Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C11/00—Alloys based on lead
  • C22C11/02—Alloys based on lead with an alkali or an alkaline earth metal as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/12—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of lead or alloys based thereon

Definitions

• Superplastic lead alloys can be prepared by casting an age hardenable lead alloy; fully age hardening the casting; and thereafter severely working or deforming the fully age hardened casting by extruding it at a low exit surface temperature of from about 120 F. to about 250 F.
• the present invention relates to superplastic lead alloys and to a process for their preparation.
• Superplasticity in metals is the ability of the metal to undergo extensive elongation, e.g., at least 100% at room temperature, without necking, i.e., reduction in cross-section area, during deformation under stresses much lower than the normal yield point. In contrast thereto, with normal plasticity the metal will undergo an elongation of only 20% to 50% at room temperature and necking occurs rapidly.
• the low resistance to flow in the superplastic state offers advantages in metal processing by allowing extensive deformation before failure and reducing the amount of energy required for forming.
• the principal object of the present invention to provide superplastic lead alloys and a process for their production such that the lead alloys will have an elongation at room temperature of at least 100%.
• the process of the present invention comprises casting an age hardenable lead alloy; fully age hardening the casting; and thereafter severely working or deforming the fully age hardened casting under controlled extrusion temperature conditions.
• Useful lead-calcium-tin ternary alloys are those containing from about 0.03% to about 0.5% by weight calcium, an amount up to about 1% by weight tin and the balance being substantially lead and usually those containing from about 0.08% to about 0.1% by weight calcium, from about 0.7 to about 1% by weight tin and the balance being substantially lead. Normal impurities can be present in the lead alloys.
• the age hardenable lead alloys are cast as billets by conventional chill casting or continuous casting techniques well known to the art.
• the lead alloy After casting, the lead alloy is permitted to remain at room temperature or is subjected to elevated temperatures until a fully age hardened condition in achieved, i.e., the hardness of the casting or billet does not change significantly or remains steady with any further aging.
• the length of this aging treatment is dependent upon chemical composition and temperature of exposure. For example, a binary lead-calcium alloy containing 0.09% by weight calcium is fully age hardened after one days exposure at room temperature (70 F.), since it thereupon has a relative hardness number of 63 which remains steady after further aging up to 28 days.
• a ternary lead-0.1% calcium-0.3% tin alloy requires approximately 60-90 days aging at room temperature to be fully age hardened, since it thereupon has a relative hardness number of about 50 which remains steady on further aging.
• a ternary lead- 0.1% calcium-0.7% tin alloy also requires about 60-90 days aging at room temperature to be fully age hardened in view of the fact that it then has a relative hardness number of about 58 which remains steady on further aging.
• an elevated temperature e.g. 400 F.
• they are fully age hardened in a shorter period, e.g., only about 5 hours.
• an increase in temperature of aging accelerates age hardening.
• the relative hardness values were obtained using a Rockwell hardness tester with a 4;" diameter ball and a 60 kg. major load with a 10 kg. minor load applied for ten seconds.
• the fully age hardened casting is thereafter severely worked or deformed under controlled extrusion temperature conditions.
• the extrusion temperature must be controlled to provide a low exit surface temperature of from about l20 F. to about 250 F., preferably from about 150 F. to about 250 F. or at about 200 F., because at lower or higher surface temperatures of the extrusion superplasticity is not achieved in that the percent elongation to failure of the extruded product at room temperature is less than 100%.
• the exit surface temperature of the extruded product can be controlled within the required range for inducing superplasticity by regulating or correlating the extrusion reduction ratio and the rate of extrusion or ram speed as illustrated hereinbelow. As either variable increases, the rate of deformation or working increases and the temperature increases.
• the extrusion reduction ratio is between about 38:1 to about 133:1 and the extrusion ram speed is between about 1 to about 12 inches/minute, these variables being inversely correlated.
• the extrusion exit surface temperature can be further controlled within the required range while at the same time increasing productivity by water quenching or cooling the extrusions just as they leave the die face by water sprays surrounding the extruded product as also illustrated hereinafter.
• the extrusion temperature was defined as that in the plateau region of the temperature versus length curve, i.e., when the temperature of the extrusion stabilized after a period of time.
• the mechanical properties of ultimate tensile strength (UTS) in p.s.i. and percent elongation to failure [elongation (percent)] were evaluated at room temperature (70 F.) and at an elevated temperature (300 F.) to determine the effects of the above mentioned parameters on superplasticity.
• Example 28 versus Example 32 and comparative Example 31
• Metallographic analysis showed that the superplastic lead alloys had a microstructure which consisted of a majority of micrograins, i.e., small, equiaxed, recrystallized grains of about 1-5 microns in diameter, whereas the non-superplastic lead alloys had a microstructure which was predominantly stringer grains, i.e., long thin grains formed by coalescence of micrograins or recrystallization textures in the extrusion direction.
• a process for the preparation of superplastic lead alloys which comprises casting an age hardenable lead alloy; fully age hardening the casting; and severely working or deforming the fully aged hardened casting by ex- 6 truding it at a low exit surface temperature of from about F. to about 250 F.
• age hardenable lead alloy is a binary lead alloy consisting essentially of from about 0.08% to about 0.1% by weight of calcium and the balance substantially lead.
• age hardenable lead alloy is a ternary lead alloy consisting essentially of from about 0.03% to about 0.5 by weight of calcium, an amount up to about 1% by weight of tin and the balance substantially lead.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Extrusion Of Metal (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=22142414

Family Applications (1)

Country Status (11)

Cited By (7)

Families Citing this family (1)

Family Cites Families (3)

• 1970
  • 1970-10-05 US US78177A patent/US3706605A/en not_active Expired - Lifetime
• 1971
  • 1971-09-03 JP JP6757271A patent/JPS535249B1/ja active Pending
  • 1971-09-15 IT IT52894/71A patent/IT944706B/it active
  • 1971-09-23 CA CA123,524A patent/CA951941A/en not_active Expired
  • 1971-09-29 GB GB4528671A patent/GB1330388A/en not_active Expired
  • 1971-09-29 NL NL7113384.A patent/NL164612C/xx not_active IP Right Cessation
  • 1971-10-04 DE DE2149546A patent/DE2149546C3/de not_active Expired
  • 1971-10-05 AU AU34190/71A patent/AU442928B2/en not_active Expired
  • 1971-10-05 LU LU64014D patent/LU64014A1/xx unknown
  • 1971-10-05 BE BE773530A patent/BE773530A/xx unknown
  • 1971-10-05 FR FR7135860A patent/FR2111016A5/fr not_active Expired

Also Published As

Similar Documents

Legal Events