DE102019206674A1 - Process for recompaction and hardening of components made of martensitic and / or precipitation hardening steels - Google Patents

Abstract

The present invention proposes a method for re-compacting and hardening components made of martensitic and / or precipitation hardening steels, the method having the following method steps: Treating at least one component made of martensitic and / or precipitation hardening steel in a hot isostatic press at a first temperature and a first pressure, whereby the component is post-compacted in the hot isostatic press and at the same time solution annealed and / or austenitized, quenching of the component in the hot isostatic press, optional deep-freezing of the component to a freezing temperature, optional precipitation hardening or tempering of the component at a second temperature.

Description

The present invention relates to a method for re-compacting and hardening components made of martensitic and / or precipitation-hardening steels and a re-compacted and hardened component made of martensitic and / or precipitation-hardening steel.

State of the art

The mechanical properties of martensitic and / or precipitation hardening steels can be improved by heat treatments. Such steels have proven themselves in additive manufacturing and are a widely used standard quality.

DE 10 2016 225 616 A1 describes a process for additive manufacturing.

Disclosure of the invention

1. a) Behandeln von zumindest einem Bauteil aus martensitischem und/oder ausscheidungshärtendem Stahl in einer heißisostatischen Presse bei einer ersten Temperatur und einem ersten Druck, wobei das Bauteil in der heißisostatischen Presse nachverdichtet und gleichzeitig austenitisiert und gegebenenfalls lösungsgeglüht wird,
2. b) Abschrecken des Bauteils in der heißisostatischen Presse,
3. c) Optional Tiefkühlen des Bauteils auf eine Tiefkühltemperatur,
4. d) Optional Ausscheidungshärten oder Anlassen des Bauteils bei einer zweiten Temperatur.

The present invention relates to a method for re-compacting and hardening components made of martensitic and / or precipitation hardening steels, the method having the following method steps:

1. a) treating at least one component made of martensitic and / or precipitation hardening steel in a hot isostatic press at a first temperature and a first pressure, the component being post-compacted in the hot isostatic press and simultaneously austenitized and optionally solution annealed,
2. b) quenching the component in the hot isostatic press,
3. c) Optional deep-freezing of the component to a freezing temperature,
4. d) Optional precipitation hardening or tempering of the component at a second temperature.

"Additive manufacturing" is also known under the terms "3D printing" or "Additive Manufacturing" (AM). For example, components made of 1.4542 steel can be produced by selective laser beam melting or laser sintering. The components are mostly made of steel powder, which is why such processes are also known as powder metallurgical processes.

It has been shown that steels produced by powder metallurgy have to be subsequently compacted in order to achieve the desired mechanical properties due to defects such as high porosity or connection defects. Hot isostatic presses (HIP) are usually used for recompaction. In a HIP, a component is isostatically compressed in a heatable pressure vessel at high temperature and high gas pressure. Due to the high gas pressure, the same pressure acts on all sides of the component, so that the component can acquire isotropic properties.

Compared to a heat treatment following the hot isostatic pressing, the method according to the invention allows particularly efficient post-compression and hardening, so that desired mechanical characteristics can be achieved more easily.

A method for re-compacting and hardening components made of martensitic and / or precipitation hardening steels is therefore proposed.

Steels are to be understood as meaning, in particular, stainless steels, with stainless steels in the context of the present invention being understood to mean steels which are more resistant to corrosion and acids due to a high proportion of chromium. Stainless steels usually have a chromium content of more than 10.5% by weight, the chromium being dissolved in the austenitic or ferritic mixed crystal. Steels are materials whose iron mass fraction is greater than that of any other element and whose carbon content is generally less than 2% by weight. Stainless steels within the meaning of the present invention can also have further alloy components such as nickel, molybdenum, manganese, niobium, vanadium, tungsten, titanium and / or copper.

For the purposes of the present invention, martensitic steels are to be understood as meaning steels which have a martensite structure.

Precipitation-hardening steels in the context of the present invention are understood to mean steels which form precipitates at a precipitation temperature.

For the purposes of the present invention, martensitic and precipitation-hardening steels are to be understood as meaning steels which are martensitic at a precipitation temperature and which form precipitates.

