CN103114221B - Lead-free free-cutting silicon brass alloy and preparation method thereof - Google Patents

Abstract

The invention discloses a lead-free free-cutting silicon brass alloy and a preparation method thereof. The silicon brass alloy comprises the following components and contents: 28-34wt% of zinc, 2.2-3.5wt% of silicon, 0.5-1.8wt% of zinc sulfide and the balance of copper. The lead-free free-cutting silicon brass alloy has the beneficial effects that the copper content in brass alloy is less than 70%, and the free-cutting performance of brass alloy is improved through adjusting the contents of zinc, silicon and zinc sulfide added in brass alloy; the obtained free-cutting brass alloy is low in cost; and zinc sulfide is introduced in silicon brass by using an in-situ synthesis technology and is brittle, so that the effect of improving the cutting performance of brass is achieved.

Description

A kind of lead-free free-cutting silicon brass alloy and preparation method thereof

Technical field

The present invention relates to easily-cut silicon brass alloy field, particularly a kind of lead-free free-cutting silicon brass and preparation method thereof.

Background technology

Because the Application Areas of brass alloys is very extensive, so its cutting ability directly has influence on the yield rate of material machinofacture, production cost and production efficiency.Existing free-cutting brass mainly comprises leaded brass, because leaded casting yellow copper alloy has excellent cutting ability and castability and production cost is lower, so be widely applied to various fields.But, along with the development of industrialization society, lead manifests day by day to the harm of ecotope, so developed country is devoted to the research of easy-cutting lead-free brass always, easy-cutting lead-free brass is exactly by the Composition Design in improvement brass, the element substitution suitably adding other a small amount of toxicological harmlesss is plumbous, is formed with the cenotype being beneficial to and improving brass cutting ability in the alloy, reaches free machining object.These substitute plumbous element mainly bismuth, silicon, antimony, tellurium, graphite and magnesium etc.From practical angle, drop into mainly Bi brass and the silicon brass of application at present both at home and abroad.In the silicon brass developed, product can be formed and drop into the unleaded silicon brass series product mainly developed by Japanese Triratna company applied.The principal character of Triratna series product is that copper content is very high, generally all higher than 70%, so this kind of silicon brass cost is higher than general brass product, is difficult to be easily accepted by a user, thus limits applying of it.

Summary of the invention

The object of this invention is to provide a kind of castability, forgeability is excellent, the easily-cut silicon brass alloy of cutting ability, good mechanical performance, required raw metal advantage of lower cost.

According to an aspect of the present invention, provide lead-free free-cutting silicon brass alloy, its component and content

Comprise:

In some embodiments, inevitable foreign matter content≤0.8wt% in alloy.

In some embodiments, the content of zinc is 30 ~ 31wt%, and the content of silicon is 2.5 ~ 3wt%, and the content of zinc sulphide is 1 ~ 1.5wt%, and surplus is copper.

In some embodiments, the content of zinc is 31wt%, and the content of silicon is 3wt%, and the content of zinc sulphide is 1wt%, and surplus is copper.

Another aspect of the present invention also relate to a kind of preparation method of lead-free free-cutting silicon brass alloy, comprises the following steps:

Step 1, alloying constituent proportion design: zinc 28 ~ 34wt%, silicon 2.2 ~ 3.5wt%, zinc sulphide 0.5 ~ 1.8wt%, surplus is copper;

Step 2, prepare prefabricated section: copper powder, sulfuration copper powder, zinc powder are fully mixed rear compacting with the ratio of 4:3:3 and form prefabricated section;

Step 3, melting: first electrolytic copper is added smelting furnace and melt with stove, by Control for Kiln Temperature at 1040 ~ 1100 DEG C, then prefabricated section and silicon is added, can by the high temperature generation reaction in－situ of copper liquid after prefabricated section adds, after question response fully carries out, cool to 450 ~ 500 DEG C with the furnace, add pure zinc and stir, be then incubated 5 ~ 15 minutes;

Step 4, copper alloy liquid watered cast from swage and obtain silicon brass alloy ingot casting.

In some embodiments, described silicon brass alloy ingot casting is heated to 700 ~ 750 DEG C and carries out hot extrusion finished product.

The factor affecting brass material cutting ability is main relevant to alloy structure and mechanical property.If the α phase that brass tissue is single, this phase matter is soft, and its plasticity is good, adds the long bits that are easy to get man-hour continuously, entwines at cutter and workpiece, unfavorable to cutting.If other phases having other intensity, hardness, plasticity to differ larger with α phase on α phase matrix exist, especially there is β phase, γ phase time, because γ phase matter is hard and in fragility, so under action of pulling stress, these brittlement phase are easily broken, these brittlement phase organize the continuity just destroying plasticity good α phase matrix, there is the effect of chip breaking, thus be conducive to the cutting ability improving brass alloys.

Zinc is the main alloy element in brass, and the impact of change on brass alloys of its content is larger.In the present invention, the content of zinc is 28 ~ 34wt%, when Zn content is less than 28wt%, γ phase volume fraction is less, little to the effect of the cutting ability of brass alloys, along with Zn content raises, the α phase volume fraction in brass alloys reduces, and the volume fraction of β phase, γ phase increases, the cutting ability of brass alloys increases.

The change of silicone content is also larger to the performance impact of brass alloys.In the present invention, the content of silicon is 2.2 ~ 3.5wt%, when silicone content is less than 2wt%, cutting ability does not reach satisfied effect, when silicone content is higher than 3.5wt%, although the cutting ability of brass alloys is improved, but the tensile strength of brass alloys is lower, the application of brass alloys is had an impact.

Zinc sulphide improves the cutting ability of brass mutually in brass alloys mainly as chip breaking.The existence of zinc sulphide can be considered in alloy substrate the hole occurring that some are small, wherein be filled with the zns particle of fragility, these holes destroy the continuity of matrix, become stress raiser, form many reduction microcells, easily produce breeding and the motion of stress concentration and dislocation in these regions, produce notched effect, under the effect of shearing stress, realize chip breaking.In the present invention, the content of zinc sulphide is 0.5 ~ 1.8wt%, when the content of zinc sulphide is less than 0.5wt%, not obvious on the cutting ability impact of brass alloys, along with the increasing of content of zinc sulphide, the cutting ability of brass alloys is better improved, but consider the factor of the over-all properties of cost and brass alloys, so the content controlling zinc sulphide is not more than 1.8wt%.

Compared with prior art, its beneficial effect is in the present invention, and in brass alloys, copper content is less than 70%, and improved the free cutting property of brass alloys by the content of the zinc, silicon and the zinc sulphide that add in adjustment brass, gained free machining brass alloys cost is lower.Because the viscosity of brass alloys metal melt is very high, the particle diameter of the zinc sulphide added is very little, density is also lower than the density of copper liquid, after zinc sulphide joins the metal of melting, be subject to capillary effect, float over metal melt surface, the feasibility that the surface tension making these particles overcome metallic solution is distributed in melt is equably very little, so the method that the present invention relates to adopts cupric sulfide to be starting material, fabricated in situ technique is adopted to introduce zinc sulphide in silicon brass, zinc sulphide is fragility, thus reaches the effect improving brass cutting ability.

Accompanying drawing explanation

Fig. 1 is the cutting ability chip shape of the lead-free free-cutting silicon brass of the embodiment of the present invention 1;

Fig. 2 is the cutting ability chip shape of the lead-free free-cutting silicon brass of the embodiment of the present invention 2;

Fig. 3 is the cutting ability chip shape of the lead-free free-cutting silicon brass of the embodiment of the present invention 3;

Fig. 4 is the cutting ability chip shape of the lead-free free-cutting silicon brass of the embodiment of the present invention 4;

Fig. 5 is the SEM tissue topography figure of the lead-free free-cutting silicon brass of the embodiment of the present invention 1.

Embodiment

Below in conjunction with embodiment, the present invention is further detailed explanation.

One, the preparation method of lead-free free-cutting silicon brass, its concrete technology is:

Step 1, design alloying constituent proportioning, the component namely in alloy and content comprise: copper 62 ~ 68wt%, zinc 28 ~ 34wt%, silicon 2.2 ~ 3.5wt%, zinc sulphide 0.5 ~ 1.8wt%, and surplus is copper;

Step 2, prepare prefabricated section: copper powder, sulfuration copper powder, zinc powder are fully mixed rear compacting with the ratio of 4:3:3 and form prefabricated section, by the copper powder, sulfuration copper powder, the zinc powder Homogeneous phase mixing on mixed powder machine that prepare in proportion, by mixed powder briquetting on oil press.

Step 3, melting: first electrolytic copper is added smelting furnace and melt with stove, by Control for Kiln Temperature at 1040 ~ 1100 DEG C, then prefabricated section and silicon is added, can by the high temperature generation reaction in－situ of copper liquid after prefabricated section adds, after question response fully carries out, cool to 450 ~ 500 DEG C with the furnace, add pure zinc, abundant stirring makes its uniform composition, is incubated 5 ~ 15 minutes; Wherein reaction in－situ is: CuS+Zn → ZnS+Cu, thus realizes the object introducing zinc sulphide in brass alloys solution; Wherein, the melting of brass alloys is that induction melting furnace carries out frequently in a vacuum.

In the thermodynamic (al) theory of classics, usually judge that can a reaction be spontaneously carried out according to Gibbs function criterion.The process that system Gibbs function reduces can spontaneously be carried out, and is in equilibrium state when Gibbs function is constant, namely wants keeping system to stablize and must meet △ G≤0.

According to the second law of thermodynamics, under isothermal and isobaric condition, have:

$\mathrm{\Δ}{G}_T^{\mathrm{\θ}}=\mathrm{\Δ}{H}_T^{\mathrm{\θ}}-\mathrm{T\Δ}{S}_T^{\mathrm{\θ}}$

In formula, be above designated as standard atmospheric pressure, for the standard Gibbs free energy change of reaction, for the Standard Enthalpies change of reaction, for the standard entropy change of reaction, T is absolute temperature.In formula for the function of temperature, be respectively:

$\mathrm{\Δ}{H}_T^{\mathrm{\θ}}=\mathrm{\Δ}{H}_{298}^{\mathrm{\θ}}+{\∫}_{298}^T\mathrm{\Δ}{C}_p{d}_T$

$\mathrm{\Δ}{S}_T^{\mathrm{\θ}}=\mathrm{\Δ}{S}_{298}^{\mathrm{\θ}}+{\∫}_{298}^T\frac{\mathrm{\Δ}{C}_p{d}_T}{T}$

△ C in two formulas _pfor the thermal capacitance of resultant and reactant is poor, the thermal capacitance of material is the function of a temperature, i.e. following formula:

C _p=A ₁+A ₂×10 ^-3T+A ₃×10 ⁵T ^-2+A ₄×10 ^-6T ²+A ₅×10 ⁸T ^-3

A in formula ₁, A ₂, A ₃, A ₄, A ₅for being returned the constant obtained by experimental data,

Can obtain thus:

△C _p=△A ₁+△A ₂×10 ^-3T+△A ₃×10 ⁵T ^-2+△A ₄×10 ^-6T ²+△A ₅×10 ⁸T ^-3

Each reactant and resultant a ₁, A ₂, A ₃, A ₄, A ₅value all obtains by searching thermodynamic data handbook, just can be obtained gibbs free energy change value before and after the reaction under assigned temperature by calculating thus gibbs criterion can be used the feasibility of reacting under judging this temperature.This thermodynamic criterion of sulfide fabricated in situ technological basis described in the invention and designing, this reaction process: CuS+Zn → ZnS+Cu, each thermodynamic data related to is listed in table a.Can calculate according to data in table with the relation function of T.Under smelting temperature of the present invention, the Gibbs free energy of this reaction is less than 0, shows that this reaction designed can spontaneously be carried out.

Table a is the thermodynamic data of each material used

Step 4, copper alloy liquid watered cast from swage and obtain silicon brass alloy ingot casting;

Step 5, silicon brass alloy ingot casting is heated to 700 ~ 750 DEG C, and by mould and die preheating to 150 ~ 200 DEG C, is that 9:1 carries out hot extrusion finished product with extrusion ratio.

