JPS5929663B2 - High-strength Al alloy for baseball bats with excellent extrusion processability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an At alloy that has high strength and toughness, can be extruded at high speeds, and is particularly suitable for use as a baseball bat.

In recent years, A7 alloy baseball bats have come to be widely used in baseball, including high school baseball.

This At alloy baseball bat must be able to withstand high impact forces, so its manufacturing requires a tensile strength of 60kg, according to the Ministry of International Trade and Industry Safety Standards for Class A bats.
It is mandatory to use At alloys with high strength of f/i4 or more and high toughness of elongation = 9% or more. AA standard 70 Ni1 Cr: 0.18 to 0.35%, Zn:
6.8 to 8.0%, At and unavoidable impurities: remainder), and the same 7178 alloy (Cu: 1.6 to 2.4%)
, Mg: 2.4-3.1%, Cr: 0.18
~0.35%, Zn: 6.3~7.3%, A4 and unavoidable impurities: remainder), etc. are available for use.

However, these conventional high-strength At alloys have poor workability,
In particular, hot workability is a problem, and extrusion at high speeds is impossible because it causes defects due to processing cracks. Therefore, when manufacturing baseball bats, extrusion must be performed at slow speeds. However, productivity was extremely low.

Therefore, from the above-mentioned viewpoint, the present inventors conducted research in order to obtain an At alloy that has high strength and toughness that satisfies the standards set for the above-mentioned baseball bats, and has excellent extrudability. As a result, the cracks that occur during extrusion processing at high speeds in the conventional high-strength At alloy mentioned above are due to local melting, and these cracks are caused by Z as an alloy component.
It can be completely prevented by reducing the content of n, Mg, and Cu to 10.5% or less, and if Mn and Zr are also included as alloy components, a structure with an extremely strongly developed recrystallized structure, the so-called The pressing effect not only significantly improves the alloy strength to more than 60 kg・f/m4 in terms of tensile strength, but also prevents embrittlement of grain boundaries5, improving not only extrudability but also They found that the toughness was also greatly improved.

Therefore, this invention was made based on the above knowledge, and Zn: 5.2 to 6.8, Mg: 1
．． '8 to 2.8%, Cu: 1.2 to 2%, Mn: 0.
35 to 1.0%, Zr: 0.03 to 0.25%, and optionally Cr: 0.03 to 0.3 and V: 0.03 to 0.25. 1 or 2 of
Contains seeds and total amount of Zn, Mg, and Cu: 9
．． 0 to 10.5%, with the remainder being At and unavoidable impurities (the above by weight and the following by weight all mean by weight), and satisfy the standards set for baseball bats. The A7 alloy for baseball bats is characterized by high strength and toughness as well as excellent extrusion processability.

Next, the reason why the composition range of the At alloy of the present invention is limited as described above will be explained.

(a) When Z n , e Mg, and Cu alloys are subjected to normal T6 treatment, that is, aging treatment at a temperature of about 120°C, these components are mainly KMgZn2 in the matrix.
．． e Precipitates as Az2CuMg and At2Cu phases and significantly improves the strength of the alloy, but their contents are Zn: less than 5.2%, Mg: less than 1.8%, and Cu: less than 1.2%, respectively. Then, Z n0 Mg0 C
When u: is less than 9.0, the amount of the precipitated phase is too small to obtain the desired strength; on the other hand, each Zn:
6.8, Mg: 2.8%, and Cu: exceeding 2%,
And Zn + Mg + Cu: If it exceeds 10.5%, extrusion processability will deteriorate and cracks will occur during extrusion processing at high speed.
, 2-6.8%, Mg: 1.8-2.8%, Cu
: 1.2% to 2%, and the total amount of Zn, Mg, and Cu was determined to be 9% to 10.5%.

(b) Mn and Zr The Mn and Zr components include fine grains and
In addition to preventing grain boundary embrittlement and thereby significantly improving the toughness and hot workability (extrusion workability) of the alloy, it also has a recrystallization suppressing effect, that is, the strong development of a non-recrystallized structure (so-called fibrous structure) during extrusion processing. Mn has the effect of improving the strength of the alloy (so-called pressing effect), but these effects
Zr alone has little effect on Rurui, and both components need to coexist in order to obtain the desired effect.

