Tmoose
Mechanical
- Apr 12, 2003
- 5,626
ASTM A532 -II D - silicon chemical requirement is 1.0 to 2.2 % by weight.
At least one of our overseas foundries supplies a material claimed to be equivalent. Their recipe officially uses .3 -.6 Si.
In this metallurgy stuff I'm just a brochure engineer at best.
Normally I'd simply side with ASTM, but I'm in need of some professional advice about the Abrasion Resistant Cast Iron Handbook by the American Foundry Society and available on the ASM website.
The Abrasion Resistant Cast Iron Handbook seems more than once to distinctly recommend AGAINST using that ASTM A532 1.0 - 2.2% Si.
page 24 - In high-Cr AR irons, the use of Si to increase the alloy’s fluidity is kind of controversial. Chromium will tend to negate
the effect of Si on the dendritic and eutectic solidification temperatures, and, as already discussed, Si has only a minor
effect on the high-Cr alloy’s carbon equivalence. In practice, Si in the range 0.5–0.8% is believed to increase the fluidity of
high-Cr irons by forming a “slippery” SiO2 film on the surface of the liquid. How much of a fluidity boost this surface film provides is unknown, at this time, and is the subject of ongoing research, as reported in Appendix H.
page 31 - Silicon plays a diverse role in many AR cast iron’s. For example, many high-Cr irons have a nominal Si level of 0.6%.
As an alloying element, Si imparts little hardenability; contrarily, it does promote the formation of pearlite, and thus lowers the hardenability of the iron. Consequently, the main reason for adding Si to a high-Cr iron is to control the melt oxidation and increase fluidity. Silicon will form a thin
tenacious layer of SiO2 on the surface of the melt. This thin layer will hinder the formation of Cr2O3, thereby providing some measure of protection against further oxidation. Silicon is also reported to make furnace slag less viscous and easier to handle on removal, prior to tapping.
page 124 - (High-Chromium, continued) (High-Cr irons cover a range of compositions between 12 and over 40% Cr and 1–4% C,...... ) - Silicon content should be aimed at 0.7%. Less than 0.4% Si in the melt can the melt can cause difficulties with viscous slag; higher Si content can promote pearlite during heat treatment. In 26-Cr irons, higher Si improves fluidity and feeding distance and results in grain refining, with improved resistance to shock and higher bending strength. Above 1% Si, the iron becomes embrittled and the matrix structure may become partially ferritic.
At least one of our overseas foundries supplies a material claimed to be equivalent. Their recipe officially uses .3 -.6 Si.
In this metallurgy stuff I'm just a brochure engineer at best.
Normally I'd simply side with ASTM, but I'm in need of some professional advice about the Abrasion Resistant Cast Iron Handbook by the American Foundry Society and available on the ASM website.
The Abrasion Resistant Cast Iron Handbook seems more than once to distinctly recommend AGAINST using that ASTM A532 1.0 - 2.2% Si.
page 24 - In high-Cr AR irons, the use of Si to increase the alloy’s fluidity is kind of controversial. Chromium will tend to negate
the effect of Si on the dendritic and eutectic solidification temperatures, and, as already discussed, Si has only a minor
effect on the high-Cr alloy’s carbon equivalence. In practice, Si in the range 0.5–0.8% is believed to increase the fluidity of
high-Cr irons by forming a “slippery” SiO2 film on the surface of the liquid. How much of a fluidity boost this surface film provides is unknown, at this time, and is the subject of ongoing research, as reported in Appendix H.
page 31 - Silicon plays a diverse role in many AR cast iron’s. For example, many high-Cr irons have a nominal Si level of 0.6%.
As an alloying element, Si imparts little hardenability; contrarily, it does promote the formation of pearlite, and thus lowers the hardenability of the iron. Consequently, the main reason for adding Si to a high-Cr iron is to control the melt oxidation and increase fluidity. Silicon will form a thin
tenacious layer of SiO2 on the surface of the melt. This thin layer will hinder the formation of Cr2O3, thereby providing some measure of protection against further oxidation. Silicon is also reported to make furnace slag less viscous and easier to handle on removal, prior to tapping.
page 124 - (High-Chromium, continued) (High-Cr irons cover a range of compositions between 12 and over 40% Cr and 1–4% C,...... ) - Silicon content should be aimed at 0.7%. Less than 0.4% Si in the melt can the melt can cause difficulties with viscous slag; higher Si content can promote pearlite during heat treatment. In 26-Cr irons, higher Si improves fluidity and feeding distance and results in grain refining, with improved resistance to shock and higher bending strength. Above 1% Si, the iron becomes embrittled and the matrix structure may become partially ferritic.
