Disclosure of Invention
The invention aims to provide a method for improving the hardness of H13 steel, which is to weld alloy powder with high hardness on an H13 steel substrate through 3D printing so as to improve the wear resistance and heat resistance of H13 steel.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method of increasing the hardness of H13 steel, comprising:
providing H13 steel as a substrate;
providing a high hardness alloy in powder form, and overlaying one or more layers of the high hardness alloy on the surface of the substrate to produce the desired metallic material.
In a preferred embodiment, the total thickness of the layers of high hardness alloy deposited on the substrate surface is 5-25mm, more preferably 10-18mm, more preferably 12-15mm, such as 13mm, 14 mm.
In a preferred embodiment, the thickness of each layer of the high hardness alloy is 0.5-2.5mm, more preferably 0.8-2mm, more preferably 1-1.5 mm.
In a preferred embodiment, a part needing surfacing welding is machined on the surface of the base material; the high hardness alloy is built up as one or more layers at the location where build up is desired.
In a preferred embodiment, the substrate surface is pretreated at the location where the weld deposit is desired. Wherein, the pretreatment can be one or more of cleaning, heating and polishing.
Preferably, the overlaying one or more layers of high hardness alloy on the substrate surface comprises: each layer is formed by adding a material of the high-hardness alloy, irradiating the material layer with a laser or electron beam over the material layer, causing at least part of the high-hardness alloy to melt into a molten state, and cooling and forming a solidified layer.
Preferably, a layer of the high-hardness alloy is laid on the surface of the base material, preferably on the part of the surface of the base material, which needs to be subjected to surfacing, and is melted into a molten state and cooled to form a solidified layer; and continuously paving the high-hardness alloy on the surface of the solidified layer, melting the high-hardness alloy into a molten state, and cooling to form the next solidified layer.
Preferably, the Rockwell hardness of one or more solidified layers formed on the surface of the base material by the high-hardness alloy is 57-59 HRC.
Preferably, the substrate is H13 steel.
Preferably, the pretreatment of the substrate surface comprises: polishing and cleaning the surface of the base material; and preheating the substrate to a set temperature.
Preferably, the method further comprises: and performing finish machining on the surface of the metal material subjected to surfacing to form a smooth surface.
Preferably, the overlaying mode is manual arc overlaying or laser cladding.
More preferably, in the process of cladding the high-hardness alloy on the surface of the base material by adopting a laser cladding mode, the power of the laser is 1200-1800W (preferably 1400-1600W), the scanning speed of the laser is 5-10mm/s (more preferably 6-8mm/s), the powder feeding amount is 20-50g/min (more preferably 30-40g/min), and the diameter of a spot formed by the laser is 0.8-1.3mm, more preferably 1-1.1 mm.
Preferably, the substrate is maintained at room temperature during processing until printing is complete.
Preferably, the high-hardness alloy comprises the following components in percentage by weight based on the total weight of the high-hardness alloy:
c: less than or equal to 0.5 percent but not 0 percent;
Si:0.5-6%;
Mn:0.01-0.11%;
P:0.01-0.07%;
S:0.01-0.06%;
Cr:6-13%;
mo: less than or equal to 1.2 percent but not 0 percent;
Ti:0.0-0.6%;
V:1.0-1.8%;
the balance of Fe and inevitable impurities.
More preferably, the high-hardness alloy comprises the following components in percentage by weight based on the total weight of the high-hardness alloy:
c: less than or equal to 0.5 percent but not 0 percent;
Si:1.0-5%;
Mn:0.01-0.10%;
P:0.01-0.06%;
S:0.01-0.05%;
Cr:8-12%;
mo: less than or equal to 1.2 percent but not 0 percent;
Ti:0.1-0.5%;
V:1.1-1.7%;
the balance of Fe and inevitable impurities.
More preferably, the high-hardness alloy comprises the following components in percentage by weight based on the total weight of the high-hardness alloy:
c: less than or equal to 0.5 percent but not 0 percent;
Si:1.0-4%;
Mn:0.01-0.09%;
P:0.01-0.05%;
S:0.01-0.04%;
Cr:8-10%;
mo: less than or equal to 1.2 percent but not 0 percent;
Ti:0.1-0.4%;
V:1.1-1.6%;
the balance of Fe and inevitable impurities.