However, if the content is less than 0.35% Mn and less than 0.03% Zr, the desired effect cannot be obtained;
If each content exceeds 5%, huge intermetallic compounds will precipitate and extrusion workability and toughness will decrease, so the content should be reduced to Mn:0.
35-1%, Zr: 0.03-0.25%.

(c) Cr and V These components have the same effect as Mn and Zr, and when coexisting with these components, they have an even effect that further improves the pressing effect, so they are particularly effective when higher strength is required. It is included as necessary, but the content is
If Cr: less than 0.03% and V: less than 0.03%, the desired strength improvement effect cannot be obtained, while Cr: 0.3%
%, V: If the content exceeds 0.25, huge intermetallic compounds will precipitate and deterioration of extrusion workability and toughness will be observed. : 0.03~0.3%, ■=0
．． It was set at 0.03 to 0.25%.

Note that the FejSi component as an unavoidable impurity has the effect of refining crystal grains, so Fe: 0.5%
, Si: Even if the content does not exceed 0.3%, the properties of the alloy of the present invention will not be impaired in any way.

In addition, for the purpose of improving quality by refining the casting structure,
One or two of Ti and B, respectively,
:0.2%, B:0.01%.

Next, the At alloy of the present invention will be specifically explained using examples.

Example: By preparing molten metals having the compositions shown in Table 1 using the usual melting method, and casting them into billets with dimensions of outer diameter: 22.9 mm φ x length = 350 mm. , Invention At alloys 1 to 18, Comparative At alloys 1 to 12
, and conventional A4 alloy 1 (corresponding to AA standard 7te78 alloy) were manufactured, respectively.

It should be noted that Comparative At Alloys 1 to 12 all have compositions in which one of the constituent components (indicated with an asterisk in Table 1) is outside the scope of the present invention.

Next, the various At alloy ingots obtained as a result were processed using a 3,000 mm double-acting extruder to have a wall thickness of 3.
When extruding a 5 mm blank tube for a bat, the maximum extrusion speed at which the blank tube could be extruded without cracking was measured.

The measurement results are shown in Table 1.

In addition, after holding the above raw tube at a temperature of 460°C for 2 hours,
A T6 treatment consisting of water quenching solution treatment, room temperature aging for 3 days, and artificial aging maintained at a temperature of 120°C for 24 hours was performed, and the tensile properties after the T6 treatment were measured. did.

The results are also shown in Table 1. From the results shown in Table 1, conventional At alloys have high strength and toughness, but have significantly poor extrusion properties.
Furthermore, the comparative At alloys are inferior in at least one of tensile properties and extrusion processability.

On the other hand, all of the At alloys of the present invention have a tensile strength =
It has high strength and toughness of 60 kg/- or more, elongation: 9 inches or more, and has extremely excellent extrusion processability.

5K as mentioned above, the At alloy of this invention has a tensile strength of 6
It has high strength of 0 kg/m4 or more and high toughness of elongation of 9 inches or more, so it can be used for manufacturing hardball baseball bats that require these properties, and has excellent extrusion processability. Therefore, it has industrially useful properties such as a remarkable improvement in productivity.

Claims (1)

[Claims] I Zn: 5.2-6.8%, Mg: 1.8-2.8%, Cu: 1.2-2.0%, Mn: 0.35-1.0% . Contains Zr: 0.03 to 0.25%, and total amount of Zn, Mg, and Cu: 9
．． 0 to 10.5%, and the rest is 1. A high-strength A4 alloy for baseball bats with excellent extrusion processability, characterized by having a composition (J: weight ratio above A) consisting of unavoidable impurities. 2Zn: 5.2-6.8%, Mg: 1.8-2.8%, Cu: 1.2-2.0%, Mn: 0.35-1.0%, Zr: 0.03- Zn. A baseball bat with excellent extrusion processability, characterized by having a composition (weight ratio) satisfying a total content of Mg and Cu of 29.0 to 10.5%, with the remainder consisting of AA and unavoidable impurities. High strength At alloy.