Embodiment 1

Alloying constituent is designed and after preparing prefabricated section by table 1, first electrolytic copper is joined in smelting furnace and melt with stove, Control for Kiln Temperature, at 1040 DEG C, then adds prefabricated section and silicon, can by the high temperature generation reaction in－situ of copper liquid after prefabricated section adds, after question response fully carries out, cool to 450 DEG C with the furnace, add pure zinc, fully stir and make its uniform composition, be incubated 5 minutes, copper alloy liquid watered and casts from swage and obtain silicon brass alloy ingot casting; Silicon brass alloy ingot casting is heated to 700 DEG C, and by mould and die preheating to 150 DEG C, is that 9:1 carries out hot extrusion finished product with extrusion ratio.

Table 1 is braze alloy components of the present invention (wt%)

Alloying element	Copper	Zinc	Silicon	Zinc sulphide	Component in the prefabricated block quality proportioning
						Content	Surplus	28	2.2	1.8	Copper: cupric sulfide: zinc=4:3:3

Embodiment 2

Alloying constituent is designed and after preparing prefabricated section by table 2, first electrolytic copper is joined in smelting furnace and melt with stove, Control for Kiln Temperature, at 1050 DEG C, then adds prefabricated section and silicon, can by the high temperature generation reaction in－situ of copper liquid after prefabricated section adds, after question response fully carries out, cool to 450 DEG C with the furnace, add pure zinc, fully stir and make its uniform composition, be incubated 8 minutes, copper alloy liquid watered and casts from swage and obtain silicon brass alloy ingot casting; Silicon brass alloy ingot casting is heated to 750 DEG C, and by mould and die preheating to 150 DEG C, is that 9:1 carries out hot extrusion finished product with extrusion ratio.

Table 2 is braze alloy components of the present invention (wt%)

Alloying element	Copper	Zinc	Silicon	Zinc sulphide	Component in the prefabricated block quality proportioning
						Content	Surplus	30	2.5	1.5	Copper: cupric sulfide: zinc=4:3:3

Embodiment 3

Alloying constituent is designed and after preparing prefabricated section by table 3, first electrolytic copper is joined in smelting furnace and melt with stove, Control for Kiln Temperature, at 1100 DEG C, then adds prefabricated section and silicon, can by the high temperature generation reaction in－situ of copper liquid after prefabricated section adds, after question response fully carries out, cool to 500 DEG C with the furnace, add pure zinc, fully stir and make its uniform composition, be incubated 15 minutes, copper alloy liquid watered and casts from swage and obtain silicon brass alloy ingot casting; Silicon brass alloy ingot casting is heated to 700 DEG C, and by mould and die preheating to 150 DEG C, is that 9:1 carries out hot extrusion finished product with extrusion ratio.

Table 3 is braze alloy components of the present invention (wt%)

Alloying element	Copper	Zinc	Silicon	Zinc sulphide	Component in the prefabricated block quality proportioning
						Content	Surplus	31	3	1	Copper: cupric sulfide: zinc=4:3:3

Embodiment 4

Alloying constituent is designed and after preparing prefabricated section by table 4, first electrolytic copper is joined in smelting furnace and melt with stove, Control for Kiln Temperature, at 1100 DEG C, then adds prefabricated section and silicon, can by the high temperature generation reaction in－situ of copper liquid after prefabricated section adds, after question response fully carries out, cool to 500 DEG C with the furnace, add pure zinc, fully stir and make its uniform composition, be incubated 15 minutes, copper alloy liquid watered and casts from swage and obtain silicon brass alloy ingot casting; Silicon brass alloy ingot casting is heated to 720 DEG C, and by mould and die preheating to 150 DEG C, is that 9:1 carries out hot extrusion finished product with extrusion ratio.

Table 4 is braze alloy components of the present invention (wt%)

Alloying element	Copper	Zinc	Silicon	Zinc sulphide	Component in the prefabricated block quality proportioning
						Content	Surplus	34	3.5	0.5	Copper: cupric sulfide: zinc=4:3:3

In above-mentioned all embodiments, all there is inevitable impurity in silicon brass alloy, this inevitable foreign matter content≤0.8wt%.