More preferably, the high-hardness alloy comprises the following components in percentage by weight based on the total weight of the high-hardness alloy: c: less than or equal to 0.5 percent but not 0 percent;
Si:1.0-3.5%;
Mn:0.01-0.085%;
P:0.01-0.045%;
S:0.01-0.035%;
Cr:8.5-10%;
mo: less than or equal to 1.2 percent but not 0 percent;
Ti:0.2-0.35%;
V:1.15-1.55%;
the balance of Fe and inevitable impurities.
The inevitable impurities in the present invention are components that are originally contained in the raw materials or are included in the present invention by mixing in during the smelting process, and are not intentionally added components.
Preferably, the high-hardness alloy is entirely elemental powder, or at least comprises elemental powder.
More preferably, the particle size of the elemental powder is preferably 50 to 250 mesh, more preferably 60 to 200 mesh.
Further, the elemental powder described herein may be present in such a manner that the particle diameter of a part of the powder exceeds the above mesh number range, but the powder weight ratio exceeding this range cannot exceed 10%.
More preferably, the particle sizes of any two elemental powders may be the same or different.
Compared with the prior art, the invention has the beneficial effects that:
the alloy powder of the invention takes C, Si, Mn, P, S, Cr, Mo, Ti, V and the like as the strengthening elements of the steel material, and the metal material prepared by overlaying the powder on the surface of the H13 hot work die steel substrate by the additive manufacturing technology has better high-temperature wear resistance compared with the traditional H13 hot work die steel, and has the characteristics of obvious thermal fatigue resistance, higher hardness in a high-temperature state and good tempering stability.
Detailed Description
In order to make the objects, technical solutions and effects of the present invention clearer and clearer, the present invention is further described in detail below by referring to the accompanying drawings and examples, and it should be understood that the specific embodiments described herein are only used for explaining the present invention and are not used for limiting the present invention.
In the present application, the powdery high-hardness alloy for additive manufacturing contains C, Si, Mn, P, S, Cr, Mo, Ti, V, and the like as the reinforcing elements of the H13 steel material.
The action and the selection of the content range of each component of the high-hardness alloy of the present invention will be further described below, and in the following description, the addition amount of each component is expressed in weight ratio (%).
C: less than or equal to 0.5 percent but not 0 percent;
carbon (C) can improve the strength and hardness of steel and improve the wear resistance of steel. In order to ensure that the material after the quenching and tempering treatment has higher strength, the content of C is not zero. However, since too high a content of C is disadvantageous in impact toughness, the content of C needs to be controlled, and in the present invention, the content of C is controlled to 0.50% or less.
Si:0.5-6%;
Silicon (Si) is a deoxidized material, and this element promotes an increase in hardness and ensures machinability of steel. In addition, Si can be used to prevent temper softening of martensite in the base material and suppress the HAZ softening width. In order to effectively exhibit these effects, the lower limit of the content of Si is 0.5%. However, the addition of too high a content of Si is disadvantageous in toughness, and thus the content of Si is controlled to 6% or less in the present invention.
Mn:0.01-0.11%;
Manganese (Mn) is added as a deoxidizer and a desulfurizer, and the addition of a certain amount of Mn element is beneficial to the thermal stability of steel, and in addition, Mn element can cause the content of residual austenite in steel to be increased and stabilized, so that the toughness and thermal fatigue resistance of the steel can be improved, and therefore, the lower limit of the Mn content is 0.01%. However, if the Mn content is too large, the toughness of the base material is increased to lower the machinability, and therefore, the Mn content is controlled to 0.11% or less.
P:0.01-0.07%;S:0.01-0.06%;
Phosphorus (P) and sulfur (S) are used as impurity elements, which are unfavorable for the toughness of the material, probably because S forms sulfide inclusions to reduce plasticity, and (Fe + FeS) eutectic is easy to form in a sulfur-containing atmosphere to cause a cracking phenomenon, so that the content of the S is reduced as much as possible; too high a P content leads to a decrease in low-temperature toughness and an increase in cold-brittle transition temperature, so that the P content should be minimized to avoid or reduce adverse effects on plasticity. However, when the contents of S and P in the steel are lower, the cost for removing these elements will be higher, and in order to make the hot-work die steel maintain excellent performance and reduce the production cost as much as possible for mass production, the S content is controlled to 0.01-0.06% and the P content is controlled to 0.01-0.07%.
