CN1028767C - Method for low-temp annealing of forgeable cast iron - Google Patents

Abstract

The present invention relates to a low-temperature rapid annealing method of forgeable cast iron under the function of a catalytic atmosphere, which uses a catalyst of a multi-contract silanol polymer for changing the original heat preservation of a high temperature section and a low temperature section of the forgeable cast iron annealing method into the mode of carrying out the graphitization of one-time heat preservation. The annealing temperature is decreased from 930 to 980 DEG C to 830 to 890 DEG C. The low-temperature rapid annealing method has the advantages of short annealing period, low annealing temperature, high annealing quality and wide chemical ingredient range of an annealing component.

Description

Method for low-temp annealing of forgeable cast iron

The present invention relates to the method for low-temp annealing of forgeable cast iron, more particularly, relate to a kind of low temperature quick annealing method of malleable iron under the effect of catalyzer atmosphere.

As everyone knows, malleable cast iron annealing temperature height, cycle are long, temperature is up to 960 ℃ even 980 ℃, so that cause foundry goods gross distortion or damage, cycle reaches five, 60 hours, some technology reaches 70-120 hour, so not only cause production efficiency low, annealing part yield rate is low, of poor quality, also bring shortcomings such as energy consumption height, annealing box and annealing furnace life-span weak point simultaneously, so people are exploring the method that reduces annealing temperature, shortens the annealing cycle, improves the quality of products, but do not make great progress always always.

The forties, malleable iron have adopted reduction, controlled atmosphere or inert atmosphere annealing, are not subjected to or oxidated effect less but this method only plays the protection foundry goods, do not play much effects to reducing annealing temperature and shortening cycle.The auspicious slip-stick artist of sixties model essay carries out malleable iron catalysis annealing in Shijiazhuang diesel engine factory and office with metallic zinc atmosphere first, makes the cycle shorten to 24-32 hour from 80-120 hour, and at 70,80 for widespread use.Though the annealing of zinc atmosphere is just like economizing on coal, can improve advantages (seeing " malleable iron communication " 84 year 11 phase and " zinc atmosphere annealing data compilation ") such as annealing part mechanical property, cycle weak point, but because of the boiling point of zinc is 907 ℃, so can not be used to be lower than 910 ℃ low-temperature annealing, annealing temperature higher (high temperature adopts 960-980 ℃) is not resolved, need consume metallic zinc simultaneously, unfavorable saving metallic zinc resource.In recent years external report (see " malleable iron communication " 84 years 11 phase 4 pages), appropriate change spoken parts in traditional operas base Chemical Composition, make and siliceously bring up to 1.8%, on bismuth-containing 0.01% basis, add forming core essence boron and aluminium, can make annealing temperature be reduced to 820 ℃ under the annealing cycle not changing from 920 ℃, India P.L.poy etc. studies show that, the spoken parts in traditional operas blank that the molten iron of handling through sodium-chlor waters was 700 ℃ of annealing 60-90 hour.Can obtain ferrite malleable.But these researchs all are not used for actual production, and have both made and be applied to produce because of its change and inoculation of placing on Chemical Composition yet, make the mitis metal of existing general composition still can't adopt low-temperature annealing.

The object of the invention provides a kind of method of novel low-temp annealing of forgeable cast iron, it can be broken away from simple dependence energy (kinetic energy, interior energy) and change the approach that impels the annealing process greying to finish, accelerate and take to utilize katalysis to impel cementite to decompose, reach the purpose of shortening annealing cycle, reduction annealing temperature, raising annealing quality.Feature of the present invention is to utilize activated carbon and organic silicide such as trichlorine silicomethane, tetraethyl silicate or/and inorganic solvable silicide such as water glass, pure aluminium silicate, preferably the compound that adds graphite element again reacts, hydrolysis, air-dry, stewing putting and the catalyzer of the multiple silicon shrinking alcohol polymkeric substance made, it can roll off the production line at the low-temperature annealing graphitization temperature and gasify below 700 ℃, can infiltrate in the foundry goods, can after 700 ℃, decompose and produce carbonyl, ketone group, carbon silicon key compound and free carbon thereof and the silicon key atom that strong catalytic carburization body Decomposition is arranged, isoreactivity atom and group.

The present invention is different from metal atmosphere or controlled atmosphere thermal treatment, designed unique technology that a cover utilizes FD-1 catalyzer atmosphere to heat-treat voluntarily, graphited mode is carried out in former malleable cast iron annealing separation, two sections insulations of low temperature, change into and once be incubated the greying form, the high temperature use temperature of will annealing is by original 930 °-980 °, change 830 °-890 ° into, and platform-type and ascending manner is adopted in soak.

In the method for annealing of the present invention, the adding of catalyzer, be when the vanning of annealing part, it to be put into annealing box, then with the annealing part seal annealing, like this annealing enters the high temperature rear catalyst and just gasifies and infiltrate the part inside of annealing, decompose and produce active atomic and group, catalysis impels the cementite decomposition that greying is finished rapidly, and the catalyzer add-on is pressed the annealing box volume calculation, and promptly every cubic metre adds the 500-1000 gram.Annealing cycle of the present invention shortens to low temperature (830 °-890 ℃) electric furnace 9-14 hour by (930 °-980 ℃) under the former high temperature five, 60 hours, general stove 20-30 hour.

Now in conjunction with the accompanying drawings method for annealing of the present invention is made more detailed specific description by example.

Fig. 1: be first embodiment of the present invention, expression uses electric furnace to carry out the stress relief annealed process drawing of catalysis of the present invention;

Fig. 2: be second embodiment of the present invention, expression uses the common annealing stove to carry out the stress relief annealed process drawing of catalysis of the present invention;

Fig. 3: be third embodiment of the invention, expression uses large-scale annealing furnace to carry out the stress relief annealed process drawing of catalysis of the present invention.

The common annealing stove adopts 8 tons of false bottoms to account in the formula coal-powder boiler and implements, and 15 tons of false bottoms of large-scale annealing furnace employing account in the formula coal-powder boiler to be implemented, and electric furnace adopts in the box experimental furnace and implements, but the invention is not restricted to these embodiment, now concrete technology is illustrated.

For ease of understanding, earlier principle is done following brief elaboration.

Organic silicide trichlorine silicomethane is the liquid heavier than water, because si-cl key easy fracture character is active, and facile hydrolysis or alcoholysis, its hydrolysate is the silanol that is connected with three hydroxyls on the Siliciumatom.

The trichlorine silicomethane can generate multiple silicon shrinking alcohol that contains class carbonyl key and part affinity carbon silicon key compound with certain chemical composition in special reaction bed (carbon bed) hydrolysis, the oxygenizement that it can the weaken annealing process part oxidation and decarbonization that prevents to anneal.The boiling point of multiple silicon shrinking alcohol is about 250 °-300 ℃, the decomposition temperature of multiple silicon shrinking alcohol and carbon silicon key compound is at 600 °-700 ℃, decomposes produces carbonyl, ketone group (ether) they enter foundry goods when annealing after, part of hydroxyl and carbon silicon key compound free carbon, silicon key atom isoreactivity atom and group are arranged sometimes, greying process 20-40 doubly in the time of can promoting cementite decomposition quickening annealing, so can be used for the processing that malleable cast iron annealing and graphitic cast iron hard spot are eliminated, reach the processing of some steel, alloy.

Malleable cast iron annealing is the decomposition greying of high temperature carburizing body (or Cai Shi body) no matter, or the pearlitic decomposition greying of low temperature, and basic essence is that tri-ferrous carbide decomposes and generates ferrite and graphite, Fe ₃C(cementite, Cai Shi body, perlite) (△)/(catalyzer) 3Fe(ferrite)+C(graphite).The carrying out of this chemical reaction.As long as any chemical reaction can find ideal catalyst, just its speed of response can increase greatly in the presence of catalyzer.Can the crux of problem be find ideal catalyst, and how will urge the human relations agent to add solid-state metal inside.The present invention utilizes the FD-1 catalyzer can quicken cementite decomposition rate 20-40 doubly, and the characteristic that can gasify and enter foundry goods inside before 700 ℃, has solved this two very crucial and difficult problems.The outmoded conventions of the phase transformation theory of thermal treatment have in the past been broken in catalysis annealing, the catalytic theory fresh content is proposed, the present invention is changed over respectively 930 °-980 ℃ and two sections graphitizing annealings of 735 °-760 ℃ branch high and low temperatures for once carry out the process of graphitizing 830 ° of-890 ℃ of insulations, for cementite decomposes is directly or by the problem that austenitic transformation carries out this long-running argument, condition more directly perceived is provided and has enriched data.The peculiar two sections greying speed of the present invention are by the appearance that became this fact of dozens of minutes in past 12-14 hour, and katalysis accelerates cementite and decompose 20-40 doubly, can make contributions to the breakthrough in the phase transformation theory research undoubtedly.

Now malleable iron catalysis method low temperature quick annealing method is done an explanation:

(1) heat up: the present invention guarantees the synchronous of actual annealing process curve and design curve, is the key of giving full play to catalytic effect.Because it is inner and then decomposed katalysis and can keep efficiently that the time is not unlimited that foundry goods is infiltrated in catalyzer gasification back, if it is slow that annealing heated up, it is temperature required that catalyzer gasification after annealing spare does not reach greying for a long time, just have partly mistake of catalysis atmosphere ease or oxidation deactivation, the effect of catalyzed graphitization is weakened, suitable fast so after 400 ℃, heat up, be preferably in and be raised to 830 °-890 ℃ of high temperature in 4 hours.

(2) insulation: platform-type or ascending manner is adopted in the pyrographite insulation.Because the every rising of any gas temperature once volume increases by 1/273, reduce volume-diminished 1/273 once.If temperature decline 27 degree when 850 ℃ of insulations, gas volume just dwindles 1/10 in the annealing box, this moment as the bad or annealing box of sealing break (answering strictness to prevent these phenomenons), just having air (furnace gas) enters in the case, not only make 1/10 spatial annealing part lose catalysis atmosphere, ambient oxidation lost efficacy in the case but also can make.Again, if be warmed up to 850 ℃ again after the cooling, at this moment mixed atmosphere has 1/10 to fly out outside the case again in the case, from and part catalysis atmosphere ease is lost, so come and go after the lifting for several times, atmosphere will all become furnace gas in the case, so ten thousand can not adopt down gliding style or zigzag system insulation.

(3) cooling: when 830 ℃ or 890 ℃ were reduced to 780 ℃, speed can be fast, per hour descends 120 ℃ to not going wrong.The rear tapping temperature should be lower slightly, generally is advisable with 600-650 ℃, selects 600 ℃ when the annealing furnace temperature difference is big for use, has a narrow range of temperature and can select 650 ℃ for use.

(4) the present invention will pass by high temperature (930 °-980 °) and two sections graphitizing annealing methods of low temperature (735 °-760 ℃) and change into once and finishing at 820 °-890 ℃ on practical art, this is because pearlite decomposition speed of the present invention is fast, only need 30-150 minute, and all annealing furnaces are reduced to 650 ℃ all more than two hours from 820 °-890 ℃, so need not to carry out two sections insulations again.

(5) actually in the annealing process of the present invention greying is carried out the useful time (being each section time parameter) be, 400 ℃ ageing treatment 0-3 hour, 820 °-890 ℃ high temperature graphitization 3-7 hour, pearly-lustre decomposed 30-150 minute, need 4-12 hour altogether, this also is a unprecedented advance data in present all technologies.

(6) catalyzer adding method and add-on: the FD-1 catalyzer is not it to be added in the molten iron carry out inoculation, also can not in annealing process, directly add annealed casting inside, but when the vanning of annealing part, it is put into annealing box (case must not have sand, foreign material or stopping composition), then seal annealing with the annealing part, like this, when annealing enters high temperature, the FD-1 catalyzer promptly gasifies to infiltrate in the annealing part and plays katalysis.The consumption of FD-1 agent is pressed the annealing box volume calculation, and promptly every cubic metre adds the 500-1000 gram.For preventing annealing box runout rear catalyst oxidation deactivation, a little charcoal (especially in the case of high-temperature zone, top) of can when vanning, in case, packing into, every cubic metre adds the 250-500 gram.

For ease of understanding, illustrated by three kinds of different embodiment that anneal the type of furnaces of the present invention.The temperature that adopts of soak is minimum in embodiments of the present invention is 820 °-860 ℃ for electric furnace (seeing figure one), because of electric furnace has a narrow range of temperature, furnace temperature is easy to balance.Fig. 1 temperature-rise period has 2-3 hour ageing treatment at 400 ℃, is for the too fast annealing part that causes that prevents to heat up bursts apart, and also can increase annealing part graphite nuclei simultaneously, is beneficial to high temperature graphitization and carries out.Electric furnace high temperature graphitization time 3-6 hour, cooling was reduced to 600 ℃ from 860 ℃ and is 2.5-3 hour, and total cycle 9-14 hour is that the at present domestic and international cycle is the shortest, adopts the minimum unique technology of temperature.Common annealing stove (see figure 2) heats up and to be 7-8 hour, and temperature-rise period does not have 400 ℃ of ageing treatment, and because of this stove rises to 400 ℃ of needs time more than 3 hours from normal temperature, it has played ageing treatment to the annealing part simultaneously heating up.Common annealing stove soak temperature in embodiments of the present invention is the highest 840 °-890 ℃, and the longest 4-7 of soaking time hour, because this type of furnace temperature difference is big, furnace temperature was difficult for balance.The cooling conventional oven long than the electric furnace time, from 890 ℃ reduce to 650 ℃ 7-9 hour, be to cause slowly because of this stove cooling rate.Total cycle is 16-24 hour, also is to produce the skill that the last cycle is the shortest, temperature is minimum at present both at home and abroad.The Large Furnace (see figure 3) heated up the longest 12-16 hour, was because annealing part loading capacity causes greatly.More preceding two kinds of type of furnaces are slower because of heating up, so not only omit ageing treatment, and the soak temperature suitably reduced, adopt 830 °-870 ℃, soaking time suitably shortens, and adopts 3-6 hour, because the annealing part has begun greying in long temperature-rise period, the longer 9-10 of Large Furnace temperature fall time hour, reason was identical with the common annealing stove.By last three examples, as seen, give full play to the Catalytic processes advantage, should select for use heating-cooling fast, the type of furnace that has a narrow range of temperature.But be that to select for use the existing general type of furnace also can obtain very good, the effect that at home and abroad there is no at present.

In addition, holding temperature is selected (seeing the following form one) with annealing part Chemical Composition quality between 760 °-890 ℃.

Table one

Low silicon of the general Chemical Composition of the desirable strict Chemical Composition of composition and the middle special composition of chromium

760°～????800°～????840°～????860°～????890°～

800℃????850℃????870℃????890℃????930℃

The main main Si% Si1.0～Si0.75 of the main Si% of Si%～

1.2%????1.0%

1.6～2.0 1.4～1.75 1.25～or Cr0.06 or Cr0.08

1.65????～0.1%????～0.13%

The high temperature graphitization time generally can select for use 3-8 hour with the wall thickness change (seeing Table two) of annealing, and concrete time length is till checking that annealing test specimen cementite decomposition surplus reached at 1% o'clock.

Table two

＜8mm????8～12mm????12～16mm????15～20mm????20～30mm

1～3H????2～4H????3～5H????4～7H????5～8H

The present invention handles wide adaptability to the spoken parts in traditional operas molten steel preparation, its available spoken parts in traditional operas blank annealing of not breeding, also can adopt high silicon to add bismuth breeds, sial, bismuth are compound inoculated, the spoken parts in traditional operas pig-iron annealing of processing such as boron, bismuth breed, the present invention can suitably relax under the topic before not influencing the annealing performance annealing part chemical ingredients, as low silicon, high chromium spare (silicon＜1.2% even 0.8%; Cr0.06-0.13%) as long as improve annealing temperature slightly, the present invention just can make its graphite aggregateization finish and obtain well behaved qualified annealed casting.

The present invention's part of annealing is thin than the well-established law tissue, oxidation and be out of shape minimum, the mechanical property height, following table three is one group of embodiment data of the present invention.(technology is seen figure two)

