant continuous casting mold according to the present invention will be described. First, a copper alloy ingot containing the above-mentioned components in the above-mentioned range is heated to a temperature of 750 to 900°C and hot worked by a piercing method to obtain a raw pipe. Next, this raw pipe is subjected to cold drawing at a low reduction rate of 30 to 45%, and then subjected to two consecutive stages of annealing. In the first annealing process, this raw tube is
Annealing is performed by heating at a temperature of 650 to 750°C for 30 minutes to 4 hours. This uniformly recrystallizes the cold structure at a low working rate of the piercing material, and prevents cracks from occurring in the next cold drawing process. When the annealing temperature is less than 650°C, the copper alloy does not recrystallize, resulting in low elongation and poor workability. As a result, cracks occur during the next cold drawing process. On the other hand, the annealing temperature is 750℃
If it exceeds 2, recrystallization occurs and the crystal grains become larger, which weakens the grain boundaries and reduces hardness and strength. Therefore, the annealing temperature in the first annealing step is 650 to 750°C. An annealing time of 30 minutes or more is required to obtain the above effects. On the other hand, from the viewpoint of energy saving, it is wasteful to carry out heat treatment for a long time, so the annealing time is set to within 4 hours. In the second annealing step, this raw tube is annealed by heating to a temperature of 500 to 625° C. for 30 minutes to 4 hours. This second stage annealing is performed to precipitate iron phosphide (Fe ₂ P). This precipitation of Fe ₂ P increases the electrical conductivity and slightly increases the strength. but,
At temperatures below 500°C, precipitation is insufficient even if heated for 30 minutes to 4 hours, and at temperatures above 625°C, although precipitation occurs, the amount of precipitation is small.
The effect of improving conductivity is small. Therefore, the annealing temperature in the second annealing step is 500 to 625°C. When the annealing time is less than 30 minutes, precipitation is insufficient even if heated to a temperature of 500 to 625°C, and when the annealing time exceeds 4 hours, it is not economical from the viewpoint of energy saving. Therefore, the annealing time is 30 minutes to 4 hours. Next, the raw pipe is subjected to cold drawing processing, and further, for example,
Draw into a square mold shape. This cold drawing and drawing into the mold shape have a total area reduction rate of 30 to 45.
%. Next, 250 to 400 pieces of pipe material forming this mold shape are
Anneal by heating to a temperature of 30 minutes to 4 hours. This third annealing is for removing local stress caused by cold drawing. Annealing temperature is 250
This effect is small when the temperature is less than 400°C.
Annealing at temperatures above °C reduces hardness.
Therefore, the annealing temperature is 250 to 400°C. If the annealing time is less than 30 minutes, the above-mentioned effect will be small, and heating for more than 4 hours will be wasteful. Therefore, the annealing time is 30 minutes to 4 hours. Next, Examples 1 to 3 in which pipe molds for continuous steel casting with excellent heat resistance were manufactured by the method of the present invention will be described together with Comparative Examples 1 to 3. Among the copper alloys with the composition shown in Table 1 below, alloys No. 1 to No. 4 were melted under charcoal coating in a 6-ton coreless furnace to form an ingot with an outer diameter of 205 mm and a length of 1000 mm. .

[Table] Next, this ingot was cut to a length of 740 mm, and
It was heated to ℃ and hot-worked using the piercing method to obtain a raw tube with an outer diameter of 204 mm, an inner diameter of 165 mm, and a length of 4170 mm. Next, this raw tube was rapidly cooled in water from a temperature of 650 to 680°C. From this raw pipe after piercing, the thickness is 19
Cut out a test material with a width of 150 mm and a length of 200 mm.
After cold rolling at a processing rate of 40%, it was heated to a temperature of 675 to 700°C for 45 minutes as shown in Table 2 below.
A stage annealing was performed, and then a second stage annealing was performed by heating at a temperature of 525 to 600° C. for 4 hours. Furthermore, oxidized scale is removed with sulfuric acid, and the processing rate is 35%.
%, in Examples 1 to 3, the third stage of annealing was performed by heating at a temperature of 350° C. for 2 hours to remove stress. Thereafter, samples for characteristic tests were taken from each test material. In addition, in the case of Comparative Example 3 of Alloy No. 5,
The intermediate first stage annealing conditions were a temperature of 400℃ for 30 minutes,
The annealing conditions for final local stress relief were 200° C. for 2 hours. In addition, Comparative Example 1 using No. 2 alloy has 500
Although it had been annealed once at a temperature of 10°C, cracking occurred during the process after piercing. Next, various property tests were conducted using these samples. The results are shown in Table 2 below. The test method is as follows. (1) Tensile strength and yield strength were tested using a 5 mm thick JIS No. 13 B test piece cut out parallel to the rolling direction. The sample was heated to 300℃ using an infrared heating furnace.
After holding at a temperature of 15 minutes, a tensile test was performed. (2) Hardness was measured using a Bitskars hardness tester under a load of 5 kg. (3) Electrical conductivity was measured using a commercially available electrical conductivity meter. Then, using a separately prepared test piece of the same type with a thickness of 2 mm, the values measured by this conductivity measuring device and
Corrected with the measured value using the double bridge method of JISH0505. In addition, heat resistance is determined by the hardness after heating the sample for 25 hours.
It is indicated by the heat treatment temperature (°C) at which Hv reaches 80% of the initial hardness.