Cr:6-13%;
In order to improve the strength of the die, chromium (Cr) with a relatively large content is added, wherein the Cr is an essential element for obtaining good corrosion resistance and oxidation resistance, and the Cr in the steel can be combined with oxygen to form a compact oxidation film on the surface so as to contribute to improving the oxidation resistance. In order to ensure the oxidation resistance of the steel, the Cr content should be higher than 6.0%. However, when Cr is excessively added, high-temperature δ ferrite is likely to appear to deteriorate mechanical properties, and therefore, Cr is limited to 13.0% or less. Therefore, the Cr content is controlled to be 6.0-13.0%.
Mo: less than or equal to 1.2 percent but not 0 percent;
molybdenum (Mo) element has stronger carbide forming capability, improves the heat strength of the material, and simultaneously, the high-hardness dispersed carbide particles can have better wear resistance. However, the Mo content should not be too high, otherwise the impact toughness is unfavourable. From the above point of view, the amount of Mo added should not exceed 1.2%.
Ti:0.0-0.6%;
Titanium (Ti) can be preferentially combined with C to form strong carbide, the grain growth is controlled during high-temperature austenitizing, the effect of grain refinement is achieved, if the content is too high, the primary carbide formed during material solidification is too much and large in size, and the improvement of impact toughness and fatigue performance of hot-work die steel is not facilitated, so that the content of Ti does not exceed 0.6% so as to play the role of grain refinement.
V:1.0-1.8%;
Vanadium (V), like Mo, can form VC carbides during tempering, which have a large particle size and not only do not improve the properties of the steel but also reduce the toughness and thermal fatigue properties of the steel, etc., which are difficult to completely eliminate during subsequent heat treatment. Therefore, the proportion of VC primary carbides can be effectively reduced by properly reducing the content of V in the steel, and the performance of the steel is improved; however, in the tempering process, V can reduce the decomposition speed of martensite and delay the transformation of austenite, and V forms MC type secondary carbide which is fine and dispersed and difficult to gather and grow, so that in the tempering process, the secondary hardening effect is enhanced, and the thermal stability and the impact toughness of the steel are greatly improved; therefore, the content of V in the steel is controlled to be 1.0-1.8%, and the alloying effect of V is fully exerted.
The balance of Fe and inevitable impurities.
The inevitable impurities in the present invention are components that are originally contained in the raw materials or are included in the present invention by mixing in during the smelting process, and are not intentionally added components.
Example 1
High hardness alloy powders for additive manufacturing are prepared. In this example, the ratio of the components of the powder to the total weight is as follows:
C:0.5%;
Si:5%;
Mn:0.1%;
P:0.06%;
S:0.05%;
Cr:12%;
Mo:1.0%;
Ti:0.5%;
V:1.7%;
the balance being Fe.
The additive manufacturing method comprises the following steps:
machining a part to be subjected to surfacing welding on the surface of the H13 base material by a pre-machining machine, and finishing hardening heat treatment; the grain diameter of the high-hardness alloy powder is 53-150 mu m, and the powder is fed by inert gas;
the high-hardness alloy powder is subjected to overlaying welding on the surface of the H13 base material according to a set printing track by adopting a laser beam and coaxial powder feeding cladding mode, and the thickness of an overlaying layer is 14mm, so that the required metal material is prepared. Wherein the power of the laser is 1600W, the scanning speed of the laser is 8mm/s, the powder feeding amount is 40g/min, and the diameter of a facula formed by the laser is 1 mm.
Specifically, as shown in fig. 1, the welding high-hardness alloy 2 is in a powder form. The powdery high-hardness alloy 2 is uniformly converged and sent into the focused laser beam 1, and the powder flow and the laser beam 1 are coaxially coupled and output. The laser beam 1 heats the base material 4 into a molten pool 3, the powdery high-hardness alloy 2 is sprayed into the molten pool 3, and the high-hardness alloy 2 is deposited to form a formed part.
The metal material formed by laser cladding is different from H13 base material, and belongs to the combination of heterogeneous materials, but the cladding layer and the base material are well combined, no defects such as air holes, impurities, cracks and the like appear, and the Rockwell hardness of the surface layer can reach 55-57 HRC.
