CN1876879A - Micro-alloy weldable cast steel tooth stand and preparation method thereof - Google Patents

Abstract

This invention discloses a kind of microalloy welded cast-steel tooth holder, of which characteristic lies at its chemical composition: C 0.15-0.25wt%,Si 0.3-1.0wt%,Mn 0.6-1.4wt%,Cr 0.4-1.0wt%,B 0.0005-0.007wt%, Al 0.01-0.1wt%,Ce 0-0.045wt%,La 0-0.035wt%,Ti 0-0.1wt%,P<=0.03wt%,S<= 0.03wt%, and the other is iron and inevitable impurity. By double treating, the tooth holder is of moderate intensity and rigidity, high dynamic ductility, good welding performance, is especially suitable for producing tooth holder or root of tooth of digging machine bucket.

Description

A kind of micro-alloy weldable cast steel tooth stand and preparation method thereof

Technical field

The present invention relates to metal material field, particularly the cast steel field relates to a kind of micro-alloy weldable cast steel tooth stand and preparation method thereof specifically.

Background technology

Toothholder claims tooth root again, is one of vitals of excavator-type shovel clamshell excavator, is structural part, is again wearing piece.Be welded on the blade board of bucket front end by the electric welding mode during work, connect and compose the excavation assembly by pin with the disassembling bucket tooth.According to the functional analysis of toothholder, the toothholder material should have following performance:

(1) good welding property.The welding of toothholder and blade board mostly occurs in the building site, requires to adapt to welding condition and the envrionment temperature that changes, and weld seam can not crack.

(2) high impelling strength.In excavating assembly, the toothholder reliability of material will be higher than bucket tooth, and the life-span of bucket tooth is generally tens hours to hundreds of hour, and the life requirements several months of toothholder, so the impelling strength of toothholder material will be higher than bucket tooth material, general requirement A _Kv〉=30J.

(3) certain wear resistance.Surface hardness requires greater than 35HRC.

(4) proper intensity performance.General requirement σ _b〉=800MPa.

Existing toothholder material has two kinds.A kind of is common 35 ^#Cast steel, thermal treatment process are that normalizing adds toothholder head selective hardening, 35 ^#The weldability of cast steel tooth stand and wearing no resistance, impelling strength and tensile strength are also lower, welding crack and toothholder head rupture phenomenon often take place in the military service process, even fracture or crackle do not take place, owing to the surface hardness of toothholder head is crossed quick-wearing less than 30HRC, the life-span of this toothholder has only 1～2 month usually, therefore, and 35 ^#Cast steel can not satisfy the material requirements of toothholder, but 35 ^#Cast steel tooth stand cheap for manufacturing cost, price is cheap, also has certain market share.Another kind of toothholder material is a low chrome molybdenum cast steel in the low-carbon (LC), thermal treatment process is 900～950 ℃ of quenchings, 500～650 ℃ of tempering, its Chemical Composition is (w%): C≤0.28, Si0.3～0.9, Mn0.6～1.0, Cr0.9～1.2, Mo0.2～0.3, P, S≤0.03, can also add (w%) Ni1.0 as required, carbon equivalent ce 0.51～0.81, welding property are slightly inadequate, but have no problem with A3 steel or the blade board welding that is all low-carbon alloy steel, other performance all can satisfy the requirement of toothholder material preferably, weak point is the material cost height, and toothholder price height has reduced the market competitiveness.

Summary of the invention

Technical problem to be solved by this invention is to provide a kind of performance requriements that can satisfy the toothholder material at above-mentioned prior art present situation, but and material and welded cast steel toothholder material cheap for manufacturing cost.

But another technical problem to be solved by this invention is to provide a kind of method of making above-mentioned welded cast steel toothholder material at above-mentioned prior art present situation.

The present invention solves the problems of the technologies described above the technical scheme that is adopted:

Micro-alloy weldable cast steel tooth stand of the present invention is characterized in that its Chemical Composition is: C0.15～0.25wt%, Si0.3～1.0wt%, Mn0.6～1.4wt%, Cr0.4～1.0wt%, B0.0005～0.007wt%, Al0.01～0.1wt%, Ce0～0.045wt%, La0～0.035wt%, Ti0～0.1wt%, P≤0.03wt%, S≤0.03wt%, all the other are Fe and unavoidable impurities element.

Wherein the content of Ce, La is preferably: Ce0.001～0.045wt%, La0.001～0.035wt%.

Wherein the content of Ti is preferably: Ti0.01～0.1wt%.

The optimal technical scheme of micro-alloy weldable cast steel tooth stand of the present invention is: wherein the content of C, Si, Mn, Cr, B, Ce, La, Ti is: C0.15～0.23wt%, Si0.3～0.6wt%, Mn0.9～1.2wt%, Cr0.4～0.7wt%, B0.002～0.004wt%, Ce0.005～0.02wt%, La0.005～0.02wt%, Ti0.015～0.35wt%.

The present invention prepares the method for described micro-alloy weldable cast steel tooth stand, comprises molten steel melting and heat treatment step, it is characterized in that:

In the described molten steel melting step, B, Ti, Ce, La adds with the form of BFe alloy, TiFe alloy and ReSiFe alloy respectively, and the adding method is: normal process for making is finished and is added the TiFe alloy after the back rises to 1600～1610 ℃ to liquid steel temperature, molten clearly, skim, then go out molten steel, in casting ladle, drop into BFe alloy and ReSiFe alloy simultaneously to the meter ladle introversion;

The technology of described heat treatment step adds tempering for quenching, and quenching and tempering process parameters are:

(1) during B＜0.004wt%, quenching temperature is 900～950 ℃; During B 〉=0.004wt%, quenching temperature is 950～1020 ℃;

When (2) requiring surface hardness 〉=35HRC, select 200～230 ℃ of tempering 2～3 hours; When requiring surface hardness＜35HRC, select 450～500 ℃ of tempering 1～3 hour.

In the molten steel melting, the BFe alloy is packed with container made of iron, and the ReSiFe alloy encapsulates with the plastic packaging bag.

Corresponding to preferred micro-alloy weldable cast steel tooth stand technical scheme, quench in the described heat treatment step and tempering process parameters is: 920～950 ℃ of insulations quenching in 2～3 hours, 200～230 ℃ of tempering 2～3 hours.

The cast steel tooth stand material that obtains by technical scheme of the present invention top layer and sublayer phase constitution be martensite or martensitic high, medium and low temperature tempered structure, core structure is that martensite adds a little ferrite or martensitic high, medium and low temperature tempered structure adds a little ferrite.

The effect of each element is as follows:

C: be the element that influences cast steel welding property maximum, C content is high more, and welding property is poor more.C0.15～0.25wt% of the present invention belongs to the soft steel scope, and the C0.15～0.23wt% after the optimization has guaranteed the welding property that material is good, and low carbon content can be guaranteed the impelling strength of material simultaneously.

Si, Mn, Cr: be element commonly used in the steel alloy, adding these three kinds of alloying elements among the present invention is to remedy undercapacity and the not enough problem of hardening capacity that low carbon content brings, make material that enough intensity and hardness be arranged, content is controlled at the disadvantageous effect that can reduce in the optimization range welding property.

B: belong to microalloy element, the martensitic substructure of refinement greatly greatly increases the hardening capacity of steel, improves the impelling strength and the fracture toughness property of steel.

Ti: also belong to microalloy element, it mainly acts on is crystal grain thinning and fixed nitrogen, and at weld structure, the carbonitride of Ti can hinder the grain growth of welded heat affecting zone effectively, improves the intensity of heat affected zone, prevents the generation of welding crack.

Ce, La are rare earth (RE) microalloy element, mainly act as refined cast structure, purify crystal boundary, improve the form of carbide and inclusion, also have the effect of refinement martensite crystalline substance.Help improving toughness of material.

Al: be the residual content of steelmaking aluminum silk deoxidation, keep the suitable residual amount of aluminium, can prevent the secondary oxidation of molten steel.

Because microalloy element content is very low, and is very little to the influence of material welding performance, so the welding property of cast steel material of the present invention still can characterize with carbon equivalent:

Carbon equivalent ce (%)=C+Mn/6+ (Cr+Mo+V)/5+ (Si+Ni)/15

The carbon equivalent ce of calculation optimization composition (%) is 0.40～0.63 according to this, less than industrywide standard 0.68, has guaranteed material welding performance.

Press the composition of the present invention's optimization and the mechanical property such as the table 1 of the standard coupon that thermal treatment process prepares

The mechanical property of the standard coupon of table 1 cast steel of the present invention

Element term	Content (w%)	Tensile strength sigma b (MPa)	Yield strength σ s (MPa)	Unit elongation δ 5(％)	Relative reduction in area Ψ (%)	The surface is 2mm place hardness (HRC) down	Room temperature impact absorbing energy Akv (J)
								C	0.17	1080	856	3.2	9.75	37	40
Si	0.55
		Mn	1.01
Cr	0.49
		B	0.0033
Ti	0.029
		Ce	0.017
La	0.013
		Al	0.027
P	0.022
		S	0.026

The data of table 1 show that material of the present invention can satisfy the performance requriements of toothholder material fully.And the cost of material is low for it, less than 70% of low chrome molybdenum cast steel price in the low-carbon (LC).

Material of the present invention with low chrome molybdenum cast steel in 35# cast steel and the low-carbon (LC) difference be tangible, with comparing of the applicant at first to file ZL200410067527.2 " a kind of wearable cast steel in microalloy martensite ", the principle of microalloying and effect are basic identical, but because the formulation principle of basic alloy Elements C, Si, Mn, Cr is different with content, make the performance difference of material, purposes is also different.Carbon content at first to file ZL200410067527.2 " a kind of wearable cast steel in microalloy martensite " is C0.25～0.34wt%, and material has the high strength and high hardness characteristics after the thermal treatment, its tensile strength sigma _b〉=1600MPa, more than the HRC48, can not weld, be suitable for making the wearing pieces such as bucket tooth that high-strength high-wearing feature requires, and the carbon content of material of the present invention only is C0.15～0.25wt%, and intensity and hardness are moderate after the thermal treatment, and impelling strength is better than the former, welding property is good, is suitable for making toothholder or tooth root.

Embodiment

Below in conjunction with embodiment the present invention is described in further detail.

Embodiment:

Below the preparation of micro-alloy weldable cast steel tooth stand among each embodiment, comprise molten steel melting and heat treatment step:

Wherein in the molten steel melting step, B, Ti, Ce, La adds with the form of BFe alloy, TiFe alloy and ReSiFe alloy respectively, and the adding method is: normal process for making is finished and is added the TiFe alloy after the back rises to 1600～1610 ℃ to liquid steel temperature, molten clearly, skim, then go out molten steel, in casting ladle, drop into BFe alloy and ReSiFe alloy simultaneously to the meter ladle introversion;

The technology of heat treatment step adds tempering for quenching, and quenching and tempering process parameters are:

(1) during B＜0.004wt%, quenching temperature is 900～950 ℃; During B 〉=0.004wt%, quenching temperature is 950～1020 ℃;

When (2) requiring surface hardness 〉=35HRC, select 200～230 ℃ of tempering 2～3 hours; When requiring surface hardness＜35HRC, select 450～500 ℃ of tempering 1～3 hour.

In the molten steel melting, the BFe alloy is packed with container made of iron, and the ReSiFe alloy encapsulates with the plastic packaging bag.

Corresponding to preferred micro-alloy weldable cast steel tooth stand technical scheme, quench in the heat treatment step and tempering process parameters is: 920～950 ℃ of insulations quenching in 2～3 hours, 200～230 ℃ of tempering 2～3 hours.

Performance such as the table 1 (seeing page 5) and the table 2 (seeing the 6th page) of the toothholder made from the cast steel of the embodiment of the invention, wherein table 1 is the simultaneous test data of embodiment cast steel on same model toothholder 7120 of different chemical composition of the present invention, and table 2 is optimized the daily detection data of the toothholder of composition for the present invention.

By table 1 and table 2 as seen, can satisfy the requirement of toothholder material fully with the mechanical property of the toothholder of embodiment of the invention cast steel manufacturing.And on probation through the building site, prove that it can reach toothholder material welding performance and mechanical property requirements fully, can reach the level of low chrome molybdenum cast steel in the low-carbon (LC) work-ing life fully.

The detection data of 7120 toothholders of table 1 different components of the present invention

Name of product	Chemical ingredients (wt%) S, P＜0.03									Hardness (HRC) under the 2mm of surface	Room temperature impact absorbing energy Akv (J)
												C	Si	Mn	Cr	Al	Ti	B	Ce	La
	7120 toothholders	0.25	0.57	1.39	1.0	0.03		0.0005														35	31
0.25										0.57	1.39	1.0	0.03	0.097	0.0005			35	32
		0.25	0.57	1.39	1.0	0.03		0.0005	0.044											0.033	35	32.5
0.25										0.57	1.39	1.0	0.03	0.097	0.0005	0.044	0.033	35.5	37
		0.21	0.99	0.61	0.71	0.025		0.0069													44	38
0.21										0.99	0.61	0.71	0.025	0.01	0.0069			43.5	39
		0.21	0.99	0.61	0.71	0.025		0.0069	0.045											0.034	43.5	39.5
0.21										0.99	0.61	0.71	0.025	0.01	0.0069	0.045	0.034	44	43
		0.19	0.52	1.08	0.57	0.033	0.023	0.0033	0.015											0.012	42	40.5

The daily detection performance of the toothholder of the preferred composition of table 2 the present invention

Name of product	Chemical ingredients (wt%) S, P＜0.03									Hardness (HRC) under the 2mm of surface	Room temperature impact absorbing energy A kv(J)
												C	Si	Mn	Cr	Al	Ti	B	Ce	La
	1U-1254	0.23	0.55	1.04	0.49	0.028	0.035	0.003	0.013												0.012	43	41
20Y-939-2211										0.17	0.55	1.01	0.49	0.027	0.029	0.003	0.011	0.010	42	40
	3G 6304HD	0.18	0.48	0.92	0.56	0.027	0.031	0.004	0.014												0.013	36	40
3G6304										0.2	0.32	1.01	0.45	0.019	0.024	0.003	0.010	0.013	42	40
	AF01L	0.19	0.42	0.96	0.47	0.023	0.02	0.005	0.017												0.015	40	59
3G 8354HD										0.23	0.47	1.08	0.52	0.019	0.022	0.003	0.008	0.005	43	34
	3G 6304ZX	0.19	0.46	1.08	0.48	0.005	0.021	0.003	0.019												0.017	42	32
205-939-7120										0.18	0.37	1.13	0.56	0.012	0.025	0.001	0.014	0.016	40	37
	3G 8354	0.23	0.31	1.01	0.5	0.023	0.034	0.004	0.015												0.017	44	32
3G 6304HD										0.22	0.47	1.07	0.52	0.036	0.035	0.003	0.012	0.011	42.5	32
	3G 8354	0.20	0.6	1.06	0.52	0.032	0.032	0.005	0.017												0.019	40	30
1U0307										0.16	0.43	1.06	0.49	0.021	0.03	0.001	0.02	0.019	40	37.5
	1U0307	0.15	0.44	1.0	0.63	0.022	0.03	0.003	0.016												0.018	39	40
3G 6304										0.21	0.44	0.93	0.56	0.016	0.033	0.003	0.012	0.012	42	33

Claims (6)

1, a kind of micro-alloy weldable cast steel tooth stand is characterized in that its Chemical Composition is: C 0.15～0.25wt%, Si 0.3～1.0wt%, Mn 0.6～1.4wt%, Cr 0.4～1.0wt%, B 0.0005～0.007wt%, Al 0.01～0.1wt%, Ce 0～0.045wt%, La 0～0.035wt%, Ti 0～0.1wt%, P≤0.03wt%, S≤0.03wt%, all the other are Fe and unavoidable impurities element.

2, cast steel tooth stand according to claim 1 is characterized in that wherein the content of Ce, La is: Ce0.001～0.045wt%, La 0.001～0.035wt%.

3, cast steel tooth stand according to claim 1 and 2 is characterized in that wherein the content of Ti is: Ti 0.01～0.1wt%.

4, cast steel tooth stand according to claim 3, it is characterized in that wherein the content of C, Si, Mn, Cr, B, Ce, La, Ti is: C 0.15～0.23wt%, Si 0.3～0.6wt%, Mn 0.9～1.2wt%, Cr 0.4～0.7wt%, B 0.002～0.004wt%, Ce 0.005～0.02wt%, La 0.005～0.02wt%, Ti 0.015～0.35wt%.

5, a kind of method for preparing micro-alloy weldable cast steel tooth stand as claimed in claim 1 comprises molten steel melting and heat treatment step, it is characterized in that:

In the described molten steel melting step, B, Ti, Ce, La adds with the form of BFe alloy, TiFe alloy and ReSiFe alloy respectively, and the adding method is: normal process for making is finished and is added the TiFe alloy after the back rises to 1600～1610 ℃ to liquid steel temperature, molten clearly, skim, then go out molten steel, in casting ladle, drop into BFe alloy and ReSiFe alloy simultaneously to the meter ladle introversion;

The technology of described heat treatment step adds tempering for quenching, and quenching and tempering process parameters are:

(1) during B＜0.004wt%, quenching temperature is 900～950 ℃; During B 〉=0.004wt%, quenching temperature is 950～1020 ℃;

When (2) requiring surface hardness 〉=35HRC, select 200～230 ℃ of tempering 2～3 hours; When requiring surface hardness＜35HRC, select 450～500 ℃ of tempering 1～3 hour.

6, method according to claim 5 is characterized in that in the described heat treatment step quenching and tempering process parameters is: 920～950 ℃ of insulations quenching in 2～3 hours, 200～230 ℃ of tempering 2～3 hours.