HIGH DAMPING CAPACITY, TWO-PHASE FE-MN-AL-C ALLOY

Abstract: Carbon steels and other hot-and cold-workable ferrous alloys generally have poor damping capacity as compared to that cast iron (gray cast iron, malleable cast iron and ductile cast iron). This is because the graphite in cast irons helps to absorb the damping force and depresses the damping wave. But cast iron can not be rolled into strip of sheet. By controlling the correlated concentrations of manganese, aluminum and carbon, Fe-Mn-Al-C based alloys are made to be alpha + gamma two-phase alloy steel with different alpha and gamma volume fractions. With particular ferrite volumes, workable Fe-Mn-Al-C based alloys have equivalent and better damping capacity than that of cast irons especially in the high frequency side. Such alloys suppress the vibration noise that comes from machine rooms, motors, air conditioners, and etc. Chromium and other minor amount of elements can be added to this alloy system to improve the corrosion resistance.

Description: HIGH DAMPING CAPACITY, TWO-PHASE Fe-Mn-Al-C ALLOY BACKGROUND: For the past years alpha-gamma two-phasealloys have been developed by adding molybdenum and cobalt to the Fe-Ni-Cr alloy system for the purpose of making alloys having both better stress corrosion and hydrogen embrittlement resistance. But none of these alloys was designed for the purpose of higher damping: capacity. The iron-base materials that have been used for high damping capacity are the cast irons. The graphite in gray cast irons is the most important factor for absorbing the high frequency vibration wave. But cast irons generally are not workable, making them of limited value in highdamping applicactions. DESCRIPTION OF THE DRAWING In the drawing: Figure 1 depicts the damping capacity curve for an alloy of the invention; and Figure 2 depicts the damping capacity curve for ductile iron. DETAILED DESCRIPTION OF THE INVENTION; In Fe-Mn-Al-C alloys, manganese ■ •-■tnd carbon are gamma- phase formers andaluminum is an alpha-phase former. By suitable compositional arrangement, Fe-Mn-Al-C alloys canbe disigned to be fully gamma phase, such as Fe-29Mn-7Al-lC. Reduction of the manganese or carbon or both of them and the increase of aluminum can promote the appearance of alpha phase, and make the alloy an alpha+gamma to-phase steel. The volume fraction of alpha phase can be controlled bychanging the amount of manganese or aluminum or carbon or other ferrite-forming elements. Alloys according to the invention contain, in weight percent, 107. to 457 0 manganese, 47, to 127. aluminum, up to 127, chromium, 0.01% to 0.77o carbon, balance essentially iron, and are charac¬ terized by a microstructure containing about 257. to 757,ferrite, with the remainder austenite and bya high damping capacity on the order of a cast iron. Minor amounts of Ni,Mo,Cb,Co,Si, etc. may be included in the allov. Example I. "2- This example illustrates the effect of the element compositions on the change of α volume fraction in the Fe-Mn-Al-C based alloys. Manganese and carbon are austenite phase stabilizers and aluminum is a ferrite phase former. The effect of the carbon content on the ferrite fraction of the Fe-Mn-Al-C based alloys is shown in Table I. in which the chemical composition of aluminum and manganese are essentially constant and the carbon content decreases from 0.5 wt% to 0.11 wt%. With the decreasing of carbon content, the ferrite phase volume fractions of the alloys increases from 0% to 36%. With the change of manganese, carbon and aluminum contents, the volume fractions of ferrite phase and balanced γ phase is controlled to be from 25% to 75%. Within this ferrite fraction range, excellent damping capacity is always found in the Fe-Mn-Al-C based alloy. Table I Example 2. This example illustrates the good damping capacity of the said α--γ two-phase Fe-Mn-Al-C based alloys which have been measured and determined with comparison to ductile cast iron. The test sample of the invention contained 19.7Mn-5.84Al-5.74Cr-0.19C. The ferrite volume fraction is about 65% balanced with γ phase. The damping capacity curves of the damping capacity tests of the Fe-Mn-Al-C based alloy and ductile cast iron are shown in Fig. 1 and Fig. 2. It is seen that the damping capacities of the two alloys are almost equivalent. xamp e . This example illustrates the good workability of α+γ two-phase Fe-Mn-Al-C based alloys. The alloys listed in Table II were cast into ingot; homogenized at 1200°C; cut and hot forged at 1200°C; further annealed at 1150°C and descaled. The alloys were cold rolled ' into 2.0 mm thick strip and annealed. The ferrite volume percentages of these strips were measured and are listed in Table III. The mechanical properties of these annealed strips are also listed in Table III. It is seen that the alloys of the invention have good workablility and excellent mechanical properties. Table II. sample no. 0.2% proof ultimate teπsi % elongation hardness ferrite stress(ksi) stress (ksi) (Rb) % #109 45 103 42 84 45 #108 39 94 44 80 28 #320 41 98 43 82 67 #317 44 101 41 83 75 #129 61 112 38 86 65 #1 16 59 109 37 85 73

Claims: Claim: (1) A ferrite-austenite two-phase alloy of high damping capacity having composition consisting essentially of 10 to 45 wt% manganese, 4 to 15 wt aluminum, up to 12 wt% chromium, 0.01 to 0.7 wt% carbon and the balanc essentially iron, with the ferrite phase of said alloy having about 25% to 75% b volume, the remainder being essentially austenite, said alloy having a dampin capacity of about the same level as that of ductile iron. (2) The alloy of claim 1 containing 0 to 4.0. wt% molybdenum. (3) The alloy of claim 1 containing 0 to 4.0 wt% copper. (4) The alloy of claim 1 containing 0 to 2.0 wt% nickel. (5) The alloy of claim 1 containing 0 to 3.5 wt% niobium. (6) The alloy of claim 1 containing up to 500 ppm boron. (7) The alloy of claim 1 containing up to 0.2 wt% nitrogen. (8) The alloy of claim 1 containing 0 to 3.5 wt% titanium. (9) The alloy of claim 1 containing 0 to 2.0 wt% cobalt. (10) The alloy of claim 1 containing 0 to 3.5 wt% vanadium. (11) The alloy of claim 1 containing 0 to 3.5 wt% tungsten. (12) The alloy of claim 1 containing 0 to 2.0 wt% zirconium. (13) The alloy of claim 1 containing up to 2.5 wt% silicon.

Inventors: WAN CHI-MEEN, WAN, CHI-MEEN
Applicants: FAMCY STEEL CORP, FAMCY STEEL CORPORATION
Application year: 1989
Main classification: C22C38
IPC codes: C22C38