Example 2
High hardness alloy powders for additive manufacturing are prepared. In this example, the ratio of the components of the powder to the total weight is as follows:
C:0.4%;
Si:4%;
Mn:0.08%;
P:0.04%;
S:0.03%;
Cr:10%;
Mo:1.0%;
Ti:0.4%;
V:1.5%;
the balance being Fe.
The additive manufacturing method comprises the following steps:
machining a part to be subjected to surfacing welding on the surface of the H13 base material by a pre-machining machine, and finishing hardening heat treatment; the grain diameter of the high-hardness alloy powder is 53-150 mu m, and the powder is fed by inert gas; the high-hardness alloy powder is subjected to overlaying welding on the surface of the H13 base material according to a set printing track by adopting a laser and coaxial powder feeding cladding mode, and the thickness of an overlaying layer is 14mm, so that the required metal material is prepared. Wherein the power of the laser is 1600W, the scanning speed of the laser is 8mm/s, the powder feeding amount is 40g/min, and the diameter of a facula formed by the laser is 1 mm.
The metal material formed by laser cladding is different from H13 base material, and belongs to the combination of heterogeneous materials, but the cladding layer and the base material are well combined, no defects such as air holes, impurities, cracks and the like appear, and the Rockwell hardness of the surface layer can reach 55-57 HRC.
Example 3
High hardness alloy powders for additive manufacturing are prepared. In this example, the ratio of the components of the powder to the total weight is as follows:
C:0.3%;
Si:3%;
Mn:0.05%;
P:0.03%;
S:0.02%;
Cr:9%;
Mo:0.8%;
Ti:0.3%;
V:1.4%;
the balance being Fe.
The additive manufacturing method comprises the following steps:
machining a part needing surfacing on the surface of the H13 base material by a pre-machining machine, or cleaning the surface of the H13 base material needing surfacing, and finishing hardening heat treatment; the grain diameter of the high-hardness alloy powder is 53-150 mu m, and the powder is fed by inert gas; the high-hardness alloy powder is subjected to overlaying welding on the surface of the H13 base material according to a set printing track by adopting a laser and coaxial powder feeding cladding mode, and the thickness of an overlaying layer is 14mm, so that the required metal material is prepared. Wherein the power of the laser is 1600W, the scanning speed of the laser is 8mms, the powder feeding amount is 40g/min, and the diameter of a facula formed by the laser is 1 mm.
The metal material formed by laser cladding is different from H13 base material, and belongs to the combination of heterogeneous materials, but the cladding layer and the base material are well combined, no defects such as air holes, impurities, cracks and the like appear, and the Rockwell hardness of the surface layer can reach 55-57 HRC.
In the above examples 1 to 3 of the present invention, the hardness of the powdery high-hardness alloy after the build-up welding on the surface of the H3 base material is shown in table 1, wherein the current is 150A and the voltage is 22V.
TABLE 1 results of Performance test
|
Example 1
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Example 1
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Example 3
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HRC hardness (Single layer)
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57-59
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57-59
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57-59
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HRC hardness (two layers)
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57-59
|
57-59
|
57-59
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Surface smoothness
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Is substantially smooth
|
Is substantially smooth
|
Is substantially smooth
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Bonding strength with H13 steel
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Can not be separated
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Can not be separated
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Can not be separated |
The results show that the metal material which is made by using high-hardness alloy powder of C, Si, Mn, P, S, Cr, Mo, Ti, V and the like as reinforcing elements of the steel material and overlaying the high-hardness alloy powder on the surface of H13 steel by an additive manufacturing technology belongs to the combination of heterogeneous materials compared with the traditional H13 hot work die steel, but the cladding layer is well combined with the base material, the surface is flat and smooth, no defects such as air holes, impurities, cracks and the like appear, the Rockwell hardness of the surface layer reaches 57-59HRC, the performances of the hot work die steel in the aspects of hardness, wear resistance, toughness and impact resistance are greatly improved compared with H13, the process is simple and reliable, and the service life and the reliability of the hot work die are greatly prolonged.
The embodiments of the present invention have been described in detail, but the embodiments are merely examples, and the present invention is not limited to the embodiments described above. Any equivalent modifications and substitutions to those skilled in the art are also within the scope of the present invention. Accordingly, equivalent changes and modifications made without departing from the spirit and scope of the present invention should be covered by the present invention.