JPH045748B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing a copper alloy for plastic mold material. [Prior Art] Conventionally, ferrous carbon steel for machine structures or alloy steel for hot work tools has been often used as a material for plastic molding molds. Although this iron-based material has excellent high-temperature strength, it has poor thermal conductivity, so there is a large temperature gradient between the inside and outside of the mold, which makes the mold easily cracked and has a short lifespan. In addition, Cu-Cr is a material with high thermal conductivity.
Although alloys or Cu-Cr-Zr alloys are known, these materials have problems such as low strength at high temperatures. Due to improvements in quality such as strength and moldability, plastic products have come to be used in a wide variety of fields, and their production volume is increasing. The price of this plastic product is determined by how short the molding cycle time is. In particular, for large products, one cycle may take several tens of minutes, and there is a demand for the development of mold materials with high thermal conductivity in order to shorten molding time. [Problems to be Solved by the Invention] However, as mentioned above, while conventional iron-based mold materials for plastic molding have excellent high-temperature strength, they have poor thermal conductivity and are difficult to heat and cool during plastic molding. It has the disadvantage of being easily cracked by repeated thermal shocks. In addition, Cu-
Cr alloy or Cu-Cr-Zr alloy has poor high temperature strength;
When plastic molding is repeatedly subjected to compressive stress of 10 to 20 Kgf/mm ² , there is a problem in that the mold tends to deform in a short period of time. The present invention has been made in view of these problems, and is a method for producing a copper alloy for plastic molding mold material, which has excellent properties in both thermal conductivity and high-temperature strength. The purpose is to provide [Means for Solving the Problems] The method for producing a copper alloy for plastic mold material according to the present invention includes Ni; 0.4 to 4.0% by weight, Si; 0.1% by weight.
0.05 to 1.0% by weight, Zn; 0.05 to 1.0% by weight;
Contains Mg; 0.001 to 0.01% by weight (excluding 0.01% by weight), and 0.001 to 0.01% of at least one element selected from Cr, Ti, and Zr.
After hot working a copper alloy ingot containing 0.01% by weight (excluding 0.01% by weight) and the remainder being Cu and unavoidable impurities, it was heated to a temperature of 650 to 810°C for 5 minutes to 3 hours, and then It is characterized by cooling from a temperature of 600°C or higher at a cooling rate of 15°C/second or higher, and then annealing at a temperature of 400 to 550°C for 5 minutes to 4 hours. [Function] Hereinafter, the method for producing a copper alloy for plastic mold material according to the present invention will be explained in detail. Copper and copper alloys generally have excellent thermal conductivity but low high temperature strength. Therefore, in order to use it in plastic molds, it is necessary to strengthen copper alloys, and there are three types of strengthening methods for copper alloys: solid solution strengthening, work strengthening, and precipitation strengthening. Cu-Ni- excellent in both high temperature strength and thermal conductivity according to the present invention
Si-based alloys are precipitation-strengthened alloys. Next, the reasons for adding components and limiting the composition of the copper alloy according to the present invention will be explained. Ni Ni is an element that improves the strength of the copper alloy together with Si, which will be described later. If the Ni content is less than 0.4% by weight, no improvement in strength can be expected even if Si is contained in the range of 0.1 to 1.0% by weight. On the other hand, if Ni is contained in excess of 4.0% by weight, the workability of the copper alloy will deteriorate, and even if such a large amount is added, the effect of improving strength will be reduced. Therefore, the Ni content is between 0.4 and
4.0% by weight. Si Si is also an element that improves the strength of copper alloys. Si
If the content is less than 0.1% by weight, Ni is 0.4 to 4.0
Even if it is contained in weight%, no improvement in strength can be expected. Moreover, if Si is contained in excess of 1.0% by weight,
Processability and thermal conductivity are reduced, and plating properties are also reduced. Therefore, the Si content is 0.1 to 1.0% by weight.
shall be. Zn Zn is used when plating with P-containing Ni or Cr, etc.
It is an essential element to suppress the peeling. However, when the Zn content is less than 0.05% by weight, this effect is small. On the other hand, even if Zn is contained in an amount exceeding 1.0% by weight, the effect of suppressing plating peeling does not substantially improve, but the plating properties deteriorate.
Therefore, the Zn content is set to 0.05 to 1.0% by weight. Mg Mg is an essential element for improving hot workability, and reacts with low melting point S mixed into the copper alloy to form high melting point MgS. Mg content
If it is less than 0.001% by weight, the effect is small;
If it exceeds 0.01% by weight, a low-melting-point eutectic occurs with Cu, making hot working difficult and making the molten metal more likely to oxidize, reducing flowability and making it impossible to obtain a sound ingot. Therefore, the Mg content is set to 0.001 to 0.01% by weight (excluding 0.01% by weight). Cr, Ti, Zr Cr, Ti and Zr strengthen the grain boundaries of the ingot and improve hot workability. These elements strengthen grain boundaries,
It has the same effect, but if the amount added is less than 0.001% by weight, the effect will be small, while if it is contained in more than 0.01% by weight, the molten metal will be easily oxidized and a healthy ingot will not be obtained. Therefore, the contents of Cr, Ti, and Zr are all 0.001 to 0.01% by weight (0.01% by weight
). Furthermore, in addition to the above-mentioned elements, Mn, Fe, Co,
0.2% by weight of one or more elements of Sn and Al
It may be contained in the following amounts. Even if these elements are contained, the properties necessary for the product, ie, high temperature strength, thermal conductivity, heat resistance, hot workability, etc., can be maintained without causing any practical problems. Next, a method for manufacturing a copper alloy for plastic mold material having the above-mentioned composition will be explained. First, hot working is started at a temperature of 800 to 870° C., for example, to an ingot obtained by casting an alloy having the composition specified in the present invention by a normal semi-continuous casting method. In this hot working, if the finishing temperature is 825°C or higher, the crystal grains will coarsen to 50 μm or more, and although the strength will be improved after precipitation hardening annealing, which will be described later, the grain boundaries will become brittle and impact resistance at high temperatures will increase. value decreases, and thermal shock resistance deteriorates. Therefore, it is preferable to perform hot working while adjusting the temperature so that the hot working end temperature is 810° C. or lower. Because the grain size of hot-worked materials varies depending on the size of the ingot, processing schedule, or location of the workpiece, it is necessary to make the grains uniform, so
Annealing is performed by heating at a temperature of 5 minutes to 3 hours. If this annealing temperature is less than 650°C, Ni ₂ Si will precipitate, and cracks will occur when the rolled material is straightened with a leveler. On the other hand, when the annealing temperature exceeds 825°C, the crystal grains become coarse to 50 μm or more, and embrittlement cracks are likely to occur after precipitation hardening annealing. Further, if the annealing time is less than 5 minutes, the uniformity of crystal grains is insufficient, and conversely, annealing for more than 3 hours is wasteful. Therefore, the annealing time is 5 minutes to 3
Time. Next, it is cooled from a temperature of 600°C or higher at a cooling rate of 15°C/second or higher. If this cooling start (quenching) temperature is less than 600℃, even if the cooling rate is 15℃/second or higher, Ni and Si will not form a solid solution and will begin to precipitate before precipitation hardening annealing. Coagulates and becomes coarse. Similarly, if the cooling rate is less than 15°C/sec, even if cooling starts from a temperature of 600°C or higher,
Precipitates aggregate and become coarse. Therefore, the quenching temperature is
The temperature shall be 600℃ or higher, and the cooling rate shall be 15℃/second or higher. Next, the copper alloy is annealed for precipitation hardening, and this precipitation hardening annealing is performed in a temperature range where the amount of Ni ₂ Si precipitated is the largest. That is, the temperature at which the electrical conductivity is highest is 500° C., and when the annealing temperature exceeds 550° C., Ni ₂ Si dissolves in solid solution, the amount of precipitation decreases, and the electrical conductivity and thermal conductivity decrease. On the other hand, if the annealing temperature is less than 400℃, Ni ₂ Si
The amount of compound precipitated is small, and the effect of improving strength cannot be sufficiently obtained, and the thermal conductivity is also low. Therefore,
The annealing temperature is 400 to 550°C. If the annealing time is less than 5 minutes, the amount of precipitation will be insufficient, and annealing for more than 4 hours is wasteful from a thermoeconomic standpoint. Therefore,
The annealing time is 5 minutes to 4 hours. [Example] Next, regarding the results of manufacturing the copper alloy for plastic mold material according to the example of the present invention and testing its various properties, we will discuss the results of the comparison example alloy which is outside the scope of the claims of the present invention. This will be explained along with the test results. Table 1 below shows the composition of each alloy of Examples 1 to 6 and Comparative Examples 1 to 4.

[Table] An alloy having the chemical composition shown in Table 1 was melted while waiting in an electric furnace under charcoal coating, and the thickness was 50 mm.
An ingot with a width of 80 mm and a length of 180 mm was cast. Next, the front and back surfaces of each ingot were milled by approximately 2 mm, and then heated at 850°C.
and hot worked until the thickness was 15 mm.
Next, for example alloys No. 1 to 3, the temperature was 725°C.
For example alloys No. 4 to 6,
It was reheated to 800°C and then rapidly cooled down in water. The cooling rate at this time was 30°C/sec. Next, 500℃
After annealing by heating to a temperature of 2 hours, tensile test,
Specimens were taken for compression tests, Charpy impact tests, and thermal conductivity measurement tests. Table 2 below shows the test results for each property of the example alloys and comparative example alloys. However, Comparative Example 5,
Column 6 shows the properties of the Cu-1 wt % Cr alloy and carbon steel for mechanical structures, respectively.

[Table] As is clear from this Table 2, Example Alloy 1
6 to 6 are all compressive stresses of 10 to 10 that are applied to the mold during plastic molding processing even at high temperatures of 300°C.
It can fully withstand 20Kgf/mm ² and the mold will not be deformed. In addition, the thermal conductivity is approximately 0.5 cal/cm
sec° C. or more, and the copper alloys of Examples 1 to 6 have an extremely high thermal conductivity that is 5 to 8 times that of iron-based materials. Next, copper alloys manufactured by the method of the present invention will be explained together with comparative examples thereof. The front and back surfaces of ingots having the same composition as the copper alloys of Examples 2 and 5 shown in Table 1 above were milled by 2.5 mm, and then heated at 850°C.
The material is heated to a temperature of 45 mm to 15 mm, and then reheated to one of five temperatures: 700°C, 750°C, 775°C, 810°C, 825°C, and 850°C. , annealed for 30 minutes. Then, this annealed material
It was rapidly cooled by placing it in water at a temperature of 700°C. The cooling rate at this time was 30°C/sec. Next, 350 to
In the temperature range of 600°C, one of the six annealing temperatures set at intervals of 50°C was selected, and precipitation hardening annealing was performed by heating to this annealing temperature for 2 hours. Thereafter, test pieces for a tensile test and a Charpy impact test were taken. Table 3 below shows the manufacturing conditions of the example method and the comparative example method, and the test results of the alloys manufactured under the conditions. However, if the alloy composition No. column is 2, the composition of the copper alloy manufactured by each method should be the same as the above-mentioned 1.
The composition is the same as the composition in the Example 2 column of the table, and in the case of 5, the composition is the same as the composition in the Example 5 column. FIG. 1 is a graph showing the relationship between the reheating temperature after hot working on the vertical axis and the crystal grain size on the horizontal axis. In FIG. 1, the solid lines indicate alloys with the same composition as Example Alloys 1 to 3 in Table 1;
The broken line shows alloys having the same composition as Example Alloys 4 to 6, but at different reheating temperatures. As is clear from FIG. 1, when reheated to a temperature of 825° C. or higher, the crystal grain size becomes coarser to 50 μm or higher. On the other hand, when the reheating temperature is 810° C. or lower, the crystal grain size is 50 μm or lower.

[Table] Also, as is clear from Table 3, all the copper alloys produced by the example method of the present invention have excellent high-temperature elongation and sharpie impact values, and therefore are suitable for plastic molding with high thermal shock resistance. It is possible to manufacture molds for use. [Effects of the Invention] As explained above, according to the present invention, a copper alloy can be obtained which has excellent high temperature strength and thermal shock resistance and is extremely reliable as a material for plastic molds. Because of its high conductivity, it has the excellent effect of significantly shortening the time required for plastic molding.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between reheating temperature and crystal grain size.

Claims (1)

[Claims] 1 Ni; 0.4 to 4.0% by weight, Si; 0.1 to 1.0% by weight, Zn; 0.05 to 1.0% by weight, and Mg; 0.001 to 1.0% by weight.
Contains 0.01% by weight (excluding 0.01% by weight), and 0.001 to 0.01% by weight (excluding 0.01% by weight) of at least one element selected from Cr, Ti, and Zr, with the remainder being Cu. After hot working a copper alloy ingot containing unavoidable impurities, 650
Heating to a temperature of 5 minutes to 3 hours at a temperature of 810°C to 810°C, then cooling at a cooling rate of 15°C/second or more from a temperature of 600°C or higher, and annealing to a temperature of 400 to 550°C for 5 minutes to 4 hours. A method for producing a copper alloy for plastic mold material, characterized by: