The carburization process of oxidation in reducing
Technical field
The present invention relates to the carburization process of oxidation in a kind of the minimizing, the interior problem of oxidation when this technology can reduce the carburizing of instillation heat treatment furnace endothermic atmosphere.
Background technology
Traditional endothermic atmosphere thermal treatment, because its oxidizing atmosphere that certainly exists makes workpiece surface and nearly surface decarburization, oxidation is serious, has strengthened the process period and the difficulty of processing of part after the thermal treatment, also is a kind of great waste to metallic substance.
And the novel process that the nitrogen-based atmosphere heat treatment technics is a development in recent years gets up.It can replace with the oil liquefied gas is the endothermic atmosphere of raw material or ammonia dissolving atmosphere etc., because the oxidizing gas of its generation few (if the enough words of gas purity) can reach the purpose of nonoxidizing heating and chemical heat.And its atmosphere circulation ratio and carburizing homogeneity all are not less than endothermic atmosphere thermal treatment.
Along with oil, gas product price raise successively, the consumption of endothermic atmosphere thermal treatment process PetroChina Company Limited. or gas product is very big, has facilitated the nitrogen-based atmosphere heat treatment technics to the heat treated upgrading of traditional endothermic atmosphere more.
Summary of the invention
Purpose of the present invention just provides the carburization process of oxidation in a kind of the minimizing, with solve that prior art exists problem.
Technical scheme of the present invention is: adopt the cementing furnace with cup and chamber, back, it is characterized in that: may further comprise the steps:
(1) workpiece charging: workpiece is loaded on the bin;
(2) preceding cleaning and oven dry: the workpiece that will be loaded on the bin carries out routine cleaning and oven dry, removes workpiece and bin surface and is unfavorable for heat treated pollutent;
(3) workpiece is sent into the cup of cementing furnace;
(4) feed nitrogen to the back chamber of cementing furnace: get rid of the air of chamber, back, prevent interior oxidation;
(5) cup of cementing furnace ventilation: the ventilating pit before and after utilizing between the chamber, with nitrogen the air of cup is discharged, and continue to feed nitrogen;
(6) workpiece is sent into the chamber, back;
(7) chamber, back is heated to the temperature of arts demand, can obtain this temperature value through conventional test;
(8) chamber feeds methyl alcohol and propane backward, regulates the flow of nitrogen, methyl alcohol and propane according to arts demand.Can obtain the flow proportional of these three kinds of gases through conventional test.
(9) technology working time according to carburizing thickness test decide;
(10) technology is finished cooling, stops to feed methyl alcohol and propane, and continues to feed nitrogen, with the carburizing gas in the chamber after the emptying;
(11) degree drops to when hanging down, and workpiece is come out of the stove, and stops nitrogen.
Described methyl alcohol is to spray into liquid state, gasifies rapidly after spraying into and is cracked into carbon monoxide and hydrogen, and the decomposition of methyl alcohol can reach balance very soon under the temperature in stove, and methyl alcohol is as the heat treated carbon source of carburizing.
Described nitrogen is stored with liquid form, can gasify rapidly during feeding, is used as the shielding gas of carburizing; Described propane is enriched gas propane.
The volumn concentration of described carbon monoxide is to decompose fully and the ratio that feeds enriched gas propane is calculated and to be got according to methyl alcohol, there is test to draw the relation of itself and carbon potential according to the amount of carbon monoxide, determine the volume percent of gaseous methanol and gaseous nitrogen atmosphere, can realize control by controlling it to carburizing speed.
Described propane flow is about 6% (volume ratio) of gaseous methanol and gaseous nitrogen atmosphere synthetic gas total amount, is the best configuration of carburizing.
The present invention has been owing to adopted nitrogen and propane to do carrier gas, thereby the interior oxidative phenomena that occurs can effectively reduce carburizing on principle the time, the discharging of industrial harmful gas when also having reduced the atmosphere carburizing simultaneously; The undesirable gas generating unit is directly imported gas, has saved production cost, has reduced the equipment complexity, is beneficial to the maintenance of equipment; Can significantly improve carburizing speed, greatly save the energy, unit output value greatly improves.
The specific embodiment mode
Technology of the present invention is carried out in the cementing furnace with cup and chamber, back, may further comprise the steps:
(1) workpiece charging: workpiece is loaded on the bin;
(2) preceding cleaning and oven dry: the workpiece that will be loaded on the bin carries out routine cleaning and oven dry (surface does not have till the liquid), removes workpiece and bin surface and is unfavorable for heat treated pollutent;
(3) workpiece is sent into the cup of cementing furnace;
(4) feed nitrogen to the back chamber of cementing furnace: get rid of the air of chamber, back, prevent interior oxidation;
(5) cup of cementing furnace ventilation: the ventilating pit before and after utilizing between the chamber, with nitrogen the air of cup is discharged, and continue to feed nitrogen;
(6) workpiece is sent into the chamber, back;
(7) chamber, back is heated to the temperature of the thermal treatment process requirement of workpiece, obtains empirical value (specific embodiment below participating in) according to test.
