JPS5961544A - Prehardened mold material for casting high melting metal - Google Patents

Abstract

PURPOSE:To obtain a prehardened mold material for casting a high melting metal having 15-20HRC hardness by subjecting a casting alloy prepd. by adding Ni, Si and Zr to Cu to an age hardening treatment in a combination of an adequate component range and a heat treatment condition. CONSTITUTION:A casting alloy is composed, by weight %, of 2.5-8 Ni, 0.3-2 Si, 0.04-0.25 Zr and the balance Cu. Such casting alloy is hardened and cooled at the cooling rate higher than the cooling for 30min half cooling time from 850-950 deg.C and is then subjected to an age hardening treatment at 400-550 deg.C. The casting alloy may be composed of 3-6 Ni, 0.5-1.5 Si, 0.06-0.2 Zr and the balance Cu or 2.5-8 Ni, 0.3-2 Si, 0.2-1 Cr and the balance Cu.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to 7e, an OuNiSi-Zr-1Or based pre-hardened mold material suitable for a mold material for casting high melting point metals such as Ou gold alloys. High temperature Fe
, In mold casting of Ou-based alloys, heat cracks mainly in thin-walled parts due to large thermal shocks, melting of protrusions, mold warping related to the balance between thermal stress and strength due to temperature gradients, and runners. Major problems include mold warpage due to the balance between thermal stress and strength due to temperature gradients, melting loss and sagging of runners, and sagging due to mold clamping.

In addition, the strength of the mold material may decrease during use due to the thermal effect of rising temperatures in thin-walled parts of the mold and parts of the mold that are difficult to cool internally with water, and may gradually become sagging, heat cracks, and melt damage.

An example of general hot work tool steel is JIS SKD61 (50r
- Even if Mo-V@) is used, the thermal conductivity is low, and it satisfies the required usage performance because of cracks due to excessive increase in hardness when subjected to localized re-quenching effects. There were times when it was difficult.

On the other hand, using pure #il yarn material with extremely high thermal conductivity will help reduce thermal stress, but its strength is inherently low.
It is difficult to meet the required lifespan due to wear and tear due to clamping pressure, and it is practically impossible to repair the mold by welding, making it difficult to use it as a mold material.

The present invention adds Zr and Or to an Ou-Ni-Si alloy known as a Ni-3i precipitation hardening alloy,
This material has further improved resistance to softening when the temperature rises, which is necessary for a mold material, and can be applied as a mold material for casting high-melting point metals by combining the appropriate composition range and heat treatment conditions, without causing softening due to temperature rise during use. This is based on the findings that it provides a good mold life, and provides a new brihardon mold material for casting high-melting point metals.

Table 1 shows an example of the composition of the invention material and a quenching temperature of 900U.
The hardness of sheet metals subjected to age hardening at 500C for 2 hours after quenching at various cooling rates and the hardness of sheet metals subjected to air cooling at 900C and overaging at a high temperature of 600C for 2 hours are shown.

The aging hardness value is relatively high as the quenching cooling rate is low, the degree of decrease in aging hardness is relatively small, and the material has properties that prevent strength loss due to temperature rise during use. I understand.

Table 1 The quenching cooling rate for releasing 11RO15 or more required for the mold material for this purpose2) is a half-cooling time of approximately 30 m1n.

Table 2 shows the tensile properties of the materials of the present invention.

Table 2 Both have the necessary ductility as mold materials.

One of the characteristics of the material of the present invention is that it is easy to obtain high hardness, but the increase in hardness has a permissible limit depending on the balance with ductility.

Table 3 shows the thermal conductivity of the materials of the present invention.

Table 3 The materials of the present invention have a thermal conductivity lower than that of pure copper, and the pz is clearly higher than that of hot work tool steel SKD 61, which is 0.07.

Table 4 shows the heat crank resistance test results of the materials of the present invention.

The test piece is 30mmφ x 20mm, and the 30mmφ surface is heated by Nono Lee (the surface temperature of the material A of the present invention is controlled at 500C).
After repeating the water cooling operation 2,000 times, cracks appeared (crack along the center 15mm surface of 30 mm diameter)
A cross-section was observed.

Table 4 The materials of the present invention did not cause surface irregularities or heat cracks.

Comparative material L (pure copper) did not cause heat cracks, but it did have some unevenness due to its low strength.

Table 5 shows the results of the erosion resistance test for the materials of the present invention.

The test pieces in Table 5 are the results of a cylindrical test with a diameter of 30 mm (14 mm) and a 18-8 stainless steel mesh made of 1650 C and passed through the inner surface of the cylinder at high speed 500 times. The results of measuring the maximum depth of erosion on the inner surface are shown.

The melting damage size is relatively smaller than that of the material of the present invention.