[Table] In addition, Examples 1 to 3 used alloy Nos. 1 to 3, respectively, and Comparative Examples 1 to 3 used alloys Nos. 2, 4, and 5, respectively.
This is what was used. As is clear from Table 2, in Examples 1 to 3, the heat treatment temperature (heat resistance) at which the hardness Hv after 25 hours of heating is 80% of the initial hardness is as high as 340 to 360°C, and the heat resistance is high. is excellent. That is, in Examples 1 to 3, cold drawing cracking after piercing, which has been a problem in the past, does not occur, and the heat resistance is improved and the life of the mold is extended. Furthermore, it can be seen that Examples 1 to 3 are comprehensively superior to Comparative Examples in other characteristics at room temperature and high temperature. In contrast to Examples 1 to 3 above, Comparative Example 1 uses alloy No. 2 having the same composition as Example 2, but since the intermediate heat treatment was only one annealing at 500°C, A crack occurred during the piercing process. In addition, since alloy No. 4 does not contain Ag,
Comparative Example 2 using this alloy has the same heat resistance as Example 2.
Compared to 3 to 3, it is inferior at 325°C. In addition, Alloy No. 5 is a conventional phosphorus-deoxidized copper, and Comparative Example 3 using this alloy has inferior heat resistance compared to Examples 1 to 3, as well as other room temperature characteristics and high temperature (300 °C) All of the characteristics are inferior. As described above, the molds manufactured by the example method of the present invention are significantly superior to the comparative examples, especially in terms of heat resistance. Also, room temperature and high temperature (300℃)
The strength in Examples 1 to 3 was also that of Comparative Examples 1 to 3.
It is superior to . As a result, the tubular mold for continuous steel casting manufactured by the method of this example has excellent heat resistance, which is an essential property, and has high deformation resistance against thermal stress during continuous steel casting, and has a long mold life. I know it's long. [Effects of the Invention] As explained above, according to the present invention, a pipe mold for continuous steel casting can be manufactured using piercing processing in the same manner as before, and the manufacturing process is the same as that of conventional phosphorus-deoxidized copper. It can be manufactured at low cost depending on the process. The obtained mold has an electrical conductivity that is almost the same as that of the Cu-Fe-P alloy, but has higher heat resistance, which is an essential property for a mold, compared to this alloy and conventional phosphorus-deoxidized copper. performance has been significantly improved. In addition, other room temperature and high temperature (300°C) properties are also superior to conventional products. Therefore, when the mold according to the present invention is used as a tube mold for continuous steel casting, it is difficult to deform even when subjected to thermal stress. This has the excellent effect of facilitating continuous casting operations and improving productivity.

Claims (1)

[Claims] 1 0.05 to 0.20% by weight of Fe, 0.02 to 0.05% by weight of P, 0.05 to 0.20% by weight of Ag, and 0.05 to 0.05% by weight
A heat-resistant continuous casting mold characterized by being made of a copper alloy containing 0.15% by weight of Ni and the remainder being substantially Cu. 2 0.05 to 0.20 wt% Fe, 0.02 to 0.05 wt% P, 0.05 to 0.20 wt% Ag, and 0.05 to 0.05 wt%
A process of heating a copper alloy ingot containing 0.15% by weight of Ni and the remainder being substantially Cu to a temperature of 750 to 900°C for piercing, and a process of piercing the resulting raw pipe for 30 minutes.
A process of cold drawing with an area reduction rate of 45%,
a first stage annealing process of heating at a temperature of 650 to 750°C for 30 minutes to 4 hours; a second stage annealing process of heating at a temperature of 500 to 625°C for 30 minutes to 4 hours;
% of the total area reduction rate, and a third stage annealing process in which local stress is removed by heating at a temperature of 250 to 400°C for 30 minutes to 4 hours. 1. A method for producing a heat-resistant continuous casting mold, comprising: