SE435026B

SE435026B - Method for production of bodies of desired shape from metal powder

Info

Publication number: SE435026B
Application number: SE8100945A
Authority: SE
Inventors: P-E Kihlstedt
Original assignee: Kloster Speedsteel Ab
Priority date: 1981-02-11
Filing date: 1981-02-11
Publication date: 1984-09-03
Also published as: SE8100945L

Abstract

When producing bodies of desired shape from metal powder, one fills the powder into a mould, which determines the contour of the body being produced. The mould consists of a non-metallic material, and energy is supplied across the walls of the mould with power large enough and of such form that the powder in the mould bakes or melts in the outermost layer opposite the mould wall, while the metal powder further inside the powder body remains in solid phase and the mould itself remains unaffected or at least does not melt or become destroyed before said outer layer has been able to melt or bake together. After cooling down, so that the outer layer congeals into a tight shell, the thus moulded green body is compacted, preferably by thermal isostatic compaction, to complete density, in which the shell congealed together functions as a capsule for the powder inside it.

Description

8100945-så 10 15 20 25 30 35 föreslagen utvecklingslinje framställs en sintrad pulverkropp i vilken införlivas en infiltrand. Denna teknik kan emellertid endast utnyttjas för produkter med måttliga krav på hårdhet och slitstyrka. För exempel- vis snabbstålsverktyg anses en homogen snabbstålskropp vara en förut- sättning. I dessa fall förutsätter tillverkningen därför varmisostatisk kompaktering. Enligt en sådan metod, som nått en viss framgång, fram- ställs ett pulver genom vattengranulering. Pulvret glödgas därefter för att avlägsna oxider och för att sänka hårdheten. Därefter kan pulvret pressas kallt till färdig form och sintras till nästan full täthet vid så hög temperatur att strukturen påverkas. Processen kan anses lämpa sig å väl för tillverkning av slitdelar och mindre kvalificerade verktyg men I ej för snabbstålsverktyg och motsvarande med mycket höga krav på hårdhet och slitstyrka. 8100945-so 10 15 20 25 30 35 proposed development line a sintered powder body is produced in which incorporates an infiltrate. However, this technology can only be used for products with moderate requirements for hardness and durability. For example- high-speed steel tool, a homogeneous high-speed steel body is considered to be a setting. In these cases, the production therefore assumes heat isostatic compaction. According to such a method, which has achieved some success, put a powder by water granulation. The powder is then annealed to remove oxides and to lower the hardness. Then the powder can pressed cold to the finished form and sintered to almost full density at such a high temperature that the structure is affected. The process can be considered suitable well for the manufacture of wear parts and less qualified tools but I not for high-speed steel tools and the like with very high demands on hardness and durability.

För att framställa hägkvalificerade produkter, såsom snabbstålsverktyg, med färdig form från ett metellpulver, synes en förutsättning vara att man utgår från ett pulver med mycket låg syrehalt. Ett sådant pulver är det pulver som med sfärisk form som används vid ASP-processen. Ett pro- blem.i detta sammanhang är eallertid att detta sfäriska pulver ofta inte kan pressas samman till en grön kropp genom kallisostatisk press- ning. Det har därför föreslagits att anordna pulvret i höljen av olika slag, exempelvis "figurskräddade" plåtbehållare, glasbehållare och så vidare. Alla dessa metoder innebär dock fördyrande moment och är kanske den främsta anledningen till att den pulvermetallurgiska framställningen av högkvalificerade verktyg till färdig form ännu ej fått något genom- brott.In order to produce high-quality products, such as high-speed steel tools, with finished form from a metal powder, a prerequisite seems to be that it is based on a powder with a very low oxygen content. One such powder is the spherical shape powder used in the ASP process. A pro- blem.in this context, however, is that this spherical powder is often can not be compressed into a green body by cold isostatic compression ning. It has therefore been proposed to arrange the powder in casings of different sizes types, for example "figure-tailored" sheet metal containers, glass containers and so on further. However, all of these methods involve costly steps and are perhaps the main reason for the powder metallurgical preparation of highly qualified tools to finished form has not yet received any crime.

REDOGÖRELSE FÖR UPPFINNINGEN Syftet med uppfinningen är att erbjuda en metod vid framställning av kroppar med önskad form från metallpulver som.är praktiskt och ekono- É miskt fördelaktig i förhållande till tidigare föreslagna metoder. I synnerhet är ett syfte att erbjuda en fördelaktig metod att pulver- metallurgískt framställa högkvalificerade verktyg och andra kvalifi- cerade produkter till en form som nära ansluter sig till produktens slutliga form.DESCRIPTION OF THE INVENTION The object of the invention is to offer a method in the manufacture of bodies with the desired shape from metal powder that are practical and economical economically advantageous in relation to previously proposed methods. IN in particular, an object is to offer an advantageous method of metallurgically produce highly qualified tools and other qualified products into a form that is closely related to the product final form.

Vid sättet enligt uppfinningen använder man en form av icke metalliskt 10 15 20 25 30 35 8100945-8 material som bestämmer konturen på den kropp som ska framställas. Formen fylls med metallpulvret, varefter energi tillföres genom formens väggar med så stor effekt och i sådan form att pulvret i formen sintrar eller smälter i det yttersta skiktet av pulverkroppen innanför formväggen, medan metallpulvret längre in i pulverkroppen förblir i fast fas och själva formen förblir opåverkad eller åtminstone inte smälter eller destrueras innan nämnda ytskikt hunnit smälta eller sintra samman. Den sålunda formade grönkroppen avkyls, så att ytskiktet fryser saman till ett tätt skal, varefter grönkroppen kompakteras, företrädesvis genom varmisostatisk kompaktering, till fullständig täthet, varvid det hop- frysta skalet fungerar som kapsel för pulvret där innanför. Då så är önskvärt, med hänsyn till de önskade egenskaperna hos den färdiga kroppen, evakueras luften ur pulverkroppen innan alla ytor på pulver- kroppen har tätats till genom smältning och frysning av ytskiktet.In the method according to the invention a form of non-metallic is used 10 15 20 25 30 35 8100945-8 material that determines the contour of the body to be produced. The shape filled with the metal powder, after which energy is supplied through the walls of the mold with such a great effect and in such a form that the powder in the mold sints or melts in the outermost layer of the powder body inside the mold wall, while the metal powder further into the powder body remains in solid phase and the mold itself remains unaffected or at least does not melt or destroyed before said surface layer has had time to melt or sinter together. The thus formed the green body is cooled, so that the surface layer freezes together to a dense shell, after which the green body is compacted, preferably through heat isostatic compaction, to complete density, whereby the the frozen shell acts as a capsule for the powder inside. Then so be it desirable, taking into account the desired properties of the finished product body, the air is evacuated from the powder body before all surfaces of the powder the body has been sealed by melting and freezing the surface layer.

För att få grönkroppen att lättare släppa från formväggen kan dennas insida bestå av ett material som icke väts av metallen eller legeringen i den pulverkropp vars ytskikt skall smältas eller sintras. Företrädes- vis består metallpulvret av ett höglegerat stålpulver, exempelvis snabb- stålspulver. Väggen kan exempelvis bestå av ett keramiskt material, såsom aluminiumxid. Andra tänkbara material är glas och grafit samt kombinatoner där nämde material kan ingå som insida i formen.To make the green body easier to release from the mold wall can be this inside consist of a material not wetted by the metal or alloy in the powder body whose surface layer is to be melted or sintered. Preferred In this way, the metal powder consists of a high-alloy steel powder, for example steel powder. The wall may, for example, consist of a ceramic material, such as alumina. Other possible materials are glass and graphite as well combination tones where said material can be included as inside the mold.

Energin tillförs med sådan effekt genom formväggen att ytterskiktet i pulverkroppen närmast formväggen smälter eller sintrar. Olika energi- former som kan penetrera formväggen utan att skada denna, eller åtminstone låta formväggen vara intakt i tillräcklig grad tilldess ytterskiktet i pulverkroppen hunnit smälta eller sintra samman samt stabiliserats, är tänkbara. Företrädesvis används laserstrålning. Ett annat tänkbart sätt att tillföra energin till pulverkroppens ytterskikt är via ett elektro- magnetiskt fält med så hög frekvens att, väsentligen på grund av skin- effekten, endast ytskiktet på pulverkroppen smälter eller sintrar samman, medan djupare liggande delar av pulverkroppen icke uppvärms till sin- trings- eller smälttemperatur.The energy is supplied with such an effect through the mold wall that the outer layer in the powder body closest to the mold wall melts or sinter. Different energy shapes that can penetrate the mold wall without damaging it, or at least leave the mold wall intact sufficiently until the outer layer in the powder body has had time to melt or sinter together and has stabilized, is conceivable. Preferably, laser radiation is used. Another possible way to supply the energy to the outer layer of the powder body is via an electro- magnetic field with such a high frequency that, mainly due to the effect, only the surface layer of the powder body melts or sints together, while deeper lying parts of the powder body are not heated to melting or melting temperature.

Den form som används behöver icke nödvändigtvis vara sluten. Man kan även tänka sig att formen har en eller flera öppningar, vilka ej täcks 8100945-8 av en vägg. Exempelvis kan formen av ett kärl utan lock. I detta fall tillförs energin till ytskíktet av pulverkroppen på samma eller på annat sätt till de exponerade delarna av pulverkroppen.The mold used does not necessarily have to be closed. You can also imagine that the mold has one or more openings, which are not covered 8100945-8 of a wall. For example, the shape of a vessel without a lid. In this case the energy is applied to the surface layer of the powder body on the same or on another to the exposed parts of the powder body.

Claims

15 20 25 30 8100945-8 PATENT REQUIREMENTS

A method of producing bodies of the desired shape from metal powder, which method comprises filling a mold which determines the contour of the body to be produced with the metal powder, the mold consisting of a non-metallic material, and energy being supplied by the walls of the mold with such great effect and in such a form that the powder in the mold sinters or melts in the outermost layer inside the mold wall, while the metal powder further into the powder body remains in solid phase and the mold itself remains unaffected or at least does not melt or be destroyed before said surface layer melted or sintered together, characterized in that said energy is supplied in the form of laser radiation, and that the crude body thus formed is cooled, so that the surface layer freezes together into a dense shell, and is compacted, preferably by heat isostatic compaction to complete density, the frozen shell acts as a capsule for the powder inside.

2. A method according to claim 1, characterized in that the mold or at least its inner wall consists of a material which is not wetted by the metal or alloy in the powder body, preferably steel powder, the surface layer of which is to be melted or sintered.

3. A method according to claim 2, characterized in that said wall consists of a ceramic material - for example alumina -, glass and / or graphite.

4. A method according to any one of claims 1 - 3, characterized in that the air is evacuated from the mold and from the powder body before all surfaces of the powder body have been sealed by melting and freezing the surface layer. 8100945-8 _1o 15 Summum; When producing bodies of the desired shape from metal powder, the powder is filled into a mold which determines the contour of the body to be produced. The mold consists of a non-metallic material, and the energy is supplied through the walls of the mold with such great effect and in such a form that the powder in the mold sinter or melts in the outermost layer inside the mold wall, while metal powder further into the powder body remains in solid phase and the mold itself remains unaffected or at least not melted or destroyed before said surface layer has had time to melt or sinter together. After cooling, so that the surface layer freezes together into a dense shell, the thus-formed green body is compacted, preferably by hot-isostatic compaction to complete density, the frozen shell acting as a capsule for the powder inside.