This is because it has a combination of thermal conductivity, strength, and resistance to softening at elevated temperatures.

Comparative material L (pure copper) has low strength and has been subjected to relatively large blast furnace action.

Table 6 shows the weldability of the present IA-invention materials.

The welding method is 1 to 110CsφX20 fin test piece block.
A recess with a depth of 5t+mφ×lo was made, and each material was welded by TIG welding after preheating to 450C.

Table 6 The materials of the present invention can be overlaid by welding, and no internal defects were observed when cross-sectionally observed. Comparative forest material L (pure copper) could not be overlaid by welding.

This is because the heat conductivity of the welded part is high, and normal build-up is difficult.Next, the reason for the Group 1 minute limit for the material of the present invention will be described.

Ni and Si are dissolved in the matrix by solid solution treatment, and are formed and precipitated by aging treatment to form Ni-81, a gold-coated compound (Ni-81, which is precipitated) to provide the necessary basic strength as the material of the present invention.

It is also added to provide appropriate thermal conductivity and related properties such as heat crack resistance, erosion resistance, weldability, and mold clamping resistance.

If it is too high, the thermal conductivity will be excessively reduced, and if it is too low, the effect of the above addition cannot be obtained.
2.00%.

A more preferable range of N1 and Sl is N13.00 to 600.
%, and Si 0.50 to 1.50%.

Zr and Or are added to improve precipitation hardenability during aging treatment, prevent hardness from decreasing in the overaging temperature range, prevent strength from decreasing due to temperature rise during use, and improve mold life.

If it is too high, it will cause a decrease in thermal conductivity and toughness, and if it is too low, the effect of the above addition will not be achieved by 1M, so Zr is 0.0 yen-
0.25%, Or is 0.20-1. 0%. Or is cheap and advantageous for increasing aging hardness, but when prevention of softening during overaging is particularly important, addition of Zr is more effective. Depending on the purpose and use, Zr and or may be added alone or in combination. . When added alone, the more preferable range for zr is 0.06-0.20%, and the more preferable range for Or is α30-0.70%.

The heat treatment is carried out at a solution treatment temperature in the range of 850-950p to prevent coarsening of crystal grains and the formation of molten phase, and the quenching cooling rate is set to ensure the necessary hardness while preventing the generation of extremely large residual stress. In order to prevent this, the cooling rate is controlled within a range that is faster than the half-cooling time of 30mln.

If the cooling rate is slower than this, it will not necessarily be possible to obtain the required weak degree HRO of 15 or more, and on the other hand, if the awn is too high, machinability and physical properties will decrease, so the HRO should be 35 or less.

As described in Section 2 below, the material of the present invention is a 0u-Ni-8i material that utilizes precipitation strengthening of a Ni-8i gold metal compound, with the addition of Zr and Or, and is used as a mold material for casting high-melting point metals. The pre-hardened gold obtained by examining the proper combination of component balance and heat treatment to provide heat crack resistance, strength, ductility, softening resistance to high temperatures, erosion resistance, and weldability. It is a mold material that has good machinability, and can be used as is after being processed into a mold, contributing to good mold life and improved molding efficiency by shortening the molding cycle RN'=J.

Claims (1)

[Claims] L Ni2-50-8.00%, Si0.30-2.
A forged or cast alloy consisting of OO%, Zr0.04w O, 25%, and the balance O is quenched and cooled at a temperature of 400-550C from 850-950C with a cooling rate faster than half-cooling time of 30 min. H after age hardening treatment
Purino 1 for high melting point metal casting with hardness of RO15-35
-Ton type material. 2. Ni3. OO~6.00%, S10.50-1
．． 2. The Blino-ton type material for casting high melting point metals according to claim 1, comprising 50% Zr, 0.06% Zr, 20% O and the balance O. 3. N12=50~&00%, Si0.30~ZO
O%, Oro, 20~l, 00%, the balance O is a cast or @cast alloy made from 850-9501:l', and is quenched and cooled at a cooling rate faster than the half-cooling time of 8φm1℃, and then heated to 400-550fC. A Blino-ton type material for casting high melting point metals which has been age hardened at a temperature of 15 to 35 HRO. 4 Ni3. OO~6.00%, Si0.50~1.5
4. The Prino-ton type material for casting high melting point metals according to claim 3, comprising 0%, Oro, 30 to 0.70%, and the balance Ou. 5, Ni2-50-400%, Siα50-1.5
0%, Zr0.04~0.25%, 〇920~1.00
%, the balance O for forged or cast alloy 85 M
After quenching and cooling at a faster cooling rate than 50'C with a half-cooling time of 30ml, high melting point gold Jl was age-hardened at a temperature of 40o-55oC to a hardness of HRO 15 to 35.
Pre-hardened material for construction.