JPS6315979B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-resistant aluminum alloy. JISH5202 specifies AC8A and AC8B materials as alloys used at high temperatures such as in pistons. However, this standard alloy is not sufficient for parts used at higher temperatures, such as diesel engines. The present invention provides an aluminum alloy suitable for use at high temperatures. The heat-resistant aluminum alloy according to the present invention contains 8.5 to 11.5% silicon (wt%,
In this specification, all percentages indicating alloy composition are by weight), copper 0.5 to 4.0%, magnesium 0.2
~1.5%, iron 0.4-1.0%, zirconium 0.1-0.3%
with the remainder consisting essentially of aluminum, and 8.5 to 11.5% silicon, 0.5 to 4.0% copper, 0.2 to 1.5% magnesium, 0.4 to 1.0% iron, and zirconium.
0.1 to 0.3%, 0.1 to 0.3% of chromium, and the remainder substantially consists of aluminum. In the alloys of the present invention, silicon improves castability and mechanical properties at high temperatures, especially strength, and also reduces the coefficient of thermal expansion. However, when the silicon content becomes too large and becomes a hypereutectic region where primary silicon crystallizes, workability such as machinability deteriorates. Therefore, the silicon content needs to be in the range of 8.5 to 11.5%. Copper improves strength, but too much copper tends to cause casting cracks, so its content should be
Must be in the range 0.5-4%. Magnesium also contributes to improving strength like copper, but too much will make the material brittle, so its content should be 0.2~
The rate shall be 1.5%. Iron also has the effect of improving strength at high temperatures, so it is included in the range of 0.4 to 1.0%.
Previously, it was thought that a large amount of iron would cause acicular compounds to crystallize and cause embrittlement, but
It has been found that if the content is 1.0% or less, iron will combine with copper, magnesium, silicon, etc. to form irregularly shaped crystallized substances, so that embrittlement will not occur. Zirconium has the effect of improving the high-temperature properties of the alloy, particularly the creep resistance, so it is contained in the range of 0.1 to 0.3%. If the content of zirconium is too high, the melting temperature becomes high and casting becomes difficult. The alloy according to the present invention essentially consists of the above additive elements and aluminum, but if desired, it may further contain 0.1 to 0.3% chromium. Chromium has the effect of preventing needle crystallization of iron when the solidification rate is slow, but if its content is too large, coarse chromium compounds will crystallize and cause embrittlement.
Furthermore, addition of titanium and boron has the effect of making crystal grains finer and improving the castability (shrinkability) of the alloy. When either titanium or boron is used alone, it exhibits almost no crystal grain refinement effect. Titanium and boron content is less than 0.2% titanium, boron
0.05% or less is sufficient, preferably titanium 0.05%
~0.15%, boron 0.005~0.02%. The alloy of the present invention has the above composition and has superior high-temperature properties to standard alloys such as AC8A and AC8B. Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof. Examples 1 to 4 and Comparative Examples 1 to 2 Molten aluminum alloys having the compositions shown in Table 1 were
Cast in a JIS boat mold at room temperature. The obtained castings were subjected to heat treatment of T ₅ or T ₆ shown in Table 2 to prepare test pieces. After heating the test piece at 300°C for 100 hours, a tensile test and a centrifugal creep test (3000 rpm) were subsequently conducted at the same temperature. The results of the tensile test are shown in Table 3, and the results of the centrifugal creep test are shown in FIGS. 1 to 3. These results show that the alloy of the present invention has greater high-temperature tensile strength and superior creep resistance than known alloys, regardless of the heat treatment conditions.

【table】

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a graph of a centrifugal creep test of samples subjected to T ₅ or T ₆ treatment. 1; Sample of Comparative Example 1 that underwent T ₆ treatment; 2; Sample of Example 1 that underwent T ₆ treatment; 3; Sample of Example 2 that underwent T ₆ treatment; 4; Sample of Comparative Example 1 that underwent T ₅ treatment. Sample, 5; Sample of Example 1 after T ₅ treatment, 6; T ₅
Sample of Example 2 after treatment. FIG. 2 is a graph of a centrifugal creep test of a sample subjected to T ₆ treatment. 1; Sample of Comparative Example 2, 2; Sample of Example 3,
3; Sample of Example 4. FIG. 3 is a graph of a centrifugal creep test of a sample subjected to _T5 treatment. 1; Sample of Comparative Example 2, 2; Sample of Example 3,
3; Sample of Example 4.

Claims (1)

[Claims] 1. 8.5-11.5% silicon, 0.5-4.0% copper, 0.2-1.5% magnesium, 0.4-1.0% iron, 0.1-0.1% zirconium.
A heat-resistant aluminum alloy containing 0.3% and the remainder being substantially aluminum. 2 Silicon 8.5-11.5%, copper 0.5-4.0%, magnesium 0.2-1.5%, iron 0.4-1.0%, zirconium 0.1-
A heat-resistant aluminum alloy containing 0.3% chromium, 0.1 to 0.3% chromium, and the remainder substantially aluminum.