JPS6039453B2 - Manufacturing method of continuous casting mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a mold for continuous casting which has high hardness, excellent wear resistance, high thermal conductivity and excellent high temperature strength.

Copper and copper alloys are generally used in continuous casting molds for steel, and Ni or C has traditionally been used as a measure to improve lifespan.
R surface coatings have been put into practice, but they are still unsatisfactory in terms of service life.

Recently, a method of thermal spraying a Ni-based or Ni-Cr-based easily soluble alloy has been proposed as a new surface coating method, and some methods have been put into practice. In other words, there is a method in which Ni plating is applied to a steel or copper alloy slope and then thermally sprayed on top of the Ni plating without heat treatment, and a method in which Ni plating is applied on a sloped steel or copper alloy plate without heat treatment, and a method in which Ni plating is performed on a precipitation hardened steel alloy plate with the aim of restoring properties or improving adhesion after direct thermal spraying. This method involves chemical treatment, aging treatment, and precipitation aging treatment. However, since the former does not undergo heat treatment, it lacks the adhesion force required for continuous casting molds for steel, and while the latter has a considerably long life, its life varies greatly, and moreover, it is less than 10%. There was a drawback that partial peeling occurred at a ratio of h to 50 h, and repair thermal spraying had to be carried out each time. In addition, in order to investigate the thermal shock resistance of continuous casting molds using the latter direct injection method, a mold model obtained using a similar method (direct injection of a Ni-based eye-soluble alloy onto a precipitation-hardened steel alloy slope → Solution treatment at 955-1010°C for 1 hour → Rapid cooling →
As a result of repeated operations such as immersion in water after holding at 6000C for 3 minutes, all steel alloy plates and thermal spray coatings were partially or completely peeled off in 2 to 6 times. did.

However, when this mold model was subjected to solution treatment at a temperature of 1100 qo or more, no peeling phenomenon was observed even when the same operation as described above was performed and the IQ line was returned. On the other hand, regarding the effect on shrinkage alloy plates, according to research by the present inventors, such 96
If solution treatment is carried out at a high temperature exceeding 0.000 C, the crystal grains of the copper alloy will become coarser and the hardness will increase, but on the contrary, the elongation will decrease and the high temperature strength of the steel alloy will deteriorate, so heat treatment of the mold material is necessary. It was found to be inappropriate.

In addition, a Cu oxide film was formed on the peeled surface as a result of the above-mentioned repeated thermal shock test, and even in the microscopic structure, corrosion by the etching solution was severe at the interface between the copper alloy and the sprayed film, and at first glance it appeared that there was a diffusion layer (or alloy layer). ) appears to be formed, but it is thought to be an oxide film on the surface of the copper alloy. In addition, the copper oxide scale due to port treatment is 0.3.
A lateral layer was formed and this peeled off by water cooling. According to microscopic observation, the structure near the surface was clearly an oxide film. Furthermore, the results of the scale adhesion test were 4k9′ to 11k9.
'There was some variation within the candle range. Therefore, the adhesion force is low, and the thermal stress that the continuous casting mold receives is said to be as small as about 20 kg. From this point of view as well, variations in service life in practical use can be foreseen, which is not desirable. The present invention relates to a method for manufacturing a continuous casting mold that eliminates the above-mentioned drawbacks, and its gist is that Ni, Nj-Fe, Ni
-3000 after Co or Ni-Mn plating treatment
Heating at 0 to 400 oo for 2 to 8 hours produces Ni-based or Ni-Cr-based eye-soluble. 93
Pi 0~950℃×0.7 spot time~1. This is a method for manufacturing a continuous casting mold, which is characterized by performing solution treatment under conditions of approximately 100 minutes, followed by precipitation aging heat treatment in which the method is maintained at an appropriate temperature after rapid cooling.

The compositions of the Ni-Fe, Ni-Co, and Ni-Mn plating used here are as shown in Table 1 below, and the plating method may be either electroplating or electroless finishing, but the plating thickness Electroplating is more convenient since it is easier to adjust the plating composition, etc.

The plating conditions for electroplating are shown in Table 2 below. Table 1 Table 2 In this manufacturing method, the thickness of the plating layer initially performed as a base treatment is 50 to 100 mm, and then 300 mm is used to metallurgically bond this plated layer to the underlying copper alloy.
Heating is carried out at ~40,000 for 2 to 8 hours, but this heating is also meant to remove the ratio mixed in the plating layer, and if this heating treatment is not done, a blistering phenomenon will occur during the subsequent solution treatment process. It turns out.

Furthermore, the self-fusing alloy used in the present invention is a Ni-based or Ni-Cr-based alloy containing several percent of B or Si, which is melted by heating the film to 930 to 950°C after being fused with a gas flame or plasma flame. It is a material that allows the coating to be in a solid state and completely bond to the base material.