For example, this includes steels such as 1.4542 steel. Under the steel 1.4542 is the after DIN EN 1008-3 steel designated as 1.4542 or X5CrNiCuNb 16-4. In particular, the steel can for example have a composition of carbon in one Range from greater than or equal to 0% by weight to less than or equal to 0.07% by weight, silicon in a range from greater than or equal to 0% by weight to less than or equal to 0.7% by weight, manganese in one Range from greater than or equal to 0% by weight to less than or equal to 1.5% by weight, phosphorus in a range from greater than or equal to 0% by weight to less than or equal to 0.04% by weight, sulfur in one Range from greater than or equal to 0% by weight to less than or equal to 0.03% by weight, chromium in a range from greater than or equal to 15% by weight to less than or equal to 17% by weight, molybdenum in a range from greater than or equal to 0% by weight to less than or equal to 0.6% by weight, nickel in a range from greater than or equal to 3% by weight to less than or equal to 5% by weight, copper in a range from greater than or equal to equal to 3% by weight to less than or equal to 5% by weight, niobium in a range from greater than or equal to 0% by weight to less than or equal to 0.45% by weight and the remainder iron.

1. a) Behandeln von zumindest einem Bauteil aus martensitischem und/oder ausscheidungshärtendem Stahl in einer heißisostatischen Presse bei einer ersten Temperatur und einem ersten Druck, wobei das Bauteil in der heißisostatischen Presse nachverdichtet und gleichzeitig austenitisiert und gegebenenfalls lösungsgeglüht wird,
2. b) Abschrecken des Bauteils in der heißisostatischen Presse,
3. c) Optional Tiefkühlen des Bauteils auf eine Tiefkühltemperatur,
4. d) Optional Ausscheidungshärten oder Anlassen des Bauteils bei einer zweiten Temperatur.

The method according to the invention has the following method steps:

1. a) treating at least one component made of martensitic and / or precipitation hardening steel in a hot isostatic press at a first temperature and a first pressure, the component being post-compacted in the hot isostatic press and simultaneously austenitized and optionally solution annealed,
2. b) quenching the component in the hot isostatic press,
3. c) Optional deep-freezing of the component to a freezing temperature,
4. d) Optional precipitation hardening or tempering of the component at a second temperature.

It can preferably be provided that method steps a to d are carried out chronologically in the specified order.

The method according to the invention enables components made of martensitic and / or precipitation hardening steel to be compacted and hardened with less process effort.

In particular, the simultaneous re-compaction and solution annealing or austenitizing means that the component does not have to be additionally heat-treated separately after re-compaction.

The simultaneous recompaction and solution annealing or austenitizing can be achieved in particular by quenching the component in the hot isostatic press, since quenching outside the hot isostatic press would cause cooling down too slowly and thus the effect of solution annealing or austenitizing would be canceled.

By quenching the component in the hot isostatic press, it can therefore be achieved that the component does not have to be additionally solution annealed or austenitized after it has been compacted in the hot isostatic press.

In addition, it can advantageously be achieved that the formation of coarse grain is reduced or prevented, since the total annealing time, or the total time of the component at high temperature, can be shortened by combining the compression and the solution annealing and / or austenitizing.

The recompaction and austenitizing and optionally solution annealing can be carried out with a conventional hot isostatic press known to the person skilled in the art.

As a result of the treatment at the first temperature, it can be achieved that microsegregations in the component are dissolved during a solution heat treatment. For the purposes of the present invention, microscopic segregation refers to microscopic segregation of an alloy, which results in differences in the concentration of the various alloying elements within a component.

In addition, it can be achieved that the steel is austenitized, i.e. converted into an austenite structure. An austenite structure or austenitic structure is the face-centered cubic structure of iron and its alloys.

The component is then quenched in the hot isostatic press in process step b).

In the context of the present invention, quenching the component is understood to mean a rapid reduction in the temperature of the component.

This can ensure that the steel continues to be present as a homogeneous alloy and that no thermodynamically more stable compounds are deposited that could impair the mechanical properties of the component. In addition, after austenitizing, the steel can be transformed into a martensite structure and not into ferrite. In the context of the present invention, ferrite is to be understood as the body-centered cubic modification of iron and its mixed crystals.

After process step b), the component can optionally be deep-frozen to a deep-freeze temperature in process step c). For the purposes of the present invention, deep-freezing means cooling understood at least below 0 ° C. The deep freezing can be carried out using a conventional method. For example, the component can be put from the chamber into a freezer, in which it is frozen to a suitable temperature.

It can thereby be achieved that at least part of an austenitic structure of the component is converted into a martensitic structure. In particular, it can thereby be achieved that the majority of an austenitic structure of the component is converted into a martensitic structure.

After process step c), the component can optionally be precipitation hardened or tempered at a second temperature in process step d).

In the context of the present invention, precipitation hardening is understood to mean heating to a temperature at which the precipitation of phases is formed in finely divided form. Tempering in the context of the present invention is understood to mean heating to a moderate temperature at which stresses in the component are released, the temperature in any case being below the austenitizing temperature. The tempering and / or precipitation hardening can be implemented according to a conventional method, for example by heating the component in an oven.