Table three

Mechanical property

Numbering Chemical Composition %

Intensity N/M ²Unit elongation %

1 group 1. 39.8 18.6

②????38.6????16.0????C＝2.32;2.43;2.62;2.48

③????38.6????19.8

Si＝1.31;1.47;1.45;1.58

2 groups 1. 39.8 15.0

②????41.7????16.0????Mn＝0.373;0.364;0.398;0.425

③????38.3????17.0

S＝0.127;0.124;0.135;0.109

3 groups 1. 38.3 19.0

②????41.7????18.0

③????38.8????22.0????P＝0.042;0.045;0.034;0.030

4 groups of 1. 39.8 11.2 Cr=0.084; 0.130 C=3.15; 3.17

②????39.85????11.8????Si＝1.56;1.34????Mn＝0.56;0.58

③????39.3????10.6????S＝0.150;0.140????P＝0.088;0.055

The present invention is newly with stove the taking time that high temperature graphitization finishes of annealing for the first time, and is longer by 1/3 than the second stove required time always, and second stove than the 3rd furnace superintendent 1/3, four five stove after the greying deadline just be tending towards fixed range; Again, use with stove and carry out using common annealing instead after a catalysis in period is annealed, two or three a stove effect is still identical with catalysis annealing, just goes down this effect lagging reasons behind four or five stoves.Be because annealing furnace and annealing box to the cause that is absorbed with a saturation history of catalyzer.Do not notice that this puts not only beginning and can draft the failure technology that advances rashly, can think also that catalysis annealing effect is little by mistake and stop its use.Again, we do not add catalyzer (all the other all add) with the annealing box of annealing furnace central authorities in same stove, adopt Catalytic processes annealing, and this does not add the annealing part in the catalyst tank as a result, and is identical with the annealing part greying effect that respectively adds in the catalyst tank.Reason is because of annealing box is to use with the identical molten iron of part Chemical Composition of annealing to water, and both can enter after the catalyzer gasification in the annealing part, also can pass tank wall naturally and enter in other case.The advantage of this penetration phenomenon is that indivedual casees forget to add catalyzer during accidental the vanning, the living product of also unlikely appearance.But since this penetration phenomenon, the simultaneous test that can not in same stove, do to add catalyzer Yu not add catalyzer.

Method for annealing of the present invention is not only limited to the annealing of common malleable iron, also can be used for the annealing that alloy is forged cast iron and steel, and the processing of graphitic cast iron hard spot elimination, with the processing of some alloy steel products.

In sum, method for annealing of the present invention has the following advantages:

Cycle is short, can improve work efficiency. General as long as more than 20 hour, electric furnace (or special furnace) but also life cycle shortens to a few hours, shorten periodicity to ten times than current technology.

Annealing temperature is low, and the high temperature graphitization temperature becomes Baidu significantly to descend, and has reduced oxidation, distortion and the stream waste product that causes alive of annealing part, has improved yield rate. Also reduced simultaneously the rhegma of collapsing of annelaing pot, annealing kiln and lost, also further saved energy consumption, reduced cost, per ton according to the different decline 8-50 of managerial skills unit, and has saved the metallic zinc of costliness in short supply.

Annealing part performance is good. Tissue is thin than well-established law, oxidation and be out of shape minimumly, and mechanical performance is higher.

To annealing part Chemical Composition wide adaptability, not only can be used for the spoken parts in traditional operas blank that various differences breed mode, and can make underproof in accordance with regulations low silicon, the processing of high chromium blank obtain qualified product.

The present invention carries out graphitizing annealing with two sections insulations and changes into once and finishing, and easy, the easy grasp of technology is easy to utilize.

In a word, the present invention has broken the present simple heat energy that relies on and has finished forging ironcasting annealing routine, adopt catalysis method that the malleable cast iron annealing cycle is shortened, annealing temperature reduces, and annealing quality improves, and annealing part Chemical Composition scope is relaxed, malleable iron performance for a change, enlarge the malleable iron range of application, and increase alloy malleable iron kind and created condition, for new prospect has been opened up in the malleable iron development.The present invention also provides method for other metal treatment, for the metal heat treatmet theoretical investigation has increased new content.

Claims (2)

1, a kind of method of low-temp annealing of forgeable cast iron is characterized in that:

During the part of a. annealing vanning the catalyzer of multiple silicon shrinking alcohol polymkeric substance is put into annealing box, seal with the annealing part, the catalyzer add-on is with the annealing box volume calculation, and every cubic metre adds the 500-1000 gram;

B. heat up, quick heating after 400 ℃ of the furnace temperature is raised to 830 ℃-890 ℃ in 4 hours;

C. insulation, platform-type or ascending manner is adopted in the insulation of high temperature (830 ℃-890 ℃) greying;

D. cooling, when 830 ℃ or 890 ℃ were reduced to 780 ℃, speed can be fast, per hour descends 120 ℃, and tapping temperature is 600 ℃-650 ℃.

2, according to the said low-temp annealing of forgeable cast iron method of claim 1, when it is characterized in that catalyzer adds annealing box, with the annealing box volume calculation, every cubic metre adds charcoal 250-500 gram.