Comparative example

Using HPb59-1 leaded brass as comparative example, its composition is copper 57.0 ~ 60.0wt%, plumbous 0.8 ~ 1.9wt%, aluminium≤0.2, iron≤0.5, antimony≤0.01, bismuth≤0.003, phosphorus≤0.02, and surplus is zinc.

Two, the performance test of the brass alloys of each embodiment and comparative example

The alloy of the alloy and comparative example of getting the embodiment of the present invention carries out performance test under the same conditions, relates generally to the test of tensile strength, unit elongation, Brinell hardness and machinability index.

The test of machinability rating adopts external cutting test, the deliberated index of machinability mainly adopts the difficulty or ease of chip breaking: adopt GSK928TC-2 digital controlled lathe to carry out cutting test, cutter material YG8, main shaft rotating speed 1000r/min, back engagement of the cutting edge 2mm, speed of feed 0.15mm/r.

With HPb59-1 leaded brass, (composition is copper 57.0 ~ 60.0wt%, plumbous 0.8 ~ 1.9wt%, aluminium≤0.2, iron≤0.5, antimony≤0.01, bismuth≤0.003, phosphorus≤0.02, surplus is zinc) cutting ability be 80%, evaluate the cutting ability of other brass of each embodiment of the present invention with this standard.

Table 5 is the tensile strength of each embodiment and comparative example, unit elongation and Brinell hardness and machinability index

The chip shape of the lead-free free-cutting silicon brass alloy of each embodiment of the present invention as shown in Figure 1 to 4.As can be seen from the figure, chip is light and collapses the short bits of broken C type, illustrates that the cutting ability of alloy is excellent.

The displaing micro tissue topography of the embodiment of the present invention 1 lead-free free-cutting silicon brass alloy as shown in Figure 5.As can be seen from the SEM photo in figure, in lead-free free-cutting silicon brass alloy except matrix phase, also there is the Micro-v oid of particulate state and strip at intracrystalline and grain boundaries.Carried out energy spectrum analysis judgement mutually to part remaining inside hole, these holes are vestiges that ZnS particle detachment stays.The reason come off is compound ZnS is fragility, and more weak with matrix phase bonding force, easily comes off in process prepared by metallographic sample pre-grinding.According to form and the distribution at these hole places, can learn in alloy structure to there is more ZnS particle at matrix phase crystal boundary and intracrystalline, in test, metallic sulfide introducing obtains successfully.

As can be seen from Table 5, lead-free free-cutting silicon brass alloy over-all properties of the present invention is good, and the machinability index of leaded brass in its machinability index and comparative example is close, has good cutting ability.

In sum, in brass alloys of the present invention, copper content is less than 70%, the cutting ability of brass alloys is improved by the content of the zinc, silicon and the zinc sulphide that add in adjustment brass, gained brass alloys mechanical property and cutting ability good, product cost is lower simultaneously, is conducive to the practical application of brass alloys.

Claims (1)

1. a preparation method for lead-free free-cutting silicon brass alloy, is characterized in that, adopting with cupric sulfide is introduce zinc sulphide in raw-material fabricated in situ normal direction brass alloys, specifically comprises the following steps:

Step 1, design alloying constituent proportioning: zinc 28 ~ 34wt%, silicon 2.2 ~ 3.5wt%, zinc sulphide 0.5 ~ 1.8wt%, surplus is copper;

Step 2, prepare prefabricated section: copper powder, sulfuration copper powder, zinc powder are fully mixed rear compacting with the weight ratio of 4:3:3 and form prefabricated section;

Step 3, melting: first electrolytic copper is added smelting furnace and melt with stove, by Control for Kiln Temperature at 1040 ~ 1100 DEG C, then prefabricated section and silicon is added, can by the high temperature generation reaction in－situ of copper liquid after prefabricated section adds, after question response fully carries out, cool to 450 ~ 500 DEG C with the furnace, add pure zinc and stir, be then incubated 5 ~ 15 minutes;

Step 4, copper alloy liquid watered to cast from mold obtain silicon brass alloy ingot casting;

Described silicon brass alloy ingot casting is heated to 700 ~ 750 DEG C and carries out hot extrusion finished product.