With the method described above, it can therefore be achieved that components made of martensitic and / or precipitation hardening steel can be compressed and hardened with less process effort.

In one embodiment of the method according to the invention, it can be provided that method step a) is carried out at a first temperature in a range from greater than or equal to 1000 ° C. to less than or equal to 1300 ° C.

As a result, microsegregations in the component can be resolved, whereby the mechanical properties of the component can later be adjusted particularly well and / or it can be achieved that at least part of the component is converted into an austenite structure.

In one embodiment of the method according to the invention, it can be provided that in method step a) the component is treated at the first temperature for a duration in a range from greater than or equal to 30 minutes to less than or equal to 3 hours.

As a result, it can be achieved that a large part of micro-segregation in the component is dissolved, whereby the mechanical properties of the component can later be adjusted particularly well and / or it can be achieved that a large part of the component is converted into an austenite structure.

In one embodiment of the method according to the invention, it can be provided that in method step a) the component is treated at a pressure in a range from greater than or equal to 50 bar to less than or equal to 3000 bar

As a result, it can advantageously be achieved that the component is isostatically compressed particularly well.

In one embodiment of the method according to the invention, it can be provided that the component in method step a) at a first temperature in a range from greater than or equal to 1020 ° C to less than or equal to 1100 ° C, preferably greater than or equal to 1050 ° C to less or equal 1100 ° C, is austenitized, in particular without a solution heat treatment.

As a result, it can advantageously be achieved that the steel is at least partially converted into an austenite structure and alloy components of the steel can be dissolved in the austenite structure. In particular, it can thereby advantageously be achieved that the component has only a reduced amount, preferably essentially no, chromium precipitates.

In one embodiment of the method according to the invention, it can be provided that the component is solution annealed and austenitized at a first temperature in method step a). For example, one embodiment of the method according to the invention can provide that the component is solution annealed and austenitized in method step a) at a first temperature in a range from greater than or equal to 1100 ° C. to less than or equal to 1250 ° C., preferably greater than or equal to 1150 ° C ° C to less than or equal to 1200 ° C.

As a result, it can advantageously be achieved that microsegregations in the component are particularly well resolved.

In one embodiment of the method according to the invention, it can be provided that in method step b) a temperature of the component is reduced from the first temperature to a temperature of less than or equal to 200 ° C. within less than or equal to 5 minutes.

As a result, it can advantageously be achieved that essentially no or only a few chromium nitrides / carbides are precipitated and have a negative impact on the mechanical properties of the component.

In one embodiment of the method according to the invention, it can be provided that method step c) is carried out at a deep-freeze temperature in a range from greater than or equal to -273 ° C. to less than or equal to -20 ° C., in particular from greater than or equal to -196 ° C. to less or equal to -30 ° C, preferably from greater than or equal to -100 ° C to less than or equal to -70 ° C, preferably for a duration in a range from greater than or equal to 30 minutes to less than or equal to 2 hours at the freezing temperature.

The deep freezing temperature and / or the duration of the deep freezing can advantageously achieve that a large part of the austenitic structure of the component is converted into a martensitic structure. In particular, it can thereby be achieved that the austenitic structure of the component is essentially completely converted into a martensitic structure.

In one embodiment of the method according to the invention, it can be provided that the second temperature is a precipitation hardening temperature and method step d) is precipitation hardening at a precipitation hardening temperature in a range from greater than or equal to 350 ° C. to less than or equal to 750 ° C., preferably for one duration Range from greater than or equal to 1 hour to less than or equal to 6 hours.

As a result, it can advantageously be achieved that precipitates which improve the strength of the component are formed particularly effectively.

In one embodiment of the method according to the invention, it can be provided that the second temperature is a tempering temperature and method step d) is tempering at a tempering temperature in a range from greater than or equal to 180 ° C. to less than or equal to 550 ° C., preferably for one duration Range from greater than or equal to 60 min to less than or equal to 240 min.

In this way, it can advantageously be achieved that stresses that can arise in the component as a result of quenching and deep-freezing of the component are reduced particularly well.

In one embodiment of the method according to the invention, it can be provided that the component consists of 1.4542 steel and was produced by means of layer-by-layer melting of powder material, in particular by means of laser sintering.

The invention also relates to an additively manufactured component made of martensitic and / or precipitation-hardening steel, for example, the component having been post-densified and hardened according to the method described above.

It can thereby be achieved that the component has good mechanical characteristics and has a particularly low proportion of coarse grain.

Further advantages and advantageous configurations of the method and component according to the invention are illustrated by the figure and the example and explained in the description below. It should be noted that the figure and the example are only of a descriptive character and are not intended to restrict the invention in any way.

Figure list

• 1 a flow chart of the method according to the invention.

1 shows a flow diagram of the method for re-compacting and hardening components made of martensitic and / or precipitation hardening steels. The method includes the step 1 Treatment of at least one component made of martensitic and / or precipitation hardening steel in a hot isostatic press (HIP) at a first temperature and a first pressure, the component being post-compacted in the hot isostatic press and at the same time austenitized and optionally solution annealed. In a further step 2 the component is quenched in the hot isostatic press. In addition, the component is in an optional step 3 Frozen at a freezer temperature and in an optional step 4th precipitation hardened or tempered at a second temperature.

Example A:

A component made from steel 1.4542 by means of laser sintering was solution annealed in a hot isostatic press for 2 hours at a second temperature of 1150 ° C. and simultaneously compressed at 200 bar. The solution-annealed component was then quenched to 100 ° C. in the course of 4 minutes using air at 10 bar. The component was then placed in a freezer and frozen at -80 ° C for 1.5 hours. The component was then used for 1 Precipitation hardened at 480 ° C for hours.

The component that was compacted and hardened according to the invention exhibited after precipitation hardening the same mechanical parameters as a component that was separately solution annealed in a furnace after hot isostatic pressing and was not quenched in the hot isostatic press. The component according to the invention also had a lower proportion of coarse grain. The grain size of the component according to the invention is thus approximately 30% smaller than that of a conventionally treated component, as an example. In addition, the elongation at break of the component compacted and hardened according to the invention is up to 25% greater than that of an untreated component.

As a result of the method according to the invention, it was surprisingly possible to achieve that components can be compacted and hardened while saving process steps.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102016225616 A1 [0003]

Non-patent literature cited

• DIN EN 1008-3 [0013]

Claims (10)

Process for re-compacting and hardening components made of martensitic and / or precipitation hardening steels, the process comprising the following process steps: a) treating at least one component made of martensitic and / or precipitation hardening steel in a hot isostatic press at a first temperature and a first pressure, the component being post-compacted in the hot isostatic press and simultaneously austenitized and optionally solution annealed, b) quenching the component in the hot isostatic press, c) Optional deep-freezing of the component to a freezing temperature, d) Optional precipitation hardening or tempering of the component at a second temperature. Procedure according to Claim 1 , characterized in that process step a) is carried out at a first temperature in a range from greater than or equal to 1000 ° C to less than or equal to 1300 ° C. Method according to one of the Claims 1 or 2 , characterized in that in process step a) the component is treated at a pressure in a range from greater than or equal to 50 bar to less than or equal to 3000 bar. Method according to one of the Claims 1 to 3 , characterized in that the component is austenitized in process step a) at a first temperature in a range from greater than or equal to 1020 ° C to less than or equal to 1100 ° C, preferably greater than or equal to 1050 ° C to less than or equal to 1100 ° C . Method according to one of the Claims 1 to 3 , characterized in that the component is austenitized and solution annealed in process step a) at a first temperature in a range from greater than or equal to 1100 ° C to less than or equal to 1250 ° C, preferably from greater than or equal to 1150 ° C to less than or equal to 1200 ° C. Method according to one of the Claims 1 to 5 , characterized in that in method step b) a temperature of the component is reduced from the first temperature to less than or equal to 200 ° C within less than or equal to 5 minutes. Method according to one of the Claims 1 to 6th , characterized in that method step c) is carried out at a deep-freeze temperature in a range from greater than or equal to -273 ° C to less than or equal to -20 ° C, in particular from greater than or equal to -196 ° C to less than or equal to -30 ° C , preferably from greater than or equal to -100 ° C to less than or equal to -70 ° C, preferably for a period in a range from greater than or equal to 30 minutes to less than or equal to 2 hours at the freezing temperature. Method according to one of the Claims 1 to 7th , characterized in that the second temperature is a precipitation hardening temperature and process step d) precipitation hardening at a precipitation hardening temperature in a range from greater than or equal to 350 ° C to less than or equal to 750 ° C, preferably for a duration in a range greater than or equal to 1 Hour to less than or equal to 6 hours. Method according to one of the Claims 1 to 8th , characterized in that the second temperature is a tempering temperature and method step d) tempering at a tempering temperature in a range from greater than or equal to 180 ° C to less than or equal to 550 ° C, preferably for a duration in a range greater than or equal to 60 min to less than or equal to 240 min. Component, in particular additively manufactured component, made of martensitic and / or precipitation-hardening steel, the component according to one of the Claims 1 to 9 was compacted and hardened by.

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