lead in brass?

ryuen · 05-24-07, 12:49 AM

need help with this question:

Why is there lead in free-cutting brass?

ckj · 05-24-07, 01:09 AM

The lead in free-cutting brass gives the brass a higher machinability. This is important, because this type of brass is known for its ease of machinability.

I hope that's enough, in my low division courses (where I was asked this question) my answer was sufficient. You can also google "lead in free cutting brass" (no ") and get a more in depth answer there.

Moto7451 · 05-24-07, 01:16 AM

Looking it up online, it seems that that type of alloy is used to make tool and machine parts (gears, etc). I would assume its either to make the brass harder or softer.

Pure elements in many cases are poor performers depending on the intended use. For example, pure aluminum will oxidize into nothingness while aluminum oxide is a lightweight material that creates a protective oxide and in many cases can be as strong as a mild steel. Pure iron (wrought iron) is best used in decorative items because it is too weak to support any considerable load as its carbon content is too low (.2%). Adding more carbon and silicon can allow you to turn the iron into cast iron or steel, suitable for engine, steel girders, and other more useful items.

Elements are usually introduced into metals in small quantities to increase a property of the metal. .0007% Boron for example has the same effect as .7% chromium in hardening but allows for fast hardening and doesn't affect the tempering ability of the steel. However, Boron doesn't prevent oxidation and after 7x10^-3% it isn't nearly as affective at hardening as chromium. High chrome contents in many types of steel prevent major shifts in tempering (this is why a good sword is never made from stainless steel, carbon and semi-stainless tool steel are the materials of choice). Carbon allows for a harder metal, but at the cost of more difficult machining and a greater rate of oxidation.

ckj · 05-24-07, 05:07 AM

Lead makes the brass softer.

Malpine Walis · 05-24-07, 11:13 AM

Well, if you want to get technical, lead is not soluble in solid copper and it tends to fill in the voids between the crystals, thus it helps to make the resulting alloys less brittle and more easily machinable. A couple of links for you:

A short discussion with some micrographs of common lead copper alloys:

http://www.copper.org/resources/prop...d_brasses.html

Images and links to some common copper alloys:

http://www.metalreference.com/Forms_Copper_Alloy.html

05-24-07, 12:49 AM	Thread Starter #1
ryuen Member Join Date: Mar 2003 Location: at home	lead in brass? need help with this question: Why is there lead in free-cutting brass? __________________ My Heatware
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05-24-07, 01:09 AM	#2
ckj Member Join Date: Jun 2005 Location: Ca, USA	The lead in free-cutting brass gives the brass a higher machinability. This is important, because this type of brass is known for its ease of machinability. I hope that's enough, in my low division courses (where I was asked this question) my answer was sufficient. You can also google "lead in free cutting brass" (no ") and get a more in depth answer there. Last edited by ckj; 05-24-07 at 01:14 AM.
	QUOTE Thanks

05-24-07, 01:16 AM	#3
Moto7451 Senior Something Join Date: Feb 2004 Location: LA, CA	Looking it up online, it seems that that type of alloy is used to make tool and machine parts (gears, etc). I would assume its either to make the brass harder or softer. Pure elements in many cases are poor performers depending on the intended use. For example, pure aluminum will oxidize into nothingness while aluminum oxide is a lightweight material that creates a protective oxide and in many cases can be as strong as a mild steel. Pure iron (wrought iron) is best used in decorative items because it is too weak to support any considerable load as its carbon content is too low (.2%). Adding more carbon and silicon can allow you to turn the iron into cast iron or steel, suitable for engine, steel girders, and other more useful items. Elements are usually introduced into metals in small quantities to increase a property of the metal. .0007% Boron for example has the same effect as .7% chromium in hardening but allows for fast hardening and doesn't affect the tempering ability of the steel. However, Boron doesn't prevent oxidation and after 7x10^-3% it isn't nearly as affective at hardening as chromium. High chrome contents in many types of steel prevent major shifts in tempering (this is why a good sword is never made from stainless steel, carbon and semi-stainless tool steel are the materials of choice). Carbon allows for a harder metal, but at the cost of more difficult machining and a greater rate of oxidation. __________________ Intel C2D e6400 @ 375MHz x8 = 3Ghz 1.328v, Gigabyte EP43-UD3L, 3GB DDR2, GeForce 9600GT, 73GB 15K SCSI HD/Adaptec 29160 SCSI Card, 750GB SATA Drive, 320GB ATA Drive, HDTV Tuner D5 Pump • Bonneville w/ AC Heater Core • Gemeni Cooling Maze 4 Style Water Block Sager 8690: Core i7 940XM Exreme 2.13GHz (3.2GHz Turbo), 4GB DDR3, GeForce GTX 285M 1GB, 15.6" 1080 LCD, 320GB 7200RPM HD Difference Between D5 Revisions + flow mod Difference between NPSM & G1/4
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05-24-07, 05:07 AM	#4
ckj Member Join Date: Jun 2005 Location: Ca, USA	Lead makes the brass softer.
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05-24-07, 11:13 AM	#5
Malpine Walis Disabled Join Date: Nov 2001 Location: Banned Camp	Well, if you want to get technical, lead is not soluble in solid copper and it tends to fill in the voids between the crystals, thus it helps to make the resulting alloys less brittle and more easily machinable. A couple of links for you: A short discussion with some micrographs of common lead copper alloys: http://www.copper.org/resources/prop...d_brasses.html Images and links to some common copper alloys: http://www.metalreference.com/Forms_Copper_Alloy.html
	QUOTE Thanks

lead in brass?

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