Method for Producing Shaped Bodies from Aluminium Alloys

Abstract

The invention pertains to a method for producing molded articles based on aluminum alloys by metal injection molding, comprising the following steps: a) producing a feed-stock by mixing the metals contained in the desired alloy in the form of metal powders and/or one or more metal alloy powders with a binder; b) producing a green body by injection molding said feedstock; c) producing a brown body by at least partially removing the binder from the green body by catalytic and/or solvent and/or thermal debinding; d) sintering the at least partially debound brown body to obtain the desired molded article; characterized in that, in step c), the binder is completely removed, wherein thermal debinding is carried out to remove the (residual) binder, optionally after having carried out one or more previous debinding steps, said thermal debinding being carried out in an atmosphere containing at least 0.5% by volume of oxygen, whereafter the thus obtained, completely debound brown body is sintered.

1 . A method for producing molded articles based on aluminum alloys by metal injection molding, comprising the following steps:
 (a) producing a feedstock by mixing the metals contained in the desired alloy in the form of metal powders and/or one or more metal alloy powders with a binder;   (b) producing a green body by injection molding said feedstock;   (c) producing a brown body by at least partially removing the binder from the green body by catalytic and/or solvent and/or thermal debinding;   (d) sintering the at least partially debound brown body to obtain the desired molded article;   wherein in step (c), the binder is completely removed, wherein thermal debinding is carried out to remove residual binder, optionally alter having carried out one or more previous debinding steps, said thermal debinding being carried out in an atmosphere containing at least 0.5% by volume of oxygen, whereafter the thus obtained, completely debound brown body is sintered.   
     
     
         2 . The method according to  claim 1 , wherein in addition to aluminum, the aluminum alloy contains one or more metals selected from the group consisting of magnesium, copper, silicon, and manganese. 
     
     
         3 . The method according to  claim 1  or  claim 2 , wherein in addition to aluminum, the aluminum alloy contains one or more metals at a percentage of 0.5 to 25% by weight, respectively. 
     
     
         4 . The method according to  claim 1 , wherein the metal(s) is/are used as (a) master alloy powder(s). 
     
     
         5 . The method according to  claim 1 , wherein the binder is a polyacetal-based binder. 
     
     
         6 . The method according to  claim 5 , wherein the binder consists of 50 to 95% of polyacetal. 
     
     
         7 . The method according to  claim 5 , wherein the binder consists of 80 to 90% of polyacetal. 
     
     
         8 . The method according to  claim 1 , wherein step (c) only includes thermal debinding in the presence of oxygen, which is carried out in one or more steps and removes the entire binder. 
     
     
         9 . The method according to any one of the  claim 1 , wherein step (c) includes solvent debinding to remove the main part of the binder, followed by said thermal debinding to remove the residual binder. 
     
     
         10 . The method according to any one of the  claim 1 , wherein step (c) includes catalytic debinding to remove the main part of the binder, followed by said thermal debinding to remove the residual binder. 
     
     
         11 . The method according to  claim 10 , wherein the catalytic debinding is carried out in the presence of at least one acid selected from the group consisting of nitric acid, oxalic acid, formic acid, and acetic acid. 
     
     
         12 . The method according to  claim 11 , wherein the acid is sublimated oxalic acid. 
     
     
         13 . The method according to  claim 1 , wherein, said thermal debinding to remove any residual binder is carried out at a temperature below 500° C. 
     
     
         14 . The method according to  claim 13 , wherein said thermal debinding to remove any residual binder is carried out applying a specific temperature profile ranging between 100 and 420° C. 
     
     
         15 . The method according to  claim 13  or  claim 14 , wherein that the heating rate during said thermal debinding process for removing the residual binder does not exceed 5 K/min. 
     
     
         16 . The method according to  claim 15 , wherein the heating rate does not exceed 1 to 2 K/min. 
     
     
         17 . The method according to  claim 1 , wherein in step (d), the completely debound brown body is sintered while forming a liquid phase. 
     
     
         18 . The method according to  claim 17 , wherein sintering is carried out at a temperature between the solidus and the liquidus temperatures of the respective aluminum alloy. 
     
     
         19 . The method according to  claim 1 , wherein the heating rate to reach the sintering temperature after said thermal debinding step ranges from 4 to 20 K/min. 
     
     
         20 . The method according to  claim 5 , wherein the polyacetal-based binder is a polyoxymethylene binder.