(8) chamber feeds methyl alcohol and propane backward, and regulates the flow (specific embodiment below participating in) of nitrogen, methyl alcohol and propane according to arts demand.
(9) technology is decided (specific embodiment below participating in) according to carburizing thickness working time.
(10) technology is finished cooling, stops to feed methyl alcohol and propane, and continues to feed nitrogen with former flow, with the carburizing gas methyl alcohol in the chamber after the emptying.
(11) degree drops to when hanging down, and workpiece is come out of the stove, and stops nitrogen.So far finish a technological process.
Be each parameter that relates in the example explanation technology with a workpiece below:
Workpiece: 20CrMo, external diameter 90mm, high 25mm, the race ring of thick 12mm;
Client's technical requirements: carburized depth: 0.8-1.0mm;
Back chamber is heated to 920 ℃ from room temperature, is incubated 300 minutes; Carbon potential was 1.1 in wherein preceding 180 minutes, back 120 minutes carbon potentials 0.9.Carbon potential (Carbon Potential, Cp) be to characterize the carbon content that when carbon-containing atmosphere is in balance with steel piece surface at a certain temperature the steel surface is reached, the general soft steel paillon foil that adopts is measured, after placing the carburizing atmosphere medium to implement through carburizing less than the soft steel paillon foil of 0.1mm the thickness, measure the carbon content of steel foil.This numerical value i.e. the carbon potential of carburizing medium under this carburizing temperature for this reason.
Be cooled to 90 minutes carbon potentials 0.8 of 910 ℃ of insulations;
Be cooled to 850 ℃ and mend carbon carbon potential 0.7, be pulled to cup, quench.
The concentration of three kinds of gases is referring to the data of table 1, represent the volumn concentration of carbon monoxide from left number (down together) secondary series, be to decompose fully and the ratio that feeds enriched gas is calculated and get, the relation that draws itself and carbon potential of testing arranged according to the amount of carbon monoxide according to methyl alcohol.The flow of methyl alcohol is shown in the 3rd tabulation, and methyl alcohol is to spray into liquid state, gasify rapidly after spraying into and be cracked into carbon monoxide and hydrogen, temperature one regularly, the decomposition of methyl alcohol can very fast realization balance, methyl alcohol is the heat treated carbon source of carburizing.What the 4th tabulation was shown is the nitrogen flow that feeds, and nitrogen is stored with liquid form, can gasify rapidly during feeding, is used as the shielding gas of carburizing.What the 5th tabulation was shown is the volume percent of methyl alcohol (gaseous state) and nitrogen (gaseous state), can realize the control to carburizing speed by controlling it.What the 6th tabulation was shown is the flow that feeds enriched gas propane, and it plays diluent gas, through test of many times, detects the propane flow and be amount of substance about 6% of synthetic gas, is the best configuration of carburizing.
Table 1, correlation parameter table
Sequence number |
CO (%) |
CH
3OH (ml/h)
|
Gaseous state N
2 (l/min)
|
CH
3OH/N
2 |
Propane (l/min) |
1 |
15 |
1127.48 |
38.0688 |
0.2727 |
4.2 |
2 |
16 |
1200.06 |
35.9923 |
0.3077 |
3 |
17 |
1275.06 |
33.9158 |
0.3469 |
4 |
18 |
1350.07 |
31.8394 |
0.3913 |
5 |
19 |
1425.07 |
29.7629 |
0.4419 |
6 |
20 |
1500.08 |
27.6864 |
0.5 |
7 |
21 |
1575.08 |
25.6099 |
0.5676 |
8 |
22 |
1650.08 |
23.5334 |
0.6471 |
9 |
23 |
1725.09 |
21.4570 |
0.7419 |
10 |
24 |
1800.09 |
19.3805 |
0.8571 |
11 |
25 |
1875.09 |
17.3040 |
1 |
… |
… |
… |
… |
… |
12 |
33 |
2500 |
0 |
- |
In specific implementation process, carburizing speed as required and carburizing time are selected appropriate C O percentage concentration, have tested a concentration parameter 24% according to calculating, see Table the data in the 10th horizontal bar in 1.
According to the difference of concrete heat treatment material, use different technology, so temperature and time is a variable; In heat treatment process, the flow of keeping gas constant all the time (do not have cataclysm, have only less fluctuation); Furnace pressure is variable (not being vacuum oven) in process of production; The density of the liquid methanol that uses is 0.791g/cm
3The feeding amount of propane is the optimum value that goes out (about 4L/min) according to actual tests.Because industrial natural gas price lattice go up more than 10%, and methane is the main component by Sweet natural gas, therefore industrial methane price increase amplitude is very big, after adopting the present invention, can not use methane, and the cost of nitrogen and methyl alcohol is very low, thereby greatly reduces cost.