Chapter 430 Adhesive Bonding Technology

Qian Zhiyuan squatted beside the flange, holding a roughness tester, the probe sliding across the metal surface. The instrument beeped, and numbers appeared on the screen. He glanced at it, said nothing, turned off the instrument, stood up, and turned to face He Yuzhu.

He Yuzhu leaned against the scaffolding, arms crossed, waiting for him to speak.

"Dean He, the flange surface roughness is only 0.8 micrometers, it's too slippery. The adhesive won't stick."

"Suggest a solution."

"Sandblasting. Use quartz sand to roughen the surface to a texture of three to five micrometers. Adhesive must be applied within four hours after sandblasting, otherwise the surface will oxidize and the adhesive will not adhere."

He Yuzhu didn't reply. He stared at the six-meter-diameter flange, its 120 misaligned bolt holes resembling rows of open mouths, silently mocking him. The Dalian section took seven days to arrive, the Shanghai section took three months to build, and the Guangzhou section was still en route. Two millimeters short, and it was all stuck here.

"What about the sandblasting equipment?"

"Jiangnan Factory has them, for washing ship hull steel plates." Qian Zhiyuan pulled a piece of paper from his pocket, on which the equipment model and nozzle diameter were written in crooked handwriting. "You can use it by modifying the nozzle. But sandblasting produces a lot of dust, so the cleanroom must be properly sealed. If dust gets in, the adhesive layer will be ruined."

He Yuzhu jumped down from the scaffolding, his knees buckling as he landed. He braced himself with his hands, stood up, and dusted off his pants. "When will the cleanroom tent be ready?"

"The scaffolding will be erected tomorrow morning, and the tarpaulin will be installed this afternoon. The air conditioner and dehumidifier will arrive the day after tomorrow morning." Qian Zhiyuan stuffed the note back into his pocket. "Dean He, I've already told you about the constant temperature and humidity requirements—"

"Twenty days. You previously said the construction period would be extended by a month, but I'm only giving you twenty days. Not a single day more."

Qian Zhiyuan opened his mouth as if to say something, but then closed it again. He squatted down, reopened the roughness meter, and pretended to take measurements, but his finger didn't actually press the start button. He Yuzhu knew he was calculating the time in his mind, but didn't urge him. He stood there for a while, then turned and left.

The following afternoon, He Yuzhu entered the slipway. The steel pipe frame had already been erected, stretching towards the sky from around the flanges, crisscrossing like an unskinned skeleton. Qian Zhiyuan squatted under the frame, holding a measuring tape, measuring the diagonal dimensions. Workers stood on the scaffolding, hoisting bundles of canvas up one by one.

A river breeze blew by, making the canvas rustle. The unsecured corner swung back and forth in the air like a giant flag. A worker lost his grip, and the corner of the canvas slipped from his hand, snapping against a steel pipe with a crisp sound like a firecracker.

"Hold on!" Qian Zhiyuan shouted as he stood up, his voice hoarse and cracking.

He Yuzhu didn't speak, but walked to the flange. A plastic sheet was covering the flange, sealed with tape to prevent dust from getting in. He squatted down, lifted a corner, and saw that the flange surface was dusty and smooth to the touch, like touching a piece of old jade.

On the morning of the third day, the air conditioner and dehumidifier arrived. Qian Zhiyuan, along with two technicians, used a forklift to unload the equipment and push it into the cleanroom. The air conditioner's outdoor unit was placed outside the shed, with copper pipes running through the canvas wall and the gaps sealed with sealant. The dehumidifier's water pipes were connected and routed into the drainage ditch on the slipway.

He Yuzhu stood outside the shed, watching Qian Zhiyuan adjust the equipment. The temperature climbed from twelve degrees Celsius, while the humidity dropped from seventy percent. Qian Zhiyuan squatted in front of the control panel, his fingers turning the knobs, his eyes fixed on the screen, motionless.

"Dean He, it'll be 18 degrees tonight. We'll start work tomorrow morning." Qian Zhiyuan stood up and rubbed his knees, which had gone numb from squatting.

Where are you sleeping tonight?

"Inside the shed. I need to stay here in case the temperature fluctuates." Qian Zhiyuan pointed to the empty space next to the flange, where a sleeping bag had already been laid out.

He Yuzhu glanced at the sleeping bag, said nothing, and turned to leave.

On the morning of the fourth day, the sandblasting began.

Qian Zhiyuan was dressed in a full set of dustproof clothing, goggles, a mask, gloves, and shoe covers. He pulled the trigger of the sandblasting gun, and quartz sand sprayed from the muzzle, hitting the flange surface with a dense hissing sound like machine gun fire. Dust instantly exploded in the shed, and grayish-white smoke poured out from the gaps in the canvas.

He Yuzhu stood outside the shed, peering inside through a small hole in the canvas.

Less than three minutes after spraying, the vacuum cleaner hose detached from the connector. The dust suddenly thickened, and it was almost impossible to see anyone in the shed.

"Stop!" He Yuzhu shouted.

But Qian Zhiyuan didn't stop. He turned off the sandblasting gun, bent over, and felt around in the dust to find the detached pipe. He reconnected it, tightened the clamp, and gave it a couple of tugs to make sure it wouldn't fall off. He didn't look up or say a word the whole time. When he straightened up, his goggles and gloves were covered in dust. He wiped his goggles with his sleeve, shook the dust off his gloves, and picked up the sandblasting gun again.

The trigger was pulled, and the hissing continued.

He Yuzhu stood outside, his hands in his pockets, clenching them, loosening them, and clenching them again.

The sandblasting lasted for forty minutes. Qian Zhiyuan turned off the gun, stood up, and wiped the flange surface with a white cloth. The cloth was clean and spotless. He remeasured the roughness, and the number on the screen fluctuated between 3.2 and 3.8. He handed the instrument to the person next to him and nodded to He Yuzhu.

The glue applicator was pushed over. Vacuum suction cups adhered to the side of the flange, and all six suction cups simultaneously extracted air, firmly fixing the glue applicator in place. The applicator head, along with the scraper, moved slowly along the track, and nano-carbon nanotube reinforced epoxy resin was extruded from the nozzle, spreading evenly on the flange surface.

He Yuzhu stood beside the flange. The adhesive layer gleamed with an amber luster under the light; it was transparent, thick, and resembled honey that had been simmering for a long time. Where the applicator passed, the scraper removed the excess adhesive, leaving only a layer of 0.2 millimeters. The thickness sensor displayed a number in real time, fluctuating between plus and minus 0.03 millimeters.

The adhesive application took two hours. Qian Zhiyuan covered the flange surface with a release film, then laid an adhesive-absorbing mat on top of the film, and finally a vacuum bag on top of the mat. The vacuum pump was started, and the bag slowly contracted, tightly adhering to the adhesive layer, squeezing out excess air and adhesive together.

"Cure for 24 hours. Temperature 23 degrees Celsius, plus or minus 1 degree. Humidity 55 percent, plus or minus 5 percent." Qian Zhiyuan's voice came from behind the mask, muffled and emotionless.

He Yuzhu stood in the cleanroom for a while, looking at the vacuum bag. The surface of the bag had fine wrinkles, like an old man's skin. The adhesive layer was underneath, invisible, but he knew it was hardening.

At 2 a.m., the temperature alarm went off.

He Yuzhu sprang up from the folding bed, barefoot, and rushed into the cleanroom. The thermometer read 26.5 degrees Celsius, and the humidity was 63 percent. The air conditioner's outdoor unit was not running; the compressor was stopped, and the condenser fan was also not spinning.

Qian Zhiyuan squatted next to the air conditioner, a screwdriver in his hand, sweating profusely. He removed the outdoor unit's cover and threw it on the ground, pointing to a cylindrical component inside. "The capacitor is burnt out. There's no spare part."

He Yuzhu squatted down and took a closer look. There was a bulge on the capacitor casing, and a crack at the top from which dark brown electrolyte was leaking out.

"Does the shipyard's machine repair shop have capacitors?"

"Yes, but the capacity is different."

"Modify the wiring. Give me the model number, I'll go find it."

Qian Zhiyuan tore the label off the capacitor and handed it to He Yuzhu. He glanced at it, then turned and ran out of the cleanroom. Barefoot on the cement floor of the shipyard, the pebbles were cold and painful, but he didn't care. The machine repair shop door was locked. He kicked it once, but it wouldn't open. He kicked it a second time, and the door frame cracked, causing the door to spring open. He rummaged through the shelves and found five capacitors of different specifications, stuffed them all into his clothes, and ran back.

He ran into the cleanroom and handed Qian Zhiyuan the capacitor. Qian Zhiyuan picked one with the closest capacitance, modified the wiring with a soldering iron, and soldered it on. He burned his finger, shook it off, and continued soldering. The air conditioner restarted, the compressor hummed, and the condenser fan turned on.

The temperature began to drop. Twenty-seven, twenty-six, twenty-five, twenty-four.

He Yuzhu squatted next to the air conditioner, looking at the thermometer. Qian Zhiyuan squatted opposite him, with the repaired outdoor unit between them.

"It's 23 degrees Celsius," Qian Zhiyuan said.

He Yuzhu stood up and glanced at the clock on the wall. 3:40 a.m. He found his shoes next to his sleeping bag, put them on, and stepped out of the cleanroom. The river wind rushed into his collar, making him shiver. He stood on the platform, looking at the dark water on the river, unable to see any waves, only hearing the water splashing against the rocks, splash, splash.

The curing process was complete. The sample was clamped in the tensile testing machine. Qian Zhiyuan stood beside it, his hand on the start button, but he didn't press it. He glanced at He Yuzhu.

"according to."

The tensile testing machine began loading, and the numbers jumped from zero. One thousand kilograms, two thousand kilograms, three thousand kilograms. The sample made a squeaking sound, and a little white residue seeped from the edge of the adhesive layer, but it didn't crack. Five thousand kilograms, six thousand kilograms, seven thousand kilograms.

"Dean He, the yield strength of the base material is 7,500."

"continue."

Seven thousand five. The sample's base material began to thin, like a stretched rubber band. Seven thousand eight, eight thousand.

The sound of the parent material breaking was like a firecracker going off, a crisp crack, and the sample block split into two pieces.

Qian Zhiyuan squatted down, picked up the broken piece, and examined it for three seconds. The break was on the base material; the torn fibers resembled a tattered hemp rope, but the adhesive layer was intact. He handed the broken piece over.

He Yuzhu caught it and held it in his hand. The fibers on the cut surface stood upright, fluffy, like a brush. He placed it on the table and picked up the walkie-talkie.

"Lin Jianguo, notify Dalian and Guangzhou. Begin hoisting the next section tomorrow. Use adhesive bonding, no flanges."

"Understood." Lin Jianguo's voice came through the walkie-talkie, with static, but clear.

He Yuzhu stepped out of the cleanroom. The sunlight was blinding, and he squinted. On the slipway, workers had already begun dismantling the canvas. The transport barge for the third section was sailing across the river, the tugboat sounding its horn in a low, muffled tone.

Yang Xiaobing stood at the entrance of the workers' shed, holding a telegram in his hand. The scars on his face gleamed dark red in the sunlight.

He didn't say anything, but handed over the telegram.

He Yuzhu caught it and glanced at it—

"Lin Zhenbang has left the country. He holds a Portuguese passport, exited through Lisbon, and his destination is unknown. His brother claims he does not know his whereabouts."

He folded the telegram and stuffed it into his pocket.

"When did this happen?"

"Three days ago. Flying from Rio de Janeiro to Lisbon, then transferring in Lisbon. I can't find out where I transferred to."

On the river, the tugboat sounded its horn again, this time longer and more muffled than before. He Yuzhu stood on the platform, watching the barge slowly approach the shore.