During the remelting process, the B and Si contained in this thermal sprayed alloy react with the oxide formed within the thermal sprayed layer, forming a B-Si glass coffin that melts at a relatively low temperature. It removes oxides, pores, etc. Furthermore, by the above-mentioned reheating, this sprayed layer forms an alloy layer with the underlying plating layer and is completely bonded to it.In this case, if the above-mentioned plating layer does not exist on the underlying plating layer, the surface of the steel sheet will be oxidized by the thermal spraying flame. ,
There may be areas where adhesion is insufficient, and the sprayed coating may peel off during remelting or use. Among the above-mentioned self-fusing alloys, BO. 5-2
．． Weir weight %, Sil. 5-4. Weight % of CO. 03～
1.1% by weight, Fe 5% by weight or less, Col weight% or less,
The balance is Ni, and as a Ni-Cr system, C
r15-20% by weight, B3.0-4.5% by weight, Si2
．． 0-5.0% by weight, CO. 5~]. 1% by weight, Fe5
6% by weight or less, Col by weight% or less, and the balance being Ni.
A material that has thermal fatigue resistance and wear resistance at temperatures below 00°C is sprayed to a thickness of 250 to 500 mm. In addition, Cr is added to this thermal sprayed layer to increase heat resistance, corrosion resistance, and wear resistance.
It is also possible to increase the amount of C or C, add Mo or Cu to increase corrosion resistance, add AI to increase heat resistance, or add WC or WC-Co to increase wear resistance. be. The solution treatment conditions to be performed next are 930oo~9.
The reason for the extremely limited range of 50oo x 0.75 hours to 1.5 hours is that if exposed to too high a temperature for a long time, the crystal grains of the copper alloy that is the base material will become coarser, so it is also desirable to use rapid cooling and aging after that. On the other hand, if the temperature is too low and the holding time is too short, the oxide film or pores formed in the sprayed coating will not be removed sufficiently. be. The precipitation aging heat treatment carried out as the final treatment step of the present method is to obtain the desired strength by precipitation of the second phase from the supersaturated solid port* body obtained by rapid cooling following the port body forming treatment, and is usually 400 o It shall be held for 3 to 4 hours before and after. The drawing shows a cross-sectional microscopic microstructure photograph of a continuous casting mold obtained by the method of the present invention, and as is clear from this photograph, there is a strong bond between the precipitation-hardened copper alloy plate 1 and the Ni layer 2 plated on its upper surface. A bonded alloy layer 3 is formed, and a strongly bonded alloy layer 5 is also formed between the Ni layer 2 and the sprayed alloy layer 4.

When we conducted a crucian cutting adhesion test using this as a sample, we found that both the steel alloy plate 1 and the Ni layer 2 and the Ni layer 2 and the thermal sprayed alloy layer 4 had a strong adhesion of 30k9/fence, which was consistent with the above. Even after repeating the same thermal shock test of 600 oo x 30 minutes and immersion in water 10 times, no peeling phenomenon was observed. Specific examples will be shown below.

Fabricate the types of continuous casting molds shown in Table 3 below,
The results of an actual operational test were as shown in Table 4.

Table 4 also includes similar test results for conventional molds for comparison. Table 3 Table 4 As is clear from the above Table 4, the mold according to the present invention does not cause the sprayed film to peel off during use, and can be used until the lower part of the mold becomes unusable due to wear, which is 1/2 compared to the conventional mold. There is approximately a five-fold increase in service life per coating.

As described above, according to the method of the present invention, there is a plating layer mainly composed of N between the surface layer of the Ni-based or Ni-Cr-based alloy solvent layer and the underlying precipitation-hardened alloy plate. It forms a strong alloy layer with both the copper alloy plate and the sprayed layer, which has the effect of exhibiting high adhesion.
In contrast to the advantages of excellent wear resistance and high-temperature strength properties of the Ni-Cr-based or Ni-Cr-based easily soluble alloys, the life of the mold is greatly improved.

A color photograph of the same drawing as the drawing is shown for reference.

According to this reference photograph, the explanation part about the above-mentioned drawing can be understood in more detail.

[Brief explanation of the drawing]

The drawing is a cross-sectional micrograph of the mold manufactured by the method of the present application, and the magnification is 20 pm. In the figure, 1: precipitation hardened copper alloy plate, 2: Ni layer, 3: alloy layer, 4: thermal sprayed alloy layer, 5: alloy layer.

Claims (1)

[Claims] 1 Ni, Ni-Fe, N on the surface of a precipitation-hardened copper alloy plate
300 after i-Co or Ni-Mn plating treatment
Heating at ℃~400℃ for 2~8 hours, spraying Ni-based or Ni-Cr-based self-fluxing alloy, and then heating at 930℃~930°C.
A method for manufacturing a continuous casting mold, which comprises performing solution treatment under conditions of 50° C. for 0.75 to 1.5 hours, followed by rapid cooling and then precipitation aging heat treatment in which the material is maintained at an appropriate temperature.