The key technology to improve the quality of machine tool castings
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- Time of issue:2020-03-13
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(Summary description)Atpresent,mostofthemachinetoolcastingsaregraycastiron.Thequalityofgraycastironisstrictlycontrolledfromthechemicalcomposition,rawmaterialquality,ingredients,alloying,meltingtemperature,inoculationtreatmenttothermalagingandotherenvironments.1.Smeltingprocess1)Carbonequivalent.Ahighercarbonequivalentshouldbeused.HT250isbetterat3.95;HT300isbetterat3.82;HT350isbetterat3.76.2)Silicontocarbonratio.Itisrecommendedtocontrolthesilicon-carbonratioat0.55-0.62.3)Alloyingcontrol.Theadditionofalloyelementsisconducivetotheimprovementofcastingperformance,generallyw(Cu)0.4-0.6%orw(Cr)0.2-0.4%.2.IngredientsTheamountofpigironaddedshouldbelessthan10%.Atthesametime,highscrapsteelandhighcarburizationtechnologyareused,sothegraphitequalityisgood.3,moltenirontemperatureHighmoltenirontemperaturecanrefinegraphite,whichisthebasisofhighcarbonequivalentandhighstrengthgraycastiron.Whenthetemperatureofthemoltenironis1500-1550℃,theoxidationofthemoltenironwillbereduced,andtheSiO2ashwillbesignificantlyreduced.4.PregnancyThemethodofinoculationismoreimportantthanthehighefficiencyofinoculants.Accordingtotheactualsituation,westrivetoadoptinstantaneousinoculationmethodssuchasfollow-upinoculation,gatecupinoculation,floatingsiliconinoculationandin-typeinoculationtoensurethequalityofinoculation.Triangularsamples,thermalanalysiscurves,andcoldratiosbeforeandafterinoculationshouldbeusedtotesttheinoculationeffect.Itisnecessarytopreventovercooledgraphitecausedbyinadequateincubationandshrinkagecausedbyexcessiveinoculation.5.PerformancetestStrengthentheinspectionoftheperformanceoftheattachedtestrodandthemetallographicstructure,andespeciallystrengthentheinspectionofthesupercooledgraphite,carbideandpearliteinthemetallographytoimprovethemetallurgicalqualityofthecasting,sothatitsmaturity>1,hardening<1,qualityCoefficient>1.
The key technology to improve the quality of machine tool castings
The key technology to improve the quality of machine tool castings
The key technology to improve the quality of machine tool castings
(Summary description)Atpresent,mostofthemachinetoolcastingsaregraycastiron.Thequalityofgraycastironisstrictlycontrolledfromthechemicalcomposition,rawmaterialquality,ingredients,alloying,meltingtemperature,inoculationtreatmenttothermalagingandotherenvironments.1.Smeltingprocess1)Carbonequivalent.Ahighercarbonequivalentshouldbeused.HT250isbetterat3.95;HT300isbetterat3.82;HT350isbetterat3.76.2)Silicontocarbonratio.Itisrecommendedtocontrolthesilicon-carbonratioat0.55-0.62.3)Alloyingcontrol.Theadditionofalloyelementsisconducivetotheimprovementofcastingperformance,generallyw(Cu)0.4-0.6%orw(Cr)0.2-0.4%.2.IngredientsTheamountofpigironaddedshouldbelessthan10%.Atthesametime,highscrapsteelandhighcarburizationtechnologyareused,sothegraphitequalityisgood.3,moltenirontemperatureHighmoltenirontemperaturecanrefinegraphite,whichisthebasisofhighcarbonequivalentandhighstrengthgraycastiron.Whenthetemperatureofthemoltenironis1500-1550℃,theoxidationofthemoltenironwillbereduced,andtheSiO2ashwillbesignificantlyreduced.4.PregnancyThemethodofinoculationismoreimportantthanthehighefficiencyofinoculants.Accordingtotheactualsituation,westrivetoadoptinstantaneousinoculationmethodssuchasfollow-upinoculation,gatecupinoculation,floatingsiliconinoculationandin-typeinoculationtoensurethequalityofinoculation.Triangularsamples,thermalanalysiscurves,andcoldratiosbeforeandafterinoculationshouldbeusedtotesttheinoculationeffect.Itisnecessarytopreventovercooledgraphitecausedbyinadequateincubationandshrinkagecausedbyexcessiveinoculation.5.PerformancetestStrengthentheinspectionoftheperformanceoftheattachedtestrodandthemetallographicstructure,andespeciallystrengthentheinspectionofthesupercooledgraphite,carbideandpearliteinthemetallographytoimprovethemetallurgicalqualityofthecasting,sothatitsmaturity>1,hardening<1,qualityCoefficient>1.
- Categories:news
- Author:
- Origin:
- Time of issue:2020-03-13
- Views:0
At present, most of the machine tool castings are gray cast iron. The quality of gray cast iron is strictly controlled from the chemical composition, raw material quality, ingredients, alloying, melting temperature, inoculation treatment to thermal aging and other environments.
1. Smelting process
1) Carbon equivalent. A higher carbon equivalent should be used. HT250 is better at 3.95; HT300 is better at 3.82; HT350 is better at 3.76.
2) Silicon to carbon ratio. It is recommended to control the silicon-carbon ratio at 0.55-0.62.
3) Alloying control. The addition of alloy elements is conducive to the improvement of casting performance, generally w (Cu) 0.4-0.6% or w (Cr) 0.2-0.4%.
2. Ingredients
The amount of pig iron added should be less than 10%. At the same time, high scrap steel and high carburization technology are used, so the graphite quality is good.
3, molten iron temperature
High molten iron temperature can refine graphite, which is the basis of high carbon equivalent and high strength gray cast iron. When the temperature of the molten iron is 1500-1550 ℃, the oxidation of the molten iron will be reduced, and the SiO2 ash will be significantly reduced.
4. Pregnancy
The method of inoculation is more important than the high efficiency of inoculants. According to the actual situation, we strive to adopt instantaneous inoculation methods such as follow-up inoculation, gate cup inoculation, floating silicon inoculation and in-type inoculation to ensure the quality of inoculation. Triangular samples, thermal analysis curves, and cold ratios before and after inoculation should be used to test the inoculation effect. It is necessary to prevent overcooled graphite caused by inadequate incubation and shrinkage caused by excessive inoculation.
5. Performance test
Strengthen the inspection of the performance of the attached test rod and the metallographic structure, and especially strengthen the inspection of the supercooled graphite, carbide and pearlite in the metallography to improve the metallurgical quality of the casting, so that its maturity> 1, hardening <1, quality Coefficient> 1.
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